    [Radio Sets Scr-399-a and Scr-499-A]
    [From the U.S. Government Publishing Office, www.gpo.gov]

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    WAR DEPARTMENT TECHNICAL MANUAL
    NON-CIRCUUTING
    RADIO SETS
    SCR-399 -A AND
    SCR-499-A
    WARNING: This manual is the property of the United States Government, and is printed and distributed solely for the use of the •military, naval, and civilian personnel of the War and Navy Departments, and may not be published or reproduced in whole or in part, or in any manner or form (except by lawful copyright holders who may reproduce their copyrighted material in its original form) unless specifically approved by authorized military public relations agencies.
    1EAR DEPARTMENT ■ MARCH 1945
    WAR DEPARTMENT TECHNICAL MANUAL
    TM 11-281
    THIS MANUAL SUPERSEDES TM 11-281, 4 SEPTEMBER 1943; TB 11-281-1, 13 OCTOBER 1944, AND TB 11-281-2, 25 NOVEMBER 1944.
    RADIO SETS
    S C R - 3 9 9 - A A N D
    S C R - 4 9 9 - A
    WAR DEPARTMENT	•	MARCH 1 <) 4 5
    WARNING: This manual is the property of the United States Government, and is printed and distributed solely for the use of the military, naval, and civilian personnel of the War and Navy Departments, and may not be published or reproduced in whole or in part, or in any manner or form (except by lawful copyright holders who may reproduce their copyrighted material in its original form) unless specifically approved by authorized military public relations agencies.
    United States Government Printing Office
    Washington: 1945
    WAR DEPARTMENT Washington 25, D. C., 31 March 1945
    TM 11-281, Radio Sets SCR-399-A and SCR-499-A, is published for the information and guidance of all concerned.
    [AG 300.7 (8 Jan 45)]
    By order of the Secretary of War :
    Official :
    J. A. TJLIO
    Major General
    The Adjutant General
    G. 0. MARSHALL
    Chief of Staff
    Distribution :
    AAF (5) ; AGF (5) ; ASF (2) ; T of Opn (5) ; Dept (5) ; Def Comd (2) ; Base Comd (5) ; AAF Comd (2) ; Arm & Sv Bd (2) ; S Div ASF (1) ; Tech Sv (2) ; SvC (5) ; Area ASvC (2) ; WDGS Lib (5) ; PC&S (2) ; PE (2) ; Dep 11 (2) ; Gen Oversea SOS Dep (Sig Sec) (2) ; GH (2) ; M Cone C (2) ; Air Base Hosp (2) ; Gen Sv Sch (5) ; Sp Sv Sch (10) ; USMA (10) ; ROTC (5) ; Lab 11 (2) ; Sig AS (2) ; Rep Shop 11 (2) ; A (5) ; D (2) ; AF (2) ; Two (2) copies to each of the following: T/O & E 1-12; 1-27; 1-37; 1-47; 1-117; 1-127; 1-137; 1-147; 1-157S; 1-167; 1-252; 1-257; 1-267; 1-312; 1-317; 1-452T; 1-460-1S; 1-469S; 1-487; 1-487S; 1-547; 1-637; 1-637S; 1-757; 1-758; 1-759; 1-767; 1-768; 1-777S; 1-779; 1-1027; 30-47; Five (5) copies to each of the following: T/O & E 2-2; 2-22; 4-232; 4-240-1S; 5-512S; 11-7; 11-7S; 11-15; 11-18; 11-47; 11-57; 11-97; 11-107; 11-127; 11-147S; 11-157T; 11-217; 11-237; 11-247; 11-257; 11-287; 11-317; 11-338; 11-460-1S; 11-477S; 11-517; 11-537S; 11-557; 11-557T; 11-587; 11-592; 11-597; 44-7; 44-147S.
    Refer to FM 21-6 for explanation of distribution formula.
    ii
    CONTENTS
    i
    CHAPTER I. GENERAL
    Section I. Description.	Paragraph Page
    General............................................................................ 1	3
    Radio Set SCR-399-A...................................................................... 2	4
    Radio Set SCR-499-A...................................................................... 3	5
    Technical characteristics ............................................................... 4	6
    List of components and packaging data.................................................... 5	9
    Major components ........................................................................ 6	12
    Radio Transmitter BC-610-E...............................................................  7	14
    Speech Amplifier BC-614-E................................................................ 8	14
    Junction Box JB-70—A..................................................................... 9	15
    Radio Receivers BC-342-( ) and BC-312-( )................................................ 10	15
    Antenna Tuning Unit BC-939-A....................................................... 11	15
    Antenna system .......................................................................... 12	15
    Power Unit PE-95-( )..................................................................... 13	16
    Other components ........................................................................ 14	17
    Chest CH-120-A (main operating).......................................................... 15	17
    Chest CH-121-A .......................................................................... 16	17
    Chest CH-89-A ......................r.............................................. 17	17
    Chest CH-119-A .......................................................................... 18	18
    Chest CH-88-A ...........................................................:......... 19	18
    Frequency Meter Set SCR-211-( ).......................................................... 20	18
    Rectifier RA-63-(*) ..................................................................... 21	19
    Cordage ................................................................................. 22	20
    Remote control equipment................................................................. 23	23
    Batteries ............................................................................... 24	23
    Crystals ................................................................................ 25	24
    II. Installation.
    Siting .................................................................................. 26	25
    Uncrating, unpacking, and checking Radio Set SCR-399-A................................... 27	25
    Uncrating, unpacking, and checking Radio Set SCR-499-A................................... 28	26
    Installation of Radio Set SCR-399-A...................................................... 29	29
    Installation of Radio Set SCR-499-A...................................................... 30	31
    Connections and interconnections of Radio Set SCR-399-A.................................. 31	32
    Connections and interconnections of Radio Set SCR-499-A.................................. 32	32
    Installation of antennas on Radio Set SCR-399-A.......................................... 33	33
    Installation of antennas on Radio Set SCR-499-A.......................................... 34	34
    Installation of dry batteries............................................................ 35	34
    Placing storage batteries in service..................................................... 36	34
    Repacking ............................................................................... 37	34
    CHAPTER 2.	OPERATING INSTRUCTIONS.
    Section I. Controls and their use.
    General.................................................................................. 38	37
    Transmitter controls..................................................................... 39	37
    Tuning unit controls..................................................................... 40	40
    Antenna tuning unit controls............................................................. 41	40
    Junction Box JB-70-A controls............................................................ 42	41
    Speech Amplifier BC-614-E controls....................................................... 43	42
    Junction Box JB-60-A controls............................................................ 44	43
    Rectifier RA-63-( ) controls............................................................. 45	43
    II.	Tuning. Preliminary steps ......................................................................... 46	44
    Tuning Radio Transmitter EC-610-E for	c-w	operation	[master-oscillator control] ...	47	46
    Tuning Radio Transmitter BC—610-E for	c-w	operation	[crystal-control]............... 48	51
    Tuning Radio Transmitter BC-610—E for	voice	operation................................ 49	53
    iii
    III.	Normal operation.	Paragraph	Page
    C-w operation........................................................................ 50	55
    Voice operation...................................................................... 51	55
    Changing type of emission............................................................ 52	58
    Changing frequency .................................................................. 53	58
    Presetting tuning units.............................................................. 54	59
    Additional operating instructions.................................................... 55	59
    IV.	Remote control operation. Connection of remote stations............................................................. 56	60
    Remote voice operation............................................................... 57	61
    Remote c-w operation................................................................. 58	61
    Remote receiver operation............................................................ 59	61
    V.	Power source operation. Operation from commercial power source................................................... 60	62
    Operation of trailer 100 feet from truck............................................. 61	62
    Operation of trailer 200 feet fyom truck............................................. 62	62
    Use of Power Unit PE-95-( ) to supply power to auxiliary equipment................... 63	62
    Operation of low-voltage power supply system......................................... 64	63
    VI.	Equipment performance check list. Purpose and use............................................................................ 65	63
    Check list..........................................................................  66	64
    CHAPTER 3.	PREVENTIVE MAINTENANCE.
    Section I. Preventive maintenance techniques. Meaning of preventive maintenance................................................................ 67	71
    Description of maintenance techniques................................................ 68	71
    Recommended lubricants .............................................................. 69	72
    Vacuum tubes......................................................................... 70	72
    Capacitors .........................................................................  71	73
    Resistors ........................................................................... 72	73
    Fuses . ............................................................................. 73	73
    Bushings and insulators.............................................................. 74	74
    Relays......................<	m. ................................................ 75	74
    Switches ............................................................................ 76	74
    Coils ............................................................................... 77	75
    Rheostats and potentiometers......................................................... 78	75
    Terminal blocks ..................................................................... 79	75
    Multiple connectors ................................................................. 80	75
    Cords and cables..................................................................... 81	76
    Meters .............................................................................  82	76
    Pilot lamps ......................................................................... 83	76
    Jacks................................................................................ 84	76
    Dynamotors and motors................................................................ 85	76
    Cabinets, chassis, and mountings..................................................... 86	77
    Headsets, microphones, keys, and loudspeakers........................................ 87	77
    Couplings and control shafts......................................................... 88	77
    Gears .'............................................................................. 89	77
    Antennas ............................................................................ 90	77
    Reels .................’.......................................................... 91	78
    II.	Itemized preventive maintenance. General................................................................................. 92	78
    Common	materials needed.......................................................... 93	78
    Item 1.	Exterior of Radio Sets SCR-399-A	and	SCR-499-A........................... 94	78
    Item 2.	Headsets, microphones, keys, and loudspeakers.............................. 95	79
    Item 3.	Cords, cables, and connectors.............................................. 96	79
    Item 4.	Antennas .................................................................. 97	79
    Item 5. Accessories .....................-........................................ 98	79
    Item 6.	Interior of Radio Sets SCR-399-A and	SCR-499-A............................. 99	79
    Item 7.	Radio Transmitter BC-610-E................................................. 100	79
    Item 8.	Antenna Tuning Unit BC-939-A............................................... 101	79
    Item 9.	Speech Amplifier BC-614-E.................................................. 102	79
    Item 10. Junction Box JB-70-A....................................................... 103	79
    iv
    Paragraph Page
    Item 11. Rectifier RA-63-(*) ..............................................  •........ 104	80
    Item 12. Heating and ventilating system............................................... 105	80
    Item 13. Auxiliary batteries ......................................................... 106	80
    Preventive maintenance check list..................................................... 107	80
    III.	Lubrication.
    IV.	Special tools. Relay and commutator tools................................................................. 108	80
    Construction of special relay and commutator tools.................................... 109	81
    Safety shotting stick and jumper wires..............................................	110	81
    V.	Moistureproofing and fungiproofing. General................................................................................... Ill	81
    Treatment ............................................................................ 112	82
    Step-by-step instructions	for treating Radio Transmitter BC-610-E.................... 113	82
    Step-by-step instructions	for treating Speech Amplifiei1 BC-614-E.................... 114	85
    Step-by-step instructions	for treating Junction Box JB-70-A.......................... 115	86
    Instructions for treating	Radio Receivers BC—312—( ) and BC-342-( ).................. 116	87
    CHAPTER 4. AUXILIARY EQUIPMENT.
    Section I. Frequency Conversion Kit MC-509.
    Description .......................................................................... 117	91
    Installation on Antenna Tuning Unit BC-939-A........................................... 118	91
    Erection and installation of antenna mast.............................................. 119	92
    Modification of Radio Transmitter BC-610-E....................................-........ 120	93
    Operation of Radio Sets SCR-399-A and SCR-499-A in frequency range of 1.0 to 2.0 me................................................................................ 121	93
    Theory of equipment.................................................................... 122	94
    II.	Doublet antenna. Purpose ................................................................................... 123	95
    Description ........................................................................... 124	95
    Location and erection of	mast........................................................ 125	95
    Installation in Radio Transmitter BC-610-E............................................. 126	99
    Maintenance ..........................................................................  127	101
    Differences in coil units.............................................................. 128	102
    Theory of equipment.................................................................... 129	102
    CHAPTER 5. REPAIR INSTRUCTIONS.
    Section I. Simplified block diagrams.
    Radio Transmitter BC-610-E, c-w operation.............................................. 130	105
    Speech Amplifier BC-614-E............................................................   131	106
    Radio Transmitter BC-610-E and Speech Amplifier BC-614-E	[phone operation] ....	132	106
    II.	Theory of Radio Transmitter BC-610-E.
    Oscillator stage ...................................................................... 133	106
    Crystal control of master	oscillator................................................... 134	109
    Buffer-doubler stage .................................................................. 135	110
    Intermediate power-amplifier stage..................................................... 136	111
    Power-amplifier stage.................................................................. 137	111
    Antenna tuning unit.................................................................... 138	112
    Modulator section ....',.............................................................. 139	114
    Power supplies ........................................................................ 140	115
    Switches .............................................................................. 141	117
    Relays................................................................................. 142	121
    Controls and meters.................................................................... 143	122
    III	. Theory of Speech Amplifier BC-614-E.
    First a-f amplifier.................................................................... 144	123
    Second a-f amplifier................................................................... 145	123
    Third a-f amplifier and phase inverter................................................. 146	124
    Fourth a-f amplifier................................................................... 147	126
    Modulation limiter..................................................................... 148	126
    C-w sidetone.......................................................................... 149	127
    Power supply .......................................................................... 150	128
    Jacks, controls, and meters ..........................................................  151	128
    v
    Paragraph Page
    IV	. Theory of Junction Box JB-70-A. Transmitter control switch SW203...................................................... 1^2	129
    REMOTE CONTROL EE-8 switch SWJ02................................................. 453	130
    Relay RY:w ...................................................................... 154	131
    Receiver disabling switches SW200 and SW201..................................... 155
    Receiver output switch SW204..................................................... 156	133
    C.W. SIDETONE switch SW!ro....................................................... 157	133
    START-STOP switch SW208.......................................................... 158	I33
    Battery source switch SW207...................................................... 159	134
    Circuit breaker CB200............................................................ 159	134
    Surge filters ................................................................... 151	I34
    V.	Over-all system function. General............................................................................... 152	135
    C-w operation .................................................................. 163
    Phone operation.................................................................. 154	HO
    Remote operation................................................................. 165	140
    Rectifier RA-63-(*) ............................................................. 166	140
    VI.	Changes in equipment. Changes in Radio Transmitter BC-610-E.................................................. 167	142
    Changes in Speech Amplifier BC-614-E............................................. 168	143
    Wiring change in Junction Box JB-70-A............................................ 169	143
    Change in coupling coils for doublet antenna kit................................. 170	144
    VII.	Trouble shooting. General trouble-shooting information................................................... 171	144
    Voltage measurements ............................................................ 472	145
    Resistance measurements.......................................................... I?3	146
    Capacitor tests ................................................................. 474	147
    Current measurements ............................................................ 175	147
    Tube checking.................................................................... 176	148
    Analyzer BC-1052-E...........................................................     177	148
    Trouble-shooting procedures ...................................................   178	149
    Trouble-shooting charts ................................................’........ 179	149
    Sectionalizing trouble in Radio Sets SCR-399-A and SCR-499-A..................... 180	151
    Localizing trouble in Radio Transmitter BC-610-E................................. 181	152
    Localizing trouble in Junction Box JB-70-A....................................... 182	153
    Localizing trouble in Speech Amplifier BC-614-E.................................. 183	154
    VII	I. Repairs. Replacement of parts.................................................................... 184	154
    Replacement of tubes............................................................. 185	154
    Removal of Antenna Tuning Unit BC-939-A. . . . .................................. 186	155
    Removal of top of transmitter cabinet............................................ 187	155
    Removal of r-f section........................................................... 188	155
    Removal of chests from shelter................................................... 189	155
    Removal of Radio Transmitter BC-610-E............................................ 190	156
    Replacement of switches in Radio Transmitter	BC-610-E...........................  191	156
    Replacement of parts in Speech Amplifier BC-614-E................................ 192	156
    Removal of Junction Box JB-70-A.................................................. 193	156
    Rustproofing and repainting...................................................... 194	156
    War Department Unsatisfactory Equipment Report................................... 195	157
    IX	. Alignment and adjustment. Neutralization........................................................................  196	157
    Modulation limiter............................................................... 197	157
    APPENDIX I. MAINTENANCE PARTS LIST.................................................................... 182
    II. REFERENCES ...................,.......................................................... 183
    vi
    LIST OF TABLES
    Table Page
    Chests and contents................................................................................ I	25
    Typical packing list for Radio Set SCR-499-A.....................................................  II	28
    Tuning components ................................................................................ HI	51
    Tuning ranges for long wire antennas when used	with Antenna Tuning Unit BC-939-A.................. IV	51
    Crystals and operating frequencies................................................................. V	52
    Approximate dial settings using Antenna Tuning	Unit BC-939-A............................ VI	93
    List of components in doublet antenna kit........................................................ VII	96
    Continuity checks for cables and terminal strips................................................ VIII	186
    Data for checking trans^orpiers, chokes, and inductors............................................ IX	192
    Performance characteristics ....................................................................... X	194
    Characteristics of vacuurh tubes.................................................................. XI	194
    vii
    DESTRUCTION NOTICE
    WHY — To prevent the enemy from using or salvaging this equipment for his benefit.
    WHEN — When ordered by your commander.
    HOW —1. Smash — Use sledges, axes, handaxes, pickaxes, hammers, crowbars, heavy tools.
    2.	Cut — Use axes, handaxes, machetes.
    3.	Burn — Use gasoline, kerosene, oil, flame throwers, incendiary grenades.
    4.	Explosives — Use firearms, grenades, TNT.
    5.	Disposal — Bury in slit trenches, fox holes, other holes. Throw in streams. Scatter.
    USE ANYTHING IMMEDIATELY AVAILABLE FOR DESTRUCTION OF THIS EQUIPMENT
    WHAT —1. Smash — Crystals, meters, plugs, tubes, tuning controls, capacitors, resistors, sockets, insulators, microphones, headsets, relays, gas engine, and generator.
    2.	Cut — Cords, wiring, and cables.
    3.	Burn — Circuit labels, technical manuals, all papers, cords, wiring, cables, capacitors, resistors, and nameplates.
    4.	Bend — Antenna sections, panels, mounting, and nameplates.
    5.	Bury or scatter — All of the above pieces after breaking and burning.
    DESTROY EVERYTHING
    VIU
    SAFETY NOTICE
    Voltages as high as 2,600 volts are used in the operation of this equipment. These voltages are •dangerous to life.
    Do not change tubes or make adjustments inside the set with the high voltage supply ON.
    All panels giving access to voltages above 450 volts are provided with interlocks to shut off the dynamotor when opened. A few service checks must be made inside the set with the high voltage on. When making these checks, always have the immediate presence and assistance of another person capable of rendering aid. Keep one hand in your pocket while making high voltage measurements. This will prevent touching the electrical circuit with more than one part of the body at one time.
    Be sure that high-voltage plate circuits are dead before performing preventive maintenance on this equipment. High-voltage capacitors in power supplies must be discharged manually before performing preventive maintenance operations.
    Servicing should be done with the vehicular battery circuit open. Shorting this battery circuit will cause a flash and severe burns unless the power is turned off.
    First Aid for Electric Shock
    TL 15339
    Radio-frequency voltages as high as 25,000 volts may develop on the antenna of this radio set. Do not touch the antenna while the set is turned on.
    Do not add gasoline to the vehicle fuel tank when the transmitter is on. Radio-frequency voltage may cause a spark resulting in an explosion. Turn off the radio transmitter and KEEP it off until refueling is finished.
    Do not add gasoline to the vehicle fuel tank when the transmitter is on. Radio-frequency voltage present on the chassis of the vehicle may cause a spark resulting in an explosion. Turn off the radio transmitter and KEEP it off until refueling is finished.
    ix
    FIRST AID FOR ELECTRIC SHOCK
    I.	Rescue
    In case of electric shock, shut off the high voltage at once and ground the circuits. If the high voltage cannot be turned off without delay, free the victim from contact with the live conductor as promptly as possible. Avoid direct contact with either the live conductor or the victim’s body. Use a dry board, dry clothing, or other nonconductor to free the victim. An ax may be used to cut the high-voltage wire. Use extreme caution to avoid the resulting electric flash.
    2.	Symptoms
    a.	Breathing stops abruptly in electric shock if the current passes through the breathing center at the base of the brain. If the shock has not been too severe, the breathing center recovers after a while and normal breathing is resumed, provided that a sufficient supply of air has been furnished meanwhile by artificial respiration.
    b.	The victim is usually very white or blue. The pulse is very weak or entirely absent, and unconsciousness is complete. Burns are usually present. The victim’s body may become rigid or stiff in a very few minutes. This condition is due to the action of electricity and is not to be considered rigor mortis. Artificial respiration must still be given, as several such cases are reported to have recovered. The ordinary and general tests for death should never be accepted.
    3.	Treatment
    a.	Start artificial respiration immediately. At the same time send for a medical officer, if assistance is available. Do not leave the victim unattended. Perform artificial respiration at the scene of the accident, unless the victim’s or operator’s life is endangered from such action. In this case only, remove the victim to another location, but no farther than is necessary for safety. If the new location is more than a few feet away, artificial respiration should be given while the victim is being moved. If the method of transportation prohibits the use of the Shaeffer prone pressure method, other methods of resuscitation may be used. Pressure may be exerted on the front of the victim’s diaphragm, or the direct mouth to mouth method may be
    used. Artificial respiration, once started, must be continued, without loss of rhythm.
    b.	Lay the victim in a prone position, one arm extended directly overhead, and the other arm bent at the elbow so that the back of the
    TL I5338A
    X
    A
    B
    C
    D
    hand supports the head. The face should be turned away from the bent elbow so that the nose and mouth are free for breathing, as shown in A and B.
    c.	Open the victim’s mouth and remove any foreign bodies, such as false teeth, chewing gum, or tobacco. The mouth should remain open, with the tongue extended. Do not permit the victim to draw his tongue back into his mouth or throat.
    d.	If an assistant is available during resuscitation, he should loosen any tight clothing to permit free circulation of blood and to prevent restriction of breathing. He should see that the victim is kept warm, by applying blankets or other covering, or by applying hot rocks or bricks wrapped in cloth or paper to prevent injury to the victim. The assistant should also be ever watchful to see that the victim does not swallow his tongue. He should continually wipe from the victim’s mouth any frothy mucus or saliva that may collect and interfere with respiration.
    e.	The resuscitating operator should straddle the victim’s thighs, or one leg, in such a manner that the—
    (1)	Operator’s arms and thighs will, be vertical while applying pressure on the small of the victim’s back (C).
    (2)	Operator’s fingers are in a natural position on the victim’s back with the little finger lying on the last rib.
    (3)	Heels of the hands rest on either side of the spine as far apart as convenient without allowing the hands to slip off the victim (A).
    (4)	Operator’s elbows are straight and locked.
    f.	The resuscitation procedure is as follows:
    (1)	Exert downward pressure, not exceeding 60 pounds, for 1 second.
    (2)	Swing back, suddenly releasing pressure, and sit on the heels (D).
    (3)	After 2 seconds’ rest, swing forward again positioning the hands, and apply pressure for another second (B and C).
    g.	The forward swing, positioning of the hands, and the downward pressure should be accomplished in one continuous motion, which
    requires 1 second. The release and backward swing require 1 second. The addition of the 2-second rest makes a total of 4 seconds for a complete cycle. Until the operator is thoroughly familiar with the correct cadence of the cycle, he should count the seconds aloud, speaking distinctly and counting evenly in thousands. Example : one thousand and one, one thousand and two, etc.
    h.	Artificial respiration should be continued until the victim regains normal breathing, or is pronounced dead by a medical officer. Since it may be necessary to continue resuscitation for several hours, relief operators should be used if available.
    4.	Relieving Operator
    The relief operator kneels beside the operator and follows him through several complete cycles. When the relief operator is sure that he has the correct rhythm, he places his hands on the operator’s hands without applying pressure. This indicates to the operator that he is ready to take over. On the backward swing, the operator moves and the relief operator takes his position. The relieved operator follows through several complete cycles to be sure that the new operator has the correct rhythm. He remains alert to take over instantly if the new operator falters or hesitates on the cycle.
    5.	Stimulants
    a.	If an inhalant stimulant is used, such as aromatic spirits of ammonia, the individual administering the stimulant should first test it himself to see how close he can hold the inhalant to his own nostrils for comfortable breathing. Be sure that the inhalant is not held any closer to the victim’s nostrils, and then for only 1 or 2 seconds every minute.
    b.	After the victim has regained consciousness, he may be given hot coffee, hot tea, or a glass of water containing i/2 teaspoon of aromatic spirits of ammonia. DO NOT GIVE ANY LIQUIDS TO AN UNCONSCIOUS VICTIM.
    Cautions: 1. After the victim revives, keep him lying quietly. Any injury a person may have received may cause a condition of shock. Shock is present if the victim is pale and has a cold sweat, his pulse is weak and rapid, and his breathing is short and gasping.
    2. Keep the victim lying flat on his back, with
    xi
    his head lower than the rest of his body and his hips elevated. Be sure that there is no tight clothing to restrict the free circulation of blood or hinder natural breathing. Keep him warm and quiet.
    3. A resuscitated victim must be watched
    carefully as he may suddenly stop breathing. NEVER LEAVE A RESUSCITATED PERSON ALONE UNTIL IT IS CERTAIN THAT HE IS FULLY CONSCIOUS AND BREATHING NORMALLY.
    xii
    ch^r 1

    This manual supersedes TM 11-281, 4 September 1843; TB 11-281-1, 13 October 1944, and TB 11-281-2, 25 November 1944.
    CHAPTER J
    GENERAL
    Section I. DESCRIPTION
    I. General
    a. This manual covers Radio Sets SCR-399-A and SCR-499-A. There are no differences in the operating components and power sources of the two sets, but Radio Set SCR-399-A is usually installed as a mobile station (fig. 1) and Radio Set SCR-499-A is ordinarily set up as a fixed station (fig. 2). To facilitate its use as a mobile station, Radio Set SCR-
    399-A is shipped with the operating components and the power source installed in Shelter HO-17-A and Trailer K-52-( ), respectively. A shelter and trailer are not provided with Radio Set SCR-499-A, since it is not intended for mobile use. Its components are shipped in 23 boxes from which they can be unpacked and set up as a fixed station at any suitable site.
    -------- receiving antenna MAST SECTIONS
    MS-51,52,53
    ^Transmitting antenna	s'	/ \
    MAST SECTIONS	________-/	I
    MS-49,50,51,52,53-"	/	I
    / //'f/	MAST BASE MP-48
    ’MAST BASE MP-47-A* —-X-- /	--- ■__________-
    /	, \	I 1	// ______. MAST BASE MP-50-A
    SHELTER HO-I7-Ay*	i	V 7/
    _____/]	/	/	\	\	7/	TRAILER K-52-C )WlTH \	/	\	/ \ //	POWER UNIT PE-95-( )
    ayL Z[^	M j| /\ / -
    ’* A J/^\ w r
    TRUCK 2jTON 6X6	CORD CO-335	CORD CO-3IO	TLI732Q
    Figure 1.	Radio Set SCR-399-A installed as a mobile station.
    3
    4
    ’	••	|	j	ANTENNA TUNING ^’ e' i
    J CHEST CH-feO-A	UNIT BC*939*A
    /	/ RADIO TRANSMITTER ?■?
    /	/ BC-6I0-E
    If CHEST CH-I2I-A	/	/	/ CHEST
    iSP’flBi /	CH-88-a
    £/-■	•	-I. r---------k
    —x	" vT?- , '■_	i? • chest
    ***r\	* 1	U c~'’1 -’9
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    fix L, -	...*• ■	;S
    f t	'	< '-■■ is &k ■
    •<3 '	;hest . . _ w. £se< xwo
    CH-IO9-A	|Jk ! I	|y-	b',
    U7 Uf \ In* • '	'	BL--
    //	’	\ • j	x£*^HEATER I /  1 I W i
    n -«;RA-63-( ) • T	I	1 ■
    <%■>’	■S-*-;;-'?-‘* 1 r frame	j
    FM-59-A
    —■ ?—:
    CHEST CH-89-A	/	I r l 15 • > ■■ 0 ,j
    Figure 2.	Radio Set SCR-499-A, operating and accessory components arranged as a fixed station.
    b.	The following Technical Manuals are issued with the radio sets and contain detailed information on the various components as listed below:
    TM 11-333, Telephone EE-8-( ).
    TM 11-850, Radio Receivers BC-312-( ), BC-314-( ), BC-342-( ), and BC-344-( )•
    TM 11-904, Power Unit PE-95-( ).
    TM 11-300, Frequency Meter Set SCR-211-( ).
    Parts List for Shelter HO-17-A.
    c.	Trailer K-52-( ) and Power Unit PE-95-( ), used with Radio Set SCR-399-A, are also supplied with Radio Sets SCR-299-C and -D.
    d.	Official nomenclature followed by ( ) is used in this manual to indicate reference to all models of the item of equipment. Official nomen-
    clature followed by (*) refers to all models included in one Technical Manual. Therefore, Rectifier RA-63-(*) refers to Rectifiers RA-63-A and -C, treated together in this manual.
    2. Radio Set SCR-399-A
    Radio Set SCR-399-A is a relatively high-power radio communications station. Under all conditions of atmosphere and terrain, the radio set will provide voice or c-w (continuous-wave) communication over a range of more than 100 miles from a stationary position, or while moving at high speed. For mobile use, Shelter HO-17-A should be mounted on a 2^-ton, 6x6, cargo truck. (See fig. 1.) Two seats in the truck cab carry the driver and his alternate. In the shelter (fig. 3), two operators may sit at the radio station operating positions. Power Unit PE-95-( ) may be started and stopped by remote control or at the trailer. The transmitting
    5
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    igjgL^ J BG-ylAi-A k J >	“EATER’
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    FBB 00-335/	■'•	" ’ RA-63-( )...	Ml DR-4 Mlyvjt
    r / ' - I IP •	■
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    ■ *	' CHEST J	I
    | CH-89-AX^J -	1 .
    Figure 3. Radio Set SCR-399-A
    installed in Shelter H0-17-A.
    and receiving controls, tuning units, coils, crystals, and spare parts are all within reach of the operating positions. In cold weather, an electric heater maintains moderate temperature within the shelter. In warm weather, the motor-driven heater fan and a ventilating blower provide adequate air circulation. (See fig. 4.) Chest CH-89-A (seat bench) has a 4-inch cushion on each of the four lids covering its spare parts compartments, and provides sleeping quarters for one person. An additional shelter and sleeping quarters can be made with the wooden frame and tarpaulin from the trailer.
    3. Radio Set SCR—499-A
    The components of Radio Set SCR-499-A are the same as those of Radio Set SCR-399-A, except that a shelter and trailer are not provided. The components can be quickly assembled and set up as a field station in a tent, a shelter, or in the open. The installed radio set can be easily dismantled into a number of component parts, each of which is small enough for air transportation to a new site. Canvas covers are issued to provide protection for components while they are in transit, as well as to protect them if the station is set up in the open.
    6
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    !;:?•<■■•' CHEST	f VENTILATING
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    Figure 4. Shelter H0-17-A—interior view of right (or curb) side.
    4. Technical Characteristics
    a. Radio Transmitter BC-610-E (fig. 5).
    Frequency range fi
    Three channels (1, 2, and 3)........................................
    Circuit.................................................................
    Types of signals transmitted............................................
    2 me to 18 me
    master oscillator-power amplifier (mopa)
    c-w and voice
    Distance range :2
    C-w:	Stationary ...........................................250	mi
    Moving................................................250	mi
    Voice:	Stationary............................................100	mi
    Moving....... ., .....................................100 mi
    Type of modulation................................................amplitude
    Number of tubes...................................................16
    ’Refer to the frequency spectrum chart, figure 6.
    2Use the best operating frequency for the time of day and season of year.
    7
    JTLI5940
    Figure 5. Radio Transmitter BC-610-E with Antenna Tuning Unit BC—939-A in position.
    Antennas:
    Whip antenna...................................................
    Extended whip antenna......................................
    15 ft long. Consists of Mast Sections MS-49 to MS-53, inclusive
    25 ft long. Add 1 or 2 Mast Sections MS-54 to Mast Section MS-53
    25-100 ft long kit
    Straight wire antenna.............................................
    Doublet antenna...................................................
    Power output:
    C-w operation......................................................
    Voice operation ...................................................
    400 watts (approx)
    300 watts (approx)
    8
    Power input:
    115-volt, 50/60-cycle ac Power source...............
    Weight.....................
    1,700-2,000 watts
    PE-95-( ) or commercial
    401 lb
    FREQUENCY SPECTRUM: cMeqacqc&e
    o .5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0	5.5	6.0	6.5	7.0	7.5	8.0	12.5	180
    1/ i i i i I । i •" r~ i' i 1 i • i m m /	cpd.iqq.a transmitter 1.5-12.5 mc	/ /
    \	OUn loo A RECEIVER 1.5-18.0 MC	'
    /	CCD-QQQ-A CPD-liOQ-A transmitter 2.0-ie.o mc	)	\
    OUn Ooo r\ Obn *too A receiver i.5-i8.omc	f	2
    rj L	।	: j rn 3
    CP D-HAQ- f 1 TRANSMITTER 2.0-8.0 MC
    Ovn CC77 v / RECEIVER 1.5 18.0 MC	JHB tK&ffiwSSx
    T -	—	|	।	।	,	!	■	“
    ff.- 1 .	■ - I	/ ern cnn .(I transmitter 3.8-6.5 mc \
    ^□bK oy*r \/ RECEIVER 3.8-6.5MC^
    NOTE '•	avt&u/s a£&uj A-------	1
    TlzafOfttcO&'t, ftanqf ifei£ x.-	/cr'D.OQ2i-f vRAN5MiTrER3e 58“^\	I	1 ’
    7&	avuttivs wdccdOe' X———	/
    7fe nanyed	n£c€a/&M-. 4QE3I a	; /
    Ciee arttittitts ,	/ ero-Kii-/ transmitter 3.0-6.0 mc x	| ]	I
    exTChttzd /ia;tqeMC. and receiver 100'156'MC	’rsoooa
    Figure 6. Frequency spectrum chart.
    b. Radio Receivers BC-312-( ) andBC-342-( ).
    Frequency range: Band A ...........................................................
    Band B .......................................................
    Band C .......................................................
    Band D .......................................................
    Band E .......................................................
    Band F .......................................................
    Circuit...........................................................
    Types of signals which can be received............................
    Number of tubes...................................................
    Intermediate frequency ...........................................
    Method of calibration.............................................
    Antenna (whip) ...................................................
    1.5 mc to 3 mc
    3 mc to 5 mc
    5 mc to 8 mc
    8 mc to 11 mc
    11 mc to 14 mc 14 mc to 18 mc superheterodyne c-w, tone, and voice
    9
    470 kc
    Frequency Meter Set SCR-211-( )
    Mast Base MP-48 mounted in Mast Base Bracket MP-50 and Mast Sections MS-51 to MS-53
    9
    Power input:
    Radio Receiver BC-312-( )...........................................
    Radio Receiver BC-342-( )...........................................
    Power source ...........................................................
    Weight.........................................................
    50-55 watts
    70-85 watts
    12-volt battery for Radio Receiver BC-312-( )
    110-volt 50/60 cycle ac for Radio Receiver BC-342-( )
    40-50 lb (each)
    5. List of Components and Packaging Data
    The following is an alphabetical list of items issued with Radio Sets SCR-399-A and SCR-499-A. Note. Running spares are for initial issue only and are not to be requisitioned as a kit or group as shown in
    the list of components.
    Radio Set	Radio Set
    SCR-399-A	SCR-499-A	Component
    4	4	Antenna guy assembly (receiver)
    2	2	Antenna guy assembly (transmitter)
    1	1	Antenna Tuning Unit BC-939-A
    1	1	Antenna doublet kit
    1	1	Axle RL-27-B
    12	12	Battery BA-30; spare
    2	2	Battery, storage; 6-volt
    2	2	Box BX-19-A
    1	1	Box BX-34-B; with crystals
    6	0	Bracket for gasoline can
    2	2	Brush, high-voltage; for dynamotor of Radio Receiver BC-312-( ) ;
    2	2	Brush, low-voltage; for dynamotor of Radio Receiver BC-312 -( ) ; spare
    1	1	Bumper clamp (for Cord CO-335)
    1	1	Chest CH-88-A (wall)
    1	1	Chest CH-89-A (seat bench)
    1	1	Chest CH-109-A (12-volt battery)
    1	0	Chest CH-112-A
    0	1	Chest CH-112-B
    1	0	Chest CH-119-A (wall)
    0	1	Chest CH-119-B (wall)
    1	1	Chest CH-120-A (main operating)
    1	1	Chest CH-121-A (auxiliary)
    1	1	Cord CX-141/MRQ-2; Junction Box JB-70-A to Speech Amplifier BC-614-E; 3-foot
    1	1	Cord CX-143/MRQ-2 (main audio) ; 55-inch (LS-3 branch 21 inches, BC-342 branch 10 inches)
    0	1	Cord CD-201-A; Key J-37 to Junction Box JB-70-A
    1	1	Cord CX-140/MRQ-2 (auxiliary audio) ; 53-inch (BC-312-( ) branch 11 inches)
    1	1	Cord CO-313 (a-c extension) ; 100-foot
    1	1	Cord CO-314 (a-c connection) ; 3-foot
    2 .		Cord CO-316 (power and control) ; 11-foot; 1 in use, 1 spare Cord CD-318-A; for Microphone T-30
    	1
    2	1	Cord CO-335 (power and control) ; 14-foot; 1 in use, 1 spare (SCR-399-A), no spare (SCR-499-A)
    2	2	Cord CD-564 (power) ; 3-foot; 1 in use, 1 spare
    2	2	Cord CD-565 (control and power) ; 4-foot; 1 in use, 1 spare
    2	2	Cord CD-566 (control) ; 4-foot; 1 in use, 1 spare
    4	4	Cord CD-605; for Headset HS-30
    1	1	Cord CD-652 (power and control extension) ; 100-foot
    0	1	Cord CD-1117; for Loudspeaker LS-3
    1	1	Cord CD-1177 (audio patch) ; 2-foot
    1	1	Cord CD-659 (power) ; 12-volt battery to receiver; shelter connection; 6-foot
    10
    Radio Set SCR-399-A
    1
    2
    1
    1
    1
    1
    1
    1
    1
    2 (sets)
    6
    1
    1
    1
    1
    6
    4
    7 (sets)
    Radio Set SCR-499-A
    1
    2
    2
    1
    1
    1
    1
    1
    1
    1
    2 (sets)
    6
    1
    0
    1
    1 .
    14
    5
    7 (sets)
    7	7
    1	1
    4	4
    1	1
    1	1
    1	1
    3	3
    1	0
    10	7
    2	2
    2	2
    1	1
    8	8
    2 (sets)
    1	0
    2	2
    2	2
    2	2
    3	3
    0	1
    3	3
    4	4
    4	4
    6	6
    6	6
    6	6
    2	2
    2	2
    1	1
    1	0
    0	1
    Component
    Cord CD-690 (power) ; 12-volt battery to receiver; field connection; 6-foot
    Cord CD-763 (transmitter power) ; 4-foot; 1 in use, 1 spare
    Cord CD-764 (transmitter control) ; 15-foot; 1 in use, 1 spare
    Cover BG-141-A; for Chest CH-89- ( )
    Cover BG-142-A; for Chest CH-119- ( )
    Cover BG-143-A; for Chest CH-121- ( )
    Cover BG-144-A; for Chest CH-88-( )
    Cover BG-145-A; for Chest CH-120- ( )
    Cover BG-146-A; for Radio Transmitter BC-610-E and Antenna
    Tuning Unit BC-939-A
    Counterpoise CP-15-B
    Crystals in Crystal Holders FT-171-B
    Drums, gasoline; galvanized steel; with handle; capacity 5 gallons
    Frame FM-59-A; for Reels DR-4
    Frame FM-62-A; for spare tire
    Frequency Meter Set SCR-211-( ) ; with spare tubes and batteries
    Fire extinguisher; Randolph Laboratories model FF-4
    Fuse FU-21-A; for Radio Receivers BC-312-( ) and BC-342-( ) ;
    2 in use, 4 spare (SCR-399-A), 12 spare (SCR-499-A)
    Fuse FU-27; for Radio Receiver BC-342-( ) ; 1 in use, 3 spare (SCR-399-A), 4 spare (SCR-499-A)
    Fuses for Radio Transmitter BC-610-E and Speech Amplifier BC-614-E ; 1 in use, 6 spare, consisting of—
    2—25-ampere fuses
    1—20-ampere fuse
    1— 5-ampere fuse
    1— 3-ampere fuse
    Fuse; 25-ampere; 1 in use, 6 spare (used in Chest CH-109-A)
    Heater, electric; Electromode model AA-15
    Headset HS-30-( ) ; 2 in use, 2 spare
    Holder for fire extinguisher
    Junction Box JB-60-A
    Junction Box JB-70-A
    Key J-37; 2 in use, 1 spare
    Key J-45
    Lamp; 50-watt; 115-volt; 3 in use, 7 spare for SCR-399-A; 2 in use, 5 spare for SCR-499-A
    Lamp; 50-watt; 12-volt; spare
    Lamp, trouble, emergency; 115-volt; with 25-foot extension cord and 50-watt lamp
    Lamp, trouble, emergency; 12-volt; with 25-foot extension cord and 50-watt lamp
    Lamp LM-27; for radio receivers; 4 spare
    Lamp; for Trailer K-52- ( ) ; spare
    Lamp fixture (shelter)
    Lamp fixture (operating chests)
    Loudspeaker LS-3
    Mast Base MP-47-A; 1 in use, 1 spare
    Mast Base MP-48; 2 in use, 1 spare
    Mast Base Bracket MP-59-A; for Mast Base MP-47-A
    Mast Base Bracket MP-50-A; for Mast Base MP-48; 2 in use, 1 spare
    Mast Section MS-49 ; 1 in use, 3 spare
    Mast Section MS-50; 1 in use, 3 spare
    Mast Section MS-51; 3 in use, 3 spare
    Mast Section MS-52; 3 in use, 3 spare
    Mast Section MS-53; 3 in use, 3 spare
    Mast Section MS-54
    Microphone T-50; dynamic; 1 in use, 1 spare
    Microphone T-17
    Microphone T-30 (throat)
    Microphone T-45
    II
    Radio Set SCR-399-A
    3
    1 (set)
    Radio Set SCR-499-A
    3
    1 (set)
    1 each
    1 each
    20
    4
    4
    1 each
    7 each
    1 each
    1 each
    20
    4
    4
    1 each
    7 each
    1
    1
    1
    1
    1
    2
    1
    1
    1
    1
    2
    1
    2
    2
    2
    2
    2
    2
    1
    1
    1
    1
    1
    1
    1
    1
    2
    1
    1
    0
    0
    2
    3 0
    0
    2
    2
    2
    2
    2
    2 0
    1
    1
    Component
    Nozzle; for gasoline drums
    Parts, spare:
    For Radio Transmitter BC-610-E and Speech Amplifier BC-614—E consisting of 33 percent of the number of the following parts used in the radio transmitter and speech amplifier, but not less than 1 each
    Fixed and variable resistors
    Fixed capacitors
    R-f choke coils
    Every type relay used in Speech Amplifier BC-614-E, Radio Transmitter BC-610-E, and Junction Box JB-70-A
    Every type switch used, except band switch
    Each ceramic insulator used for the power-amplifier variable capacitor
    Each ceramic insulator used for the power-amplifier coil unit Each ceramic spacer used for the power-amplifier coil unit Circuit breaker for Junction Box JB-70-A
    Every pilot lamp and dial lamp used in Radio Transmitter BC-610-E and Speech Amplifier BC-614-E (For itemized list of resistors, capacitors, and chokes supplied as spares, see the maintenance parts list, par. 198)
    Power Unit PE-95-( ) ; including tools, 2 batteries (6-volt), and spare parts
    Radio Receiver BC-312-( ) ; including Mounting FT-162 and 2 Mountings FT-178
    Radio Receiver BC-342-( ) ; including Mounting FT-162 and 2 Mountings FT-178
    Radio Transmitter BC-610-E; including 24 tuning units, 14 coil units, 2 Capacitors CA-423, and 2 sets tuning charts
    Rectifier RA-63-(*)
    Reels DR-4
    Rope RP-5; 50-foot
    Speech Amplifier BC-614-E
    Shelter HO-17-A (mobile)
    Speaking tube
    Stake GP-8; with 10 feet of copper braid
    Strap ST-19-A
    Table frame; for mounting Chests CH-120-A and CH-121-A in Shelter H0-17-A
    Part List for Shelter HO-17- ( )
    TM 11-281; for Radio Sets SCR-399-A and SCR-499-A
    TM 11-904; for Power Unit PE-95-( )
    TM 11-850; for Radio Receivers BC-312-( ) and BC-342-f )
    TM 11-300 ; for Frequency Meter Set SCR-211-( )
    TM 11-333; for Telephone EE-8-( )
    Telephone EE-8-( )
    Tire and wheel; spare for truck and trailer
    Tool equipment TE-48
    Set tools and repair equipment consisting of—
    1 Analyzer BC-1052-E
    1 can carbon tetrachloride
    1 drill, electric; 110-voltac; ^-inch
    1 drill, twist; carbon-steel; %-inch
    1 drill, twist; carbon-steel; i/2-inch
    2 pair pliers
    1 hammer, claw; 16-ounce
    1 set hardware, assorted
    1	hydrometer; for storage batteries
    2	battery lift strap
    5	pounds solder, rosin-core
    1 can machine oil
    1 Soldering Iron TL-120
    3 rolls tape, friction; Va-inch
    12
    Radio Set SCR-399-A
    Radio Set SCR-499-A
    4	4
    16	16
    4	4
    4	4
    2
    6
    4
    6
    2
    2
    6
    5
    5
    2
    2
    2
    2
    6
    1
    1
    1
    1
    2
    12
    7
    12
    4
    4
    10
    8
    8
    4
    4
    3
    3
    7
    10
    1 0
    1
    1
    Component
    1 roll tape, rubber; 1/9-inch
    1 Torch TL-130
    2 No. 6-32 Allen head wrench
    2 No. 8-32 Allen head wrench
    2 Allen head wrench for 14-inch screw
    1 sheet crocus cloth
    Tube VT-65-A (JAN-6C5G) ; for Radio Receivers BC-312-( ) and BC-342-( ) ; 4 installed, 4 spare
    Tube VT-66-A (JAN-6F6G) ; for Radio Receivers BC-312-( ) and BC-342-( ) ; 2 installed, 2 spare
    Tube VT-86-A (JAN-6K7G) ; for Radio Receivers BC-312-( ) and BC-342-( ) ; 8 installed, 8 spare
    Tube VT-87-A (JAN-6L7G) ; for Radio Receivers BC-312-( ) and BC-342-( ) ; 2 installed, 2 spare
    Tube VT-88-A (JAN-6R7G) ; for Radio Receivers BC-312-( ) and BC-342-( ) ; 2 installed, 2 spare
    Tube VT-97 (JAN-5W4) ; for Radio Receiver BC-342-( ); 1 installed, 1 spare
    Tube VT-46-A (JAN-866-A/866) ; for Radio Transmitter BC-610-E ; 2 installed, 4 spare (SCR-399-A), 10 spare (SCR-499-A)
    Tube VT-95 (JAN-2A3) ; for Radio Transmitter BC-610-E; 2 installed, 2 spare (SCR-399-A), 5 spare (SCR-499-A)
    Tube VT-100 (JAN-807) ; for Radio Transmitter BC-610-E; 2 installed, 4 spare (SCR-399-A), 10 spare (SCR-499-A)
    Tube VT-107 (JAN-6V6) ; for Radio Transmitter BC-610-E; 1 installed, 1 spare (SCR-399-A), 3 spare (SCR-499-A)
    Tube VT-115 (JAN-6L6) ; for Radio Transmitter BC-610-E; 1 installed, 1 spare (SCR-399-A), 3 spare (SCR-499-A)
    Tube VT-139 (JAN-OD3/VR-150) ; for Radio Transmitter BC-610-E; 3 installed, 3 spare (SCR-399-A), 7 spare (SCR-499-A)
    Tube VT-145 (JAN-5Z3) ; for Radio Transmitter BC-610-E; 2 installed, 3 spare (SCR-399-A), 6 spare (SCR-499-A)
    Tube VT-218 (JAN-100-TH) ; for Radio Transmitter BC-610-E;
    2 installed, 3 spare (SCR-399-A), 6 spare (SCR-499-A)
    Tube VT-220 (JAN-250-TH) ; for Radio Transmitter BC-610-E;
    1 installed, 1 spare (SCR-399-A), 3 spare (SCR-499-A)
    Tube VT-80 (JAN-80) ; for Speech Amplifier BC-614-E; 1 installed, 1 spare (SCR-399-A), 3 spare (SCR-499-A)
    Tube VT-103 (JAN-6SQ7) ; for Speech Amplifier BC-614-E; 1 installed, 1 spare (SCR-399-A), 2 spare (SCR-499-A)
    Tube VT-233 (JAN-6SR7) ; for Speech Amplifier BC-614-E; 1 installed, 1 spare (SCR-399-A), 2 spare (SCR-499-A)
    Tube VT-94 (JAN-6J5) ; for Speech Amplifier BC-614-E; 2 installed, 2 spare (SCR-399-A), 5 spare (SCR-499-A)
    Tube VT-231 (JAN-6SN7GT) ; for Speech Amplifier BC-614-E;
    3 installed, 3 spare (SCR-399-A), 7 spare (SCR-499-A)
    Typewriter, portable; with telegrapher’s keyboard; includes case
    Trailer K-52-( )
    Wire, antenna; 100-foot
    Wire W-110-B (on Reels DR-4) ; 4,800-foot.
    cS""paragraph 27 for Packing data on Radio Set SCR-399-A and Table II (par. 28) for data on Radio Set oLK-4yy~ A.
    6. Major Components
    The major components of Radio Set SCR-399-A are furnished installed in a shelter and trailer. Shelter H0-17-A contains the components which comprise the radio station, and should be mounted on a 2i/2-ton, 6x6 cargo truck for mobile use. Trailer K—52—( ) contains
    Power Unit PE-95-( ). The major components of the set are:
    Radio Transmitter BC-610-E (par. 7) Speech Amplifier BC-614-E (par. 8)
    Junction Box JB-70-A (par. 9)
    Radio Receivers BC-342-( ) and BC-312-( ) (par. 10)
    13
    Antenna Tuning Unit BC-939-A (par. U)
    Antenna (par. 12)
    Power Unit PE-95-( ) (par. 13)
    R-FOUTPUT
    terminals
    R-F CHASSIS
    MODULATOR CHASSIS
    AUDIO INPUT
    FROM SPEECH AMPLIFIER BG-6I4-E
    A-C POWER
    SUPPLY FROM JUNCTION BOX JB-7O-A
    ■
    POWER CHASSIS
    iJ TL159221
    Figure 7. Radio Transmitter BC-610-E chassis assembly—rear view.
    14
    7.	Radio Transmitter BC-610—E (fig. 7)
    a.	The transmitter assembly is made up of three chassis. The top chassis is referred to as the r-f (radio-frequency) section and includes all of the r-f components. The center chassis is called the modulator section, since it contains most of the audio and modulator equipment. The bottom chassis includes the high-voltage powersupply and overload relay. It is called the powersupply section. The three chassis are assembled into a sheet steel cabinet with a front panel upon which the external controls and metering instruments are mounted. (See fig. 5.)
    b.	The transmitter is bolted to the cradle frame shock-mounting base which is anchored to the floor with wrench nuts. The weight of the transmitter is 450 pounds; installed, the over-all weight is approximately 500 pounds.
    c.	The frequency range of the transmitter is 2 to 18 megacycles. This wide frequency range is covered by means of three sets of plug-in tun
    ing units, eight to a set; two sets of plug-in coil units, seven to a set; and Capacitor CA-423. Each tuning unit and associated coil unit, or coil unit with capacitor, covers a portion of the range. (See table III.) The frequency is controlled by the master oscillator or the crystal oscillator, depending on the position of the M.O.-XTAL switch on the tuning unit. The transmitter can be used for radiotelegraph and radiotelephone communication. At frequencies below 8 megacycles the power output of the transmitter exceeds 400 watts on continuous wave and 300 watts on voice. The power output is somewhat less at higher frequencies. The transmitter will operate satisfactorily with input power of 1,700 to 2,000 watts from a 115-volt, 50/60 cycle a-c (alternating-current) source.
    8.	Speech Amplifier BC-614-E (fig. 8)
    a.	The amplifier is shock-mounted to the top
    Figure 8. Speech Amplifier BC-614-E and Junction Box JB-70-A in Chest CH-120-A —front view.
    15
    of Junction Box JB-70-A in Chest CH-120-A. For convenient removal, four snap fasteners are used to anchor the speech amplifier to its shock-mounting. The weight of the speech amplifier, less shock-mount, is approximately 31 pounds.
    b.	The speech amplifier raises the microphone output to a level suitable for voice modulation of the transmitter. It also provides sidetone for headset monitoring of c-w transmissions. Speech Amplifier BC-614-E contains its own plate and filament supply unit which draws approximately 40 watts from the 115-volt, 50/60-cycle, a-c source.
    9.	Junction Box JB-70-A
    a.	The junction box is a junction point for most of the cords and cables which interconnect the various components. Power and control cords plug into either the bottom (through the bottom of Chest CH-120-A) or the side of the junction box. Key and headset connections are plugged into the jacks on the front panel.
    b.	Junction Box JB-70-A serves as a control center for the station. The front panel controls (fig. 8) provide for:
    (1)	Starting or stopping Power Unit PE-95—( ).
    (2)	Resetting the circuit breaker in the power mains.
    (3)	Selection of 12-volt battery source.
    (4)	Control of transmission and reception.
    (5)	Remote control operation.
    (6)	Choice of manual or automatic receiver disabling.
    (7)	Choice of receiver output to headset.
    (8)	A sidetone signal to monitor transmission during c-w operation.
    10.	Radio Receivers BC—342—( )
    and BC-3l2-( )
    a.	Radio Receiver BC-342-( ). Radio Receiver BC-342-( ) is in Chest CH-120-A. It is anchored by Mountings FT-162 and FT-178. This receiver is powered by the 115-volt, 50/60-cycle, a-c source. It is capable of receiving c-w, voice-modulated, or tone-modulated signals over an r-f range of 1.5 to 18 megacycles.
    b.	Radio Receiver BC-312-( ). Radio Receiver BC-312-( ) is anchored in Chest CH-121-A by Mountings FT-162 and FT-178. It is a d-c (direct-current) receiver with the same receiving characteristics as Radio Receiver BC-342-( ), except that a crystal filter is not in
    cluded. The battery in Chest CH-109-A or the battery in Power Unit PE-95-( ) may be used as a source of power. For further information on the receivers, consult TM 11-850.
    I I. Antenna Tuning Unit BC-939—A (fig. 9) The tuning unit is mounted on top of Radio Transmitter BC-610-E and is fastened securely by four wingnuts. It couples the output of the transmitter to the transmitting antenna. All controls are mounted on the front panel. The unit weighs 48 pounds.
    Caution: WHEN THE TRANSMITTER IS IN OPERATION DO NOT TOUCH ANY PART OF THE ANTENNA TUNING UNIT, EXCEPT THE FRONT PANEL CONTROLS.
    12.	Antenna System
    The antenna system consists of a transmitting antenna and two receiving antennas. (See fig. L)
    a.	Transmitting Antenna. Mast Base MP-47-A and Mast Sections MS-49 to MS-53, inclusive, form the transmitting antenna (whip). Mast Base Assembly MP-47-A is mounted through the roof of Shelter H0-17-A and is connected to Antenna Tuning Unit BC-939-A. Mast Section MS-53 is screwed into the mast base to form the lowest section, and Mast Section MS-49 forms the top section of the assembly. For mobile use, the antenna is bent backward (fig. 1) and held in a horizontal position by an insulated guy to the rear of the roof. This provides clearance and keeps the antenna from whipping about while the vehicle is in motion. The snap-catches on the guy permit the release of the antenna to a vertical position to provide more uniform radiation while the set is stationary. When the transmitting antenna is operated vertically, one or two additional Mast Sections MS-54 may be added. A doublet antenna is furnished for operation from a fixed site, since it provides a considerably greater range of communication than the whip antenna. (See par. 123.) A straight wire antenna can be used; 100 feet of wire is issued for this purpose. (See table IV.)
    Caution: EXTREMELY DANGEROUS VOLTAGES ARE PRESENT ON THE ANTENNA AND ITS INSULATORS DURING TRANSMISSION. DO NOT TOUCH.
    b.	Receiving Antenna. Mast Base MP-48, mounted in Mast Base Bracket MP-50-A, and Mast Sections MS-51 to MS-53 make up a re-
    16
    Figure 9. Antenna Tuning Unit BC-939-A.
    ceiving antenna. Two receiving antennas are used, since each receiver operates from a separate whip antenna. The antennas are mounted on the upper rear corners of Shelter H0-17-A. (See fig. 1.)
    13.	Power Unit PE—95—( )
    Power Unit PE-95-( ) is a complete, self-contained, gasoline-driven generating unit, capable of delivering 5 kilowatts of a-c power (singlephase 60-cycle at 115 volts) for the operation of Radio Set SCR-399-A, Radio Set SCR-499-
    A, or other equipment. Power Unit PE-95-( ) can be:
    a.	Installed in Trailer K-52-( ). (See fig. 10.)
    b.	Operated 100 feet from the truck by using the extension cables provided with the set.
    c.	Operated 200 feet from the truck by using two extension cables. (Under this condition, the power unit must be started and stopped at the trailer.)
    d.	Used as a source of power for lights, etc., at a distance of up to 200 feet from the trailer.
    17
    ---- POWER
    FRAME FM-62-A JNt
    \ IMl B ' StT r ELgC-   5-GALLON 4 /GAS 0RuMS
    ^*7	l'l
    A’lW ’ I X •
    -’.‘’’r chest CH-II2-A ES t
    \/\ tfia i
    CORD GO-3I3-A «L I
    vMld shz t ' CORD CO-XI6
    z	Ek */
    „	.	'	. ..XSl
    Figure 10. Power Unit PE-95-( ), installed in Trailer K—52—( ).
    14.	Other Components
    The following paragraphs describe the main chests in the radio set and important components other than the major components described above. The chests and additional components are:
    Chest CH-120-A (par. 15)
    Chest CH-121-A (par. 16)
    Chest CH-89-A (par. 17)
    Chest CH-119-A (par. 18)
    Chest CH-88-A (par. 19)
    Frequency Meter Set SCR-211 (par. 20)
    Rectifier RA-63-(*) (par. 21)
    Cordage (par. 22)
    Remote control equipment (par. 23) Batteries (par. 24)
    Crystals (par. 25)
    15.	Chest CH—120—A (Main Operating)
    For field use (Radio Set SCR-499-A), Chest CH-120-A is mounted as shown in figure 11. In Radio Set SCR-399-A, the chest is mounted on a frame against the left (or road) side of Shel
    ter HO-17-A and is held in place by a combination of cleats and turnbuckles. (See fig. 3.) All of the necessary radio components (table II) for one operating position are mounted in this chest. Junction Box JB-70-A and Speech Amplifier BC-614-E control transmission and change-over from transmission to reception. Radio Receiver BC-342-( ) and Loudspeaker LS-3 provide for reception. Box BX-19-A contains spare fuses, tubes, and lamps for the receiver. The lower half of the front cover of Chest CH-120-A swings down to form an operating desk large enough for a portable typewriter. Field legs (fig. 11) are strapped to this chest when it is to be set up away from the shelter. The total weight of the chest, including legs and full complement, is 292 pounds.
    16.	Chest CH-12 l-A (fig. 12)
    The chest is mounted beside Chest CH-120-A in Shelter HO-17-A (fig. 3) and provides a second operating position. When removed from the shelter and set up in the field, Chest CH-121-A becomes a remote operating position from which the transmitter can be modulated over Telephone EE-8-( ), or keyed with Key J-45, through Junction Box JB-60-A (fig. 13). Chest CH-121-A contains Radio Receiver BC-312-( ), Loudspeaker LS-3, Box BX-19-A containing spare parts, and other accessories. A set of field legs is also supplied for this chest. The lower front cover of Chest CH-121-A opens to form a desk top. The total weight of the chest, including legs and full complement, is 157 pounds.
    17.	Chest CH-89-A
    Chest CH-89-A is a combination parts compartment and seat bench. (See fig. 14.) In Shelter H0-17-A, the chest is parallel to the operating chest and fastened to the floor by means of wing bolts. (See fig. 3.) It is 6 feet 8 inches long, 141/2 inches high (not including cushions), and 18 inches wide. Fully packed, the chest weighs approximately 300 pounds. Its top is divided into four lids, which can be cushioned to serve as a seat for the operators. The compartment below each lid is subdivided for storage of spare parts, repair equipment, etc., as indicated on the chart attached to the chest. See table I for a typical list of the material packed in Chest CH-89-A. Two movable back rests, together with Straps ST-19-A hooked to Chest CH-89-
    18
    LAMP FIXTURE
    SPEECH AMPLIFIER BC-6I4-E
    JUNCTION BOX JB-70-A
    COMPARTMENTS containing:
    HEADSETS HS'3O CORDS CD-605 MICROPHONE T-5O MICROPHONE T-17
    -BOX BX-I9-A
    KEYJ-37
    Figure 11. Chest CH-120-A with equipment installed—front view.
    RADIO RECEIVER BC-342-( )
    TELEPHONE
    EE"8-( )
    MICROPHONE
    T-5O
    LOUDSPEAKER
    LS-3
    COMPARTMENT FOR SPARE CORDS
    UI5923,
    A, secure the operator in place when driving on rough roads.
    18.	Chest CH-1 19-A (fig. 15)
    In Shelter H0-17-A, Chest CH-119-A is placed along the right (curb) wall and is held in position by four, trunk clasps. (See fig. 3.) The chest is 55 inches long, 32% inches high, 12% inches deep and weighs approximately 287 pounds (loaded). Two sliding front panels permit access to the interior compartments in which are stowed the frequency meter, the portable typewriter, box of crystals, Cord CD-652, and tool equipment. Some additional storage space is available for other material. In Radio Set SCR-499-A, the compartment for Cord CD-652 is replaced by compartments for spare tubes, and Chest CH-119-A becomes Chest CH-119-B.
    19.	Chest CH-88-A (fig. 16)
    The chest is mounted inside the shelter and on top of Chest CH-119-A. (See figs. 3 and 4.) It is held to the side of the shelter by four trunk clasps. It is 55 inches long, 18 inches high, and 12% inches deep; fully packed, it weighs approximately 165 pounds. Two sliding front panels permit access to the many compartments in which tuning units and other items are stowed.
    20.	Frequency Meter Set SCR-21 l-( )
    The frequency meter set is carried in Chest CH-119-A where it is firmly held in place by a strap. (See fig. 15.) It serves as a frequency standard for the radio set, so that the operating frequency of the transmitter and the receivers may be determined accurately in the field. TM 11-300 is supplied with the meter and describes its operation in detail.
    19
    21.	Rectifier RA-63-(*) (fig. 17)
    Rectifier RA-63-(*) is a selenium type of battery charger which is used for charging the
    12-volt battery in Chest CH-109-A. The rectifier also furnishes power to operate the keying and disabling relays when Chest CH-109-A is
    RECEIVER ANTENNA (MAST SECTIONS MS-51,-52 AND-53)
    CHEST
    CH-I2I-A
    |CHEST CH-I09-A
    TLI5924:
    LAMP
    LOUDSPEAKER LS-3
    B0X-8X-I9-A
    TELEPHONE
    EE-8-C )
    RADIO RECEIVER BC-3I2-C )
    Figure 12. Chests CH-121-A and CH-109-A, as used at a remote position.
    JUNCTION BOX JB-60-A
    CORD
    CD-690 V
    I STAKE 1 GP-8
    20
    removed to a remote position. The rectifier unit is fastened to the floor of the shelter, near the left wall and approximately midway between the two operating chests. (See fig. 3.)
    Figure 13. Junction Box JB-60-A.
    22.	Cordage (fig. 155)
    a.	Cord CD-564 (power) is a 3-foot power cord connecting Radio Receiver BC-342-( ) with the a-c receptacle in the right side of Junction Box JB-70-A.
    b.	Cord CD-565 (control and power) is a 4-foot power and control cord connecting Radio Receiver BC-312-( ) with its receptacle in the junction box.
    c.	Cord CD-566 (control) is a 4-foot control cord connecting Radio Receiver BC-342-( ) with its receptacle in the right side of the junction box.
    d.	Cord CX-141/MRQ-2 (operating control) is 29 inches long and conducts control circuits between Junction Box JB-70-A and Speech Amplifier BC-614-E. The cord terminates in a plug receptacle on the panel of the speech amplifier and at a terminal strip in the junction box.
    e.	Cord CX-143/MRQ-2 (main audio) carries the audio output from Radio Receiver BC-342-( ) to switching circuits in Junction Box JB-70-A. This same cord also feeds Loud-
    speaker LS-3 and Telephone EE-8-( ), both in Chest CH-120-A.
    f.	Cord CX-140/MRQ-2 (auxiliary audio) carries the audio current from Radio Receiver BC-312-( ) to Junction Box JB-70-A and also feeds Loudspeaker LS-3 in Chest CH-121-A.
    g.	Cord CD-763 (transmitter power) is 14 feet long. It connects Radio Transmitter BC-610-E with its a-c power receptacle in the junction box.
    h.	Cord CD-764 (transmitter control) is 15 feet in length. It carries speech and control connections from Speech Amplifier BC-614-E to Radio Transmitter BC-610-E and, in addition, furnishes Speech Amplifier BC-614-E with a-c power. The transmitter end of the cable plugs into the rear modulator apron of the transmitter ; the speech-amplifier end plugs into its front panel socket on Speech Amplifier BC-614-E.
    i.	Cord CO-335 (power and control) is 14 feet long and is used to carry power and control circuits between Junction Box JB-70-A and the shelter outlet to Power Unit PE-95-( ). In mobile operation, the plug end is connected to the bumper bracket underneath the rear of the truck. The cord passes through the hole in the shelter and then through the bottom of Chest CH-120-A. The plug on this end seats in the receptacle inside Junction Box JB-70-A.
    j.	Cord CD-652 (power and control) is a 100-foot cord for extending all connections between the shelter and trailer. It is equipped with a heavy-duty plug at each end for quick attachment to the system.
    k.	Cord CO-313 (a-c power) is a 100-foot cord for extending the a-c power connection of the power unit. One end of this cord is provided with a heavy-duty plug which fits the power plug at the tongue of the trailer. The other end of the cord has two lug type terminals from which a-c power can be taken for general use.
    I.	Cord CD-314 (a-c power) is a 3-foot cord for connecting any outside source of a-c power to Shelter H0-17-A for the operation of the radio set. The cord has a heavy-duty plug on one end for connection to the shelter, and a pair of lug type terminals for attachment to the source of power.
    m.	Cord CD-659 (12-volt battery cord) is 6 feet long and connects between the outlet receptacle on Junction Box JB-70-A and the plug outlet on Chest CH-109-A.
    n. Cord CD-690 (power) is 6 feet long. It is used to connect Radio Receiver BC-312-( ) in
    Th 1594 4
    21
    MAST BASE SPRING ASSEMBLY FOR MP-47
    •TROUBLE
    LAMP
    CHEST CH-89-A
    VACUUM TUBE VT-22O
    OPERATING
    SPARES
    ELECTRIC DRILL
    RECEIVING ANTENNA GUY ASSEMBLY
    COUNTERPOISE
    Figure 44. Chest CH.-89-A, parts compartments (open) and seat bench (closed)
    OPERATING SPARES HARDWARE
    ROLL OF SOLDER
    MAST SECTIONS
    [ MS-49,-50,-51,-52,-53,-54 STAKE ASSEMBLY GP-8 AXLE RL-27-A
    22
    Figure 15. Chest CH-119-A—front panels removed.
    TUNING UNITS
    COIL UNITS
    CAPACITORS
    ’TLI5927I
    —1
    Figure 16. Chest CH-88-A—front panels removed.
    "	CORD CD-652
    I®*	\	EXTERNAL SPEAKING
    FREQUENCY METER SET TUBE ' SCR-2II-( )
    TYPEWRITER
    ri-15926
    TOOL BOX
    BOX BX-34-B	TE-48
    .■ TU-47, ■ 48,-49-50 i 51-52-53,AND
    54	.
    1	MICROPHONE
    BATTERIES
    BA-30 AND BA-2
    23
    COIL UNITS
    TUNING UNITS

    BOX BX-34-B
    TYPEWRITER

    CHEST CH-88-A
    CHEST
    CH-II9-A,
    TOOL BOX TE-48
    REELS
    DR-4

    GHEST CH-I09-A
    WIRE W-IIO-B
    HEATER
    CHEST CH-89-Aj
    RECTIFIER
    RA-63-( )
    CORD CD-652
    FRAME FM-59-A
    •Tl1594b
    Figure 17. Accessory components of Radio Sets SCR 399-A and SCR-499-A.
    Chest CH-121-A to the storage battery m Chest CH-109-A, when both of these units are removed from the radio station.
    o.	Cord CO-316 (power and control) is a 6-conductor cord, 8.3 feet long. One end connects to the terminal board of the power unit; the other end connects to the power plug under the rear of the truck.
    p.	Cord CD-201-A is used to connect Key J-37 to Junction Box JB-70-A.
    q.	Cord CD-1117 is supplied with Loudspeaker LS-3.
    23.	Remote Control Equipment
    a.	When connected as directed in section IV, chapter 2, the remote control equipment provides for remote keying and voice modulation of Radio Transmitter BC-610-( ), reception with Radio Receiver BC-312-( ), and communication with the operator at the radio station. The remote operating position may be as much as 1 mile from the set. When receiving and transmitting from a remote position, switching of the remote telephone circuit from transmit
    to receive must be accomplished at the radio set. Remote keying of c-w transmissions may be effected at the remote position; reception is then provided by using Radio Receiver BC-312-( ), Cord CD-690, and the 12-volt battery (in Chest CH-109-A) at the remote point. (See fig. 13.)
    b.	The equipment for remote control consists of—
    (1)	Two Telephones EE-8-( ), one in Chest CH-120-A and one in Chest CH-121-A.
    (2)	Junction Box JB-60-A, stowed in Chest CH-121-A.
    (3)	Key J-45, stowed in Chest CH-121-A.
    (4)	Two Reels DR-4, mounted in Frame FM-59-A. (See fig. 17.)
    (5)	Wire W-110-B, approximately % mile on each Reel DR-4.
    (6)	Axle RL-27-B, stowed in Chest CH-89-A.
    24.	Batteries
    a. The 12-volt battery in Chest CH-109-A (figs. 2, 3, and 12) consists of two 6-volt storage batteries connected in series. They are in-
    24
    terchangeable with the batteries in Power Unit PE-95-( ). The battery output is obtained through a polarized socket mounted on Chest CH-109-A.
    b. The batteries in Power Unit PE-95-( ) and those in Chest CH-109-A are exactly alike. In some installations, a switching arrangement is provided to permit the use of either set of batteries for operation of Radio Receiver BC-312-( ).
    Figure 18. Carbon Microphone T-17.
    Figure 19. Microphone T-50.
    c. Dry-cell batteries are issued with various components and should be installed in accordance with the instructions in paragraph 35.
    25. Crystals
    Two sets of crystal holders (36 to the set) are provided in Box BX-34-B (fig. 15), so that the transmitter may be operated at any of the frequencies listed in table V.
    Figure 20. Headset HS-30-( ).
    Figure 21. Key J-37.
    ' TU5627 *
    25
    Section II. INSTALLATION
    26. Siting
    Note. The following siting information for Radio Set SCR-499-A is also applicable to Radio Set SCR-399-A as a fixed station.
    Radio Set SCR-499-A should be set up on a hilltop, elevated ground, or on terrain which is flat over a wide area. A valley or other low ground is to be avoided as much as possible, since the surrounding higher terrain absorbs r-f energy and limits the operating range of the set. Particular care should be taken to avoid a site under or close to steel bridges, underpasses, power lines, and power units, because of the extremely short range possible from any of these sites. If the doublet antenna is used, its directional characteristics should be considered, as explained in paragraph 129.
    27. Uncrating, Unpacking, and Checking Radio Set SCR-399-A
    a.	A shipment of Radio Set SRC-399-A consists of two boxes. One contains Shelter HO-17-A with operating components installed, weighs 7,255 pounds, and is 13'-3" long, 7'-8" wide, and 6'-8" high. The second contains Trailer K-52-( ) with Power Unit PE-95-( ) installed, weighs 4,900 pounds, and is 9'-2" long, 6'-5" wide, and 6'-6" high. Two packing lists are shipped with each box, one attached to the outside and one inside the box. For greatest convenience, the radio set should be uncrated and unpacked as near the operating site as possible. Do not open any box until ready to use its contents.
    b.	The recommended procedure for uncrating, unpacking, and checking Radio Set SCR-399-A is as follows:
    (1)	Use nail pullers and pry bars to remove the top of the box containing Shelter H0-17-A. The top must always be removed first, so that the sides are free for the next step.
    (2)	Attach one end of a steel cable or strong rope to the rear of a truck. Fasten a hook to the other end of the cable and catch this hook over the top edge of one side of the shelter box. Use the truck to pull this side from the crate.
    (3)	Repeat step (2) to remove the other side and the ends of the box. (If a truck is not available, use nail pullers and crowbars.)
    (4)	Carefully remove the waterproof wrappings from about the shelter.
    (5)	The openings (windows, doors, etc.) in
    the shelter are covered with adhesive tape over which a sealing compound has been placed. (See fig. 22.) To remove this protective material, loosen a small section with a sharp object such as a screwdriver or chisel. Grasp the adhesive tape and pull it away from the shelter. The compound will come off with the tape.
    (6)	Remove the four corner bolts to free the shelter from the crate platform. (See fig. 23.)
    Figure 22. Shelter HO-17-A, sealing compound in place.
    (7)	Enter the shelter and carefully remove the shoring (wooden props) and bags of silica gel.
    (8)	Remove the straps which hold the separately packaged components (antenna tuning unit, masts, etc.), in position on the floor of the shelter.
    (9)	Check the contents of each box against the packing list.
    (10)	Open each chest and check its contents against the chart on the chest. Refer to table I and to the chest lay-out diagram. (See figs. 137 through 145.)
    Table I. Chests and contents
    Note. This tabulation is general; an itemized list of contents accompanies each chest. See figures 137 through 145 for lay-out and dimensional drawings of the chests.
    CHEST CH-88-A (fig. 138)
    24 Tuning units
    14 Coil units
    1 Microphone T-50
    3 Capacitors
    *1 Carton spare fuses Spare pilot lamps
    * Complete list of contents in carton
    26
    CHEST CH-89-A (fig. 140)
    *8 Cartons operating spares
    *2 Cartons hardware
    1 Analyzer
    1 Hydrometer Antenna assembly
    Tools
    Cords
    1 Trouble lamp
    Spare lamp bulbs
    Spare tubes
    3 Straps ST-19
    1 Roll solder
    1	Anticorona ball
    Machine oil
    Carbon tetrachloride
    CHEST CH-109 (fig. 141)
    2	Storage batteries
    CHEST CH-112 (fig. 145)
    1 Cord CD-659, operating
    1 Cord CO-335, operating
    1 Cord CO-652, spare
    1 Cord CO-313, spare
    CHEST CH-119 (fig. 143)
    1 Box BX-34-B, complete with 72 crystals
    1	Typewriter
    2	Trouble lamps, 110-volt
    1 Frequency Meter Set SCR-211
    1 Tool Box TE-48
    Miscellaneous tubes
    CHEST CH-120-A (fig. 146)
    Junction Box JB-70-A
    Speech Amplifier BC-614-E
    Radio Receiver BC-342-( )
    Loudspeaker LS-3
    Lamp fixture
    Headsets HS-30-( )
    Microphone T-50-( )
    Key J-37
    Field Telephone EE-8-( )
    Box BX-19-A, containing spare fuses, tubes, and lamps for receivers
    CHEST CH-121-A (fig. 147)
    Radio Receiver BC-312-( )
    Loudspeaker LS-3
    Headsets HS-30-( )
    Spare battery cord
    Field Telephone EE-8-( )
    Lamp fixture
    Box BX-19-A
    Key J-37
    * Complete list of contents in carton
    (11)	The second box (fig. 24) contains Trailer K-52-( ) in which Power Unit PE-95- ( ) is installed prior to shipment. With nail pullers and prybars, remove the top of this box.
    (12)	Remove the four sides of the trailer box.
    (13)	Remove the waterproof wrapping from about the trailer.
    (14)	Remove the shoring and straps which hold the trailer to the bottom of the box. (See fig. 25.)
    (15)	Remove the trailer from the bottom of the box.
    (16)	Check the contents of the' trailer against the packing list.
    28.	Uncrating, Unpacking, and Checking Radio Set SCR-499-A
    a.	A shelter and trailer are not supplied with Radio Set SCR-499-A. Its components are shipped in 23 boxes. (See table II.) Two packing lists are shipped with each box; one inside

    CORNER BOLT
    :holo down ASSEMBLY
    -LIFTING-_____J
    'STRAPS S123 .0
    Figure 23. Shelter HO-17-A on shipping crate platform.
    £ SEALING
    *" COMPOUND f-'
    27
    Figure 24. Shipping Box for Trailer K-52-( ) with Power Unit PE—95—( ) installed.
    the box and one outside. Do not open any box until its contents are needed for immediate use. For example, if Radio Set SCR-499-A is to be operated on local commercial power, do not open box No. 17 which contains six gasoline cans.
    b.	The following procedure for uncrating, unpacking, and checking Radio Set SCR-499-A is recommended.
    (1)	Use nail-pullers and prybars to open each crate.
    (2)	Remove the outer wrappings and bags of silica gel.
    (3)	Check the contents of each box against the packing list.
    Figure 25. Trailer K—52—( ~) with Power Unit PE-95-( ) installed, on shipping crate.
    28
    Table II. Typical packing list for radio set SCR-f99-A
    No. of boxes: 23	Dimensions				Shipping weights		Weight of various items (lb)2
    Contents	Length (inches)	Width (inches)	Height (inches)	Cubic feet	Gross (lb)	Net (lb)
    BOX NO. 1 1 Transmitter BC-610-E 1 Cord CD-763 1 Cord CD-764	38 32%	34 21%	47, 39%	35.1	755	497	452
    BOX NO. 2 1 Chest CH-120-A1	59 50 y2	25 16%	35 23%	30.2	560	292	286
    BOX NO. 3 1 Chest CH-121-A1	39 31	23 16%	30 23%	15.5	340	162	155
    BOX NO. 4 1 Antenna Tuning Unit BC-939-A	31 23%	16 11%	21 15%	6	125	48	48
    BOX NO. 5 1 Chest CH-89-A1	85 80	23 18%	19 141%,	21.4	492	330	300
    BOX NO. 6 1 Chest CH-109-A with: 2 6-volt batteries	31 25%	12 9%	14 11%	3	140	101	101
    BOX NO. 7 1 Chest CH-112-B with: Cords CO-335, CD-659, CD-652, CO-313	49 431%	18 13%	23 18%	11.7	292	196	196
    BOX NO. 8 1 Mast Base Bracket MP-59-A 1 Antenna plate 10 Fastener assemblies Linoleum 1 Base heater mounting 1 Base rectifier mounting 1 Strap 1 Ground lead assembly Copper rope 1 Concentric lead Miscellaneous hardware	21	19	16	3.7	74	34
    BOX NO. 9 1 Fire extinguisher 1 Holder, for extinguisher 3 Seat bench backs	40 13%s	18 4%4	8 18%	3.3	86	28	17%
    BOX NO. 10 2 Mast Base Brackets MP-50-A 1 Mast Base MP-47-A 2 Mast Base MP-48 (assembled)	27 ■	15	12	2.8	89	57
    BOX NO. 11 1 Electric heater 1 Rectifier RA-63-(*)	31 12% 13%	18 11 % 9%	17 12 7%	5.4	111	42	17% 29%
    BOX NO. 12 1 Frame FM-59 1 Bumper clamp	24	20	17	4.4	75	31	(see box No. 16, Reels DR-4).
    BOX NO. 13 7 Seat bench cushions 6 Covers (chest and transmitter)	33	25	25	11.8	153	75
    BOX NO. 14 1 Chest CH-88-A1	63 58	26 12%	19 19%	17.5	343	175	165
    BOX NO. 15 1 Chest CH-119-B	63 57	19 12%	40 321%	27.3	453	236	287
    BOX NO. 16 2 Reels DR-4 (with wire)	26	17	24	6	229	165	190
    1 See table I for list of equipment installed in chest.
    2 Approximate weight of item when set up for use:
    3 Length of nozzle attachment,
    4 Diameter of tank.
    29
    Table II. Typical packing list for radio set SCR-499-A (contd)
    No. of boxes: 23			Dimensions					Shipping weights		Weight of
    Contents			Length (inches)	Width (inches)		Height (inches)	Cubic feet	Gross (lb)	Net (lb)	items (lb)2
    BOX NO. 17 6 Gasoline cans (5 gal)			31		22	21	7.8	120	60
    BOX NO. 18 7 Mast Sections MS-44-A 1 Canvas Cover BG-176			70% (Packe	(1	. io% in Roll	6% BG-176)	2.6	75	47	47
    BOX NO. 19 7 Mast Sections MS-44-A 1 Canvas Cover BG-176			70% (Packe	d	. io% in Roll	6% BG-176)	2.6	75	47	47
    BOX NO. 20 7 Mast Sections MS-44-A 1 Canvas Cover BG-176			70% (Packe	d	. io% in Roll	'63% BG-176)	2.6	75	47	47
    BOX NO. 21 1 Power Unit PE-95-( 3 Gas can spouts 1 Cord CO-316 1	Set running spares 2	6-volt batteries	)		80 67%.		35 28%	48 38%	78	2190	1600	1556
    BOX NO. 22 1 Canvas Cover BG-1 3 Guy GY-24-A 12 Insulators IN-82-A 18 Stakes GP-2 3 Mast Base MP-19 9 Guy Plate MP-20 6 Guy GY-22-A	02-A		20% (Packe	d	18% in Bag	13% BG-102	2.7 -( ))	97	73	23
    BOX NO. 23 1	Cord CD-1290 Wire W-28, 250 ft 2	Reel RL-29 12 Guy GY-41 1	Steel tape, 100-ft 2	Instruction sheets for doublet antenna kit 1 Bag BG-102-( )			20% (Packe	d	18% in Bag	13% BG-102	2.7 -( ))	55	31	31
    2 Approximate weight of item when set up for use.
    29.	Installation of Radio Set SCR-399-A
    a. Mobile Installation. If Radio Set SCR-399-A is to be used as a mobile station, Shelter H0-17-A should be installed on a 21/2-ton, 6x6, cargo truck. (See fig. 1.) The following procedure for setting up the radio set for mobile use is recommended:
    (1)	Remove the canvas cover, roof bows, and side framing from the truck; drop the tail gate.
    (2)	With all equipment installed, the shelter weighs about 214 tons. If a suitable hoist, is available, lift Shelter iH0-17-A by its four lifting straps (fig. 23) and place it on the truck body so that the entrance door is toward the rear. If no hoist is available, some other method must be devised for raising the shelter to truck level and sliding it on to the truck. This work is easier if the heavy items of radio equipment are first removed from the shelter, as explained in paragraphs 189 and 190.
    (3)	Attach the hold-down clamps (two on
    each side of the shelter) to the truck body sides to hold the shelter firmly in place. If the cargo truck has a wooden body, bolt on the four clamp anchors. (See Parts List for Shelter HO-17-A.)
    (4)	Place Antenna Tuning Unit BC-939-A on top of the transmitter and fasten it in position.
    (5)	Bolt Mast Base Brackets MP-50-A with Mast Bases MP-48 to the rear of the shelter. (See fig. 26.) Attach the short external lead wire between the mast bases and the lead-in bushings. Bolt Mast Base MP-47-A in place on the roof of the shelter and attach the antenna lead wire between the binding post on the mast base and the binding post at the rear of Antenna Tuning Unit BC-939-A. For information on assembling the antennas, see paragraph 33.
    (6)	Attach the bumper bracket for Cord CO-335 to the left-hand bumper at the rear of the truck. Do not drill holes in the truck. If the truck body is wooden, chip a small amount of
    30
    ‘	.TRANSMITTER ANTENNA
    .. MAST SECTIONS
    I	MS-49-50,-51,-52,-53 f	TRA.LER K-52-()
    RECEIVING ANTENNA	I	W|TH P0WER UNiT .
    f	MAST SECTIONS____	/	PE-95'( )
    MS-51,-52,-53	*"/
    ।	MAST BASE MP-47-A	* I
    /,	MAST BASE	I	MAST	BASE
    /	I	./MP-48
    BRACKET MP-50-A	.
    r :	B' ____________________  P	»
    •	t ,	.<■ -	.-■■ *^8898
    w -■	___—.—.i	,•<	., tvsSsBs-'
    " ; ' • : » *. ■
    ■ I J	' ’
    '	.'I	!	.... I	.. BV ' Vjl	''»
    f® j I •	’	SB	1 1
    li r /IL^<
    f IT ! ’	V WML--
    fK?y	. ■
    ;'T .*A- I	. -	. JiLAi ’ W
    I .	c	x |
    I	-r--	"
    /	f	I	Ly/'
    /	/	I	I
    . SHELTER HO-I7-A&...	/	FAIRLEADS '• . .
    / I
    I	'	CORD BUMPER	CORD ■•
    \	uo-3351 \ clamp-
    Figure 26. Shelter H0-17-A and Trailer K-52-( ), whip antennas, Cord CO-335, and Cord CO-316 installed.
    wood from the floor beam which extends over the bumper. (See fig. 27.)
    (7)	Extend Cord CO-335 through the hole and clamp in the rear of the shelter. Bring the outer plug down behind the truck body and clamp it into the bumper bracket. (See figs. 26 and 27.)
    (8)	Attach the flexible section of the speaking tube to the fitting at the front of the shelter, and route the speaking tube into the left-hand truck window. (See fig. 28.) Hook the speaking tube mouthpiece inside the truck cab where it will be convenient to the driver.
    (9)	Attach one end of the ground strap to the terminal at the front of the shelter. If the truck has a metal body, bolt the other end of the ground strap to the nearest available point. If the truck has a wooden body, run the ground strap to the nearest point on the metal chassis and clamp it securely. (See fig. 28.) Connect an
    additional ground strap between the stud at the rear of the shelter and the steel frame of the truck.
    (10)	Couple the trailer to the rear of the truck and plug Cord CO-316 into the receptacle clamped in the bumper bracket.
    b. Fixed Installation. If the shelter and trailer are to be used in a fixed location, the truck will not be necessary and may be released for other uses. In this case, the procedure for installation is as follows:
    (1)	If possible, select a site for the shelter in accordance with the instructions given in paragraph 26. Raise the shelter above the ground and block it in position.
    (2)	Place the trailer in any convenient position near the shelter. By proper use of the extension cords (par. 56), the trailer may be placed at a distance of up to 200 feet from the shelter.
    31
    le
    le
    ie le
    id he ed 'or
    in
    rand
    isi-
    JX* be the
    Figure 27. Bumper bracket attached to rear of truck.
    Figure 28. Speaking tube and ground lead from Shelter FIO-17-A to truck.
    (3)	See FM 5-20 and apply camouflage to the shelter and trailer as required.
    (4)	Follow the instructions given in a (4) and (5) above.
    (5)	Connect Counterpoise CP-15-B to the ground binding post at the front of the shelter. Lay the counterpoise on the ground and fan out the individual conductors.
    (6)	Bring Cord CO-335 out through the clamp in the rear of the shelter.
    (7)	Connect Cord CO-316 to Cord CO-335 directly, or through extension cords.
    30. Installation of Radio Set SCR-499-A
    a.	General. (1) If possible, provide protection from the weather by setting up the equipment in a tent or shed. If Radio Set SCR-499-A is set up in the open, every precaution should be taken to protect the transmitter from rain and dirt. The major components are provided with canvas covers which should be used to protect them from the weather.
    (2)	Components supplied with Radio Set SCR-499-A are listed in paragraph 5. Use figure 2 as a guide in placing the various components, so that the interconnecting cords will reach from one to the other as required.
    b.	Transmitter. Set up the transmitter with the antenna tuner fastened in place as shown in figure 5. If the installation is made on bare ground, raise the transmitter above the ground and block it on wooden skids or planks to keep the base dry.
    c.	Transmitting Antennas. (1) Long wire antenna. If a long wire antenna is used, choose the best length for the operating frequency. (See table IV.) Insert an antenna insulator between the outer end of the wire and the rope used to anchor it to a tree or other convenient support. Keep the antenna as high and free of surrounding objects as possible. Attach a lead-in to the antenna binding post on Antenna Tuning Unit BC-939-A.
    (2) Whip antenna. Mount Mast Base Bracket MP-59-A on the rear of the transmitter by hooking it to the bolts which hold the antenna tuning unit in place. Mount Mast Base MP-47-A in the mast bracket and insert the five-section whip antenna consisting of one each Mast Sections MS-49 to MS-53, inclusive. For detailed instructions on assembling the transmitting whip antenna, see paragraph 33.
    (3) Doublet antenna. For information on the
    EXTERNAL
    SPEAKING TUBE
    » GWiJ’lO LEU®
    j^RQUND CLAMP

    32
    installation and use of the doublet antenna, see section II, chapter 4.
    d. Other Operating Components. (1) Set up the following components as shown in figure 2:
    (a) Chest CH-120-A, CH-121-A, and CH-109-A.
    (fi) Rectifier RA-63-(*).
    (c) Electric heater and blower, if necessary.
    (2)	Choose a suitable point within reach of the power extension cords provided with the set, and set up Power Unit PE-95-( ) in accordance with the instructions in TM 11-904.
    (3)	Set the accessory components (Chests CH-89-A, CH-119-B, and CH-88-A) out of the way until the connections and interconnections have been made (par. 32) ; then place these components convenient to the operating positions, as shown in figure 2.
    31.	Connections and Interconnections of Radio Set SCR-399-A
    When shipped, the operating components of Radio Set SCR-399-A are completely installed, mounted, and interconnected. (See figs. 3 and 4.) Make a general inspection of the equipment and check with the cording diagram (fig. 155) to see that:
    a.	Power Unit PE-95-( ) is properly connected, both mechanically and electrically, to Shelter H0-17-A.
    b.	Receiver, speech-amplifier, and transmitter cords are properly plugged into their respective sockets.
    c.	All wingnuts, wing head bolts, turnbuckles, etc., are tight.
    32.	Connections and Interconnections of Radio Set SCR-499-A
    a.	After the components of Radio Set SCR-
    ’ —........................ \
    ■*---
    Jr ■'	«	I 1
    / \
    «	■ /	flmX-	1
    ......f -JI . H
    • W	sozoo	-w	.-IT-	\
    LAMP ■	■ Z1 LAMP (ROOF)	-	''	/
    ' 'a	7	/	-
    ! oTkffl -> X, LX •= ■	?
    j TO LAMP	' Xi	TO RADIO TRANSMITTER BC~6lO~EFj
    INCHEST.	.
    CH-I2I-A ■	To SMBE .^^^LOwtR	(JMIWPjrZgr	:	7-	I I
    i \	I	f 0 ‘ / ■ si
    J . /X	ij&sc	I
    \ so^ '	Z- E%q ■ ■	B g'
    //	'	X—S°eo’	a	^B	CC
    r	Wr?	W z |	r di
    TO CHEST .	. - .	***	B
    I ' LX \	..1J	S°20S CORD 00-565 TO 00-5)2	RECTIFIER	•’ ' H	V
    W
    --	\ .kJL B\ TO HEATER
    .Xx	' M| * |l\ in
    AUO.O BC-512	W f»®SHELTER *	*
    ...	.W soeo< ......
    '^ \	/jfTO FfADIO RECEIVERS	B IT ZV
    ■	\	jff BC-3I2-I )	. :	K	| ,	nil
    ■ / TO VENTILATOR ’ B •	.	I ]	X®	I ’	’	do
    / BLOWER IN jf X.	' t-1 ISLzc'.,	®	■ 14	\
    SHELTER IF \	. |;f TO RECTIFIER |g tg Z ' I
    i.	TO SPEAKER 2ND AUDIO JA-3K - RA‘63'< 1	■	• If
    z | g ON RADIO RECEIVER 8C-3l2-( )	/ 'ME P ‘ /
    ,?;M^ -Xi. h -.a.	. • tm . .'\	/	. H ■ BAn -TLi5932
    ’ an
    TO POWER
    UNIT PE-95R )
    Figure 29. Cord connections through bottom of Chest CH-120-A to bottom of Junction Box JB-70-A.
    33
    499-A have been placed in their operating positions, use the cording diagram (fig. 155) and the bottom view of Chest CH-120-A (fig. 29) as guides for connecting:
    (1)	Cord CD-763 from the transmitter to Junction Box JB-70-A.
    (2)	Cord CD-764 from the transmitter to Speech Amplifier BC-614-E.
    (3)	Cord CD-659 from Chest CH-109-A to Junction Box JB-70-A.
    (4)	Cord CD-565 from Radio Receiver BC-312-( ) to Junction Box JB-70-A.
    (5)	Cord from Rectifier RA-63-(*) to Junction Box JB-70-A.
    (6)	Cords from the blower and the heater to Junction Box JB-70-A, if these two items are needed.
    (7)	Cord CD-564 from Radio Receiver BC-342-( ) to the Junction Box JB-70-A.
    (8)	Cord CD-566 from Radio Receiver BC-342-( ) to the Junction Box JB-70-A.
    (9)	Cord CX-140/MRQ-2 (auxiliary audio) from Chest CH-121-A to Junction Box JB-70-A.
    (10)	Cord CX-141/MRQ-2 from Junction Box JB-70-A to Speech Amplifier BC-614-E.
    (11)	Cord CX-143/MRQ-2 from Radio Receiver BC-342-( ) to Junction Box JB-70-A.
    (12)	All key, loudspeaker, and lamp cords, as required.
    (13)	Cord CO-335 to Junction Box JB-70-A.
    (14)	Cord CO-316 from Power Unit PE-95-( ) to Cord CO-335, directly or through extension cords, as required.
    b.	Connect Counterpoise CP-15-B to the ground binding post of the transmitter. Lay the counterpoise on the ground and fan out the individual conductors.
    33.	Installation of Antennas on
    Radio Set SCR-399-A
    a.	Select the following items from Chest CH-89-A. (1) One Mast Section MS-49.
    (2)	One Mast Section MS-50.
    (3)	One Mast Section MS-51, to which a metal S-link has been attached (for guying down the transmitter antenna).
    (4)	Two Mast Sections MS-51.
    (5)	Three Mast Sections MS-52.
    (6)	Three Mast Sections MS-53.
    (7)	Insulated guy ropes for the transmitting antennas.
    (8)	Two insulated guy ropes for the receiving antennas.
    b.	Assemble the transmitting antenna (fig. 26) as follows:
    (1)	Screw Mast Section MS-49 into Mast Section MS-50. Use two pairs of gas pliers to tighten the connection. Tape the joint with 1^-inch friction tape.
    (2)	Repeat this procedure with Mast Sections MS-51, MS-52, and MS-53.
    Note. Any mast section with a lower number is above that with a higher number.
    (3)	Carry the guy rope and the assembled antenna sections onto the shelter roof, and screw Mast Section MS-53 into Mast Base MP-47-A.
    (4)	Attach the catches at the rope end of each guy rope to the holes in the corners of Mast Base Brackets MP-50-A.
    (5)	With hand outstretched at shoulder height, stand at the center of the roof and bend the antenna backwards to a horizontal position.
    (6)	Hold the antenna down in this position, walk to the rear of the roof, and with the other hand pick up the insulator end of the guy rope and attach it to the S-link on Mast Section MS-51.
    c.	Assemble the left-hand receiving antenna (fig. 26) as follows:
    (1)	Screw Mast Section MS-51 into MS-52. Use two pairs of gas pliers to make the connection tight. Tape the joint with 1/2-inch friction tape.
    (2)	Screw Mast Section MS-53 into Mast Section MS-52.
    (3)	Screw Mast Section MS-53 into Mast Base MP-48 on the left rear corner of the shelter.
    d.	Assemble the right-hand receiving antenna by.repeating steps c(l) and (2) above. Screw the assembled sections into Mast Base MP-48 on the upper right rear corner of the shelter.
    e.	Attach guy rope insulators to the receiving antennas. Tie the guy ropes to the rear corners of the truck or shelter.
    f.	Use these two guy ropes to pull the receiving antennas down when driving in a city or under low obstacles. (See fig. 1.) However, better reception will result with receiving antennas in the vertical position.
    g.	For information on the use of the doublet antenna, see section II, chapter 4.
    34
    34.	Installation of Antennas on
    Radio Set SCR-499-A
    a.	Assembly and installation of the whip antennas for Radio Set SCR-499-A is the same as for Radio Set SCR-399-A (par. 33), but with the following exceptions:
    (1)	Mount the assembled transmitting antenna in Mast Base Bracket MP-59-A, which is hooked to the transmitter.
    (2)	Put the two assembled receiving antennas into their respective antenna receptacles on Chests CH-120-A and CH-121-A. (See fig. 2.)
    (3)	Use the antennas in their vertical positions.
    b.	For information on the use of the doublet antenna, see section II, chapter 4.
    35.	Installation of Dry Batteries
    a.	Telephones EE-8-( ), Frequency Meter SCR-211-( ), and Analyzer BC-1052-E require dry batteries as listed below:
    Component
    Telephone EE-8-( )
    Frequency Meter Set SCR-211-( )
    Analyzer BC-1052-E
    b.	To install or replace dry batteries, carefully follow the instructions in the technical manual or instruction sheet issued with each component.
    36.	Placing Storage Batteries in Service
    Caution: If electrolyte spills on skin or clothing, wash off immediately with cold water. Apply bicarbonate of soda or ammonia to the affected parts, if available.
    a.	Instructions. Examine the storage batteries for Chest CH-109-A and Power Unit PE-95-( ). A card attached to each battery gives the manufacturer’s instructions for preparing that battery for service. READ THE MANUFACTURER’S INSTRUCTIONS AND FOLLOW THEM CAREFULLY.
    b.	Example. The following is an example of the information which appears on a manufacturer’s instruction card:
    (1)	This battery is of the dry-charged type.
    (2)	The electrolyte to be used is diluted sulphuric acid having a specific gravity of 1.256 at 80° F. It is packed in a separate container. In tropical climates, use electrolyte having a specific gravity of 1.200, produced by mixing 10
    parts of the 1.265 electrolyte with 3 parts of water. Be sure to use distilled water, or other water known to be suitable for use in a lead-acid storage battery.
    Caution: Never add the water to the acid.
    (3)	Remove the vent caps. Remove and destroy the scotch tape which covers the vent holes. Fill each cell with the correct electrolyte to a level % inch above the tops of the separators. Replace the vent caps and tighten securely.
    Caution: Do not put cold electrolyte into a warm battery, or warm electrolyte into a cold battery. Severe damage will result.
    (4)	If the battery is filled with 1.200 electrolyte for tropical use, stamp the numeral 1 on the lead top connector at the positive cell, for the information of anyone servicing the battery in the future.
    (5)	Before placing the battery in service, allow it to stand from 4 to 12 hours after filling.
    Note. In an emergency, the battery may be placed in service 1 hour after it has been filled with the proper electrolyte. This is not good practice.
    Batteries
    2 BA-30
    6 BA-2
    4 BA-23
    1 No. 2 dry cell
    ____________2 BA-34 (7i/2-volt, “C”)
    (6)	If possible, give the battery a freshening charge at 6.0 amperes for 16 to 20 hours before placing it in service. It will give satisfactory results without this charge if the battery temperature is above 50° F. If the battery temperature is below 50° F., it must be given a freshening charge.
    37.	Repacking
    a.	The components of Radio Set SCR-499-A can be quickly disconnected to dismantle the station into a number of relatively small items for transport by aircraft or other suitable conveyance.
    b.	The circumstances of field transportation differ widely and, therefore, no definite repacking procedure can be given. The following procedure is recommended as a guide for preparing Radio Set SCR-499-A for field transportation.
    (1)	Set the accessory Chests CH-119-B, CH-89-A, and CH-88-A where they can be repacked conveniently as their original contents are removed from the set.
    (2)	Remove the seat cushions and backs
    35
    from Chest CH-89-A and tie them into a secure and compact bundle.
    (3)	Disconnect the set cording, keys, lamps, and other small components from the set.
    (4)	Pack each of these items in the accessory or operating chests as indicated in the contents chart of each chest.
    (5)	Remove and disassemble the transmitting and receiving antennas.
    (6)	Pack the antenna mast sections in Chest CH-119-B.
    (7)	If possible, place protective wrappings about the heater, fire extinguisher, Rectifier RA-63-(*), and other components for which
    there is no space in the chests. These items are usually handled separately. (See fig. 17.)
    (8)	Before - closing and locking the chests, stuff any available filler into compartments that require such material to prevent damage to their contents.
    (9)	Cover the components for which canvas covers are provided.
    (10)	Repack the doublet antenna components in their original shipping bags.
    (11)	Carefully store and secure the repacked components in the conveyance being used for transporting the equipment.
    Note. For emergency field transportation, Radio Set SCR-399-A can be removed from Shelter HO-17-A. (See pars. 189 and 190.)
    CHAPteR 2
    TL 17321
    CHAPTER 2
    OPERATING INSTRUCTIONS
    Note. For information on destroying the equipment to prevent enemy use, see destruction notice at front of manual.
    Section I. CONTROLS AND THEIR USE
    38. General
    The controls of Radio Sets SCR-399-A and SCR-499-A are described in this section. A series of line drawings, keyed to the text, are used to illustrate the controls and to show their location on the equipment.
    an approximate setting for the PLATE TUNING wheel.
    b. PLATE TUNING wheel controls the tuning of the p-a (power-amplifier) tank circuit. Its position is registered on the PLATE TUNING dial directly above. The lock holds the PLATE TUNING wheel securely in position.
    c. P. A. PLATE meter measures the current in the p-a plate circuit, thus indicating correct tuning of the p-a stage.
    4		@	g
    4
    To o /
    / ©@
    4^	©©©	\
    TLI6507
    o. MODULATOR BIAS control adjusts the This switch has two positions, ON and OFF.	bias iectihei and, therefore, of
    In the ON position, plate power is applied to all e m° u a or u es-
    tubes in the transmitter which had not been	I	_ —i
    previously turned on by the FILAMENT	11	--- ,; 11 ij 1 \
    POWER switch. A red pilot lamp above this	T &MP-
    switch lights when plate power is applied.	• I i ) B o	L—-■
    Caution: The receiver disabling circuits are
    inoperable with this switch in the ON position;
    do not key the set under this condition.
    n. FILAMENT VOLTAGE control adjusts
    the filament voltage of all tubes in the trans-	• • •
    mitter except the bias rectifier and the drivers.	4	~	"jX q 11
    The circuits are so arranged that a FIL. VOLT-	,*fPSVr
    [plate ------------------
    T---------—WEf? sw'*ch \ I-1	/
    I	LJ lj ~~i4f l«J /	A r? swUchj
    /	\	<(Q)> / -----------------
    ' , ©	©) . -XZ ,-i
    [____________/	{(□)	. fp' r yZa>
    ^\/tlI6506	TLI6508
    40
    p. FUSES FSn FS2, FS3, FS4, and FS5 are located on the front panel of the transmitter. FUSES FSX and FS2 are line fuses. FUSE FS3 is in the primary of transformer T6. FUSE FS4 protects transformers T2, T3, T4, and T5; relays RYn RY2, RY3, and RY4; and lamp LM3. FUSE FS5 protects transformer Tx and the primary of the speech-amplifier power supply.
    40.	Tuning Unit Controls
    a.	The crystal jack is a two-pin receptacle to accommodate a Crystal Holder FT-171-B containing a crystal within the frequency range of the tuning unit.
    b.	M.O.-XTAL switch is thrown to the M.O. position for m-o (master-oscillator) operation and to the XTAL position for crystal-controlled operation.
    c.	M.O. control determines the frequency of the master oscillator. Calibrations on the dial of this control permit it to be set to any frequency within its range through reference to the tuning chart.
    d.	DOUB control is used to tune the bufferdoubler tank circuit to resonance with the sig-
    I--------------------
    nal from the oscillator. An approximate setting for this control can be obtained from the tuning charts.
    e. 1NT AMP control is used to tune the i-p-a tank circuit to resonance with the signal from the buffer-doubler. An approximate setting for this control is also found on the tuning charts.
    41. Antenna tuning Unit Controls
    a.	COUPLING INCREASE control is an antenna-coupling adjustment knob. The setting of this knob is determined from the tuning charts and is read on counters directly above the knob.
    b.	FREQUENCY 18MC-INCREASE-10MC control is the high-frequency tuning adjustment for the antenna. It is set approximately by the tuning charts and is read on counters directly above the control.
    ED | O
    -----^eter ) (
    Antenna X CC3 J range switch /C
    -------tt-tZJ
    c.	FREQUENCY 10MC-INCREASE-2MC control is the low-frequency tuning adjustment for the antenna. It is set approximately by the tuning charts and is read on counters directly above the control.
    d.	ANTENNA CURRENT meter, in series with the antenna coupling control, measures the r-f current in the antenna circuit.
    e.	Antenna range switch is marked 2-10MC LONG WIRE 10-18MC. In the 2-10MC position this switch matches the whip antenna to the low-frequency range of the transmitter. In the LONG WIRE position the antnena is so arranged that the transmitter will work on any frequency within its range into a long-wire antenna. In the 10-18MC position the switch matches the whip antenna to the high-frequency range of the transmitter.

    TL165II
    TLI65IO
    41
    r RECEIVER \ DI SABLIN G I
    © © \
    A/—J \
    © SWp>
    TLI65I2
    42.	Junction Box JB-70-A Controls
    a.	REMOTE TELEPHONE terminals are for the connection of up to a mile of Wire W-110-B from remote Telephone EE-8-( ) or from remote Key J-45.
    b.	BC-312 RECEIVER DISABLING switch has two positions, marked ON and OFF. With this switch in the ON position, Radio Receiver BC-312-( ) SEND-RECEIVE switch in the SEND position, and the transmitter carrier on, disabling occurs as follows: The disabling short-circuits the receiver input connections to protect the antenna coils, and also short-circuits the loudspeakers to prevent acoustic feedback to the dynamic microphone. In the OFF position no power is applied to the antenna-disabling relay in the receiver, and the loudspeakers are not short-circuited; therefore, the receiver is operative at all times.
    c.	BC-342 RECEIVER DISABLING switch functions for Radio Receiver BC-342-( ) in the manner described above for Radio Receiver BC-312-( ).
    I' /
    ©	© X
    TLI65I3 ^^*** 0 8 SZXT
    ( © ©0)©	©©© (gj <
    I___1  —____I T L16 Si 6
    TRANS. OFF position, no keying or modulation of the transmitter may occur (except in emergencies when the transmitter PLATE POWER switch is turned ON). In the REC. TO EE-8 position (with the REMOTE CONTROL EE-8 switch other than NORMAL), the remote location can hear the signals being received in the shelter.
    i. START-STOP buttons are remote controls for Power Unit PE-95-( ). Pressure on the START button applies current to the starting
    k.	C.W. SIDETONE switch has three positions, marked TO BC-312, OFF, and TO BC-342. In the TO BC-312 position, sidetone from the transmitter is applied to the HEADSETS jacks on the left side of Junction Box JB-70-A panel and to the loudspeaker in Chest CH-21-A. In the OFF position, no sidetone is applied. In the TO BC-342 position, sidetone from the transmitter is applied to the HEADSETS jacks on the right side of Junction Box JB-70-A panel and to the loudspeaker in Chest CH-120-A. The same sidetone is applied to the remote telephone line in either TELEGRAPH position of REMOTE CONTROL EE-8 switch.
    I.	RECEIVER OUTPUT switch in the normal position connects the left HEADSETS jacks to Radio Receiver BC-312-( ) and the right HEADSETS jacks to Radio Receiver BC-342-( ). In the TRANSPOSED position the left HEADSETS jacks are connected to Radio Receiver BC-342-( ) and the right HEADSETS jacks are connected to Radio Receiver BC-312-( ).
    43.	Speech Amplifier BC—614—E Controls
    a.	CARBON MIC. 1 is the panel marking for a gain control and jack for Microphone T-17 or T-30. When using Microphone T-17 or T-30, plug it into the CARBON MIC. 1 jack and adjust the corresponding gain control as described in paragraph 51.
    43
    Xx
    XX XU------f=t\
    X&X©© Q \
    *r©@	/
    (g © I
    TLIS5I8
    MENT POWER switch is in the ON position.
    e.	An auxiliary KEY jack on the speechamplifier panel makes it possible to key the transmitter in emergencies.
    Caution: The receiver disabling circuits are inoperative when this key jack is used. To avoid burning out the receiver input circuits, turn off the receivers during transmission from this key jack, or make sure that they are tuned to a frequency considerably different from the transmitted frequency but not to an harmonic of the transmitted frequency.
    f.	The eight-pin receptacle marked TO BC-610 is used to connect Cord CD-764 to the transmitter.
    b.	DYNAMIC MIC. 2 marks the location of the gain control and jack for Microphone T-50. This gain control is also used to control the output of Telephone EE-8-( ) when used in a remote position. The adjustment of the gain for Microphone T-50 and for remote Telephone EE-8-( ) is described in paragraph 51.
    w)
    ^^\_^--^TLl6520
    £© (rxIp^Qx^
    /	El
    W ©	JkZ^q
    \	r
    /O ©X^ig)
    /—---
    A=r, ZZS-L^X-'--1 ,
    - '	T L16 5 22
    c.	MODULATOR PLATE meter indicates the current in the plate circuit of modulator tubes V3 and V4. Its readings are controlled by the adjustment of the MODULATOR BIAS control on the transmitter panel and by adjustment of either microphone gain control on the speech-amplifier panel.
    d.	A red pilot lamp on the speech-amplifier panel is lighted when the transmitter FILA-
    g. The eight-pin receptacle marked TO JB-70 is used to connect Cord CD-566 to Junction Box JB-70-A.
    44.	Junction Box JB-60-A Controls
    a.	LINE terminals are used to connect to Wire W-110-B (up to a mile in length) from the REMOTE terminals on Junction Box JB-70-A.
    b.	A KEY jack permits remote keying of the transmitter through the connecting field-wire line.
    c.	A cord marked EE-8 connects Telephone EE-8-( ) into Junction Box JB-60-A. The remote operator is thus able to modulate the transmitter and to hear the signals being received in the shelter.
    45.	Rectifier RA-63-(*) Controls
    a. The rectifier main control switch has three positions marked TRICKLE, OFF, and HI CHARGE. In the TRICKLE position a low voltage is applied to the rectifier and enough charging current is supplied to the battery to
    44
    offset the load under operating conditions. In companying high charging rate of the battery, the OFF position no charge is applied to the b. The button marked PUSH TO RESET is battery. In the HI CHARGE position full used to reset the circuit breaker if it has opened voltage is applied to the rectifier with an ac- as a result of an overload.
    Section II. TUNING
    46.	Preliminary Steps	_________________________________
    a.	Safety Notice. Reread the safety notice
    in front of book.	((	(TY (TY (T/l
    b.	Receiver Disabling. (1) Always leave \k // \k J)
    RECEIVER DISABLING switches on Junction ------
    Box JB-70-A at ON.	Z^^\@
    (2)	Always leave the SEND-REC. switches ((	J J (( Jy Innl
    on Radio Receivers BC-312-( ) and BC-342-	Z^****^
    ( ) at SEND.	______ a
    c.	Gasoline Tanks. Never fill gasoline tanks	—	V^****/
    © O °
    ( RECEIVER	------
    r—[ DISABLING I-	k ----------------------------------------
    ‘	\ of either truck or trailer when transmitter is
    ____\ in operation.
    / d. Power Unit PE-95-( ). (1) Start and y/ check the unit. Turn OFF THE large ON-OFF < switch marked CIRCUIT BREAKER (located /^n	V 0/^ X on blc contr°l panel of the power unit). Check
    the operation and condition of the power unit
    Z"X	\r V in accordance with procedure described in TM
    \	11-904.
    ® o©© / ___________________________________________________________
    OOoooo
    K	z^x	z©=©\©
    /)y<-x lfFx\	(( H (( a n
    / /	©	------ /s'-'A °
    \ © o
    \	OO O —-------------------------------------------l. 1,435
    \	xz'	(2) Stop the unit. When completely checked,
    /	vzll 11(3 pUSh the ST0P button of the START-STOP
    /	switch (on the control panel of the power unit)
    /	and hold it until the power unit stons.
    \	| I J~X	Note. Some power units are issued which contain a
    \	(1	momentary push-to-stop switch which does not have to
    \________ ______________________ be held in until the power unit stops. In general, the
    stop button must be held in on Ford-powered units, TL 14801 while Willys-powered units have the momentary push-to-stop switches.
    -----	~~	(/) BATTERY SOURCE switch.
    7^X\	1' Power Unit PE-95-( ) is pro-
    ((	)) ((	))	\x_)) \\}/	vided with 12-volt terminals and
    x^—^z x/—JA	Cord CO-316 is connected to these
    terminals, set the BATTERY \\ Fna? \ r?=^i	SOURCE switch on Junction Box
    JB-70-A at PE-95.
    ------- ®	°	m © © °	i
    _________________™J 1
    (3) Set circuit breaker. Set the ON-OFF
    (CIRCUIT BREAKER) switch of the power	M II CM ° ©I--------------
    unit at ON.	|g]	B q
    0 0)00) OOO 0
    VI	yr I TLI4803
    _____________x\
    \y
    2* ^ie 12-v0^ supply in Chest CH-/	109-A is to be used, set the BAT-
    1----/	TERY SOURCE switch at AUX.
    S	and set the Rectifier RA-63-(*)
    switch at TRICKLE. If Radio Re-ceiver BC-312-( ) is to be used, /	set the rectifier switch at HJ
    (	CHARGE.
    r~...	r \_______________________________________
    tl 14802	\	/V
    J	o	//>}/
    e. Position of Switches and Controls. (1)	/	J*/O'/ \
    Speech Amplifier BC-61A-E. Rotate the gain	I	ZrV \
    control knobs of both CARBON MIC. 1 and	I	buhL \
    DYNAMIC MIC. 2 to their extreme counter-	I.	P"1	I""! n	\
    clockwise positions (minimum gain).	Hjl	|B| |M|	3
    (2) Junction Box JB-70-A. (u) Set trans- j	__ \
    mitter main control switch at TRANS. OFF. /	/ y	\
    (6)	Set C.W. SIDETONE switch at OFF.	/	\
    (c)	Set both receiver disabling switches / (Cj) v^v w
    (marked RECEIVER DISABLING) at ON. /	\^\	v£\	\
    (d)	Set RECEIVER OUTPUT switch at	X\< \ \<\ /
    NORMAL.
    (e)	Set REMOTE CONTROL EE-8 switch
    at NORMAL.	TLI4804
    46
    Caution: When Radio Receiver BC-312-( )	of the START-STOP switch. When the RE-
    is to be turned off for more than 1 hour, turn	CEIVER OUTPUT switch is set at NORMAL
    the rectifier switch to TRICKLE.	(par. 421), the left-hand pair of headset jacks
    (g)	See that key plugs are in proper jacks.	is connected to Radio Receiver BC-312-( ) and
    (3)	Radio Transmitter BC-610-E. (a) Set	the right-hand pair of headset jacks is con-
    FILAMENT POWER switch at OFF.	nected to Radio Receiver BC-342-( ).
    (h)	Set PLATE POWER switch at OFF.	Note. When no commercial power is available, Power
    /	\ „ ■. .. amadt l xx t x* t> tt> o/o / । ex	., . x onx/n Push the START button on Junction Box JB-
    342-( ). Set SEND-REC. switches at SEND. A ... tt	, . , ,	.
    T ,. -XT -	•	70-A until Power Unit PE-95-( ) starts and
    Caution: Leave these switches in SEND posi- pickg up gpeed.
    tion hl nil tiixiGs.	STEP 2
    f. Drying Out the Transmitter. Start Tllpn . . . .... . r,. , ^TT . n TT -x -nm n- / x . ,	^TTA I urn on the electric lights m Chest CH-120-A,
    Power Unit PE-95-( ) and turn on FILA- pi,,,. PTt 1Q1 a . • t u	xi
    watt TJMAATmD -X u r T? j• m -xx Chest CH-121-A, and m the shelter over the MENT POWER switch of Radio Transmitter transmitter
    BC-610-E. In damp locations this should be
    done at least 15 to 30 minutes before turning
    on the high voltage. The drying process can be
    accelerated by turning on the heater in the shelter.
    g. Radio Receivers BC-312-( ) and BC-	—------------------------------
    342-( ). (1) Check the operation and condi-	O o
    tion of Radio Receivers BC-312-( ) and BC-	O
    342-( ) as outlined in TM 11-850.	~	Si
    (2) Remove two Headsets HS-30-( ) with \ ODD [■} \ OF
    Cords CD-605 from Chest CH-120-A. On June- \	N"
    tion Box JB-70-A, plug one headset into one \
    of the jacks marked HEADSET located to the \	(Q)
    left of the START-STOP switch, and plug the ■	----
    other headset into one of the jacks to the right	tli4808
    47
    COIL UNIT VACUUM CAPACITOR	Zu	TUNING UNIT
    y	।	CHANNEL I CHANNEL 2 CHANNELS
    7... • — —	.
    , ' & - :C ..•?:■ W'■ ... ■	\	fcJtt'
    «l a
    ■ "JHWO"	■	1	<* ’ IB
    ‘	।	4	|B
    S&	I II	r>
    IRtit - ’ZlXW
    M . t ._ *♦•< A
    II - bA x? « » *Eri /■k> »l j	Kri©	i Vwi
    SBS& I® ’ ..|..\ .gaOl
    ('-U ':	-^WBi^WTHrAi/n. 11if ih & fMk «•_
    K.' IMBB*********“!	■**r; •	------I
    ■ .. - “ -----------------------------------------.
    1	I
    ..--, -_______.......-
    \	.','47'7'	'3BI	ass^w.
    fefey 'i -j***
    27x2*7.	\ '^Lr •
    Figure 30. Radio Transmitter BC—610—E, top covers removed.
    STEP 3
    Turn on the electric heater or the ventilating /	'
    blower, if either is desired.	/	vEy
    STEP 4	/	\
    See that the PLATE POWER switch of the r------------------------------\
    transmitter is at OFF and is left there. (See	A ©	©	\
    j 4.0/v \ _—.	\
    \	/ I □ □□	\
    ©^© V
    /	(O/x	STEP 6
    \	0	P Set the FILAMENT POWER switch of the
    \	/ transmitter at ON. The green pilot lamp and
    TL.I4 3H	the PLATE TUNING dial should now light.
    The FIL. VOLTAGE meter should register.
    STEP 5	• (Allow 1 minute for the filaments to come up
    Make sure that the transmitter control switch to the proper operating temperature.) Adjust on Junction Box JB-70-A is at TRANS. OFF. the FILAMENT VOLTAGE control of the
    48
    __	STEP 8
    I -----\	Open the right-hand door in the cover of the
    Sm-—	in?_____	transmitter and firmly insert the tuning unit
    V___________________________ / in one °f the three available receptacles, marked
    X	1, 2, and 3. (Locate the tuning unit so that the
    \	/ switch marked M.O.-XTAL faces the front
    \ ---- ------- --- «■■■■»	7 panel of the transmitter.)
    \	|^%]	/ STEP 9
    \ '---' ----' '----	/ From Chest CH-88-A, select one coil unit cov-
    ---- -----L-----	/	ering the desired frequency. Remove Capacitor
    x i \	CA-423 from Chest CH-88-A, if operation in
    i \	/""x /o i \ the 2.0-to 2.5-mc (megacycle) range is desired.
    X	I)	Open the left-hand door	in	the	cover	of	the
    xp> X	X <	I
    o/	4	transmitter and insert the	coil unit	(and	Capac-
    X /	'y	j	itor CA-423 if required).
    >------------'	A---------\	STEp 10
    /	X X	s' Set the M.O.-XTAL switch of the tuning unit
    / X X	\ at M.O.
    /	©XX ©
    /	XXX □ □	--------
    / [3/	\ 0s
    \ ®X\^/
    T L 14 8 0 7	r
    transmitter until the FIL. VOLTAGE meter	1—	-   ________ . I
    indicates 5.0 to 5.3 volts.	P) X Xi
    STEP 7
    From Chest CH-88-A, select one tuning unit	x
    XJ ovAy _ _ _ /
    \	STEP 8	TUI48I0
    A	pIrrAniQU)
    \ L VJ n®wR7 step 11
    I 111	I)	BAND SWITCH on the front panel of
    fl 11 I --------- I / IPiAigV'i	transmitter at the number which corre-
    \	l /	Ill'll U	sponds to the	socket in which the tuning unit
    z	k 7	» /AdrtP \	was placed.
    /—/aLIx-----------n	F ^T7a	step 12
    / —	\\<w>
    49
    STEP 14	for maximum reading as indicated on the EX-
    Set the EXCITATION METER SWITCH on CITATION METER,
    the front panel of the transmitter at INT. AMP.
    GRID. Set the EXCITER PLATE POWER
    switch of the transmitter at ON.	Z^X.
    ZL’Z
    ------	sVs x
    r—	Z\
    ss	<—	T TF-y#
    ... >4______ oh©	/	[5|O|I3|5  A fl'	S	/	XX
    y*X V	/r—i, , — A / Z	Z xxZ
    Cjtzt~~~-ZZJ nZ^v i	xivNa-—zzz—
    ®\	\ pZj° L—X
    O'-------\	^B □□
    nuait	\	Z\
    -^Xs\y	------
    STEP 15
    QTTpp IO
    Loosen the thumbscrew lock on the M.O. dial
    of the tuning unit. Set the M.O. dial to the de- Repeat steps 16 and 18 until the maximum pos-sired frequency as indicated by the tuning chart sible deflection *S °kRdned on ^he EXCITA-of Radio Transmitter BC-610-E which pertains	ETER. The EXCITATION METER
    to the tuning unit in use. For greater accuracy s ou d indicate between 60 and 100 ma (milliuse Frequency Meter Set SCR-211-( ). (See ‘™^GJ
    TM 11-300.) Tighten the dial lock.	m ___ _
    STEP 16	the EXCITER PLATE POWER switch at
    Adjust the center knob of the tuning unit ST^p^^l^ (marked DOUB) for maximum reading as indi-	.
    cated on the EXCITATION METER.	certam that both doors m the top cover
    of the transmitter are firmly closed upon the interlock switches; otherwise plate power can-= y	not be applied.
    STEP 22
    \ . step^	Set the HIGH VOLTAGE PROTECT switch at
    USt \	< HIGH V0LTAGE PROTECT. Always do this
    ft **	A ,i- i,_ n before tuning the final amplifier or the antenna
    p^pp|1/ tuning unit.
    (o) IL© @( । -....................................... /
    F I ° I	\
    #	Zo ©	----X
    z_x	A? DJbv/	/X	X
    =	J-n STEP 23 X \C7
    NZ	(Q) U^ANS, OM >W Y
    STEP 17
    Set the EXCITATION METER SWITCH on	(g)	X3X
    the front panel of the transmitter at P.A. GRID.	Xs^ x_z xLz	X
    STEP 18	-----------------------------X
    Adjust the INT. AMP. knob of the tuning unit	TL14814
    50
    STEP 23
    Set the transmitter control switch on Junction .______
    Box JB-70-A at TRANS. ON. The red pilot	\_____Z
    lamp on the transmitter should now light.	T—	______ g,,, 111 tti ,	\-\
    step 24	A 'V Pw OO
    Press and hold down Key J-37 while making \	(_____)	X.	J
    subsequent tuning adjustments. The P.A. \	L_J *________
    PLATE meter should indicate a flow of current \
    in the circuit. The quantity of current will de-	/	(uWDJ	z"-*\ \Uy /
    pend upon the setting of the PLATE TUNING (	(vx)	(
    dial.	\	\
    1	\	10 me. If a long wire antenna is used, set the
    I	\	knob at LONG WIRE. Set COUPLING IN-
    ------------------“	' y	CREASE control at about 2.0. From the tuning y	3ZX s'	chart, determine the approximate setting of
    k	k^gi5	antenna tuning inductor for the selected fre-
    \ /	quency. Turn antenna tuning inductor crank
    v	to approach this setting and watch for an indi-
    STEP 25	cation of rising plate current on the P.A.
    Unlock the PLATE TUNING dial by pushing PLATE meter on the transmitter, down on the small knurled knob and adjust the Note. If the operating frequency is in the range of 2 wheel until the P.A. PLATE meter dips to a	tncrf aUi^Vm c c marked FREQUENCY 10MC-
    11N CKJLAbK-21VLC. If the operating frequency is m the minimum reading.	ONCE THIS ADJUST-	range of 10 to 18 me, use the crank marked FRE-
    MENT IS MADE	DO NOT CHANGE	IT	QUENCY 18MC-INCREASE-10MC. When the an-
    IVilLlNl ID 1V1AU1L,	VU 1NU1 UHAlWiL	11	tenna p g switch j t t LONG WIRE use the
    UNTIL THE TRANSMITTER IS TO	BE	crank marked FREQUENCY 10MC-INCREASE-2MC.
    TUNED ON A NEW FREQUENCY. Lock the	be found that feweF turns. of tbe loadi.n£ coiJ
    Will be necessary when a long wire antenna is used PLAIE 1 UNING dial by pushing the lock lever instead of a whip antenna.
    to the right.	Adjust the proper crank for maximum indica-
    a______________ tion of the P.A. PLATE meter. Either increase
    se7 ot262 o ynnriTz STEP 26	”1 or decrease the degree of coupling with the
    1 V LoJtJ y ^we’en^io^toisSc COUPLING INCREASE knob of the antenna ----\--------------------------' tuning unit to keep the P.A. PLATE meter Xen°2.oretqou ilX / f ------------------ reading at 100 ma. The ANTENNA CURRENT
    ■	y [—-	KSet knob(see text) meter will now give some indication of antenna
    current. _________________________
    /	|	STEP 27
    n,4a,s Throw the HIGH VOLTAGE PROTECT switch of the transmitter to NORMAL. Press Key STEP 26	J-37. The P.A. PLATE meter of the transmit-
    On Antenna Tuning Unit BC-939-A, set the	ter and the ANTENNA CURRENT meter of
    range switch knob at 2—10MC if operating	the antenna tuning unit will now indicate sub-
    below 10 me, or at 10-18MC if operating above stantially higher readings.
    51
    STEP 28	moment, throw the transmitter control switch
    Alternately adjust the COUPLING INCREASE on the junction box to TRANS. OFF. control and the tuning inductor crank until the maximum antenna current occurs when the	____
    P.A. PLATE meter reads 290 ma.	f~ / >	Z
    /x	r XXm A
    w5SL_0 © fl I \	y	STEP 2 8	"V	[X
    TLI48I9
    yr’1	S
    \	k pO°------------- Note. To turn off the transmitter completely, set
    /	f	the FILAMENT POWER switch on Radio Transmitter
    \	I '' jr ---- T	BC-610-E at OFF.
    \ I (	| p >	Table III. Tuning components
    W\	Z7N	Component	Frequency Range (me)
    /SXX (vA	r—-—-	Tuning Unit
    I___I J	TU-47	2.0 to 2.5
    /	TU-48	2.5 to 3.2
    X	7^\ /\	TU-49	3.2 to 4.0
    V\®	/ x/ x. TL14818	TU-50	4.0 to 5.0
    TU-51	5.0	to	6.35
    TU-52	6.35	to	8.0
    Caution:	NEVER	EXCEED	A	P.A.	PLATE	™-53	8.0	to	12.0
    1 U— 54	12.0	to	18 0
    METER READING OF 300 MA on c-w opera- Coil Unit
    tion. It	is	permissible	to	reduce coupling until	C-387-B (with Capacitor	2.0	to	2.5
    ,	V>A—4Zo )
    plate current is as low as 200 ma, if satisfactory	C-387-B	2.5	to	3.5
    c-w communication is still maintained. Do not XoonX	to
    readjust the PLATE TUNING dial after it is	C-390-A	5.7	to	8.0
    once adjusted for the frequency on which opera-	£-447	,?’2	!°
    . .	. .	, .	,	G-448	.	11.0 to 14.0
    tion is to take place.	C-449	14.0	to	18.0
    STEP 29	----:-------------------------
    Release Key J-37. With the opening of the key, Table IV. Tuning ranges for long wire antennas when ,, nvnTr_mT_AT ~	,	.A.’	used with Antenna Tuning Unit BC-939-A
    the EXCITATION, P.A. PLATE, and AN-
    TENNA CURRENT meters should return to Antenna lengths (ft.)	| Useful frequency range (me)
    zero.	25	2	to	10;	15 to	18
    STEP 30	45	I	!°	}1 f°	J!
    Press Key J-37	and check the FIL. VOLTAGE	65	2	to	3 \	9 to	18
    meter. If necessary reset the FILAMENT --------------—-------------------------—
    VOLTAGE knob until this meter reads 5.0 to
    5.3 volts; then release the key. This completes	48. Tuning	Radio Transmitter BC-6I0-E for
    the tuning procedure, and the transmitter is	C-W Operation [Crystal Control]
    ready for c-w operation. Keying of the trans-	STEP 1
    mitter may be checked by depressing the key	Perform all	operations in steps 1 through 9 and
    and noting the meter indications. Data on meter	11 through	13 in paragraph 47, then proceed
    readings will be found in the equipment per-	as follows:
    formance check list. (See par. 66.)	STEP 2
    STEP 31	Set the tuning unit M.O.-XTAL switch at
    If c-w transmission is not desired at the XT AL. Insert into XT AL jack Crystal Holder
    52
    FT-171-B with a crystal of proper frequency as listed in table V.
    Note. At frequencies between 2 and 4 me, the trans-	I/"—xYk
    mitter output frequency is the same as the crystal fre-	y (	\ '	) Yx.	\
    quency and a circuit controlled by the DOUB. knob /	<----1 ■--------'	r
    functions as a buffer stage. At frequencies between 4 i ________________J _________LL__\ o
    and 12 me, this stage acts as a doubler; hence the out- /
    put frequency is twice that of the crystal. For example,	— I
    a crystal with a frequency of 2,200 kc (kilocycles) may	( ((O)))
    be used with Tuning Unit TU-47 to produce the same
    frequency in the transmitter output or it may be used	^\>	W? "Sv
    with Tuning Unit TU—50 to operate the transmitter on I
    4,400 kc. At frequencies between 12 and 18 me this
    stage quadruples the crystal frequency. For example,	Y	'	1 ~ ~~~~T
    a 4,000-kc crystal will produce a transmitter output	/	/
    frequency of 16,000 kc.	/	O O	/
    STEF 3	~	\
    Set the EXCITATION METER SWITCH on / O	M	\
    the transmitter at INT. AMP. GRID. Set the /	[■■I fl I"1	/
    EXCITER PLATE POWER switch on the /	3 / LJ U U V
    transmitter at ON.	/	\	/
    STEP 4
    Perform all operations listed in steps 16
    through 30, paragraph 47.	TL,482°
    Table V. Crystals and operating frequencies
    Note. Radio Sets SCR-399-A and SCR-499-A include* two sets of Crystal Holders FT-171-B whose crystals have the following operating frequencies. For convenience, a third column is included to show the additional operating frequencies which may be obtained by use of different tuning units. Two groups of crystals are shown, only one of which is supplied with each set.
    GROUP 1	GROUP 2
    Crystal	Operating	Tuning	Additional possible	Tuning	Crystal	Operating	Tuning	Additional possible	Tuning
    frequency	frequency Unit	operating frequencies Unit	frequency	frequency	Unit	operating frequencies	Unit
    (kc)	(kc)	(kc)	(kc)	(kc)	(kc)
    2,030	2,030	TU-47	4,060	TU-50	2,030	2,030	TU-47	4,060	TU-50
    2,220	2,220	TU-47	4,440	TU-50	2,052.5	2,052.5	TU-47	4,105	TU-50
    2,258	2,258	TU-47	4,516	TU-50	2,085	2,085	TU-47	4,170	TU-50
    2,300	2,300	TU-47	4,600	TU-50	2,117.5	2,117.5	TU-47	4,235	TU-50
    2,360	2,360	TU-47	4,720	TU-50	2,160	2,160	TU-47	4,320	TU-50
    2,390	2,390	TU-47	4,780	TU-50	2,200	2,200	TU-47	4,400	TU-50
    3,510	3,510	TU-49	7,020	TU-52	2,217.5	2,217.5	TU-47	4,435	TU-50
    3,520	3,520	TU-49	7,040	TU-52	2,390	2,390	TU-47	4,780	TU-50
    3,550	3,550	TU-49	7,100	TU-52	2,415	2,415	TU-47	4,830	TU-50
    3,570	3,570	TU-49	7,140	TU-52	2,436	2,436	TU-47	4,872	TU-50
    3,580	3,580	TU-49	7,160	TU-52	2,532.5	2,532.5	TU-48	5,065	TU-51
    3,945	3,945	TU-49	7,890	TU-52	2,647.5	2,647.5	TU-48	5,295	TU-51
    3,955	3,955	TU-49	7,910	TU-52	2,772	2,772	TU-48	5,544	TU-51
    2,045	4,090	TU-50	2,045	TU-47	2,980	2,980	TU-48	5,960	TU-51
    2,065	4,130	TU-50	2,065	TU-47	3,000	3,000	TU-48	6,000	TU-51
    2,105	4,210	TU-50	2,105	TU-47	3,035	3,035	TU-48	6,070	TU-51
    2,105	4,210	TU-50	2,105	TU-47	3,100	3,100	TU-48	6,200	TU-51
    2,125	4,250	TU-50	2,125	TU-47	3,120	3,120	TU-48	6,240	TU-51
    2,145	4,290	TU-50	2,145	TU-47	3,150	3,150	TU-48	6,300	TU-51
    2,155	4,310	TU-50	2,155	TU-47	3,155	3,155	TU-48	6,310	TU-51
    2,260	4,520	TU-50	2,260	TU-47	3,232.5	3,232.5	TU-49	6,465	TU-52
    2,282.5	4,565	TU-50	2,282.5	TU-47	3,265	3,265	TU-49	6,530	TU-52
    2,290	4,580	TU-50	2,290	TU-47	3,322.5	3,322.5	TU-49	6,645	TU-52
    2,305	4,610	TU-50	2,305	TU-47	3,417.5	3,417.5	TU-49	6,835	TU-52
    2,320	4,640	TU-50	2,320	TU-47	3,475	3,475	TU-49	6,950	TU-52
    2,415	4,830	TU-50	2,415	TU-47	3,588	3,588	TU-49	7,170	TU-52
    2,435	4,870	TU-50	2,435	TU-47	3,665	3,665	TU-49	7,330	TU-52
    2,442.5	4,885	TU-50	2,442.5	TU-47	3,725	3,725	TU-49	7,450	TU-52
    2,532.5	5,065	TU-51	2,532.5	TU-48	3,785	3,785	TU-49	7,570	TU-52
    2,545	5,090	TU-51	2,545	TU-48	3,792.5	3,792.5	TU-49	7,585	TU-52
    2,557.5	5,115	TU-51	2,557.5	TU-48	3,850	3,850	TU-49	7,700	TU-52
    3,202.5	6,405	TU-52	3,202.5	TU-49	3,865	3,865	TU-49	7,730	TU-52
    3,215	6,430	TU-52	3,215	TU-49	3,905	3,905	TU-49	7,810	TU-52
    3,237.5	6,475	TU-52	3,237.5	TU-49	3,935	3,935	TU-49	7,870	TU-52
    3,250	6,500	TU-52	3,250	TU-49	3,995	3,995	TU-49	7,990	TU-52
    3,322.5	6,645	TU-52	3,322.5	TU-49	3,997.5	3,997.5	TU-49	7,995	TU-52
    ______________________________________________________I ______________I___________________________________________
    53
    Note. Although no crystals are included for	fre-	tion. (This increases the bias so that the MOD-
    quencies above 8 me, the following examples show typi-	ttt atAP PT ATF motor Inoatod nn Snoorh Am-
    cal crystal and operating frequencies in this range.	U^A 1 UK FLA 1 IL meter, located on bpeecn Am-
       plifier BC-614-E, will not indicate until further crvstai	uncrating	Tuning	adjustments have been made.) Set the C.W.-
    ZXZ  /SX>	TuZ	pH0NE switch at pH0jjE.
    4,500	9,000	TU-53	Caution: Never throw this switch while the
    5,500	11,000	TU-53	n .	•	4- u
    3 5Q9	14 ooo	TU-54	final amplifier	is	turned on.
    4’500	is’ooo	TU-54	STEP 4
    ■--—---------------------------------- Remove Microphone T-50 from its mount in
    Chest CH-120-A and connect it to the recep-49. Tuning Radio Transmitter BC-6I0-E	taele marked DYNAMIC MIC. 2 located on the
    for Voice Operation	speech-amplifier panel.
    STEP 1	______________
    Perform all operations in paragraph 47 or 48	[✓‘“xl I---1
    (depending upon whether the operation is to	(©) © Q_j I—
    be m-o controlled or crystal controlled), then	(g) ©	11 1
    proceed as follows:
    nZ Z/z	° V»V
    x^<	D	II
    STEP 2	k °
    On Junction Box JB-70-A set the transmitter	\z
    control switch at TRANS. OFF. Set REMOTE
    CONTROL EE-8 switch at NORMAL. Set STEP 5
    C.W.	SIDETONE at OFF	Press the switch on the microphone and note
    ,	that this puts the transmitter carrier on the
    k________ air. The P.A. PLATE meter should read ap-
    (	Adjustuee	text) y	lAIDT	proximately 250 ma, which is the normal plate
    v	=	current for voice operation. If the transmitter
    \y\	r-1©	/Ox
    xAJ 1	//^X
    vu., /zx\
    1/	WwaA—
    I ^0	1 I I la
    j STEP 3 X	1	Bl/
    Extreme X (6)	Bhi ■■	I______I /
    I counterclockwise^/	yl	Z
    \ /	TLt4822	-- --------- \
    STEP 3	(fcy)	® \
    Set the MODULATOR BIAS control on trans-	—
    mitter to the extreme counterclockwise posi-	J--------------------S
    <____________________Z T L14 8 2 4
    54
    has been tuned to 290 ma on c-w operation, the	STEP 9
    plate current will be 250 ma when switched to	When REMOTE CONTROL EE-8 switch is in
    voice because the C.W.-PHONE switch auto-	either TELEPHONE position, voice transmis-
    matically reduces the final amplifier plate volt-	sion can be obtained without pressing the mi-
    age. If the P.A. PLATE meter reads more than	crophone switch. When using this method, set
    260 ma, the COUPLING INCREASE control	the transmitter control switch at TRANS. ON
    on the antenna tuning unit should be adjusted	during transmission periods and to TRANS,
    until the plate current is reduced to the proper	OFF to terminate transmission. This procedure
    value.	is not recommended for general practice.
    STEP 6	STEP 10
    Hold the microphone in the left hand, press the	To turn transmitter off completely, set the
    microphone switch, and with the right hand ad-	transmitter control switch on Junction Box JB-
    just the MODULATOR BIAS control on the	70-A at TRANS. OFF and set FILAMENT
    transmitter until the MODULATOR PLATE	POWER switch on the transmitter at OFF.
    meter on Speech Amplifier BC-614-E indicates
    40 ma. Release the microphone switch.	.» -... ■	....■	=y
    STEP 7	H-------------------------------C
    Hold the microphone in the normal speaking	--------- \
    position (position varies with voice character-	z—x -y
    istics, from 2 to 6 inches from mouth), press	oJTRa^i	\ H	Ol r
    the microphone switch, and speak into the mi-	Pjf—	x JI	/
    crophone. While pressing the switch and talk- (Qj	f
    ing into the microphone, adjust the gain control	(£§}) dp})((§)) xrz
    (marked DYNAMIC MIC. 2) until the MODU-LATOR PLATE meter indicates approximately ----------------------------------------'
    200 ma on voice peaks. If the pointer swings higher than 200 ma on extreme voice peaks,	---
    reduce the gain control to prevent exceeding .	_________w'	■
    200 ma. (This figure represents 100 percent	__________________ /
    modulation when the transmitter is fully 	\
    loaded.) The same procedure applies to the use J------------ \
    of carbon Microphone T-17. Only one gain con-	I	\f7
    trol should be open (turned away from the O	I___J _____) (__. L_/
    position) at a time, however.	____ ______U---- |/
    STEP 8	7
    Release the microphone switch, taking the	/C?\	/
    transmitter off the air. Voice transmission can	x	<
    now be accomplished by pressing the micro-	x.
    phone switch and speaking into the microphone.-------------------------------------X
    	I	\	|STEP|0 \ 'X
    O'A I	A
    © ©@© \
    TLI4825	TL14826
    55
    Section III. NORMAL OPERATION
    Caution: Before attempting operation of the minute for the filaments to reach operating equipment, read paragraphs 38 through 46. temperature. See the transmitter C.W.-PHONE When thoroughly familiar with their contents, switch at C.W. proceed with the operation of the set.
    50. C-W Operation
    To operate the transmitter on continuous wave, perform the following steps:	Zv
    STEP 1	>—	KZ^ VJZ^
    Push ST ART button on Junction Box JB-70-A	/	/ G^/Z
    until Power Unit PE-95 starts and picks up \	q	.
    speed.	J n
    ------------,	lx. OSO ©
    F - - a --------------------1
    /	\ V	TLI4827
    /	7	STEP 4
    /	________ Set the transmitter control switch on Junction
    / II V	^2^	Box JB-70-A at TRANS. ON.
    V I -------------------------- ।1	(
    \	------1 \
    \----------------------------- I	■■ /Zxn /
    TL18001 (SlTrans. off	f
    STEP 2	(qJ	O I
    Turn on the electric lights in Chest CH-120-A,	tgj ({§))	\
    Chest CH-121-A, and in the shelter over the	______ \
    transmitter.	'
    ifWz© 5	i—	z
    \ xrf 3k -v S pin py
    x ©> _ qJ xA,	\ J \	'5=^ (§>	©
    /X-J0 □ □ 0 J---------------------------------------------------(
    /		I °ff >n □ o □
    TL 14828
    STEP 3	/x O	(□
    See that the PLATE POWER switch of the x.	< x.
    transmitter is OFF. Set FILAMENT POWER x. / switch of the transmitter at ON and wait 1	\Z
    56
    STEP 5	5|, Voice Operation
    Set the C.W. SIDETONE switch in the position To operate the transmitter on voice, perform corresponding to the receiver being used.	the following steps:
    STEP 6	STEP 1
    Use Key J-37 to send any desired messages. In Perform all operations in steps 1 through 3, addition to Keys J-37 located in the operating	paragraph 50.
    chests, Key J-45 may be used to key the trans-	STEP 2
    mitter at the auxiliary KEY jack located on the Set the transmitter control switch on Junction front of the speech-amplifier panel. Keying of Box JB-70-A at TRANS. OFF, and the C.W. the transmitter at the auxiliary key jack will SIDETONE switch at OFF. be necessary if the source of 12-volt d-c power STEP 3
    fails, since the auxiliary jack is the only direct Set the C.W.-PHONE switch of the transmitter connection to the cathode circuit of the trans- at PHONE, mitter oscillator.	STEP 4
    Press the microphone switch on Microphone —1T-50, and speak into the microphone to modu-
    /	x ।	—/
    /	,—® A /
    \-----------/pSuw-------------/ tel	o f
    \	Qj I	(g)	k
    < Z\p n □
    x.	/	x. ./X J	,	1^
    tli483o rZZZZZZZ	X
    Caution: Relay RY200 does not function with	I/^nI K\|
    this method of keying; therefore, automatic re-	C___J .___J C__, C /
    ceiver disabling cannot occur. See paragraph	____ _____U____	7
    43 before using this jack.	Z7
    STEP 7	vOR	(J
    To turn the transmitter off completely, set the	'xZ^xN	(xX) /
    transmitter control switch on Junction Box JB-	(
    70-A at TRANS. OFF, and set the FILAMENT_____________________________\
    POWER switch on the transmitter at OFF. 1°;	U
    use, and setting the transmitter control switch	I Xfe,- sXf	I
    to TRANS. ON.	1
    b.	Changing from Continuous Wave to	'mPIM PI
    Voice. After the transmitter has been operated	A
    ®	।--1
    11 ~	- y	© ’
    □ 0 NORMAL
    /x	lx	\
    (Qj [qV	\	X/
    _.	I s T E PI a 4 fl	\ x.
    Km	I See tp ♦	>11	'i	tuning units, each of which may be instantly
    nruji eX*/M	selected by the BAND SWITCH. Each tuning
    Jr	unit may be tuned to a separate frequency and
    ZSk z2S\ z^\/~x	\>-> left Pegged in ready for use when needed.
    O) (©/ (©)(©)	Since there are three sets of tuning units, it is
    X	possible to install three tuning units of the same
    *	f	range which would be covered by one coil unit.
    TLI4837 With each unit pretuned to a different frequency on continuous wave, it can be switched imme-	within	the ran?e’ change of transmitting fre-
    diately to voice by resetting the transmitter	quency	1S accomplished as follows:
    control switch at TRANS. OFF, setting the STEP 1
    C.W. SIDETONE switch at OFF, and then set-	Set the	transmitter control switch at TRANS,
    ting the C.W.-PHONE switch at PHONE.	OFF if	operating on continuous wave. Release
    the- microphone switch if operating on voice.
    53.	Changing Frequency	STEP 2
    a.	Case 1. Provision is made in the transmit- ReSet the BAND SWITCH to the desired chanter for simultaneously accommodating three nel numfoer
    /X	STEP 3
    XX J	Set the HIGH VOLTAGE PROTECT switch at
    HIGH VOLTAGE PROTECT.
    XJFB	STEP 4
    /q\	Set the transmitter control switch to TRANS.
    __	I	X7	ON and close the key if operating on continuous
    .—./	wave. Leave the transmitter control switch at
    ZXx3 X	TRANS. OFF and press the microphone switch
    if operating on voice.
    /	STEP 5
    -------------------1	Slightly retune the PLATE TUNING dial for a /	a dip in the P.A. PLATE meter.
    VTX<5 71-1	>	STEP 6
    /	Adjust the proper antenna tuning inductor
    crank for a rise in indication of the P.A. PLATE meter.
    59
    STEP 7	quency range of the coil unit is correct. If not,
    Throw the HIGH VOLTAGE PROTECT switch remove it and replace it in Chest CH-88-A. to NORMAL.	STEP 2
    STEP 8	Set the BAND SWITCH to the desired channel
    Adjust the COUPLING INCREASE control of number.
    the antenna tuning unit until the P.A. PLATE step 3
    meter reads 290 ma (on continuous wave) or	T x n -i -x xi	p
    \ r> x xi x • -ix	Install a coil unit of the proper frequency.
    250 ma (on voice). Reset the tuning inductor	J
    crank for maximum indication of the AN- STEP 4
    TENNA CURRENT METER.	Close the cover doors. Set the C.W.-PHONE
    Note. When the difference in frequency is small, switch of the transmitter at C.W. only steps 1, 2, and 4 may be necessary, though disre-
    garding the other steps is not recommended.	STEP 5
    ____________ Since the tuning unit has been tuned previously, "___________for c"w °Peration it will be necessary to tune
    |____J a	on]y the final and antenna circuits as outlined
    J '--1 in steps 22 through 31 in paragraph 47. If voice
    /m?) z-x	\ Set BAND SWITCH I operation is required, throw the C.W.-PHONE
    switch to PHONE at the completion of step 31,
    /	_____ A--------------1	paragraph 47,
    \	®	°	\	I
    \ © ©I	1	54. Presetting Tuning Units
    \ n □ o 0	J	Tuning units may be tuned one after another
    I	for m-o operation by following steps 5 through
    18002
    b.	Case 2. When the three tuning units	_
    plugged into the transmitter cover two or more 1 J 1 H~P H-"
    different frequency ranges, it is necessary to \ -----U----J (----J
    proceed as follows:	\	/TX
    r----------------7	) ®	®
    A rt AAA-------------------------------------------------------------
    /	r—L/ /© x*©
    /	/7	\ □ □ □ □
    I	I	\	\
    31	I	\	\	-——____________________________—
    /	/	TL 14839
    P	—f	\	20, paragraph 47, or for crystal-controlled op-
    I____\	eration by following steps 1 through 4, para-
    x \	/	graph 48.
    ‘ ___
    STEP 1	55. Additional Operating Instructions
    Before moving the BAND SWITCH to the de- a. When Station Is In Motion. Speak into sired channel number, open the cover door over the microphone with the lips almost touching it the coil unit and determine whether the fre- so as to exclude unwanted noises. To avoid over-
    60 modulation, readjust the gain control on the (3) Use an auxiliary transmitting antenna, speech amplifier. Use of Microphone T-30	... _	xx- x-xt
    /xx x\ • i	j j 4? j • xi	(4) Decrease the setting of the COUPLING
    (throat) is also recommended for reducing the	a n-n x , x, x x
    , n + i	•	INCREASE control on the antenna tuning unit
    ex erna oise.	until the P.A. PLATE meter reads 200 to 210
    b. During Transmission On Critical Fre-
    quency. The frequency range of 2 to 2.5 me is
    critical in damp weather and at high altitudes z'^X
    because extreme voice peaks may cause flash- / /XX
    overs. These trip the overload relay which mo-	/ / /	^^X^X
    mentarily interrupts communication until the /X/xZX
    relay is reset. If this should happen, do one of \\Xj >^4__________________________
    the following:	x N \ J	-----
    X/X O • IQI_____________________
    S'" il	‘—1
    3	0 © Q © 0
    	X—-___ ------------------------------------------------------------1--— TLI484I
    31	ma. DO NOT REDUCE BELOW 200 MA.
    CY	Under this condition less modulation is re-
    @	quired; therefore the gain control should be ad-
    __________________justed so that voice peaks do not cause swings Z_________________above 150 ma on the MODULATOR PLATE
    ©	©	meter.
    0 □ □ □
    J	c. Overload Reset Switch. If the high-volt-
    age circuits are overloaded (by excessive plate
    (1)	Switch to a more favorable operating cu’Tent plus heavy modulation) the overload frequenev	relay will trip and shut off the plate power. In
    this case, press the OVERLOAD RESET switch
    (2)	Stop the truck and transmit from a fixed on the front panel of the transmitter and proposition after unguying the antenna and insert- ceed with the transmission. If the overload pering one or two Mast Sections MS-54 to provide sists, check tuning adjustments and meter read-added height.	ings.
    Section IV.	REMOTE CONTROL OPERATION
    Note. The description of remote control operation and STEP 1
    power source operation for Radio Set SCR-399-A is	..	. . „ .	.	„„ « , k
    given below. These instructions will apply equally to	Remove the unconnected Telephone EE—8—( )
    d^t°d^e^ SCR“499-A references to the truck are	from its mounting compartment in Chest CH-
    121-A. Before leaving the truck, make sure the telephone batteries are in good condition and
    56.	Connection of Remote Stations	the screw switch is set to LB.
    A complete description of the equipment and STEP 2
    facilities provided for remote control will be Remove Junction Box JB-60-A and Key J-45 found in paragraphs 16 and 23. Follow the from Chest CH-121-A.
    steps below in connecting the remote control STEP 3
    equipment.	Remove Axle RL-27-B from Chest CH-89-A
    61
    for use with either or both Reels DR-4 which should be dismounted, as required, from Frame FM-59-A.
    STEP 4
    Carry Telephone EE-8-( ), Junction Box JB-60-A, and Key J-45 to the point where remote control is to be established.
    STEP 5
    Connect the cord of Junction Box JB-60-A at terminals Lx and L2 of Telephone EE-8-( ). STEP 6
    Insert the plug on the cord from Key J-45 into the jack on Junction Box JB-60-A.
    STEP 7
    Using Wire W-110-B from Reel DR-4, run the line between the remote station and the radio station in the truck. (If less than one full reel of wire is used, do not cut the wire, but pull out the inner end from the center of the reel.) In some cases it will be more convenient to leave reels of wire in Frame FM-59-A and pay out the wire through the fairleads in the back of the shelter.
    STEP 8
    Connect the two leads of one end of the line to the two line terminals on Junction Box JB-60-A.
    STEP 9
    Connect the leads at the other end of the line to terminals marked REMOTE TELEPHONE outside Junction Box JB-70-A. The telephone at the remote station is not connected to the telephone in the truck. Communication between these two points may be established by operating Telephone EE-8-( ) in accordance with instructions contained in TM 11-333.
    57.	Remote Voice Operation
    a.	The remote station operator may now request the radio operator at the truck to turn on the radio transmitter for voice operation and to adjust the speech-amplifier gain so that the remote station can properly modulate the transmitter. This is accomplished by following the procedure outlined in step 7, paragraph 49, and in step 4, paragraph 51. It should be noted that both telephones are on the same circuit and accordingly both share the same facilities. Therefore, the radio operator may switch in the output of either receiver so it may be heard at the remote station.
    b.	Since the transmitter cannot be operated by pressing the microphone switch when using a telephone line, the remote operator should signal the radio station operator when end of transmission is desired. The radio station operator can throw the transmitter control switch to obtain reception or shut down the station, as required.
    58.	Remote C-W Operation
    a.	If remote keying of c-w transmission is desired, the radio station operator should be instructed to place the transmitter in c-w operation and to set the REMOTE CONTROL EE-8 switch on Junction Box JB-70-A to either TELEGRAPH position. Then Key J-45 at the remote location can be used to key the transmitter.
    b.	Remote keying of the transmitter in two-way communication or net operation may be accomplished without the assistance of a radio station operator if there is an independent means of reception at the remote station.
    59,	Remote Receiver Operation
    When necessary, Chest CH-121-A with Radio Receiver BC-312-( ) may be removed from the truck to a remote point for operation. This is accomplished as follows:
    STEP 1
    Disconnect the antenna lead from the fitting at the top of the chest.
    STEP 2
    Disconnect the key cord and the main audio cord between Chest CH-121-A and Junction Box JB-70-A.
    STEP 3
    Disconnect Plug PL-114 of Cord CD-565 from Socket SO-94 on the receiver.
    STEP 4
    Disconnect the ground strap from the terminal under Chest CH-121-A.
    STEP 5
    After removing safety wires from wingnuts, loosen the turnbuckles holding Chest CH-121-A to the table frame in Shelter H0-17-A.
    STEP 6
    Remove Chest CH-121-A from the shelter.
    62
    STEP 7
    Remove Chest CH-109-A (12-volt battery) after pulling out the plug of Cord CH-659.
    STEP 8
    Remove the four legs from the top of Chest CH-120-A and one each Mast Sections MS-51, MS-52, and MS-53 from Chest CH-89-A.
    STEP 9
    Move the two chests, the legs, the mast sections, and Cover BG-143-A to the desired location. STEP 10
    Set up Chest CH-121-A on its legs. (See fig.
    13.)
    STEP 11
    Remove Cord CD-690 from Chest CH-121-A
    and connect it between Chest CH-109-A and the receiver.
    STEP 12
    Screw the mast sections together and into the fitting in the top of Chest CH-121-A.
    STEP 13
    Remove the headset from Chest CH-121-A and plug it into the PHONES jack on Radio Receiver BC-312-( ). The receiver is now ready for operation.
    STEP 14
    If the radio station is to be operated with Chest CH-109-A removed as described above, turn the switch on Rectifier RA-63-(*) to FULL CHARGE to furnish 12-volt power for relays.
    Section V.	POWER SOURCE OPERATION
    60.	Operation from Commercial Power Source Operation from a 117-volt, 50/60-cycle, singlephase, a-c commercial source may be effected as follows:
    a.	Plug one end of Cord CD-652 into the power plug at the rear of the truck and plug Cord CD-314 into the other end of the power plug.
    b.	Connect the leads from the other end of Cord CD-314 directly to the source of power.
    61.	Operation of Trailer 100 Feet From Truck
    a.	Disconnect the trailer power Cord CO-316 from Cord CO-335 at the bumper clamp underneath the rear of the truck. (See fig. 27.) Also disconnect the cable which delivers power to the running lights on the trailer.
    b.	Unhitch the trailer from the truck.
    c.	Drive the truck to any point up to 100 feet from the trailer.
    d.	Remove Cord CD-652 from Chest CH-119-A.
    e.	Insert one end into the plug in the bumper bracket of the truck, then insert the other end into the plug on the power cord of the trailer. Operation may now proceed normally with remote control of the power unit from the transmitter location.
    62.	Operation of Trailer 200 Feet From Truck
    a.	Proceed as in paragraph 61a and b, but drive the truck to any point within 200 feet of the trailer.
    b.	Remove Cord CD-652 from Chest CH-119-A, Cord CO-314 from the seat bench, and
    Cord CO-313 from Chest CH-112-A in the trailer.
    c.	Insert one end of Cord CD-652 into the power plug at the rear of the truck. Insert the plug of Cord CO-314 into the other end of this cord.
    d.	Twist the leads of Cord CO-314 around the terminals of Cord CO-313 and tape up these connections.
    e.	Insert the plug of Cord CO-313 into the power plug at the trailer. Operation of the power unit at distances greater than 100 feet is an emergency measure, and is not ordinarily used. Therefore it will be necessary to start or stop Power Unit PE-95-( ) at the trailer instead of at the transmitter location.
    63.	Use of Power Unit PE-95-( ) to supply power to Auxiliary Equipment
    a.	If the radio set is not in use, power may be supplied at distances up to 200 feet from Power Unit PE-95-( ) as follows:
    (1)	Remove the plug of the trailer power cord from the plug at the rear of the truck.
    (2)	Connect one end of Cord CD-652 to the trailer power cord.
    (3)	Plug Cord CO-313 into the other end of Cord CD-652. Connect the load to the terminals at the end of Cord CO—313 and start the power unit.
    b.	If Radio Set SCR-399-A or SCR-499-A must be used while the auxiliary power is being generated, proceed as follows:
    (1)	Leave the trailer connected and hitched to the truck.
    63
    (2)	Connect the terminals of Cord CO-313 to the a-c terminals on the power panel of Power Unit PE-95- ( ).
    (3)	Plug Cord CO-314 into the other end of Cord CO-313.
    (4)	Connect the bare ends of Cord CO-314 to the load. With the radio set and the heater in operation, this additional load should not exceed 1 kilowatt. If the heater is not being used, the total external load may be 2.5 kilowatts. Before operating in this manner, check the rated capacity of the power unit.
    64.	Operation of Low-voltage Power Supply System
    a.	The 12-volt battery system is used to furnish power for Radio Receiver BC-312-( ), as well as for operating the keying relay and the disabling relays.
    b.	With the BATTERY SOURCE switch on Junction Box JB-70-A at AUX. (par. 42e), the 12-volt supply is obtained from the 12-volt bat-
    EQUIPMENT PERFORMANCE CHECK LIST
    Section VI.
    65.	Purpose and Use
    a.	General. The equipment performance check list (par. 66) will help the operator determine whether Radio Set SCR-399-A or SCR-499-A is functioning properly. The check list gives the item to be checked, the conditions under which the item is checked, the normal indications and tolerances of correct operation, and the corrective measures that the operator can take. Items 1 to 28 are checked before starting, items 29 to 34 when starting, items 35 to 44 during operation, and items 45 to 49 when stopping. Items 35 to 44 on this check list should be checked at least once during a normal operating period or at least four times a day during continuous operation.
    b.	Action or Condition. For some items the information given in the action or condition column consists of the settings of various switches and controls under which the item is to be checked. For other items it represents an action that must be taken in order to check the normal indication given in the normal indication column.
    c.	Normal Indications. The normal indications listed include the visible and audible signs that the operator will perceive when he checks the items. In the case of meter readings, the allowable tolerances of the readings are given. When a meter reads between the limits speci
    tery in Chest CH-109-A.
    c.	Rectifier RA-63-(*) charges the battery in Chest CH-109-A. When using this battery, turn the switch on the rectifier to TRICKLE. If the battery is low, set the switch on the rectifier at HI CHARGE.
    d.	Keep the battery fully charged at all times. Do not let the level of the electrolyte fall so low that the plates become uncovered. Check the state of charge of the battery with the hydrometer provided.
    e.	Some Power Units PE-95-( ) are provided with 12-volt terminals. With Cord CO-316 connected to these terminals, the 12-volt supply may be obtained from the power unit by setting the battery switch on Junction Box JB-70-A to PE-95.
    /. With Chest CH-121-A and Chest CH-109-A removed from the shelter as described in paragraph 59, the 12-volt supply for the radio station relays is obtained from Rectifier RA-63-(*) with its switch set at HI CHARGE.
    fied, operation can be considered satisfactory. A meter reading outside the limits given is a sign of impending trouble. If the indications are not normal, the operator should apply the recommended corrective measures.
    d.	Corrective Measures. The corrective measures listed are those that the operator can make without turning the equipment in for repairs. A reference to part five in the table indicates that the correction of the trouble cannot be effected during operation and that trouble shooting by an experienced repairman is called for. If the set is completely inoperative or if the recommended corrective measures do not yield results, trouble shooting is necessary. However, if the tactical situation requires that communication be maintained and if the set is not completely inoperative, the operator must maintain the set in operation as long as it is possible to do so.
    e.	Items 1 to 34. Items 1 to 34 should be checked each time the equipment is put into operation.
    f.	Items 35 to 38. Items 35 to 38 show correct meter readings when the transmitter is properly tuned and in operation.
    g.	Items 39 to 44. These items represent general operating characteristics of the radio set. The operator must become familiar with the characteristics of the set during normal opera
    64
    tion; he must use that knowledge as a basis for recognizing changes in audible and visible indications, such as relay clicks, sidetone, flicking of the meter needles, etc., when the set is not operating properly. By becoming familiar with the operation of the receiver, the operator will know the normal position of the VOL control. This will aid in determining the sensitivity and
    amplification of the receiver.
    h.	Items 45 to 49. Items 45 to 49 are checked whenever the station is taken out of operation. Any abnormal indications at this time are probably caused by trouble in the set and should be corrected before the next expected period of operation.
    66.	Check List
    a. Power Unit PE-95-( )
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    PREPARATORY	1	CIRCUIT BREAKER ON-OFF switch. (Main power switch if commercial power source is used)	Set at ON
    b. Junction Box JB-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    PREPARATORY	2 3 4 5 6 7 8 9 10	Transmitter control switch C.W. SIDETONE switch REMOTE CONTROL EE-8 switch Keys J-37 BATTERY SOURCE switch 1 RECEIVER OUTPUT switch Headsets HS-30-( ) RECEIVER DISABLING switches RECEIVER OUTPUT switch	Set at TRANS. OFF Set at OFF for voice transmission. Set at TO BC-312 or TO BC-342 for c-w transmission a.	Set at NORMAL unless remote control operation of transmitter is desired b.	Set at TO BC-312 TELEPHONE or TO BC-342 TELEPHONE for remote voice operation c.	Set to proper TELEGRAPH position for remote c-w operation Keys plugged in KEY jacks a.	Set at PE-95 if 12-volt supply of Power Unit PE-95-( ) is used b.	Set at AUX. if 12-volt supply in Chest CH-109-A is used Set at NORMAL Headsets plugged into proper HEADSETS jacks (one on either side of START-STOP switch) Set both switches at ON Set at NORMAL unless headsets are to be transposed
    65
    66. Check List (Con+'d)
    c. Rectifier RA-63-(*)
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    PREPARATORY	1 1	Main control switch	If 12-volt battery in chest is used, set switch at TRICKLE
    d. Radio Receivers BC-312-( ) and BC-342-( )
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    PREPARATORY	12 13 14 15	SEND-REC. switches BAND CHANGE switches FAST TUNING control C.W.-OSC. switch	Set both switches at SEND Set to correct band Set to approximate frequency required a. Set at ON for c-w reception
    e.	Radio Transmitter BC-610-E
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    	16	FILAMENT POWER switch	Set at OFF (down)
    	17	PLATE POWER switch	Set at OFF (down)
    	13	EXCITER PLATE POWER switch	Set at NORMAL (down)
    	19	HIGH VOLTAGE PROTECT switch	Set at NORMAL (down)
    	20	C.W.-PHONE switch	Set at C.W. or PHONE, as desired
    P4	21	Tuning units	Check selection of proper tuning unit
    O H P4	22	BAND SWITCH	Set to channel corresponding to desired tuning unit
    -W Ph -	23	Coil unit	Check selection of proper coil unit for frequency desired
    	24	M.O.-XTAL switch of tuning unit	a.	Set switch at M.O. for master-oscillator control b.	Set switch at XTAL for crystal-frequency control. Check selection of proper crystal holder for frequency desired
    	25	PLATE TUNING wheel	Has been set to proper reading
    66
    66. Check List (Con+'d)
    f.	Antenna Tuning Unit BC-939-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    	26	Antenna range switch	Set to desired band
    o	27	COUPLING INCREASE	Has been set to desired
    <1		knob	position
    	28	FREQUENCY crank	Crank for band being
    			used has been set to
    P4 Oh		•	desired position
    g.	Junction Box JB-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    START	29 30	START button Electric lights	Push START button to control Power Unit PE-95-( ) Turn on electric lights in Chest CH-120-A, in Chest CH-121-A, and in shelter over transmitter	Power Unit PE-95-( ) starts Normal line voltage (110-125 volts) indicated on A.C. VOLTAGE meter on Power Unit PE-95-( ) panel Lamps light up	a.	Check Cords CO-335 and CO-316 b.	Check for discharged battery in Power Unit PE-95-( ) Change lamps Check associated cords and plugs
    h.	Radio Transmitter BC-610-E
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    START	31	FILAMENT POWER switch	Set switch at ON. (Wait 1 minute for filaments to reach operating temperature. Wait 30 minutes if transmitter is damp)	a.	Green pilot lamp and PLATE TUNING dial on transmitter light b.	Red pilot lamp on Speech Amplifier BC-614-E lights c.	FIL. VOLTAGE meter reads 5 to 5.3 volts	a.	If only one lamp lights, replace the other lamp. If both lamps are out, check Fuses FSi, 2, 4, and Cord CD-763. Check that V13, V14, and Vis are firmly seated in their sockets b.	Replace lamp if lamps in a above light c.	Adjust FILAMENT VOLTAGE control
    i.	Junction Box JB-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    START	32	Transmitter control switch	a.	For c-w transmission, set at TRANS. ON b.	For voice transmission, set at TRANS. OFF	a.	Red pilot lamp on transmitter lights. Plate power relay RYi clicks b.	Red pilot lamp is out	a.	If the relay clicks but the red pilot does not light, check fuse FS3. (See ch. 5) b.	See chapter 5
    bl
    66. Check List (Cont'd)
    j. Radio Receivers BC-312-( ) and BC-342-( )
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    START	33 34	OFF-M.V.C.-A.V.C. switch VOL control	Turn toM.V.C. or A.V.C. position. (If Radio Receiver BC-312-( ) is used, set Rectifier RA-63-(*) switch at HI CHARGE) Rotate clockwise	Dial lights unless dial light switch is provided. If Radio Receiver BC-312-( ) is used, the dynamotor starts Signal or noise is heard.	Check panel fuses. Check Cords CD-565 and CD-566 and associated plugs See TM 11-850
    k. Radio Transmitter BC-610-E
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    EQUIPMENT PERFORMANCE	35 36	EXCITATION METER SWITCH P.A. PLATE meter	Key J-37 held closed or microphone press-to-talk switch operated. EXCITATION METER SWITCH set to— a. DOUBLER PLATE b. INT. AMP. GRID. c. INT. AMP. PLATE. d. P.A. GRID. a.	Voice operation; microphone press-to-talk switch operated b.	C-w operation; Key J-37 closed	a.	25 to 45 ma. b.	1 to 8 ma. c.	125 to 175 ma. d.	60 to 100 ma. a.	200 to 260 ma. b.	200 to 300 ma.	a.	If the meter does not indicate in any position, check— (1)	The installation and tuning of the tuning unit (2)	The setting of the BAND SWITCH (3)	The position of the M.O.-XTAL switch on the tuning unit b.	If the meter readings are improper, retune the transmitter, replace Vs, Vg, Vio, or Vn if necessary Retune transmitter. Check coil unit L7. Operate OVERLOAD RELAY. Check antenna coupling. Replace V6, V7, or Vie if necessary. (See ch. 5)
    I. Antenna Tuning Unit BC-939-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    EQUIPMENT PERFORMANCE	37	ANTENNA CURRENT meter	Key J-37 held closed or microphone press-to-talk switch operated. Operating frequency is— a.	2 to 8 meg. b.	8 to 12 meg. c.	12 to 18 meg.	ANTENNA CURRENT meter reads: a.	7 to 14 amp. b.	5 to 12 amp. c.	2% to 10 amp.	Check control settings, tuning, coupling, and antenna range switch. (See ch. 5)
    68
    66. Check List (Cont'd)
    m. Speech Amplifier BC-614-E
    	Item No.	Item	Action dr condition	Normal indications	Corrective measures
    EQUIPMENT PERFORMANCE	38	MODULATOR PLATE meter	Microphone press-to-talk switch operated and— a. With no modulation b. With modulation	MODULATOR PLATE meter reads— a. 35 to 50 ma. b. 200 ma on voice peaks	a.	Check fuse FSs and adjustment of MODULATOR BIAS control b.	Check gain control of CARBON MIC. 1 or DYNAMIC MIC. 2, tube V5, and fuse FS5. (See ch. 5)
    n. Junction Box J B-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    EQUIPMENT PERFORMANCE	39 40	Key J-37 (c-w operation) Microphone (voice operation)	Key operated Press-to-talk switch operated	Sidetone is heard. Relays in junction box and receiver click. P.A. PLATE, EXCITATION, and ANTENNA CURRENT meter needles flick. The receivers are disabled. Meters indicate as in items 35 to 38. Receivers are disabled	Check key cord, plug, and jack. (See ch. 5) • Check microphone cord, Amphenol plug and receptacle
    o. Receivers BC-312-( ) and BC-342-( )
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    W //	41	VOL control	Control rotated clockwise	Increased output is heard in the headset or loudspeaker	Tighten setscrew. See TM 11-850
    Ph Ph	42	Headset or loudspeaker	Set operating normally. Plug inserted completely	Signal is heard	Check plug and cable connections. Tune receiver
    Ww	43	ALIGN INPUT control	When rotated	Response varies	See TM 11-850
    Ph	44	CRYSTAL PHASING control (when provided)	When rotated	Response varies	Sec TM 11-850
    p. Junction Box JB-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    STOP	45	Transmitter control switch	Set to TRANS. OFF	Red pilot lamp goes out	See chapter 5
    69
    66. Check List (Cont'd)
    q. Radio Transmitter BC-610-E
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    STOP	46	FILAMENT POWER switch	Set to OFF	a.	Green pilot lamp and PLATE TUNING dial lamp go out b.	Pilot lamp on Speech Ampli her B C-614-E goes out c.	No voltage indication on FIL. VOLTAGE meter	See chapter 5
    r. Receivers BC-312-( ) and BC-342-( )
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    STOP	47	OFF-M.V.C.-A.V.C. switch	Turn to OFF position	Receiver turned off	See TM 11-850
    s. Junction Box JB-70-A
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    STOP	48	STOP button	Push red STOP button	Power Unit PE-95-( ) stops	See chapter 5
    t. Rectifier RA-63-(*)
    	Item No.	Item	Action or condition	Normal indications	Corrective measures
    STOP	49	Main control switch	Set at OFF. Check the battery with the hydrometer	1.265 specific gravity at 70° F •	Recharge the battery with Rectifier RA-63-(*). Add distilled or battery-approved water to the battery if insufficient liquid is present to obtain a reading on the hydrometer
    CHAP’rER 3
    CHAPTER 3
    PREVENTIVE MAINTENANCE
    Section I. PREVENTIVE MAINTENANCE TECHNIQUES
    67. Meaning of Preventive Maintenance
    Preventive maintenance is a systematic series of operations performed at regular intervals on equipment, when turned off, to eliminate major break-downs and unwanted interruptions in service, and to keep the equipment operating at top efficiency. To understand what is meant by preventive maintenance it is necessary to distinguish between preventive maintenance, trouble shooting, and repair. The prime function of preventive maintenance is to prevent break-downs and therefore the need for repair. On the other hand, the prime function of trouble shooting is to locate existing defects making repairs possible. The importance of preventive maintenance cannot be overemphasized. The entire system of radio communication depends on each set’s being on the air when it is needed and also upon its operating efficiency. It is vitally important that radio operators and repairmen maintain their radio sets properly.
    Note. The operations in sections I and II are considered first and second echelon (organization operators and repairmen) maintenance. Some operations in sections III and V are considered higher echelon maintenance.
    68. Description of Maintenance Techniques
    a.	General. Most of the electrical parts in Radio Sets SCR-399-A and SCR-499-A require routine preventive maintenance. Those requiring maintenance differ in the amount and kind required. Because hit-or-miss maintenance techniques cannot be applied, definite and specific instructions are needed. This section of the manual contains these specific instructions and serves as a guide for personnel assigned to perform the six basic maintenance operations, namely: FEEL, INSPECT, TIGHTEN, CLEAN, ADJUST and LUBRICATE. Throughout this manual the lettering system for the six operations will be as follows:
    F—Feel	C—Clean
    I—Inspect	A—Adjust
    T—Tighten	L—Lubricate
    The first two operations establish the need for
    the other four. The selection of operations is based on a general knowledge of field needs. For example, the dust encountered on dirt roads during cross-country travel filters into the equipment no matter how much care is taken to prevent it. Rapid changes in weather (such as heavy rain followed by blistering heat) excessive dampness, snow, and ice tend to cause corrosion of exposed surfaces and parts. Without frequent inspections and the necessary performance of tightening, cleaning, and lubricating operations, the equipment will become undependable, and subject to break-down when the equipment is most needed.
    6.	Feel. The feel operation is used most often to check rotating machinery, such as blower motors, drive motors, etc., and to determine whether electrical connections, bushings, etc., are overheated. Feeling indicates the need for lubrication or the existence of similar types of defects requiring correction. The maintenance man must become familiar with the normal operating temperatures of motors, etc., in order to recognize signs of overheating.
    Note. It is important that the feel operation be performed as soon as possible after shut-down and always before any other maintenance is done.
    c.	Inspect. Inspection is the most important operation in the preventive maintenance program. A careless observer will overlook the evidences of minor troubles. Although these defects may not interfere with the performance of the equipment, valuable time and effort can be saved if they are corrected before they lead to major break-downs. Make every effort to become thoroughly familiar with the indications of normal functioning, in order to be able to recognize the signs of a defective set. Inspection consists of carefully observing all parts of the equipment, noticing their color, placement, state of cleanliness, etc. Inspect for the following conditions:
    (1)	Overheating, as indicated by discoloration, blistering, or bulging of the parts or surface of the container; leakage of insulating
    72
    compounds; and oxidation of metal contact surfaces.
    (2)	Placement, by observing that all leads and cables are in their original positions.
    (3)	Cleanliness, by carefully examining all recesses in the units for accumulation of dust, especially between connecting terminals. Parts, connections, and joints should be free of dust, corrosion, and other foreign matter. In tropical and high-humidity locations, look for fungus growth and mildew.
    (4)	Tightness, by testing any connection or mounting which appears to be loose.
    d.	Tighten, Clean, and Adjust. These operations are self-explanatory. Specific procedures to be followed when performing them are given wherever necessary throughout this section.
    Caution: Screws, bolts, and nuts should be tightened carefully. Fittings tightened beyond the pressure for which they are designed will be damaged or broken.
    Whenever a loose connection is tightened, it should be moistureproofed and fungiproofed again by applying the varnish with a small brush. See section V for details of moistureproofing and fungiproofing.
    e.	Lubricate. Lubrication refers to the application of grease or oil to the bearings of motors or other rotating shafts. It may also mean the application of a light oil to door hinges or other sliding surfaces on the equipment.
    69.	Recommended Lubricants
    The following table lists the lubricating material necessary in servicing the equipment:
    Approved Symbol	Standard nomenclature	Specification No.
    OE 30	Oil, Engine, SAE 30	U. S. Army 2-104B
    OE 10	Oil, Engine, SAE 10	U. S. Army 2-104B
    PS	Oil, Lubricating, Preserva-
    	tive, Special	U. S. Army 2-120
    GL	Grease, Lubricating, Special Ordnance	AXS-637
    SD	Solvent, Dry-cleaning	Federal P-S-661a
    70.	Vacuum Tubes
    Note. Avoid doing work on the tubes immediately after shut-down. Severe burns may result from contact with the envelopes of hot tubes.
    a.	Inspect (I). (1) Inspect glass and metal tube envelopes, tube caps, and tube connector clips for accumulation of dirt and for corrosion. Tubes with loose plate caps, grid caps, or envelopes should be replaced if possible.
    (2)	Examine the spring clips that make contact with the grid caps for corrosion and for loss of tension. Check the condition of the wires soldered to the spring clips. The wires should be free from frayed insulation and broken strands.
    (3)	Inspect the firmness of tubes in their sockets. Make the inspection by pressing the tubes down in the sockets and testing them in that position; not by partially withdrawing the tubes and jiggling them from side to side. Movement of a tube tends to weaken the pins in the base and unnecessarily spread the contacts in the socket. It is desirable to inspect the sockets of the tubes at the time the tubes are removed.
    (4)	When it is necessary to remove a tube from its socket, especially if it is a high-power
    tube, great care must be used. Never jar a warm tube. Connections to the grid caps and plate caps must always be removed.
    b.	Tighten (T). Tighten all loose connections to the tube sockets or to the tubes. If the connections are dirty or corroded, clean before tightening. When tightening locknuts that hold the sockets to the insulated bushings, do not apply excessive pressure. Too much pressure will crack the bushings.
    c.	Clean (C). (1) Clean the tubes only if inspection shows cleaning to be necessary. Tubes operated at high voltages and with exposed plate and grid connections must be kept free of dirt and dust because of possible leakage between grid and plate terminals. Tubes operating at low voltages and not having exposed grid and plate caps do not require frequent cleaning. However, do not permit dirt to accumulate on low-voltage tubes.
    (2)	Remove dust and dirt from the glass or metal envelopes with a clean, lint-free, dry cloth. If proper care is exercised, the grid and plate caps may be cleaned with a piece of #0000 sandpaper. Wrap the paper around the cap and gently run along the surface. Excessive pres
    73
    sure is not needed; do not grip the cap tightly. Wipe with a clean dry cloth.
    (3)	When tube sockets are cleaned and the contacts are accessible, fine sandpaper may be used to remove corrosion, oxidation, and dirt.
    d.	Adjust (A). Adjust loose tube connector clips. Do not flatten tube connector clips during adjustment. Flattened clips do not make adequate contact with the surface of the tube cap. If the clip is made of thin metal, it can be adjusted by gently compressing it with the fingers. If it is made of heavy-gauge metal, suitable pressure can be applied with a pair of long-nose pliers.
    71.	Capacitors
    a.	Inspect (I). (1) Inspect the terminals of large fixed capacitors for corrosion, loose connections, cracks, and breakage. Carefully inspect the mountings to discover loose mounting screws, studs, or brackets. Examine the leads for poor insulation, for cracks, and for evidences of decay. Cut away frayed strands on the insulation. If the wire is exposed, wrap it with friction tape.
    (2)	Inspect the case of each large fixed capacitor for leaks, bulges, and discoloration.
    (3)	Inspect the plates of variable capacitors for dirt, dust, or lint. Examine the movable set of plates for signs of damage or misalignment that would cause them to touch the fixed plates during tuning. Rotate the movable plates, using the panel tuning control, and thus check for operation of the capacitor.
    b.	Tighten (T). Tighten loose terminals, mountings, and connections on the capacitors. Do not break the bushing or damage the gasket.
    c.	Clean (C). (1) Clean the cases of fixed capacitors, the insulating bushings, and connections that are dirty or corroded. The capacitor cases and bushings can usually be cleaned with a dry cloth, but if the deposit of dirt is hard to remove, moisten the cloth in a dry-cleaning solvent.
    (2	) Clean the plates of variable capacitors with a small brush, removing all dust and lint.
    72.	Resistors
    a.	Inspect (I). Inspect the coating of the vitreous-enameled resistors for signs of cracks and chipping, especially at the ends. Examine the bodies of all types of resistors for blister
    ing, discoloration, and other indications of overheating. Inspect leads and all other connections for corrosion, dirt, dust, looseness, and broken strands in the connecting wires. Check the security of all mountings. Do not attempt to move resistors with pigtail connections, because there is danger of breaking the connections at the point where they enter the body of the resistor. Such defects cannot be repaired.
    b.	Tighten (T). Tighten resistor connections and mountings whenever they are found loose. If a resistor is allowed to remain loose, vibration may break the connection or damage the body.
    c.	Clean (C). (1) Clean all carbon resistors with a small brush.
    (2	) Vitreous-enameled resistors must be kept clean to avoid leakage between the terminals. They are ordinarily wiped with a clean dry cloth. However, if the dirt deposit is unusually hard to remove, use a dry-cleaning solvent.
    (3	) Resistors with discolored bodies cannot be cleaned. Discoloration indicates that there has been overloading and overheating at some time prior to the inspection. The discoloration is probably due to circuit trouble which requires analysis and correction. Trouble-shooting procedures are described in chapter 5.
    73.	Fuses
    a.	Inspect (I). Inspect the fuse caps for evidence of burning. Any evidence of burning indicates that the fuse contact is not tight. Examine the fuses and holders for signs of corrosion, dirt, loose connections, and loss of spring clip tension.
    b.	Clean (C). Clean fuse ends and fuse clips with #0000 sandpaper; then wipe them with a clean cloth. If the fuse clips are burned and pitted, use a fine file to dress the clips properly, and finish with emery cloth to leave a smooth surface. Be sure to remove all traces of emery dust because emery dust is a good conductor of electricity and may cause short circuits.
    c.	Tighten (T). Tighten all loose wire connections to the fuses. Make certain that all connections are clean before tightening.
    d.	Adjust (A). Adjust the spring tension on the fuse clips if necessary. Use a pair of long-nose pliers for this operation. Do not flatten the clip while adjusting because a flattened clip makes poor contact.
    74
    74.	Bushings and Insulators
    a.	Description. (1) Insulated bushings are used in the high-voltage and r-f circuits. They are constructed of ceramic material with a glazed surface. Because an insulator is no better than its surface, deposits of foreign substances on the surface will materially reduce the insulation value of the bushing. Therefore, it is very important that all bushings used in the high-voltage circuits be inspected frequently.
    (2) Insulator bushings are used as supports for high-voltage tube sockets, for high-voltage terminals of capacitors, and for tank coils. They are used as mountings for resistors in high-voltage circuits and as supports for panels which mount other parts. The condition of insulator bushings that are used solely as panel supports is not critical, but the condition of bushings used as high-voltage insulators is extremely important.
    b.	Inspect (I). Inspect the physical condition of the insulator bushings. They should be clean and free from cracks or chips. It is possible for a highly glazed insulator to develop fine-line surface cracks where moisture and dust will accumulate and eventually form a leakage for a high-voltage flash-over. Consequently, the surface of the bushings must be inspected to detect such cracks. As a rule, the bushings are held in position with nuts screwed onto the threaded conductors. These bushings can be replaced very easily by unscrewing the nuts. If replacement is not possible because of a shortage of supplies, frequently clean the defective bushing thoroughly with dry-cleaning solvent. Sometimes it is difficult to see dust on a glazed surface. A satisfactory check can be made by sliding a clean finger across the bushing.
    c.	Tighten (T). The procedure to be used in tightening loose bushings is self-evident. However, one precaution must be observed. Do not force the nuts or screws down too fight. Excessive pressure exerted on the bushings will cause damage. If the threads on bushing stud bolts are found stripped so that they cannot be tightened, replace the entire bushing.
    d.	Clean (C). Insulating bushings are easily cleaned. Never use abrasive materials because the glazed finish will be destroyed. A clean cloth is usually satisfactory. If deposits of grime or dirt on the surface of a bushing are hard to remove, use dry-cleaning solvent. After the sur
    face has been cleaned with a solvent, it should be carefully polished with a clean dry cloth. Otherwise, a thin film of the solvent will be left which will impair the effectiveness of the bushing as a high-voltage insulator.
    75.	Relays
    a.	General. Relays normally require very little attention. Extreme care should be used during all operations of preventive maintenance; otherwise, these same operations may result in trouble that would not have existed if the relay had not been tampered with.
    b.	Inspect (I). Inspect the mechanical action of the relays to make certain that when the moving and stationary contacts come together they make positive contact and are directly in line with each other. Inspect the contacts for dust that may result in poor contact or arcing. Do not mistake the brown stain often found on silver contacts for corrosion. This brown stain is silver oxide and is a good conductor.
    c.	Tighten (T). Tighten all loose connections and mounting screws, but do not apply enough force to damage the screw or to break the parts it holds.
    d.	Clean (C). Brush the exterior of the relay with a soft brush to remove dust. If inspection shows that the contacts require cleaning, clean them with a strip of white paper placed between the contacts. Close the contacts on the paper just enough to grip the paper snugly, and draw the paper between the contacts. Dry-cleaning solvent may be used on the paper if corrosion is present or if dirt deposits are not readily removed with the dry paper. If the contacts are burned or pitted, they may be dressed down with a fine file followed with a burnishing tool and crocus cloth.
    e.	Adjust (A). Adjust the contacts of the relays only if they do not close evenly and securely. Too frequent adjustment of the relays usually results in equipment failure.
    76.	Switches
    a.	Inspect (I). (1) Inspect the mechanical action of each switch and, while doing so, look for signs of dirt or corrosion on all exposed elements. In some cases, examine the elements of the switch visually; in others, check the action of the switch by flipping the control knob or toggle, or press the switch button and note the
    75
    freedom of movement and the amount of spring tension.
    (2) Examine the ganged multiple-section switches to see whether they are properly lubricated and whether the contacts are clean. The inspection is visual. Do not pry the leaves of the switch apart. The rotary members should make good contact with the stationary members; and as the former slides into the latter, a spreading of the stationary contact leaves should be noticeable. The switch action should be free. The wiping action of the contacts usually removes any dirt at the point of contact.
    b.	Clean (C). With a small brush, clean dust and dirt from all switches. Be very careful while brushing around exposed contacts.
    c.	Lubricate (L). If necessary, lubricate the bearing surfaces of the multiple-section switches (such as the BAND SWITCH on Radio Transmitter BC—610-E and the antenna band switch on Antenna Tuning Unit BC-939-A). Apply only a thin film of special lubricating preservation oil (PS). Do not permit excess oil to run down onto wires or other parts.
    77.	Coils
    a.	Inspect (I). Inspect all coils for dirt, poor connections, and damaged insulation. The coil forms supporting the transmitter coils should be inspected for cracks in the insulation and loose joints in the insulation supporting the coil windings. Examine the pins of the plug-in coils for damaged or defective pins. See that the pins maintain the necessary spring action to insure good contact in the pin sockets.
    b.	Tighten (T). Tighten all loose connections on coils, after first making certain that the connection is free of dirt or corrosion. Recement loose joints in the insulation supporting the coil windings. Tighten the nuts supporting the pins in plug-in coils, if the pins are found to be loose. Do not exert excessive pressure while tightening these nuts; excessive pressure will crack the supporting insulator.
    c.	Clean (C). Clean the coil form and coil with a soft brush. Remember that the ceramic coil form is actually performing the function of a high-voltage insulator, hence the same preventive maintenance applies to the coil form as to high-voltage insulators and bushings.
    78.	Rheostats and Potentiometers
    a.	INSPECT (I). Inspect all rheostats and po
    tentiometers for cleanliness and mechanical action. Potentiometers which are protected with dust covers should be inspected externally only. Do not remove the dust covers. Look for loose connections and loose mounting nuts. Examine the sliding arm of exposed rheostats and potentiometers for firm contact with the resistance element. Look for corrosion on the contact of the sliding arm.
    b.	Tighten (T). Tighten any loose connections or mounting nuts.
    c.	Clean (C). Use a soft brush to clean dust and dirt from the exposed resistance elements and sliding arms. Use crocus cloth to remove corrosion from the contact surface of exposed, wire-wound resistance elements, and from the contact surface of the sliding arm of exposed rheostats and potentiometers.
    d.	Adjust (A). If inspection reveals that the sliding arm is not making adequate contact with the resistance element, increase the spring tension. Any adjustment to the spring tension should be made with extreme caution to avoid damaging the control.
    79.	Terminal Blocks
    a.	Inspect (I). Inspect the terminal blocks for cracks, breakage, dirt, and loose connections or mounting screws.
    b.	Tighten (T). Tighten loose screws, lugs, and mounting bolts. When tightening screws, be sure to select a screw driver of correct size. Do not exert too much pressure.
    c.	Clean (C). Remove all dust and dirt from the terminal blocks with a small brush. Remove corrosion from connections with #0000 sandpaper.
    80.	Multiple Connectors
    a.	Inspect (I). Inspect the exterior of all multiple connectors, male and female, for dust, dirt, corrosion, or damaged pins. Look for traces of moisture on the insulated portion of the connector. Inspect the interior of the connectors for loose connections and broken strands of wire to the various pins. Loose strands should be soldered in place. If the insulation on each wire connected to the pins does not extend entirely to the pin, wrap the bare wire with friction tape to prevent short circuits.
    b.	Clean (C). Remove all dust and dirt from the exterior and interior of the connectors. Wipe the moisture out with a clean dry cloth. In tropical areas, the insulated portion of the connector
    76
    will mold rapidly if moisture is not removed at frequent intervals. Light mold may be removed by wiping with a clean dry cloth. If mold is excessive, use a cloth dampened with dry-cleaning solvent. Use #0000 sandpaper for removing corrosion from metal parts of the connector.
    81.	Cords and Cables
    a.	Inspect (I). Inspect the cables for cracked or deteriorated insulation, frayed or cut insulation at the connecting and supporting points, and improper placement which puts the cables or connections under strain. Watch for kinks which will damage the wires within the cable. Examine for oil or grease on the rubber insulation. Oil or grease causes rapid deterioration of rubber.
    b.	Tighten (T). Tighten loose cable clamps, coupling rings, and cable connections.
    c.	Clean (C). Remove all dust, dirt, oil, grease, and foreign matter from all cables and cords. Dirt often hides defects in the cable insulation. These hidden defects may result in equipment failure.
    82.	Meters
    a.	Inspect (I). Inspect the connections for loose, dirty, or corroded connections. Look for cracked meter glass. Inspect for loose meter mounting screws.
    b.	Tighten (T). Tighten all loose connections to the meter. Make certain that connections are clean before they are tightened. Tighten the meter mounting screws if necessary.
    c.	Clean (C). Clean the entire exterior of the meter with a clean dry cloth. Clean cor-rodded connections with #0000 sandpaper.
    d.	Adjust (A). Meters normally register zero when the equipment is turned off. Occasionally a meter will become out of adjustment and require adjustment. Before adjusting, however, a test should be made to determine whether the meter has acquired a charge of static electricity as a result of cleaning the meter glass with a dry cloth. Such a static charge will cause a meter movement to register above (or below) zero reading with the equipment shut off. To test the meter for static charge, dampen the fingers of one hand and place the little finger firmly on a screw head or other metal part of the component to place the body at a chassis ground potential. Brush the
    dampened thumb slowly across the face of the meter glass. The static charge should drain off, releasing the meter movement so that the meter will register zero. In some cases this discharge is not effected, but the meter needle deflection will vary during the time that the thumb is brushed over the glass if a static charge is present. In this case, allow the meter to remain idle for 5 minutes to allow a natural drain. If the meter movement is not affected in any way by the above test, no static charge is present. To adjust the movement, use a small thin-blade screw driver in the adjustment screw in the lower edge of the meter face. Rotate the screw to the right or left as required to bring the needle to zero.
    83.	Pilot Lamps
    a.	Inspect (I). Inspect the pilot lamp assembly for loose lamps, loose mounting screws, and loose, dirty, or corroded connections. If a pilot lamp is found with a loose glass envelope, replace the lamp.
    b.	Tighten (T). Tighten loose mounting screws and resolder loose connections. If the connections are dirty or corroded, clean before soldering. Tighten loose lamps in their sockets.
    84.	Jacks
    a.	Inspect (I). Although jacks require very little attention, inspect them periodically for cleanliness and tightness. Insert the proper plug in the jack and note the action of the jack. Contact to the plug should be secure.
    b.	Tighten (T). Tighten the mounting nut or screws on all jacks, if they are found to be loose.
    c.	Clean (C). Clean the jacks thoroughly with a stiff brush. If the contacts on the jacks are corroded, clean them with crocus cloth.
    d.	Adjust (A). Adjust the spring contact of the jacks only if inspection shows that the jacks are not making firm contact with the plugs. Bend the spring contact with a pair of long-nose pliers. Check the action of the jack with a plug after each adjustment.
    85.	Dynamotors and Motors
    a.	Inspect (I). Inspect for dust and dirt around the commutator and brushes. Inspect the brushes for wear and signs of arcing. Check the tension of the brush springs. Look for poor connections at the brushes as well as at the plug.
    77
    b.	Feel (F). Feel the bearings as soon as possible after shut-down of the equipment, to determine whether the bearings are running hot. Become accustomed to the amount of heat to expect at the bearings under normal conditions.
    c.	Tighten (T). Tighten the mounting bolts securing the dynamotor or motor. Tighten any loose connections at the brushes or plugs.
    d.	Clean (C). Use a dry clean cloth to remove dust and dirt from the exterior of all dynamotors and motors. If heavy dirt deposits are not readily removed, use dry-cleaning solvent on a clean cloth. Use an air stream from an air compressor to blow the dust out of the interior of motors if dry compressed air is available. Use a soft brush to remove the dust if dry compressed air is not available.
    e.	Lubricate (L). Lubricate the ventilating fan air-control plate screw sparingly with oil. Lubricate the ventilating fan motor bearings and the heater fan motor bearings with oil as follows:
    (1	) Temperatures above -[-32° F. Use engine oil SAE 30 (OE 30).
    (2	) Temperatures from	t° 0° F-
    Use engine oil SAE 10 (OE 10).
    (3	) Temperatures below 0° F. Use special preservative lubricating oil (PS).
    86.	Cabinets, Chassis, and Mountings
    a.	Inspect (I). Inspect all cabinets and chests for cleanliness. Examine all chassis and mountings for loose screws, dirt, and corrosion or rust. Check all panels for loose knobs.
    b.	Tighten (T). Tighten all loose mounting screws, loose chassis screws and bolts, and all loose knobs or handles. Tighten all wingnuts and turnbuckles which secure the various components to their mountings or the mountings to the shelter.
    c.	Clean (C). Wipe all dust and dirt from the exterior and interior of the cabinets and chests. Brush out the dust and dirt from the chassis and mountings. Use dry-cleaning solvent on a clean cloth to remove stubborn accumulations of dirt. Use #0000 sandpaper to remove corrosion and rust. Cover all bare spots on metal surfaces with touch-up paint.
    d.	Lubricate (L). Lubricate the hinges on chests, the threads on turnbuckles, and the threads on wingnuts with a light oil (special preservative lubricating oil (PS)).
    87.	Headsets, Microphones, Keys, and Loudspeakers
    a.	Inspect (I). Inspect all external surfaces for dirt and corrosion. See that all cord connections are tight and that plugs and jacks fit together properly. Inspect the key for proper operation.
    b.	Clean (C). Wipe the dust and dirt from all external surfaces with a clean dry cloth. Use crocus cloth for removing corrosion from the connecting plugs.
    c.	Lubricate (L). Lubricate all key bearings with light oil (special preservative lubricating oil (PS)), if needed.
    88.	Couplings and Control Shafts
    a.	Inspect (I). Inspect couplings and control shafts for tightness and cleanliness. If the setscrews securing the couplings and control shafts are loose, the switches or capacitors connected to the shafts wrill not rotate through the correct arc, and inaccuracy will result.
    b.	Tighten (T). Tighten all setscrews securing the couplings and control shafts.
    c.	Lubricate (L). Lubricate bearings of capacitor shafts (front and rear) and tuningcontrol shaft bearings with 1 or 2 drops of oil. For temperatures above 0° F., use engine oil SAE 10 (OE 10). For temperatures below 0° F., use special preservative lubricating oil (PS). Lubricate the following points on Antenna Tuning Unit BC-939-A with special lubricating grease (GL) :
    (1)	Antenna high-frequency loading coil contact roller shaft.
    (2)	Antenna coupling adjustment coil contact roller shaft.
    (3)	Antenna coupling adjustment control bevel pinions.
    (4)	Antenna high-frequency tuning control bevel pinions.
    (5)	Antenna low-frequency tuning control bevel pinions.
    89.	Gears
    a.	Inspect (I). Inspect the teeth of the gears on the tuning-capacitor drive mechanism for cleanliness and freedom of operation.
    b.	Clean (C). Remove all dust and dirt with a small brush. If dirt accumulation is great, use a brush dipped in dry-cleaning solvent.
    90.	Antennas
    a.	Inspect (I). Inspect antenna mast sec
    78
    tions for cleanliness and tightness of joints. Examine antenna insulators for cracks, chips, and dirt. Examine antenna lead-in wires for poor connection, kinks, frayed insulation, and dirty connections.
    b.	Tighten (T). Tighten all mounting bolts supporting the antenna mounting bracket. Tighten loose antenna mast sections.
    c.	Clean (C). Wipe all dust and dirt from the antenna mast sections and insulators with a clean dry cloth. If dirt accumulations are difficult to remove, use dry-cleaning solvent on the cloth. If dry-cleaning solvent is used as a cleaning agent, wipe the antenna insulators with a clean dry cloth. Use #0000 sandpaper to remove corrosion from antenna connections. Use #0000 sandpaper to remove corrosion or rust spots on the antenna mast sections. Cover any bare metal spots with touch-up paint.
    91.	Reels
    a.	Inspect (I), Inspect reels for dirt, rust,
    and corrosion. Check to see that the reel operates freely.
    b.	Clean (C). Remove all dirt from reels with a stiff brush. If rust or corrosion is present, use #0000 sandpaper to remove these spots. Repaint, if necessary, with touch-up paint.
    c.	Lubricate (L). Lubricate the bearings of the fixed handle of reel hand Axle RL-27, by applying lubricant liberally at the opening between the shaft and the inner end of the handle. To lubricate the handle bearings and lock, remove the handle, clean the lock and flush out the bearings, then relubricate. Clean dirt from the handle shaft before replacing the handle. The correct lubricants to use are:
    (1)	Temperatures above -\-S2° F. Use engine oilSAE 30 (OE 30).
    (2)	Temperatures from -j-32° F., to 0° F. Use engine oil SAE 10 (OE 10).
    (3)	Temperatures below 0° F. Use special preservative lubricating oil (PS).
    Section II. ITEMIZED PREVENTIVE MAINTENANCE
    92.	General
    For ease and efficiency of performance, it is suggested that preventive maintenance on Radio Sets SCR-399-A and SCR-499-A be broken down into operations that can be performed at different time intervals. In this section the preventive maintenance work to be performed on the radio set at specified time intervals is broken down into units of work called items. The general techniques involved and the application of the FITCAL operations in performing preventive maintenance on individual parts are discussed in section I. These general instructions are not repeated in this section. When performing preventive maintenance, see section I if more information is required for the following items. All work is to be performed with the power removed from the equipment. After preventive maintenance has been performed, the equipment should be put into operation and checked for satisfactory performance. (See check list, par. 66.)
    93.	Common Materials Needed
    The following materials will be needed in performing preventive maintenance:
    Common hand tools (TE-41 or equivalent)
    Clean cloth
    #0000 sandpaper
    Crocus cloth
    Fine file or relay burnishing tool Dry-cleaning solvent (SD) Small soft brush
    Small stiff brush
    Small inspection mirror
    Note. Leaded gasoline will not be recommended as a cleaning fluid for any purpose. Dry-cleaning solvent (SD), a cleaning fluid, is available through established supply channels. Oil, Fuel, Diesel, U. S. Army Specification 2-102B, may be used for cleaning purposes when dry-cleaning solvent is not at hand. Since unleaded gasoline is available only in limited quantities, and only in certain locations, it should be used for cleaning purposes only when no other agent is suitable. Carbon tetrachloride, or fire-extinguishing liquid (carbon tetrachloride base), may be used if necessary, but only on contact parts of electronic equipment.
    94.	Item I. Exterior of Radio Sets SCR-399-A and SCR-499-A
    OPERATIONS
    I T C	L	Cabinets and mountings
    I T C	Control knobs
    I T	Pilot lamps
    REMARKS: Maintenance operations in item 1 do not require the removal of the chassis from their cabinets. Pilot lamp connections inside the cabinets will be handled with items 7 and 9.
    79
    95.	Item 2. Headsets, Microphones, Keys, and Loudspeakers
    OPERATIONS
    IC	Headsets
    IC	Microphones
    I C L	Keys
    IC	Loudspeakers
    REMARKS:	Check connecting cords	for breaks
    under	the insulation. Adjust keys	after	per-
    forming preventive maintenance.
    96.	Item 3. Cords, Cables, and Connectors OPERATIONS
    I T C	Cords and cables
    I T C	Multiple connectors
    REMARKS: Perform operations on external surfaces only for multiple connectors. Internal operations will be handled with items 6, 9, and 10.
    97.	Item 4. Antennas
    OPERATIONS
    I T C	Antenna mast sections
    I C	Antenna insulator
    I T C	Mounting bracket
    I T C	Antenna lead-in
    REMARKS: When equipment is used in vehicles, check the tie-down ropes and insulators for security.
    98.	Item 5. Accessories
    OPERATIONS
    I C L	Reels
    I C	Shelter	H0-17-A
    I T C L	Chests
    REMARKS: Keep all cords and cables off the floor. The shelter must be kept clean and orderly. Keep instruction books in their proper compartment when not in use.
    99.	Item 6. Interior of Radio Sets SCR-399-A and SCR-499-A
    OPERATIONS
    I T C Chassis of each main component
    I T L	Couplings and control	shafts
    IC	Gears
    I T C	Multiple connectors
    REMARKS: Disassemble multiple connectors and check for poor connections, frayed insulation, and broken strands of wire. Do not attempt to remove individual pins within the connector.
    100.	Item 7. Radio Transmitter BC-6I0-E
    OPERATIONS
    I T C A Vacuum tubes
    I T C	Capacitors
    I T C	Resistors
    I T C A	Fuses
    I T C	Bushings and insulators
    I T C A	Relays
    I C L	Switches
    I T C	Coils
    I T C A Rheostats and potentiometers
    I T C	Terminal blocks
    I T C A	Meters
    I T Pilot lamps
    REMARKS: Test the transmitter after performing preventive maintenance to be sure that all circuits are correct.
    101.	Item 8. Antenna Tuning Unit BC-939-A
    OPERATIONS
    I T C	Capacitors
    I T C	Coils
    I T C	Bushings	and insulators
    I C L	Switches
    IC	Gears
    I T L	Couplings and control shafts
    REMARKS: Test for performance after completing preventive maintenance.
    102.	Item 9. Speech Amplifier BC-6I4-E
    OPERATIONS
    I T C A	Vacuum tubes
    I T C	Capacitors
    I T C	Resistors
    I T C	Bushings and insulators
    I T C A	Potentiometers
    I T C Terminal blocks
    I T C A Meter
    I T	Pilot lamp
    I T C A	Jacks
    I T C	Multiple connectors
    103. Item 10. Junction Box JB-70-A
    OPERATIONS
    ITC	Capacitors
    ITC	Resistors
    ITC	Terminal blocks
    ITC A	Jacks
    ICL	Switches
    ITC	Multiple connectors
    80
    REMARKS: Use great care when handling the junction box when the chassis is out of its cabinet. The socket insulators break easily if the chassis is not handled properly.
    104.	Item I I. Rectifier RA-63-)*)
    OPERATIONS
    I T C A	Relay
    I T C	Terminal	block
    I C L	Switch
    REMARKS: Wipe dust, dirt, and moisture from the rectifier unit with a clean dry cloth. Tighten the mounting screws.
    105.	Item 12. Heating and Ventilating System OPERATIONS
    F I T C L Motors
    IC	Switches
    REMARKS: Examine the heating element for loose or corroded connections. Clean dust from the heating coil with a soft brush. Do not allow any inflammable material to come in contact with the heating coil.
    106.	Item 13. Auxiliary Batteries OPERATIONS
    I C	Storage batteries
    ICT	Battery connections
    REMARKS: Test the specific gravity of the storage batteries in accordance with TM 11-430.
    107.	Preventive Maintenance Check List
    a. General. The following check list is a summary of the preventive maintenance to be performed on Radio Sets SCR-399-A and SCR-499-A. Some items require preventive maintenance more frequently than others. For this reason the check list divides the preventive maintenance items into daily, weekly, and monthly tasks. This recommended frequency of operation may be varied at the discretion of the commanding officer. Similarly, the check list indicates the echelon most fitted to perform the various tasks. The echelon performing any given item may be changed at the discretion of the commanding officer.
    b. Check List
    Item No.	Operations	Item	When performed					Echelon
    			Before operation	After operation	Daily	Weekly	Monthly
    1 2 3 4 5 6 7 8 9 10 11 12 13	1 T C L 1 C L I T C I T C I T C L I T C L I T C A L I T C L I T C A I T C A L I T C A L F I T C L I T C	Exterior of Radio Sets SCR-399-A and SCR-499-A Headsets, microphones, keys, and loudspeakers Cords, cables, and connectors Antennas A c cess on es Interior of Radio Sets SCR-399-A and SCR-499-A Radio Transmitter BC-610-E Antenna Tuning Unit BC-939-A Speech Amplifier BC-614-E Junction Box JB-70-A Rectifier RA-63-(*) Heating and ventilating system Auxiliary batteries	X		X	X	X	1st 1st 1st 1st 1st 2d 2d 2d 2d 2d 2d 2d 1st
    Feel	Inspect	Tighten
    C Clean
    L Lubricate
    Section III. LUBRICATION
    Note. Lubrication orders are not required for Radio Sets SCR—399—A and SCR—499—A. All lubrication instructions on the equipment are included in section I.
    Section IV. SPECIAL TOOLS
    108.	Relay and Commutator Tools
    A number of items in preventive maintenance require work of a special and somewhat delicate nature. These include cleaning silver-plated relay contacts, removing pitted surfaces from contacts, polishing and dressing commutators
    and slip-rings, and dressing motor and generator brushes. To do the work properly, special supplies and a few specially constructed tools are needed. Most of the required materials are furnished with the radio set, but a few must be improvised.
    81
    109.	Construction of Special Relay and Commutator Tools
    Crocus-cloth, canvas, and sandpaper sticks are constructed in the following manner:
    a.	Obtain one length of wood (or suitable substitute) 1/32 inch thick, % inch wide, and 3% inches long; and three lengths of wood (or suitable substitute) 14 inch thick, 1 inch wide, and 8 inches long. Cut two pieces of crocus cloth, one piece 1 inch wide and 2i/2 inches long, and the other 1 inch wide and 5*4 inches long. Cut one piece of #0000 sandpaper and one piece of canvas, each 1 inch wide and 5© inches long.
    b.	Cement the small piece of crocus cloth to the small stick, as shown in figure 31 (A). Note that both sides of the stick are covered. Place the stick in the vise until the cement hardens. The pieces of crocus cloth which extend over the edge of the stick may be cut off with a knife. The finished product is shown in figure 31 (A).
    c.	The long, narrow pieces of crocus cloth, sandpaper, and canvas are cemented to the three long sticks, as shown in figure 31(B). Note that in this case, the fold is over one end of the stick rather than over the side. Again the vise should be used to hold the cover material flat on the stick until the cement has hardened. This finished product is shown in figure 31(B).
    I 10. Safety Shorting Stick and Jumper Wires It will be necessary for the maintenance personnel to construct a safety shorting stick and several jumper wires. The suggested method of construction is as follows:
    a. Secure a dry piece of wood or some other material which is a good electrical insulator. It should be about 15 inches long and about 1
    inch square. The latter dimension is not very important. Securely fasten a piece of copper or brass rod (or thin tubing) to one end of the stick in such a manner that the rod extends 12 inches beyond the end of the stick. The free end of the rod should be bent in the form of a small hook. Solder a piece of heavy flexible hook-up wire about 18 inches long to the metal rod at the point where it is fastened to the stick. Attach a heavy clip to the free end of the wire.
    b. The jumper wires are made from heavy flexible wire, about 18 inches long, with heavy clips attached to each end. These are intended for use as shorting links across high-voltage capacitors in components that are being repaired or cleaned.
    Section V. MOISTUREPROOFING AND FUNGIPROOFING
    III.	General
    The operation of Signal Corps equipment in tropical areas where temperature and relative humidity are extremely high requires special attention. The following items represent problems which may be encountered in operation:
    a.	Resistors, capacitors, coils, chokes, transformer windings, etc., fail.
    b.	Electrolytic action takes place in resistors,
    coils, chokes, transformer windings, etc., causing eventual break-down.
    c.	Hook-up wire and cable insulation breakdown. Fungus growth accelerates deterioration.
    d.	Moisture forms electrical leakage paths on terminal boards and insulating strips, causing flash-overs and crosstalk.
    e.	Moisture provides leakage paths between battery terminals.
    p,x- y	t ®
    (J %
    CROCUS CLOTH
    -------w-------->1 AO,,LESS
    F
    GLUE HERE /	CROCUS CLOTH
    END VIEW-I J
    GLUE HERE
    '--------8’------------ @
    2*/2'->
    ~~1	SUITABLE
    ________________X f WIDTH
    a. SANDPAPER OR GLUE HERE-^y^-A/F CROCUS CLOTH
    I	J© ,/r
    GLUE HERE-%©--^^^	TL327OI
    Figure 31. Relay and commutator tools, method of construction.
    82
    I 12. Treatment
    A moistureproofing and fungiproofing treatment has been devised which if properly applied provides a reasonable degree of protection against fungus growth, insects, corrosion, salt spray, and moisture. The treatment involves the use of a moisture- and fungi-resistant varnish applied with a spray gun or brush. See TB SIG 13, Moistureproofing and Fungiproofing Signal Corps Equipment, for a detailed description of the varnish-spray method of moistureproofing and fungiproofing and the supplies and equipment required in this treatment.
    Caution: Varnish spray may have toxic effects if inhaled. To avoid inhaling spray, use respirator if available; otherwise, fasten cheesecloth or other cloth material over nose and mouth.
    I 13. Sfep-by-Step Instructions for Treating Radio Transmitter BC-610-E
    a.	Preparation. Make all repairs and adjustments necessary for the proper operation of the equipment.
    b.	Disassembly. (1) Remove seven screws holding cover plate to back of the set; remove plate.
    (2)	Tilt the set forward, or place it on its face. Be careful not to rest it on any of the projecting dials or knobs on the front panel.
    (3)	Remove resistor R19 from its socket. This resistor is not to be treated.
    (4)	Remove Tubes VT-218 from sockets V3 and V4. These tubes are not to be treated.
    (5)	Remove capacitor C28 from its contact clips. This capacitor is not to be treated.
    (6)	Remove antenna coil unit. Antenna coils are not to be treated.
    (7)	Remove crystals from tuning units. Do not treat crystals.
    (8)	Clean all dirt, dust, rust, fungus, oil, grease, etc., from the equipment to be processed.
    c.	Masking. Cover the following .components with masking tape as shown in figures 32, 33, 34, 35, and 36.
    (1)	Interlock switch SW5, item A, figure 32.
    (2)	Contacts on socket SO6, item B, figure 32.
    Figure 32. Radio Transmitter BC-610-E—rear interior view of chassis, showing method of masking.
    Jf A	L-

    G
    B
    83
    Figure 33. Radio Transmitter BC-610-E—rear interior view of chassis, showing method of masking.
    (3)	Socket of resistor R19, item C, figure 32.
    (4)	Variable resistor R12, item D, figure 32.
    (5)	Tube socket V4, item E, figure 32.
    (6)	Contacts on four leads to Tubes VT-218, item F, figure 32.
    (7)	Relay RY3, item G, figure 32.
    (8)	Contacts of push-button switch SW12, item A, figure 33.
    (9)	Variable resistor R18, item B, figure 33.
    (10)	Tube socket V3, item C, figure 33.
    (11)	Sliding contact area of variable resistor Rn, item D, figure 33.
    (12)	Audio socket SO5, item E, figure 33.
    (13)	Wafers of BAND CHANGE switch, item A, figure 34.
    (14)	EXCITATION METER switch SW8, item B, figure 34.
    (15)	Underside of jacks which receive antenna coil, item C, figure 34.
    (16)	Relay RY4, item D, figure 34.
    Figure 3L Radio Transmitter BC-610-E—bottom interior view of r-f chassis, showing method of masking.
    D '
    /
    E '
    __A	- , ~_____b ____ c
    A	B	c	D
    84
    Figure 35. Radio Transmitter BC-610-E—top interior view of r-f chassis, showing method of masking.
    of a number of electric lamps placed inside the cabinet. It is recommended that treatment be carried out immediately after a long period of operation.
    e.	Varnishing. (1) Spray three coats of moistureproofing and fungiproofing varnish (Lacquer, Fungus-resistant, Spec. No. 71-2202 (Stock No. 6G1005.3), or equal) on all components of all three chassis on the transmitter rack, allowing a 15- to 20-minute drying period after each coat.
    (2)	Using a brush, apply the varnish to those components not reached by the spray. Make sure that all components are adequately protected by varnish.
    f.	Reassembly. (1) After the varnish is dry, remove the masking tape from all components.
    (2)	Reassemble by following instructions for disassembly in reverse order.
    (3)	Test the operation of the transmitter.
    g.	Marking. Mark the transmitter with “MFP” and the date of treatment.
    Example: MFP—27 September 1944.
    (17)	Jacks which receive antenna coil, item A, figure 35.
    (18)	Interlock switch, item B, figure 35.
    (19)	Plates of variable capacitor Ci2 and clip contacts of capacitor C28, item C, figure 35.
    (20)	Drive gears of capacitor Ci2, item D, figure 35.
    (21)	Interlock switch, item A, figure 36.
    (22)	Tuning unit crystal sockets, item B, figure 36.
    d. Drying. (1) Place the transmitter in a baking oven, and bake approximately 2 to 3 hours at 160° F.
    Caution: Do not exceed 160° F. If wax should begin to melt in any of the components, decrease the temperature and increase the baking time approximately 1 hour for each decrease of 10° F., in temperature.
    (2) If a suitable oven for drying is not available, Radio Transmitter BC-610-E may be dried by using a truck as a bake oven, by means of infrared lamps, or in an emergency, by use
    Figure 36. Radio Transmitter BC-610-E—top interior view of exciter stages, showing method of masking.
    85
    I 14. Step-by-Sfep Instructions for Treating Speech Amplifier BC-6I4-E
    a.	Preparation. Make all repairs and adjustments necessary for the proper operation of the equipment.
    b.	Disassembly. (1) Loosen four fasteners
    lustration, d. Drying. Place the speech amplifier in a baking oven and bake approximately 2 to 3 hours at 160° F.
    Caution: Do not exceed 160° F. If wax should begin to melt in any of the components, decrease the temperature and increase the baking
    Figure 37. Speech Amplifier BC-61A-E—front panel, showing method of masking.
    and remove speech amplifier from its case.
    (2) Clean all dirt, dust, rust, fungus, oil, grease, etc., from the equipment to be processed.
    c.	Masking. Cover the following components with masking tape as shown in figures 37 and 38.
    (1)	Socket SO1O3 on front panel, item A, figure 37.
    (2)	Two microphone jacks on front panel, item B, figure 37.
    (3)	KEY jack on front panel, item C, figure 37.
    (4)	Socket SO1O2 on front panel, item D, figure 37.
    (5)	Lamp socket LM101, item A, figure 38.
    (6)	Key jack J101, item B, figure 38.
    (7)	Contacts of jacks J]02 (not shown in il
    time approximately 1 hour for each decrease of 10° F., in temperature.
    e. Varnishing. (1) Spray three coats of moistureproofing and fungiproofing varnish (Lacquer, Fungus-resistant, Spec. No. 71-2202 (Stock No. 6G1005.3), or equal) on all components, allowing a 15- to 20-minute drying period after each coat.
    (2) Using a brush, apply the varnish to those components not reached by the spray. Make sure that all components are adequately protected by varnish.
    f. Reassembly. (1) After the varnish is dry, remove the masking tape from all components.
    (2) Reassemble by following the instructions for disassembly in reverse order.
    A
    C
    D
    O
    86
    Figure 38. Speech Amplifier BC-6H-E—bottom
    interior vieto of chassis, showing method of masking.
    (3) Test the operations of the speech amplifier.
    g. Marking. Mark the speech amplifier with “MFP” and the date of treatment.
    Example: MFP—27 September 1944.
    I 15. S+ep-by-Step Instructions for Treating Junction Box JB-70-A
    a.	Preparation. Make all repairs and adjustments necessary for the proper operation of the equipment.
    b.	Disassembly. (1) Loosen four fasteners and remove junction box from its case. Disconnect the four wires attached to the terminal strip on the inside rear of the junction box.
    (2) Clean all dirt, dust, rust, fungus, oil, grease, etc., from the equipment to be processed.
    c.	Masking. Cover the following components with masking tape as shown in figures 39 and 40.
    (1) Holes in case of receiver output switch SW204, item A, figure 39.
    (2) Contacts of wafer switch SW205, item B, figure 39.
    (3)	Three jacks J20i, J204, and J2n5, item C, figure 39.
    (4)	Contacts of push-button switch SW20c>, item D, figure 39.
    (5)	Contacts of transmitter receiver switch SW203, item E, figure 39.
    (6)	Three jacks J200, J202, and J203, item F, figure 39.
    (7)	Holes in case of receiver disabling switch SW 201, item G, figure 39.
    (8)	Contacts of wafer selector switch SW202, item H, figure 39.
    (9)	Holes in case of receiver disabling switch SW200, item I, figure 39.
    (10)	Socket SO205 on side of chassis, item A, figure 40.
    (11)	Socket SO209 on side of chassis, item B, figure 40.
    (12)	Six jacks on front panel, item C, figure 40.
    (13)	Twelve sockets on bottom of chassis, item D, figure 40.
    (14)	Two terminal posts on front panel, item E, figure 40.
    TL14157.
    87
    ■.;.............. ■ _____	TL 14158
    Figure 39. Junction Box JB-70-A—top interior view of chassis, showing method of masking.
    d.	Drying. Place the junction box in a baking oven and bake approximately 2 to 3 hours at 160° F.
    Caution: Do not exceed 160° F. If wax should begin to melt in any of the components, decrease the temperature and increase the baking time approximately 1 hour for each decrease of 10° F., in temperature.
    e.	Varnishing. (1) Spray three coats of moistureproofing and fungiproofing varnish (Lacquer, Fungus-resistant, Spec. No. 71-2202 (Stock No. 6G1005.3), or equal) on all components, allowing a 15- to 20-minute drying period after each coat.
    (2)	Using a brush, apply the varnish to those components not reached by the spray. Make
    sure that all components are adequately protected by varnish.
    f.	Reassembly (1) After the varnish is dry, remove the masking tape from all components.
    (2)	Reassemble by following the instructions for disassembly in reverse order.
    (3)	Test the operation of the junction box.
    g.	Marking. Mark the junction box with “MFP” and the date of the treatment.
    Example: MFP—27 September 1944.
    I 16. Instructions for Treating Radio Receivers BC-3 12—( ) and BC-342-( )
    For instructions for moistureproofing and fungiproofing Radio Receivers BC-312-( ) and BC-342-( ) see C 1, TM 11-850.
    ABC	DEF	G H |
    88
    Figure Jf.0. Junction Box JB—70—A—bottom view of chassis and front panel, showing method of masking.
    B
    A	\
    «	.. v
    G
    D
    E
    chapter 4
    JSXBJ®
    CHAPTER 4
    AUXILIARY EQUIPMENT
    Section I. FREQUENCY CONVERSION KIT MC-509
    I 17. Description
    a.	Frequency Conversion Kit MC-509 is used to extend the transmitter frequency range of Radio Sets SCR-399-A and SCR-499-A to cover the additional range of 1.0 to 2.0 me.
    b.	The component parts of Frequency Conversion Kit MC-509 are:
    1 Chest CH-251
    3 Tuning Units TU-61 (range 1.5 to 2.0 me)
    3 Tuning Units TU-62 (range 1.0 to 1.5 me)
    2 Coil Units C-454 (range 1.5 to 2.0 me)
    2 Coil Units C-455 (range 1.0 to 1.5 me) 2 vacuum capacitors, 100-mmf
    2 vacuum capacitors, 50-mmf
    1 Antenna AN-168, long wire
    7 Mast Sections MS-44
    1	Mast Base MP-19
    2	Guy Plates MP-20
    6	Stakes GP-2
    1 Guy GY-24-A (halyard)
    4 Guys GY-22-A (2 in use, 2 spares)
    1 Roll BG-176, antenna
    1 BagBG-102-( ) antenna accessories
    1 Wire W-128, 2-foot
    1 bag of hardware, including:
    1 lug, solder (with %-inch hole)
    1 lug, solder (with 8-32 machinescrew hole)
    1 screw, machine, 8-32 x 1% inches long
    1 lockwasher, 8-32
    1 nut, hexagonal, 8-32
    I 18. Installation on Antenna Tuning Unit BC-939-A
    Antenna Tuning Unit BC-939-A may be modified by the use of Frequency Conversion Kit MC-509 to allow operation of Radio Sets SCR-399-A and SCR-499-A on frequencies from 1.0 to 2.0 me. To install, refer to figure 41 and proceed as follows:
    TO MAST BASE MP-47-1 )--J
    2-IOMC	/
    I Pl!I y6 r----------------X/ °
    I <—>	°--------1
    |	1 Y, (	' k | _
    ।	--------pX
    f i'I;/ I <-->	-^VACUUM^r
    I	' ~l <-----'	CAPACITOR \	7
    i	u.	[	1 <—>
    i	<	I	II
    1	§	|	;	<—;
    I	UJ	I	1	Y
    1	>	|------- 2-10
    ।	g	।____________Sa sw/9 1
    1	* I I	X / °~|	r-4—
    f I._______ xJ r=t^->
    TO BC-	\	°	/	’ ,__>
    610-C )	1---1	\ ADD THIS	/	_____)
    I__	\ WIRE	/	<
    ; Y /	(—;
    (--— F I 1	2 /	---H L44
    P ^Pl-3 Epp x x—x x x x l
    --- L5	[ M4 | antenna current
    —	METER
    | TL 13803
    Figure 41.	Modification of Antenna Tuning Unit BC-939-A.
    a.	Open the coaxial line inside Antenna Tuning Unit BC-939-A by removing the center conductor of the coaxial line from point Y. Bend this wire away from the insulator, and tape. Attach one end of a 17-inch length of Wire W-128 to point Y.
    b.	Remove the lead running from coupling coil L5 to the ANTENNA CURRENT meter M4 at terminal 1.
    c.	Attach the free end of the 17-inch length of Wire W-128 to the ANTENNA CURRENT Meter M4 at terminal 1.
    d.	Remove the lead from the high-frequency inductor coil L44 to the ANTENNA CURRENT meter M4 at terminal 2. Do not remove the other lead on this same post which runs to a contact of switch SW9tl.
    91
    92
    e.	Place the antenna range switch of An-	results, select a location away from power lines,
    tenna Tuning Unit BC-939-A in the 2-10MC	tall trees, or other obstructions. However, neces-
    position.	sity for cover will not always permit selection
    of the best location. In any case, use the best
    I 19. Erection and Installation of Antenna Mast compromise between cover and a clear antenna. The choice of location for the erection of the a. Refer to the table of approximate dial antenna is largely dependent upon tactical con- settings (table VI) and determine whether to siderations. (See par. 26.) For best operating use the 125-foot or the 75-foot antenna. Add
    MAST BASE MP-47-( )	/	\\ \	/	/	\
    MOUNTED ON ROOF OF SHELTER	/	\\ \	/	/	\
    AND CONNECTING ANTENNA TO ANTENNA	/	\\ \	/ cJ	\
    TUNING UNIT BC-939-A	/	'	\	O	/ it	\
    /	\ Jk /	/	'
    /	block---.	nn /	//
    O---------------------“-------------------------------------------center ring
    GUY GY-24-A_______ J® I) <§1	(A
    .	(HALYARD)
    GROUND DISTANCE	\	_____// ____________\	/
    ' ---------------------- 120 FT.	\\	//	\	/
    GUYING DETAIL
    FOR FREQUENCIES 1.0-15 MC, USE 125 FT
    FOR FREQUENCIES 1.5-20 MC. USE 75 FT ZGUY PLATE MP-20
    /\
    \	INSULATORS^	/	\	\
    —----,N 86	/	\	\
    MAST BASE MP-47-( )	/	\	\
    (SEE ABOVE)	nb	/	\	\
    / 1 7 MAST \ \	SECTIONS \
    V*	/	\	MS 44	\
    gLTER	/	I -	\ 35FT
    / GUY GY-24 A —J	\
    A------------------1 GUY GY- 2 2 A — -A
    /	GUY PLATE	\
    /	MP-20	\
    / \
    ScpK? । MAST BASE
    -----------------------------------------------------------------------------------------------------------------'WWiW*------------------------------------------ 20 F T---------------------------------------------------------------------------------------------------------------Tt । p3O8A
    MAST DETAIL
    Figure 42.	Installation of antenna.
    93
    a few feet to this length when locating the mast.
    b. Erect the mast as directed in paragraph 125cZ(2) through (7), (9), (10), and (11). However, since 1 Guy Plate MP-20 and 4 Guys GY-41-A are not used in this installation, note the following exceptions:
    (1) In paragraph 125cZ(2) omit 4 Guys GY-41-A, and use only two Guy Plates MP-20 instead of three.
    (2) In paragraph 125(Z (5) omit reference to Guy Plate MP-20 at the junction of the fourth and fifth sections.
    c. All necessary items for installation of the antenna mast are provided in Frequency Conversion Kit MC—509. If the %-inch screw originally supplied in Mast Base MP-47-A is no longer available, use Mast Section MS-53.
    120.	Modification of Radio Transmitter BC-6I0-E
    a.	Unsolder one end of the 700-ohm, 20-watt resistor R9 which is located adjacent to r-f choke CH4 on the under side of the p-a tank capacitor bakelite mounting panel.
    Caution: Failure to do so before operating the transmitter may result in damage to the 700-ohm resistor R9 and r-f choke CH4.
    b.	To operate on the higher frequency, re
    solder the open connection of resistor R9.
    121.	Operation of Radio Sets SCR-399-A and SCR-499-A in Frequency Range of 1.0 to 2.0 MC.
    To operate Radio Sets SCR-399-A and SCR-499-A in the frequency range of 1.0 to 2.0 me, proceed as follows:
    a.	From the table of approximate dial settings (table VI), determine the correct antenna length for the selected frequency. If a 125-foot antenna is required, connect a short jumper wire around the insulator separating the 75-foot and the 50-foot lengths of antenna wire. (See fig. 42.) If a 75-foot antenna is required, omit this jumper wire.
    b.	From the table of approximate dial settings (table VI), determine the correct tuning unit, coil unit, and p-a fixed vacuum capacitor to be used for the desired frequency. Install these units in the radio transmitter.
    c.	The exciter stages are tuned by the M.O., DOUB, and INT AMP controls on the tuning units. See paragraph 47 for procedure to be followed in tuning the exciter stages.
    d.	To tune the final amplifier stage and adjust the antenna circuit with the p-a amplifier, proceed as follows:
    Table VI. Approximate dial settings using antenna tuning unit BC-939—A
    Frequency (me)	Tuning unit				Transmitter			Antenna tuning crank 2-10MC	Antenna length (ft)
    	Tuning Unit	M.O.	DOUB	INT AMP	Coil Unit	PLATE TUNING dial	Vacuum capacitor (mmf)
    1.0	TU-62	4	3.3	1.5	C-455	33	100	13	125
    1.1	TU-62	34	4.7	3.0	C-455	78	100	20	125
    1.2	TU-62	54	6.2	5.0	C-455	37	50	28.8	125
    1.3	TU-62	69	7.4	6.9	C-455	63	50	33.6	125
    1.4	TU-62	80	8.5	7.8	C-455	86	50	38.3	125
    1.5	TU-62	90	10.0	9.0	C-455	20	0	44.2	125
    1 .5	TU-61	12	3.2	2.2	C-454	54	50	26	75
    1.6	TU-61	32	4.6	4.3	C-454	74	50	29.7	75
    1.7	TU-61	49	5.7	5.2	C-454	9	0	33.2	75
    1.8	TU-61	63	6.7	6.2	C-454	22	0	36.3	75
    1.9	TU-61	75	7.3	7.1	C-454	33	0	39.6	75
    2.0	TU-61	85	8.2	8.0	C-454	42	0	42.1	75
    (1)	Refer to the table of approximate dial settings (table VI) for approximate setting of the PLATE TUNING dial and the 2-10MC antenna tuning crank on Antenna Tuning Unit BC-939-A.
    (2)	Throw the HIGH VOLTAGE PROTECT switch to HIGH VOLTAGE PROTECT.
    Caution: Be sure that plate power is turned off when making coupling adjustments.
    (3)	Set the movable coupling link located in the tank coil (Coil Unit C-454 or C-455) at minimum coupling. Minimum coupling is obtained when the movable coil is at right angles to the tank coil.
    (4)	Set the transmitter control switch on the Junction Box JB-70-A to the TRANS. ON position.
    (5)	Place the antenna range switch of An
    94
    tenna Tuning Unit BC-939-A in the 2-10MC position.
    (6)	Depress the sending key and adjust the PLATE TUNING dial until the P.A. PLATE meter dips to minimum.
    Note. P-a tuning may differ by several divisions from the tuning charts when a vacuum capacitor is inserted across the p-a tank capacitor because of the production tolerances in manufacture of these capacitors. Precautions should be taken to see that the p-a plate current is at the minimum dip when tuning the PLATE TUNING wheel.
    (7)	Turn the 2-10MC antenna tuning crank to the approximate position indicated in table VI for the desired frequency. As this setting is approached, observe the P.A. PLATE meter for a rising plate current indication. Adjust the crank for maximum current as indicated by the P.A. PLATE meter.
    (8)	If the current indicated on the P.A. PLATE meter exceeds 110 ma, the coupling is too close and should be decreased. If the meter indicates less than 110 me, the coupling should be increased. After the coupling has been reset, readjust the PLATE TUNING dial for minimum reading of the PLATE CURRENT meter.
    (9)	Repeat the steps in (6), (7), and (8) above until maximum antenna current is obtained.
    Note. Keep in mind the 110-ma maximum allowable P.A. PLATE meter reading.
    (10)	Throw the HIGH VOLTAGE PROTECT switch to NORMAL. The P.A. PLATE meter should read approximately 290 ma.
    (11)	Carefully repeat the steps in (6), (7), and (8) above with the HIGH VOLTAGE PROTECT switch in the NORMAL position, and adjust for a reading of 290 ma on the P.A. PLATE meter. The transmitter is now ready for c-w operation. For voice operation proceed as above and then refer to paragraph 49.
    122. Theory of Equipment
    a.	General. To extend the frequency range of Radio Transmitter BC-610-E from 2.0 to 1.0 me, three factors are involved:
    (1)	A means must be provided for tuning the oscillator, buffer-doubler, and i-p-a stages over the range of 2.0 to 1.0 me.
    (2)	The p-a tank circuit must be provided with increased inductance and capacitance to tune over the required frequency range.
    (3)	The antenna must operate efficiently on frequencies from 1.0 to 2.0 me, and a means must be provided for coupling the antenna to the p-a tank circuit.
    (4)	The function of the electrical components of Frequency Conversion Kit MC-509, which make possible the extended frequency range of Radio Transmitter BC-610-E, is discussed in b, c, and d below.
    b.	Tuning Units TU-61 and TU-62. The tuning circuits for the oscillator, buffer-doubler, and i-p-a stages of the transmitter are included in plug-in tuning units. Tuning Unit TU-61 covers a frequency range of 2.0 to 1.5 me, and Tuning Unit TU-62 covers a frequency range of 1.5 to 1.0 me. The electrical parts of these tuning units perform the same functions as the electrical parts of Tuning Units TU-47 to TU-54. See chapter 5 for the functioning of these parts.
    c.	Coil Unit C-454 or C-455 and Vacuum Capacitors. The p-a plate circuit of the transmitter is tuned over a frequency range of 1.0 to 2.0 me by the use of a proper combination of Coil Unit C-454 or C-455 and vacuum capacitors of 50 mmf (micromicrofarads) or 100 mmf respectively. (See table VI.) Coil Units C-454 and C-455 are provided with variable coupling links. By varying the position of the coupling link relative to the p-a tank coil, the operator can secure the required plate power input when loading the transmitter with the antenna.
    d.	Antenna System. To secure efficient operation of the transmitter on frequencies from 1.0 to 2.0 me, a long wire antenna is used. The antenna operates as a grounded quarter-wave antenna. For frequencies from 1.0 to 1.5 me the physical length of the antenna is 125 feet, and for frequencies from 1.5 to 2.0 me the physical length is 75 feet. Electrically, these antennas are much shorter than a quarter-wavelength; therefore, tuning the antenna to resonance at the operating frequency requires the use of a variable series inductance. By making a slight wiring change in Antenna Tuning Unit BC-939-A, coil L6 is connected in series with the antenna and the variable coupling link of the p-a tank coil. Figure 43 is a schematic diagram of the p-a plate circuit and Antenna Tuning Unit BC-939-A, after the tuning unit wiring has been changed. The antenna, being shorter than a quarter-wavelength, represents a highly capacitive load to the transmitter. However, the antenna can be tuned to resonance at the operating frequency by the proper adjustment of coil L6. When the antenna is tuned to resonance, maximum r-f current is indicated by ANTENNA CURRENT meter M4 and the an
    95
    tenna presents a purely resistive load to the transmitter. The radiation resistance at the base of a quarter-wave grounded antenna is approximately 36 ohms. The purpose of the variable coupling link of the p-a tank coil is to reflect this resistance into the p-a plate circuit. The magnitude of the reflected resistance depends on the amount of mutual reactance existing between the variable coupling link and the p-a tank coil. The effect of the reflected resistance is to reduce the Q of the p-a tank circuit, and consequently, the impedance of the p-a plate circuit. When the impedance in the p-a plate circuit is lowered, the p-a tube draws more plate current. The correct setting of the variable coupling link is that setting which allows the p-a tube to draw the recommended d-c plate current.
    LONG WIRE I ANTENNA |___
    r ~i
    SWITCH
    I SWq SET AT
    I 3 Q
    2-IOMC ‘ SWQ_
    o
    COUPLING COILS	X
    C-4 54 OR C-455 I ( d
    v|6 JvT-220 "	j I
    T# I
    HIGH VOLTAGE	4 c2 LZ ANTENNA ^9.1 I
    •«----- ------ _23 55	I CURRENT
    B+	l_______________j
    -1-	c12	ZC	ANTENNA TUNING	UNIT
    r	/o	BC-939-A AFTER	WIRING
    cll #	________ g	CHANGE
    0.002 MF
    ~	TL13804
    Figure ^3._ P-a plate circuit and Antenna Tuning Unit BC-939-A—schematic diagram.
    Section II. DOUBLET ANTENNA
    123.	Purpose
    The doublet antenna is furnished for operation from a fixed location. It is used to extend the transmitting range of Radio Transmitter BC-610-E several hundred miles. Use of the doublet antenna will increase the range of communication many times over the range obtained with the whip antenna.
    124.	Description
    a.	The doublet antenna consists of a halfwave doublet antenna (cut to operating frequency by the operators of the radio set) which is fed by means of a coaxial cable. One end of the coaxial cable is connected to the center of the antenna and the other end is coupled to Radio Transmitter BC-610-E by means of a variable link coil which is part of the transmitter tank coil. Cord CD-1290 is a coaxial cable, 50 feet long, with a connector on each end. The antenna is supported by three masts, each made up of Mast Sections MS-44-A. The masts may be improvised from other materials, if necessary.
    b.	A list of components contained in the doublet antenna kit follows. There are two Quantity columns. The first quantity column indicates the number of items required for an installation where masts must be used. The second quantity* column indicates the number of
    items required for the antenna and coupling system when other means of supporting the antenna are used.
    Note. In later models the components making up the doublet antenna set are issued as part of Radio Sets SCR-399-A and SCR-499-A.
    c.	The coil units are contained in a package prepared for oversea shipment. Mast Sections MS-44-A are packed in the three canvas Rolls BG-176, seven mast sections to each roll. All of the guys, guy plates, mast bases, and stakes are packed in one Bag BG-102-( ). The remaining items, which are required for the antenna system only (column 3), are packed in the other Bag BG-102-( ).
    d.	As soon as circumstances will permit, Radio Sets SCR-399-A and SCR-499-A will be delivered with the variable link coupling tank coils listed above instead of with fixed link coupling tank coils. When the doublet antenna kit is issued for use with such sets, either the coils will be omitted from the kit or, if issued, should be returned to stock.
    125.	Location and Erection of Mast
    a.	The choice of location for the erection of the antenna is largely dependent upon tactical considerations. If possible, a location away from power lines, tall trees, or other obstructions should be selected for best operating results. Consideration of cover will not always permit
    96
    selection of the best location. In any case, use the best compromise between cover and a clear antenna. The radio set and the antenna must be so located that the cable assembly will reach from the top of the center mast to the transmitter output.
    Table VII. List of components in doublet antenna kit
    Article	Quantity
    	Complete doublet kit	Antenna system only
    Roll BG-176	3
    Bag BG-102-( )	2	1
    Mast Section MS-44-A	21
    Mast Base MP-19	3
    Guy Plate MP-20	9
    Guy GY-22-A	6
    Guy GY-41	12
    Guy GY-24-A	3	3
    Insulator IN-86-A	12	12
    Stake GP-2	18
    Reel RL-29	2	2
    Steel tape (100-foot)	1	1
    Wire W-28	250 ft	250 ft
    Cord CD-1290 (50 ft)	I1	ll
    Coil Unit C-387-D	P	P
    Coil Unit C-388-G	P	P
    Coil Unit C-389-C	I2	P
    Coil Unit C-390-C	P	P
    Coil Unit C-447-B	I2	P
    Coil Unit C-448-B	P	I2
    Coil Unit C-449-B	P	I2
    1 This cord is so designed that if additional distance between the doublet antenna and the radio set is required, several sections may be joined together until the desired length is obtained.
    2 See d below.
    b.	The doublet antenna radiates strongest in a direction at right angles (90°) to the plane of its wire. Remember this, as well as the location of the station with which communication is desired, when selecting the position of the masts.
    c.	Three masts are used to support the antenna; the center mast is used to support the weight of the coaxial-cable feeder line.
    d.	Erect the masts and install the antenna in accordance with the following procedure:
    (1) Cut the antenna wire for the lowest operating frequency to be used. This may be obtained from the formula:
    468 Antenna length in feet = ------
    F (me)
    (F(mc) is the lowest operating frequency in megacycles.) The frequency vs length curve (fig. 44) can be used to obtain the approximate antenna length. To obtain the distance separating the outer masts, add 6 or 8 feet to the length determined above. The third antenna mast is erected at the midpoint, in line with the two
    outer masts. See figure 46 for the general layout to be followed.
    (2) Select the following parts from the kit for one mast:
    7 Mast Sections MS-44-A
    6 Stakes GP-2
    3 Guy Plates MP-20
    1 Mast Base MP-19
    2 Guys GY-22-A
    1 Guy GY-24-A (antenna halyard)
    4 Guys GY-41
    (3)	At the point selected for one of the outer masts, stake Mast Base MP-19 to the ground with two Stakes GP-2. Use the hammer supplied with the radio set.
    (4)	Using a radius of 20 feet from Mast Base MP-19, drive in the remaining four Stakes GP-2, 90° apart from one another and at an angle of 45° with the antenna wire. (See fig. 45.)
    Note. When measuring off distances on the ground to determine the position of the stakes, a mast section may be used conveniently since its over-all length is 51/2 feet (5 feet NOT INCLUDING the 6-inch ferrule (smaller diameter portion)) at one end.
    (5)	Assemble the seven Mast Sections MS-44-A with one Guy Plate MP-20 at the top of the mast, another at the junction of the fourth and fifth sections, and the remaining guy plate at the junction of the first and second sections.
    (6)	Slip the bottom mast section over the mast base.
    (7)	To one hole in Guy Plate MP-20 at the top of the mast, attach the two ends of Guy GY-22-A and the block of Guy GY-24-A (halyard) by means of the snap hooks. (See fig. 45.) To the hole in the opposite end of the top guy plate, attach the two ends of the remaining Guy GY-22-A. Place all of the rings with block attached (not the center ring) over the corre-ponding Stake GP-2.
    (8)	To Guy Plate MP-20 at the junction of the fourth and fifth sections near the center of the mast, attach one end of each of the 4 Guys GY-41-A, using two snap hooks in each of the two holes. Since these guys are not used in raising the mast, temporarily tie the loose ends near the bottom of the mast to avoid tangling when the mast is raised.
    (9)	Guy GY-24-A is used as a halyard to raise and lower the antenna wire. Make sure that this guy will be on the antenna side of the mast after erection. Secure both ends of this guy to a point near the bottom of the mast to
    97
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    keep it out of the way while the mast is being raised, and also to prevent either end from accidentally getting out of reach.
    (10) The mast can now easily be raised. One man grasps the center ring of Guy GY-22-A and walks toward the base of the mast. (See fig. 46(A).) Another man assists in the erection procedure by lifting the mast from the ground
    in a manner similar to that used in raising a ladder. At the same time, a man guides the bottom of the mast onto Mast Base MP-19 until the mast is halfway erect, then quickly grasps the center ring of the remaining Guy GY-22-A (fig. 46(B)) and makes the necessary adjustment on the length of the guy when the mast is erect. When the mast has been brought into a
    98
    / A \W [Si /	' z/,z \\
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    B*GY-24-A
    GUYING DETAIL	AM
    GUY PLATE MP-20 ,6" FERRULE ABOVE PLATE	——JL--------------=-	__ ANTENNA WIRE W-28
    --------------------------------------------------------------------------- ■" ^§) © (§/-------------------------------------!>
    H	~iK|/ I '-WIRE W-28	__ \ -zQx
    f	I	‘-INSULATOR IN-86
    / X	\ Xj /
    /	- I \	\	Z<-|NSULATED COAXIAL-CABLE
    /	I \	/ TERMINATlNG BLOCK
    NOTE; MAST OF 7 SECTIONS.	/	I \	\ fej /
    EACH 5FT. LONG	/	I \	\ !§] /
    /	/	\	COAXIAL CABLE	I
    / MAST SECTION /	\	ASSEMBLY   W
    / MS-44-A	/	\
    GUY GY-22-a/	I	\
    V / JUNCTION OF I	\	DETAIL OF CENTER OF
    7 iWrlrMl 5TZ^_ _^/	\	ANTENNA AT CENTER
    / “^rrr^L \	MAST
    3 5'	/	yT / / Xv	\	MATERIALS REQUIRED TO
    /	/	l\	\	ERECT ONE MAST
    /	/ I / X	\	7 MAST SECTIONS MS-44-A
    /	/	I	\	\	4 GUYS	GY-41
    /	~	\	2 GUYS	GY-22-A
    /	/—GUY GY-24-X	\	1 GUY	GY-24-A
    /	/	I	X	\	3 GUY PLATES MP-20
    /	GUY PLATE' I	\	1 MAST BASE	MP-19
    /	MP-20 J	\	6 ^STAKES GP-2
     S) (7f	,,
    /fOy /	< APPROX 70 OHMS
    _______________)	—TL 13805
    Figure 79. Method of feeding power to the antennas.
    b.	CORD CD-1290 (50-foot). When an untuned transmission line is used to feed power to the antenna, the line must be terminated in its characteristic impedance. The characteristic impedance of coaxial-cable Cord CD-1290 is approximately 70 ohms. Therefore, an impedance match is effected by connecting the coaxialcable (Cord CD-1290) directly to the center of a half-wave doublet antenna. Cord CD-1290 is supplied in 50-foot lengths. Several lengths can be connected without materially increasing the losses in the transmission line.
    c.	Coupling Coils. The coupling coils supplied with the doublet antenna kit couple the power amplifier to the transmission line. The seven coils cover a frequency range of 2.0 to 18.0 and are provided with variable link coils. These coils take the place of the fixed link p-a tank coils normally supplied with the transmitter. The desired power output from the power amplifier is obtained by varying the degree of coupling between the p-a plate circuit and the load. This is accomplished as follows: One end of Cord CD-1290 is connected to the center of the half-wave doublet antenna, and the other end is connected to the variable link coil inside
    103
    the p-a tank coil. The transmission line, which is terminated in its characteristic impedance, represents a purely resistive load of approximately 70 ohms. (See fig. 49.) This resistance is reflected into the p-a plate tank circuit because of the mutual reactance existing between the variable link coil and the p-a tank coil. The magnitude of the reflected resistance increases or decreases as the coupling between the va
    riable link coil and the p-a tank coil is increased or decreased. The reflected resistance lowers the Q of the p-a plate tank circuit, and consequently, the impedance in the p-a plate circuit. When the impedance in the p-a plate circuit is lowered, the d-c plate current increases. The correct setting of the variable link coil is the setting which allows the p-a tube to draw the recommended d-c plate current.
    CHAPtER 5
    CHAPTER 5
    REPAIR INSTRUCTIONS
    Note. Failure or unsatisfactory performance of equipment used by Army Ground Forces and Army Service Forces will be reported on WD AGO Form 468 (Unsatisfactory Equipment Report). For particulars see paragraph 195. If Form 468 is not available, see
    TM 38-250. Failure or unsatisfactory performance of equipment used by Army Air Forces will be reported on Army Air Forces Form No. 54 (Unsatisfactory Report).
    Section I. SIMPLIFIED BLOCK DIAGRAMS
    130.	Radio Transmitter BC-6I0-E, C-W Operation (fig- 50)
    Radio Transmitter BC-610-E is a masteroscillator power-amplifier transmitter. The frequency of the transmitted signal is accurately controlled by a variable-frequency or crystal-controlled master oscillator, which is keyed for c-w operation. The output of the oscillator is fed into a buffer-doubler stage. When the variable-frequency master oscillator is used, the buffer-doubler stage operates as a frequency doubler for all frequencies up to 12 me, and as a frequency quadrupler for frequencies from 12 to 18 me. For crystal operation in the 2- to 4-mc range, the buffer-doubler stage is tuned to the crystal frequency, and operates only as a buffer amplifier; in the 4- to 12-mc range, this stage operates as a buffer-doubler; and in the 12- to 18-mc range, it operates as a frequency quadrupler. The buffer-doubler stage
    improves the frequency stability of the transmitter by isolating the oscillator stage from the i-p-a and p-a stages. The r-f output of the buffer-doubler stage is adequate to excite the i-p-a stage. In turn, the i-p-a stage develops the power necessary to drive the p-a stage. The p-a stage develops the r-f energy which is radiated from the transmitting antenna. The tuned circuits for the oscillator, buffer-doubler, and i-p-a stages are mounted in a single plug-in tuning unit. The transmitter accommodates three of these plug-in tuning units, any one of which can be selected by the BAND SWITCH. Seven plug-in tank coils and a vacuum capacitor are provided for tuning the p-a stage over the frequency range of the transmitter. The vacuum capacitor is required when operating on frequencies from 2 to 2.5 me. Antenna Tuning Unit BC-939-A couples the transmitting antenna to the output of the p-a stage.
    ____________________________________________ TRAN SM IT TINgX/^ ANTENNA
    I I- L
    I	I
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    | osc	|	UNIT
    ©t \	TWO	I N I
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    I	I
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    | RADIO TRANSMITTER BC-6I0-E	TLI4473
    _______________________________________________________1
    Figure 50. Radio Transmitter BC-610-E—simplified block diagram, c-w operation.
    105
    106
    131. Speech Amplifier BC-614-E (fig. 51)
    When in use, the remote telephone or the dynamic microphone is connected to the input of the first a-f (audio-frequency) amplifier, but the carbon microphone is connected to the input of the second a-f amplifier. This arrangement provides proper impedance matching without complicated switching arrangements. The output of the first amplifier is applied to the input of the second amplifier which in turn feeds the third a-f amplifier and the phase inverter. A portion of the a-f output of the third amplifier is applied to the modulation limiter. The modu-
    used to excite the driver stage for the modulator in Radio Transmitter BC-610-E. The c-w sidetone oscillator and the sidetone amplifier supply a sidetone signal to the headsets during c-w operation.
    132. Radio Transmitter BC-6I0-E and Speech Amplifier BC-614-E [Phone Operation] (hg- 52) The output of the speech amplifier is applied to the push-pull driver stage in Radio Transmitter BC-610-E. The power output of the driver is sufficient to operate the push-pull modulator which develops power enough to
    I	।
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    TELEPHONE EE-8-Q |	1 ST A-F AM PLIF IE R	SIDETONE
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    I VT - 231 J --r*-
    V J	I CI.RCUIT
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    '	LIMITER
    CARBON	|	'—
    _____MICROPHONE------1---------- , >	---------- Lf-	’ I
    1 'll	. (
    I 2D A-F AMPLIFIER	JAN-6SR7	SIDETONE
    __________ AMPLIFIER - I
    X \	XX\	I TO HEADSET JACKS ON
    IVT-941	IVT-94I	-(-►
    J	\______J	| JUNCTION BOX JB-7O-A
    |	JAN-6J5	‘	JAN-6J5	|
    | ------------ -------- ------------------------------------- |
    I	H	I
    !	3D A-F AMPLIFIER AND	4TH A-F AMPLIFIER ।
    PHASE INVERTER	| To RAD|0
    1	X------X	----- /-----------------\	|	TRANSMITTER
    I	( VT-231 )	-----*•--- ( VT-231 )	-‘-►BC-CIO-E
    |	X-	J	X.______y	|	DRIVER STAGE
    DUAL TRIODE	DUAL TRIODE
    JAN-6SN7GT	JAN-6SN7GT
    ;	I.
    SPEECH AMPLIFIER BC-6I4-E	j TLI4464
    Figure 51. Speech Amplifier BC-614-E—simplified block diagram.
    lation limiter produces a d-c control voltage which is applied to the second audio stage as a bias voltage which reduces the gain and prevents over-modulation of the transmitter. The outputs of the third a-f amplifier and the phase inverter are coupled to the fourth amplifier. The output voltage of the fourth amplifier is
    modulate the transmitter properly. The output of the push-pull modulator is applied to the p-a stage in which the r-f and a-f voltages are combined to produce the amplitude-modulated r-f energy that is radiated from the transmitting antenna. For a discussion of the other stage shown in figure 52, see paragraphs 130 and 131.
    Section II. THEORY OF RADIO TRANSMITTER BC-610-E
    133. Oscillator Stage
    The m-o stage develops r-f oscillations which are stable in frequency. The m-o stage can be operated as an electron-coupled variable-frequency oscillator, or as a crystal-controlled electron-coupled oscilla
    tor. (See fig. 53.) The M.O.-XTAL switch SWi5 on the tuning unit is used to select the desired type of m-o operation. For simplicity, only the variablefrequency oscillator is called the master oscillator; however, the crystal oscillator is also a master oscil-
    107
    TRANSMITTING V 7 ANTENNA	X /
    r------------------------------------------------------------.
    1	I PA
    । MO 0R	BUFFER	LT-l0d	I ANTENNA
    I CRYSTAL OSC	DOUBLER	X--/	TUNING
    ©Z X	TWO	Z	I UNIT
    —*  IVT-II51	—* 	JAN-607	-»—	(VT-220)	--!•— BC-939-A
    V Z	IN PARALLEL	y
    | JAN-6V6	JAN-6L6	Z^N	JAN-250TH |
    ' M e —
    RADIO TRANSMITTER BC-6I0-E	”
    REMOTE	। 	! _____________________________I
    TELEPHONE EE-a-0 | 1ST A-F AMPLIFIER	I
    ।	| DRIVER	MODULATOR I
    (VT-1031	I Z \	Z "X
    DYNAMIC l\.y	I (VT-95)	(VT-218)
    prx_____MICROPHONE	>--/	___________ V y	\ J
    I JAN-6SQ7	MODULATION I	---Z	----'
    CARBON I ------------------ LIMITER I	TWO	TWO
    MICROPHONE I	f \	' JAN-2A3	—w—	JAN-IOOTH I
    UJ------------------1----1	”	|--*--- IVT-233 J | IN PUSH-PULL IN PUSH-PULL
    i —I——L	O ।	I
    | 2D A-F AMPLIFIER JAN-6SR7 |	I X	f \	|
    l	O'	V7	I
    I
    I ____,________	_____________ ।
    | JAN-6J5
    #	-	l
    3D A-F AMPLIFIER AND	4TH A-F AMPLIFIER	I
    PHASE INVERTER ____PUSH-PULL	1
    /-----\	/-----X	1
    (vT-23lJ	—	(vT-23l)	I
    DUAL TRIODE	DUAL TRIODE
    I	JAN-6SN7GT	JAN-6SN7GT
    SPEECH AMPLIFIER BC-6I4-E	! TLI446S
    Figure 52. Radio Transmitter BC—610—E and Speech Amplifier BC—614—E—simplified block diagram, phone operation.
    lator in Radio Transmitter BC-610-E. The operation of both oscillators is explained in terms of the Hartley oscillator.
    a. Hartley Oscillator. For purposes of comparison, each part in the Hartley circuit (fig. 54(A)) is given the part number of the corresponding part used in Radio Transmitter BC-610-E. The functioning of the parts in the shunt-feed Hartley oscillator (fig. 54(A) ) is as follows:
    (1)	The screen grid of tube V8 (Tube JAN-6V6 (VT-107) ) acts as the anode (plate) of a triode oscillator for which the control grid and cathode form the other two triode elements.
    (2)	Inductor L8 is connected so that the turns between 1 and 2 are between the grid and cathode,
    and the turns between 2 and 3 are between the cathode and plate.
    (3)	Capacitors C3i and C36 are connected in parallel across inductor L8 so that L8 and C3i plus C36 form the resonant LC circuit. The resonant frequency can be adjusted by means of variable capacitor C3i.
    (4)	Capacitor C42 is the grid capacitor.
    (5)	Capacitor C2 blocks the d-c plate voltage from the tuned circuit and the grid, but couples r-f variations to inductor L 8.
    (6)	Choke coil CHi isolates r-f voltages on the grid.
    (7)	Resistor Ri is a grid leak and acts with the grid capacitor to provide grid bias.
    108
    C.I3 tuning unit	CRYSTAL CONTROL	i i
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    |	XTAL ]	^X-^yT-107
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    TO KEYING CIRCUIT
    Figure 53. Functional diagram of oscillator stage.
    109
    (8) Before the key is closed, the bias is zero. When the key is closed, d-c supply voltage is applied between the oscillator anode and cathode. This change of plate voltage causes a flow of energy from the anode through capacitor C2 and the plate section (2-3) of coil L8 to the cathode. This current in the plate section of L8 induces a voltage across both the plate and the grid section (1-2) of L8. The voltage induced across L8 charges capacitor C3i and C36, and the resonant circuit starts oscillating. The oscillating current in L 8 causes an r-f voltage across both sections of the coil. The voltage across the grid section (1-2) is coupled through the grid capacitor to the grid, and this voltage is the grid excitation voltage. The excitation voltage is an r-f voltage at the resonant frequency of L8, C3X, and C32. As the excitation voltage varies the grid to cathode voltage, corresponding variations of anode voltage occur and additional energy is fed back through C2 to the plate section of L8 in the resonant circuit. The energy thus fed back is sufficient to make up for the losses in the resonant circuit, so that its oscillations continue. As the grid excitation voltage swings the grid positive, capacitor C42 charges to a voltage nearly equal to the positive peak of the excitation voltage. The voltage of C42 acts as a bias voltage. Grid leak Ri prevents C42 from discharging rapidly when the excitation voltage is lower than the grid capacitor voltage. In other words, the grid capacitor and the grid leak work together to develop the bias voltage for the oscillator stage.
    b. Modified Hartley Circuit in Master Oscillator. The modified Hartley circuit of Tuning Unit TU-47 (fig. 54(B) ) operates the same as the ordinary Hartley circuit, except for the following circuit changes:
    (1)	Chokes CH2 and CH 9 are inserted between the cathode of V8 and the key.
    (2)	R35 is across CH9 and acts as a parasitic suppressor.
    (3)	Capacitor Ci is between the cathode of V8 and point 2, the junction of the plate and grid sections of L8.
    (4)	When the key is closed, the cathode is connected through the low d-c resistance of choke coils CH2 and CH9 to ground. The oscillator action is then the same as explained in a above, except that the high r-f impedance of choke coils CH2 and CH 9 forces the r-f variations at the oscillator anode to feed back through the lower r-f impedance of the cathode section (2-3) of L8. Capacitor Cx is included to keep the d-c current from flowing through the cathode section of L8, but Ci effectively connects the cathode to point 2 at radio frequencies.
    Thus in this circuit, the cathode is above ground at r-f potentials.
    v® z-4-x c42	”3
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    Figure 55. Functional diagram of buffer-doubler stage.
    135.	Buffer-Doubler Stage (fig. 55)
    The r-f signal from the oscillator is fed through blocking capacitor Ci3 to the grid of tube V 9 (Tube JAN-6L6 (VT-115)), which is operated as a Class C amplifier. The operating grid bias is developed across grid leak R23 when excitation voltage is applied to the grid. When no excitation voltage is applied to the grid, a protective bias is provided by the cathode bias resistor R24 which is bypassed by capacitor C8. This bias prevents excessive plate current through V 9 during the key-up periods of c-w transmission as well as when the grid is not properly excited because of oscillator failure. The plate-tank circuit consists of variable capacitor C32 and coil L2 0 in the tuning unit and it is connected to the plate of tube V 9 through contacts on switch SWn. The plate-tank circuit is tuned by variable capacitor C32, which is controlled from the tuning unit by a knob marked DOUB. Plate voltage is supplied by the exciter
    power supply, and is applied through coil L20, r-f choke coil CII5, and meter shunt resistor R33. Choke CH 5 offers high impedance to r-f currents, and accordingly these currents flow to ground through bypass capacitor C26 which has negligible reactance at operating frequencies. The tube receives screen-grid voltage through screen-dropping resistor R25 and meter shunt resistor R33. Bypass capacitor C4 maintains the screen grid at r-f ground potential. When switch SW8, the EXCITATION METER SWITCH, is set to DOUBLER PLATE, the EXCITATION METER Mi indicates the sum of the plate and screen currents through tube V 9. When the master oscillator is used, the buffer-doubler stage operates as a frequency doubler for all frequencies up to 12 mc; for frequencies from 12 to 18 mc, the buffer-doubler stage operates as a quadruples When the crystal oscillator is used, this stage operates as a buffer amplifier in the 2-to 4-mc
    range; as a frequency doubler in the 4- to 12-mc range; and as a quadrupler in the 12-to 18-mc range. The r-f output from the buffer-doubler tank is coupled through capacitor Ci4 to tubes Vio and Vn.
    136.	Infermedia+e-Power-Amplifier Stage (fig. 56)
    Tubes V10 and Vn (Tubes JAN-807 (VT-100) ) are connected in parallel and operated as a Class C amplifier stage. The grid bias for Class C operation is furnished by the bias power supply and applied to the grids of tubes Vio and Vn through parasitic resistors R2i and R22, r-f choke coil CH7, resistor R8, and meter shunt resistor R28. A small amount of self bias is obtained as a result of rectified gridcurrent flow through resistor R8. This feature improves the Class C operation. When switch SW 8 is set to INT. AMP. GRID, meter Mi indicates the grid current for tubes Vio and Vn. Grid excitation voltage is obtained from tube V 9 through coupling capacitor Ci4. The excitation voltage is applied to the grids of tubes Vio and Vn through parasitic resistors R2i and R22 which effectively prevent this stage from producing parasitic oscillations. The high r-f impedance of choke CH7 confines the r-f excitation voltage to the grids of Vio and Vn, thus keeping r-f energy out of the bias power-supply circuits and insuring maximum grid excitation voltage. The plate-tank circuit consists of variable capacitor C34 and coil L2e, in the tuning unit, and it is con
    nected to the plates of tubes V10 and Vn through the contacts on switch SWn. The plate-tank coil is tuned to resonance by variable capacitor C34, which is controlled by the knob marked INT AMP on the tuning unit. Plate voltage is supplied by the exciter power supply and is applied to the plates of tubes Vio and Vn through coil L26, r-f choke coil CH6, and meter shunt resistor R27. R-f energy is kept out of the power-supply circuit by the action of choke CH6 and bypass capacitor C24. The screen grids obtain voltage through screen-dropping resistors R6 and R7 and meter shunt resistor R27. Capacitors C6 and C7 are the screen grid r-f bypass capacitors. When switch SW8 is set to INT. AMP. PLATE, meter Mi indicates the total plate and screen current for tubes V10 and Vn.
    137.	Power-Amplifier Stage (fig. 57)
    The r-f output of the intermediate power amplifier is coupled through capacitor C15 to the grid of poweramplifier tube Vie. Tube Vi6 (Tube JAN-250-TH (VT-220) ) is operated as a Class C, plate-neutralized, power amplifier. The grid bias required for this class of operation is furnished by the bias power supply. It is applied to the grid of tube VX6 through r-f choke coil CH8 and meter shunt resistor R26. Choke CH8 confines the r-f excitation voltage to the grid and keeps r-f energy out of bias powersupply circuit. When switch SW 8 is set to P. A. GRID, meter Mi indicates the p-a grid current,
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    Figure 56. I-p-a amplifier stage—functional diagram.
    112
    tube Vie. The plate-tank circuit consists of variable capacitor Ci2 and p-a tank coil L7. The p-a tank circuit is tuned to resonance by the variable capacitor C12 which is controlled by the PLATE TUNING dial on the front of the transmitter. Plate voltage for tube V16 is furnished by the high-voltage power supply and is applied to the plate through P. A. PLATE meter M2, r-f choke coil CH4, and coil L7. For phone operation the secondary winding of modulation transformer T 9 is also included in the plate-voltage circuit. Meter M2 indicates the p-a plate current. Radio frequency energy is kept out of the plate power supply circuit by means of bypass capacitor Ou. The inductance of choke CH4 together with its distributed capacitance forms a parallel-resonant circuit at a frequency between 2 and 4 me. Accordingly resistor R9 is placed in parallel with choke CH4 to prevent a high oscillating current in the choke coil. An out-of-phase voltage is fed back to the grid of tube Vi6 through capacitors Ci8 and C29 to neutralize the effect of the interelectrode capacity existing between grid and plate in the p-a tube (plate neutralization). Capacitor C29 has a low reactance at the signal frequency and serves only as a d-c blocking capacitor to isolate the neutralizing capacitor C48 from the high d-c voltage of the p-a plate-tank circuit. Bypass capacitors C9 and Ci0 maintain the filament circuit of tube Vi6 at r-f ground potential, and filament meter M3 indicates the a-c voltage applied to the filament. R-f power is taken from the p-a tank circuit by means of a link inductively coupled to the tank coil, and power is fed to the antenna tuning unit through a short coaxial cable. When the transmitter is not in operation, contacts on relay RY4 short circuit the coupling link and
    detune the transmitting antenna so that it does not absorb signal energy at the frequency to which the radio receiving equipment is tuned.
    138.	Antenna Tuning Unit ( g. 58)
    Antenna Tuning Unit BC-939-A is used to match the impedance of the transmitting antenna to that of the final p-a tube plate circuit. The tuning unit is so designed that the transmitter will operate satisfactorily with a five-section rod antenna or with a long wire auxiliary antenna over a frequency range of 2.0 to 18 me. Figure 59 is a functional schematic drawing of the antenna tuning unit when it is connected to a five-section rod antenna and the antenna range switch SW9 is set to 2-10MC. Since the antenna is electrically much shorter than a quarter-wavelength, it presents a highly capacitive load to the transmitter. This capacitive antenna can be tuned to resonance by the addition of a portion of inductance L6, the low-frequency loading coil, which is made variable by a movable tap is controlled from the front panel of the tuning unit by a crank handle marked FREQUENCY 10MC— INCREASE—2MC. When the inductive reactance of coil L6 is made equal to the capacitive reactance of the antenna, the load presented to the transmitter is purely resistive. Coupling coil L5, which is link-coupled to the p-a tank coil, acts as an impedance-matching transformer so that the resistance of the antenna, as reflected back into the p-a tank circuit, presents the optimum plate-load resistance, as viewed from the plate of the p-a tube. Coil L5 is made variable by a movable tap which is controlled by a knob marked COUPLING INCREASE. Figure 60 is a functional schematic of the tuning unit connected to a five-section rod
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    Vacuum capacitor C3o is included in the circuit to provide the necessary capacitance when the reactance of the antenna is inductive because of the length of the wire and the frequency used. ANTENNA CURRENT meter M4 indicates the r-f current flowing in the series circuit which consists of the antenna and the antenna loading circuit. R-f current will be at maximum when the antenna is tuned to resonance with the transmitter frequency by means of the antenna loading circuits in the antenna tuning units.
    139.	Modulator Section
    a.	Driver Stage (fig. 62). Tubes Vi and V2 (Tubes J AN-2 A3 (VT-95) ) are operated as Class AB], a-f amplifiers connected in a push-pull circuit. The suffix 1 after AB denotes that grid current is not allowed to flow during any part of the input cycle. Plate voltage for tubes Viand V2 is furnished by the bias-voltage power supply. This power supply has the positive side of the output voltage grounded, and therefore the ungrounded side of the output voltage is approximately 360 volts negative with respect to ground. The filaments of the driver tubes are connected through resistor R20 to 360 volts negative, and the plates are connected to ground through the center tap of driver transformer T 8. This places the plates at a potential of approximately 300 volts positive with respect to the filaments. Approximately 60 volts negative grid bias is obtained as a result of the voltage drop
    across resistor R20 because of the d-c plate-current flow. The grids are connected to the negative side of resistor R20 through the center tap on input transformer T7. Resistor R20 is bypassed by capacitor C27 which has enough capacity to offer a very low reactance to all audio frequencies above approximately 50 cps (cycles per second). Its purpose is to keep the a-f voltage out of the bias power supply and to prevent degeneration of the a-f signal in self-biasing resistor R20. A-f voltage is fed to the primary winding of transformer T7 over a 500-ohm transmission line. The secondary winding of transformer T7 is connected to the grids of tubes Vi and V2; the grid circuit is completed to the filaments through the center tap on transformer T7 and resistor R20. The primary-to-secondary turns ratio of transformer T7 is such that when the secondary is loaded by resistor Ri4 and Ri5, the impedance, looking into the primary winding, is 500 ohms. This is the correct impedance to properly terminate the a-f transmission line from the speech amplifier. The driver stage is coupled to the modulator stage by transformer T 8. The secondary winding of transformer T8 is loaded by resistors Rig and R17 to provide a more constant plate-load impedance for the driver tubes.
    b.	Modulator Stage (fig. 62). Tubes V3 and V4 (Tubes JAN-100-TH (VT-218) ) are operated as a Class B push-pull modulator stage. Class B operation requires that the tubes be biased near plate current cut-off. Under this condition, the
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    Figure 62. Driver and modulator stages—functional diagram.
    TL 14462
    I 15
    plate current which flows when no signal is applied to the grids is relatively small; but when peak signal voltage is applied to the grids, the plate current may rise to several times the zero signal value. Grid bias for tubes V3 and V4 is furnished by the bias power supply, and during phone operations, is applied to the grids through contacts on relay RY3 and the secondary center tap on transformer T8. The bias voltage is set to the correct value by potentiometer R12, the MODULATOR BIAS control on the front of the transmitter. During c-w operation, potentiometer Ri2 is disconnected by contacts on relay RY3, and the total output voltage of the bias power supply is applied to the grids of tubes V3 and V4 through resistor R34. This voltage is sufficient to cause plate current cut-off. Plate voltage for the modulator stage is furnished by the high-voltage power supply, and is applied to the plates through the center tap on modulation transformer T 9. The filaments of tubes V3 and V4 are connected to ground through resistor R5 in parallel with MODULATOR PLATE meter Mi Oi. Meter Mioi is located in the speech amplifier and indicates the d-c plate current for tubes V3 and V4. If meter Mioi or the circuit to the meter becomes open, resistor R 5 provides a protective bias for tubes V3 and V4, regardless of the setting of MODULATOR BIAS control R12. In addition, it maintains the filament circuit
    of the modulator tubes and the wiring to the meter near ground potential. Under certain conditions, it may be necessary to apply plate power to the transmitter without having the speech amplifier and junction box connected. This can be done by setting PLATE POWER switch SW6 to ON; resistor R5 affords the protection described above. The a-f voltage developed across the secondary of transformer T 9 adds to and subtracts from the d-c plate voltage applied to the p-a tube. Because the r-f output voltage of a Class C amplifier is proportional to the applied plate voltage, the r-f carrier is amplitude modulated by the a-f voltage developed in the modulator stage. Transformer T9 is, in effect, loaded by a resistor whose value is equal to the d-c plate resistance of the p-a tube. Because of the impedance-transforming properties of transformer T 9, the resistance which is reflected into the primary circuit is the optimum plate-load impedance for modulator tubes V3 and V4. During c-w operation, the secondary winding of transformer T9 is short-circuited by a pair of contacts on relay RY3.
    140. Power Supplies
    a. Exciter Power Supply (fig. 63). The exciter power supply furnishes plate and screen-grid voltage for oscillator tube V8, buffer-doubler tube V9 and intermediate-amplifier tubes Vio and Vn. Fila-
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    Figure 63. Exciter power supply—functional diagram.
    116
    ment transformer T4 has three low-voltage secondary windings. They are: (1) 5.0-volt, 10.5-ampere, (2) 6.3-volt, 3.5-ampere, and (3) 5.0-volt, 3-ampere. The 5.0-volt, 10.5-ampere winding furnishes filament current for p-a tube VieJ the 6.3-volt, 3.5-ampere winding furnishes heater current for tubes V8, V9, Vio, and Vn; and the 5.0-volt, 3-ampere winding furnishes filament current for rectifier tube Via. Rectifier tube Vi2 (Tube JAN-5Z3 (VT-145)) is connected in a full-wave rectifier circuit. The
    a-c plate voltage for tube Vi2 is furnished by the high-voltage secondary winding on transformer T5. The rectified output voltage of tube Vi2 is applied to a pi-section filter consisting of filter capacitors Ci7 and Ci6 and choke Lx. R4 is in series with capacitor Ci7 to prevent key clicks due to excessive voltage surges when the transmitter is keyed. Resistor Rio is the power-supply bleeder resistor which serves to discharge the filter capacitors when the power supply is turned off.
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    Figure 64.	Bias power supply—functional diagram.
    b.	Bias Power Supply (fig. 64). The bias power supply furnishes filament and plate voltage for tubes Vi and V2, and bias voltage for tubes Vio, Vn, Vi6, V3 and V4. Transformer Tx supplies filament and plate voltage to rectifier tube V5 (Tube JAN-5Z3 (VT-145) ) which is connected as a full-wave rectifier. The rectifier output voltage is applied to a choke input pi-section filter consisting of filter chokes L2 and L3, and capacitors C20 and C2i. Resistor R11 and potentiometer Ri2 connected across the output of the power supply serve as bleeder resistors. The voltage regulation of this power supply is relatively good because of the use of a choke input filter and a high value of bleeder current. An adjustable tap is provided on resistor R11 for the purpose of adjusting the bias voltage to tubes Vio, Vn, and Vie to the correct value. Filament current for modulator tubes V3 and V4 is supplied by filament transformer T3. The function of all other parts shown in figure 64 has been described in other paragraphs.
    c.	High-voltage Power Supply (fig. 65). The high-voltage power supply furnishes d-c plate voltage for modulator tubes V3 and V4, and p-a tube V16. Tubes V6 and V7 (Tubes JAN-866A (VT-46A)) are connected in a full-wave rectifier circuit. Transformer T2 furnishes filament current to the rectifier tubes; transformer T6 furnishes the high a-c voltage to the rectifier plates. The rectified high voltage is applied to an L-section filter consisting of filter choke L4, and filter capacitors Ch9 and C23 in parallel. Resistor Ri3, the bleeder resistor, is connected across the output of the power supply and serves to discharge capacitors Ch 9 and C23 when the power is turned off. Switch SW7, the C.W.-PH0NE switch, reduces the voltage applied to the plates of the rectifier tubes during phone operation. Switch SW4 is the HIGH VOLTAGE PROTECT switch. When set to HIGH VOLTAGE PROTECT it connects resistor R19 (heater element) in series with one side of the primary of transformer T6 to reduce the output voltage of the rectifier during tune-up
    117
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    Figure 68. HIGH VOLTAGE PROTECT and PLATE POWER switches—functional diagram.
    to HIGH VOLTAGE PROTECT, it connects re- Rx9, and thus applies full voltage to the plate of the sistor Ri 9 in series with the primary winding of p-a tube. Lamp LM4 lights a red jewel above the transformer T6. Resistor Ri 9 is a 16-ohm, 600-watt switch when power is applied to high-voltage heater element and reduces the plate voltage applied transformer T6.
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    Figure 69. C.W. PHONE switch—functional diagram.
    119
    of the transmitter. When set to ON, it applies voltage to the coil of relay RYi. A pair of contacts on relay RYi applies power to the primary winding of high-voltage transformer T6.
    e. C. W. Phone Switch SW7 (fig. 69). C. W. PHONE switch SW7 is a four-pole, double-throw toggle switch located on the front panel of the transmitter. Its purpose is to select either c-w or phone operation. In the C. W. position, switch SW7 applies a-c power to only a portion of the primary winding of transformer T6. Thus full plate voltage is applied to the p-a tube. In the PHONE position, switch SW7 applies a-c power to the whole primary winding of transformer T6 and, as a result, reduced plate voltage is applied to p-a tube Vi6 and modulator tubes V3 and V4. Two poles of switch SW7 are connected in parallel to carry the primary current required by transformer T6. In the PHONE position, another pole on switch SW7 applies voltage to the coil of relay RY3. The con
    tacts on relay RY3 short-circuit the secondary winding of modulation transformer T 9, and these contacts remain closed until current flows through the coil of relay RY3. One pole on switch SW 9 is not used.
    Caution: Never throw this switch when the plate power is turned on. To do so will damage the switch, because the switch is not designed to break the primary current to high-voltage plate-power transformer T6.
    f. Band Switch SWu (fig. 70). Switch SWu is a four-section, three-position switch, controlled from the front panel of the transmitter by a knob marked BAND SWITCH. Its purpose is to provide selection of any one of three tuning units which have been set to a predetermined frequency. The switch sections are numbered (on the functional schematic diagram) SWu-i, SWu.2, SWu-3, and SWn.4. Section 1 is the section nearest the front panel of the transmitter. Switches SWu-i and
    REPRESENTATIVE TUNING UNIT
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    amplifier tubes Vio and Vn. When the switch is	interlock
    set to INT. AMP. PLATE, meter Mi is connected	I ZSWITCHES | >R
    in the plate circuit of intermediate-amplifier tubes	0SW5	4®	>I6H.
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    h.	Overload Reset Switch SWi2 (fig. 72).	K 1	K
    Switch SWi2 is a momentary push-button type of	C*	t6 o
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    The switch is normally closed; but when pressed, it A_c C0MM0N	|	|
    interrupts the energizing current through the coil	4	TL14403
    of overload reset relay RY2, which in turn operates Figure 73. Interlock switches—fzmctional diagram.
    121
    high voltages. Their purpose is to disconnect the a-c power from the primary winding of high-voltage power transformer T3. On transmitters with aerial numbers below 5191, switches SW2, SW5, SWi0, and SWi3 are connected in series with the coil of relay RYi. Beginning with serial number 5191, the interlock wiring has been changed; and switches SW2 and SWi3 are connected in series with the contacts of relay RYi, providing positive protection even though the contacts on relay RYi should freeze closed. Interlock switch SWi0 is not used on transmitters with serial numbers above 5191. Switch SW2 is located on the under side of the lefthand top cover just above the r-f tank coil. Switch SW 6 is located on the rear apron of the modulator deck of the transmitter in such a manner that the switch opens when the rear cover of the transmitter is removed. Switch SWi3 is located on the under side of the right-hand top cover and operates when the door over the tuning units is opened. On transmitters with serial numbers below 5191, switch SWio is installed in such a manner as to disconnect the a-c power from transformer T6 when the entire top section of the transmitter is removed.
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    Figure 74. Plate power relay RY,—functional diagram.
    142. Relays
    a.	Plate Power Relay RYi (fig. 74). Relay RYi is a double-pole, single-throw relay located on the modulator deck of the transmitter. Its purpose is to apply plate power to the transmitter. When the coil of relay RYX is energized, one pair of the relay contacts applies a-c power to the primary winding of the high-voltage power transformer T6 and the other pair of contacts apply a-c power to the primary winding of the exciter power-supply transformer T5.
    b.	Phone-continuous Wave Switching Relay RY3 (fig. 75). Relay RY3 is a double-pole, doublethrow relay located on the modulator deck of the transmitter. This relay operates in conjunction
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    Figure 75. Phone-continuous wave switching relay RY3—functional diagram.
    with the C.W. PHONE switch SW7 and its purpose is to select either c-w or phone operation. When switch SW7 is set to C.W., no current flows through the coil of relay RY3 and a closed pair of contacts short-circuit the secondary winding of modulation transformer T 9. When switch SW7 is set to PHONE, the coil of the relay is energized and the closed contacts which short-circuit the secondary winding of transformer T 9 are drawn apart, removing the short circuit. At the same time, another pair of contacts on relay RY3 close and these contacts apply the correct bias for Class B operation of modulator tubes V3 and V4 through potentiometer R12-
    c. Antenna Shorting Relay RY4 (fig. 76). Relay RY4 is a double-pole, double-throw relay located on the r-f deck of the transmitter near the p-a tank coil. Its purpose is to short-circuit the antenna-coupling coil of the p-a tank coil when the transmitter is not in operation. The coil of relay RY4 is connected in parallel with the coil of relay RYi; therefore both relays operate at the same time. When relay RY4 is not energized, the contacts are connected in series across the antenna-coupling coil, shorting it out. When the relay is energized, the contacts are drawn apart, removing the short circuit from across the coupling coil.
    d. Overload Protection Relays RY2 and RY5 (fig. 72). Relays RY2 and RY5 are located on the lower deck of the transmitter. They protect high-voltage rectifier tubes V6 and V7 from damage due to heavy current surges or serious overloads. All current drawn from the high-voltage power supply must pass through the coil of relay RY5 and is designed to operate the contacts when the current through the coil exceeds approximately 750 ma.
    122
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    123
    meter indicates the p-a grid current on the 0- to 150-ma scale; resistor R26 is the meter shunt resistor.
    d.	P. A. Plate Meter M2 (fig. 65). P. A. PLATE meter M2 is a 0- to 500-ma, d-c milliameter located on the front panel of the transmitter. Its purpose is to indicate the d-c plate current of p-a tube Vi6. The meter is connected in the high-voltage plate lead to tube Vi6, and is isolated from the radio frequency in the tank coil by r-f choke coil CH4 and bypass capacitor Cm
    e.	Fil. Voltage Meter M3 (fig. 66). Filament voltage meter M3 is a 0- to 10-volt a-c voltmeter
    located on the front panel of the transmitter. It indicates the filament voltage to p-a tube Vi6. The meter is connected directly across the filament winding of transformer T4 which supplies filament current to p-a tube Vi6. Since the primary windings of transformers T2, T3, and T4 are connected in parallel and receive a-c primary current through the common variable resistor Ri8, it necessarily follows that when resistor Ri8 is adjusted so that meter M3 indicates the correct voltage across the filament winding of transformer T4, the filament voltages supplied by transformers T2 and T3 will also be nearly correct.
    Section III. THEORY OF SPEECH AMPLIFIER BC-6I4-E
    144.	First A-F Amplifier (fig. 78)
    Tube Vioi (Tube JAN-6SQ7 (VT-103) ) is connected as a triode in a Class A resistance-coupled amplifier stage. Its purpose is to amplify the output of dynamic Microphone T-50 or remote Telephone EE-8-( ). The tube is self-biased as a result of the d-c voltage drop across the cathode-bias resistor Rio6- Plate voltage is furnished by the power supply in the speech amplifier, and is applied to the plate of tube Vioi through a decoupling resistor Ri28 and plate-load resistor R107. Capacitor Cm is the a-f bypass capacitor for decoupling resistor Ri28. The filter, consisting of resistor R428 and capacitor Cm, prevents feedback from succeeding stages because of coupling through the common impedance of the power supply. The network in the grid circuit, consisting of resistors R101, R102, R103, Ri04, and Rio5, is designed to properly match the impedance of either dynamic Microphone T-50 or a telephone line, the far end of which is connected to a field Telephone EE-8-( ). Microphone T-50 requires high-impedance input; Telephone EE-8-( ) requires a low-impedance input. In addition to matching impedance, the network also provides the correct attenuation of the input a-f voltage when using Microphone T-50 or field Telephone EE-8-( ). This is a necessary function because the output voltage levels of Microphone T-50 and Telephone EE-8-( ) differ considerably. Solution of the resistance network, consisting of resistors R101, R102, R103, R104, and Rios, yields the equivalent circuits shown in figure 78(A) and (B). Figure 78(A) is an equivalent circuit of the 1st a-f amplifier stage when using Microphone T-50; figure 78(B) is an equivalent circuit when using remote Telephone EE-8-( ). In either case, the a-f voltage applied to the grid of tube Vioi is, in effect, obtained from a tap on a voltage divider. When using Microphone T-50, the microphone output voltage is attenuated
    approximately 15 decibels; when using remote Telephone EE-8-( ), the degree of attenuation is approximately 20 decibels. Capacitor Ci30 is an r-f bypass capacitor to prevent high-frequency interference from affecting the amplifier when the input is connected to a telephone line. The output voltage of tube Vioi is developed across resistor Ri07 and is applied to the grid of the second a-f amplifier through audio-coupling capacitors C102 and C119.
    145.	Second A-F Amplifier (fig. 79)
    Tube V102 (Tube JAN-6J5 (VT-94)) is operated as a Class A resistance-coupled amplifier stage. Its purpose is to amplify the output of the first a-f amplifier tube Vioi and to amplify the output of a carbon microphone when one is used. Bias voltage is provided partly by the modulation limiter and partly from the self-biasing action of resistor Rn2 in the cathode circuit. The action of the modulation limiter is described in paragraph 148. Plate voltage is applied through decoupling resistor RX27 and plate-load resistor Rm. Capacitor Cm is the a-f bypass capacitor for decoupling resistor Rm. The decoupling filter consisting of resistor R427 and capacitor Cn2 performs the same function as the decoupling filter described in paragraph 144. When a dynamic microphone or field telephone is used, the output voltage of the first a-f stage is impressed on the grid of tube V102 through coupling capacitor Ci02, resistor Rios, potentiometer Rm (gain control), and another coupling capacitor Cn9. Capacitor C119 also serves as a d-c blocking capacitor for the bias voltage supplied by the modulation limiter. The purpose of resistor Rios is to provide a more constant plate-load impedance for tube Vioi as the gain control Rm is varied. This improves the low-frequency response of the amplifier at low settings of gain control Rm. Gain control Rm controls the output of the speech amplifier when using a dynamic
    124
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    Figure 79. Second a-f amplifier stage—functional diagram.
    of tube Vio3. The plate circuit of this section of tube V103 provides, through capacitor Choe, a signal for grid 2 of tube Vi04 which is opposite in polarity at any instant to the signal applied to grid number 1 of tube Vio4- This signal voltage also appears across resistors Rn9 and Ri20. Resistors Rug and Rii9 are equal in resistance value. As the signal applied to grid 1 of tube Vi 0 4 becomes greater than the signal applied to grid 2, the polarity, at any instant, of the voltage developed across resistor Ri2o is such as to cause greater instantaneous output from the phase inverter section of tube Vi03. The two grids of tube Vi04 are therefore excited almost equally, and the voltage drop across resistor
    R120, caused by the signal applied to grid 1 of tube Vio4, is almost cancelled by a voltage of opposite polarity and nearly equal amplitude caused by the signal applied to grid 2 of tube Vio 4. The remaining uncancelled voltage across resistor R120 corresponds to the unbalance between the signals applied to the two grids of tube Vi04. This unbalanced voltage then excites the grid of the phase-inverter section of tube Vi 03 so that the output of the phase inverter tends to reduce the unbalance. The high gain of tube Vi03 results in a very small percentage of unbalance, even with considerable variations in the two sections of tube V103 and variations in circuit constants.
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    126
    147. Fourth A-F Amplifier (fig. 81)
    Tube V104 (Tube JAN-6SN7 (VT-231) ) is connected in a Class A push-pull amplifier stage. Its purpose is to amplify the output of the third a-f amplifier stage sufficiently to excite the grids of the push-pull driver stage located in the transmitter. The tube is self-biased as a result of the d-c voltage drop across cathode-bias resistor Ri24 which is bypassed for audio frequencies by capacitor Ci07. Plate voltage is obtained from the speech-amplifier
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    Figure 81. Fourth a-f amplifier stage—functional diagram.
    power supply, and is applied to the plates of the tube through the center tap on the push-pull output transformer Ti02. Transformer Ti02 is designed to match the plate-to-plate impedance of tube V104 to a 500-ohm transmission line. Grid excitation for tube V104 is provided by the third a-f amplifier and phase inverter. The a-f output voltage appearing across the secondary winding of the output transformer is fed to the driver stage in the transmitter over a 500-ohm transmission line.
    148. Modulation Limiter (fig. 82)
    Tube V105 (Tube JAN-6SR7 (VT-233) ) is com nected in a modulation limiter circuit. Its purpose is to produce a d-c control voltage which is proportional to the peak amplitude of the speech-amplifier output voltage. This d-c control voltage is then used to bias the second a-f amplifier tube; its effect is to vary the gain of the second a-f amplifier tube V4 02 in inverse proportion to the amplitude of the output voltage of the speech amplifier. Tube V-ot performs two functions: The triode section of the tube functions as an a-f amplifier, and the two diodes are connected in a full-wave rectifier circuit. The tube is self-biased as a result of the d-c voltage across cathode-bias resistor R13i and plate voltage is applied through decoupling resistor R129 and plate-load resistor R130. Capacitor Cn5 is the a-f bypass capacitor for resistor R129. Excitation voltage for the grid of tube Vi0Sis obtained from one of the grids of tube Vi04 through potentiometer R134, the modulation LIMITER CONTROL. The a-f output voltage of tube V405 appears across resistor R130 and is applied to the primary winding of transformer Ti04 through audio-coupling capacitor Cn4. The a-f voltage appearing across the secondary winding of transformer Ti04 is applied to the two diodes of tube V405 and the diodes are returned to ground through the center tap of the secondary winding and diode load resistor R i33. The rectified a-f voltage which appears across resistor R133 is filtered by an RC (resistance-capacitance) network consisting of resistor Ri32 and capacitor Cn6. The d-c voltage appearing across capacitor Cn6 is ap-
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    127
    proximately equal to the peak amplitude of the signal applied to the diodes of tube V105, and this d-c voltage is applied to the grid of tube V102 through resistor Rio9. Tube V102 is operated on the curved portion of its mutual characteristic curve. Under this condition the transconductance of the tube varies rapidly with variations in grid bias; that is, an increase in grid bias decreases the transconductance, and vice ve^sa. When the LIMITER CONTROL (potentiometer Ri34) has been properly adjusted, the modulation limiter provides a minimum: of 3 decibels compression at 100 percent modulation; this has the effect of raising the average modulation level approximately 7 decibels without exceeding 100 percent modulation on voice peaks. For the adjustment procedure for the LIMITER CONTROL see paragraph 197.
    149. C-W Side+one
    a. Sidetone Oscillator (fig. 83). Tube V106 (Tube JAN-6SN7 (VT-231) ) is connected in a multivibrator circuit. Its purpose is to generate a sidetone signal for monitoring the c-w transmission. When the transmitter is keyed, the cathode circuit
    of tube V106 is completed to ground through the contacts on switch SW206B and relay RY20q. The multivibrator circuit is essentially a two-stage, resistance-coupled amplifier in which the voltage developed by the output of the second tube is fed back to the input of the first tube. Tube V106 is a dual triode tube and is self-biased as a result of the d-c voltage drop across the cathode-bias resistor Ri36. Capacitor Ci28 is the a-f bypass capacitor for resistor Ri36- Plate current flow through the left-hand triode of tube Vi06 causes a voltage drop across plate-load resistor Ri39. This voltage drop is applied to the grid of the right-hand triode through capacitor Cu8. This change of grid voltage produces a corresponding change of plate current and voltage drop across plate-load resistor Ri40. The voltage drop across resistor R140 is then applied to the grid of the left-hand triode through capacitor Cm. Resistor Ri35 is the grid resistor for one triode section; resistor RX38 in series with potentiometer R137 forms the grid resistor for the othei triode section. The frequency oscillation is determined by the values of coupling capacitors Ch? and Cji8 and the grid resistors. The audio output of the sidetone oscillator appears across potentiometer Rm-
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    Figure 83. Sidetone oscillator circuit—functional diagram.
    b. Sidetone Amplifier (fig. 83). Tube Vios (Tube JAN-6J5 (VT-94) ) is connected as a cathode-follower amplifier. Its purpose is to isolate the headphones from the sidetone oscillator and to provide a low-impedance output to which the headphones are connected. This stage, strictly speaking, is not an amplifier because theroetically the gain of the stage can never exceed unity and practically the gain of a cathode-follower stage is in the range of 0.6 to 0.8. In this type of amplifier, the plate of the tube is connected directly to B + ; and the cathode-bias resistor serves as the load resistor.
    Resistor Ri22 is the cathode-bias resistor for tube Vios and also acts as the load resistor. Grid excitation voltage for tube Vios is obtained from the movable contact on potentiometer Rm which also serves as the d-c grid return to ground. Potentiometer Rm controls the volume level of the sidetone signal applied to the grid of tube Vio8; resistor Rm limits the maximum signal that can be applied to approximately two-thirds the available output of the sidetone oscillator. The output voltage appear -ing across Ri22 is applied to the headphones through resistor Ri4i. The output impedance of tube Vies
    128
    is approximately 300 ohms; accordingly, resistor Rm is connected in series with the cathode of
    tube Viog and the headphones to provide a better impedance match.
    t~~ZLvt-8o	CHiot
    T £ 250 V 07/T\	1 -■=
    103 £ .r*c	---—---------GTCWP—--------—
    ----(L,L-?-X £*-4-^ 	( rio3 "
    50,01	RYpoO	1+ SRI01 >200M	<
    C|23=|=	200	^|2v R|05 < IM
    AsW202C KZSET AT NORMAL
    TL 14485
    Figure 86. Dynamic microphone circuit—functional diagram.
    through pin No. 2 on socket SOwi and relay RY2Oo. Capacitor CX23 is an r-f bypass to prevent high-frequency interference from entering the amplifier by way of the microphone cords. Capacitor C424 prevents sparking at the microphone switch contacts when breaking the d-c current through relay RY200. The DYNAMIC MIC. 1 control (resistor Rin) functions as a gain control for the speech amplifier when a dynamic miscrophone or field telephone is used to modulate the transmitter. (See fig. 79.)
    c. Modulation Limiter Control. The LIMITER CONTROL (resistor Ri34) (fig. 82) is located on the front panel of the speech amplifier behind a cover plate. Its purpose is to control the amplitude of the a-f signal applied to the modulation limiter tube Vio5. The control is provided with a slotted shaft which is accessible when the cover plate is removed. See paragraph 197 for instructions as to the proper procedure for adjusting the modulation limiter control.
    d. Sidetone Volume Control. The sidetone volume control (fig. 83) is located on the rear side of the speech-amplifier chassis. Its purpose is to
    Section IV. THEORY OF
    Note. Junction Box JB-70-A (fig. 124) contains all the electrical circuits necessary for the control of Power Unit PE-95-( ), Radio Transmitter BC-610-E, and Radio Receivers BC-312-( ), BC-342-( ). A-c power outlets are provided for Rectifier RA-63-(*), lights, heater, blower, etc.
    152. Transmitter Control Switch SW203
    a. General. The transmitter control switch SW203 is a three-position lever-key type of switch and is located on the front panel of the junction box. The switch is marked TRANS. ON TRANS. OFF REC. TO EE-8. The switch performs four major functions:
    control the amplitude of the a-f signal applied to the grid of the sidetone amplifier tube Vio.
    e. Auxiliary Key Jack. The KEY jack located on the front panel of the speech amplifier is connected in the cathode circuit of oscillator tube V8, located in the transmitter. The jack accommodates Plug PL-55. The transmitter can be keyed for c-w operation by inserting a key plug into this jack.
    Caution: When the transmitter is keyed from this jack, the receiver disabling circuits do not operate. Therefore, be sure that neither radio receiver is tuned to the transmitter frequency or a harmonic thereof.
    f. Modulator Plate Meter. The MODULATOR PLATE meter Mioi (fig. 62) indicates the d-c current to the Class B modulator tubes V3 and V4. Correct zero-signal bias to tubes V3 and V4 is obtained by adjusting the MODULATOR BIAS control (located on the front panel of the transmitter) while observing the indication of the meter. When modulating the transmitter, the microphone gain controls are adjusted properly by observing the indication of the meter on voice peaks.
    JUNCTION BOX JB-70-A
    (1)	Applies 115 a-c volts to coils of relays RY4 and RY4.
    (2)	Connects coil of relay RY200 to KEY jacks or remote telephone line through contacts on switch SW202b.
    (3)	Connects remote telephone line through capacitor C202 and contacts on switch SW202c to input of speech amplifier.
    (4)	Connects remote telephone line through capacitor C202 and contacts on switch SW202a to the receiver outputs.
    b. Trans, on Position (fig. 87).
    130
    (1)	When switch SW203 is set to TRANS. ON and the REMOTE CONTROL EE-8 switch SW202 is set to NORMAL, switch SW203 performs two functions:
    (a)	Switch SW 2o3 applies 115 a-c volts to relays RYi and RY4. Relay RYX applies plate power to the transmitter; relay RY4 is the antenna shorting relay. See paragraph 142 for a detailed description of the functions of these relays.
    (b)	Switch SW203 connects one side of the coil of relay RY2oo to the KEY jacks located on the junction box. Relay RY2oo is keyed during c-w operation. For a detailed description of relay RY200 see paragraph 154.
    (2)	When switch SW203 is set to TRANS. ON and switch SW202 is set to either TELEPHONE position, switch SW203 performs three functions:
    (a)	Switch SW203 applies 115 a-c volts to relays RYi and RY(.
    (6)	Switch SW203 applies 12 d-c volts to the coil of relay RY200.
    (c)	Switch SW 203 connects the ungrounded REMOTE TELEPHONE terminal through capacitor C202 to the grid of the first a-f amplifier tube V101.
    (3)	When switch SW203 is set to TRANS. ON and switch SW202 is set to either TELEGRAPH position, switch SW203 performs two functions:
    (a) Switch SW203 applies 115 volts a-c to relays . RYX and RY4.
    (5) Switch SW203 connects one side of the coil of relay RY2Oo to the ungrounded REMOTE TELEPHONE terminal of the junction box. The transmitter can then be keyed from the far end of a telephone line connected to the REMOTE TELEPHONE terminals.
    c. Trans. Off Position. In the TRANS. OFF position, all circuits to which switch SW203 is connected are open.
    I	POSITION OF SW202
    ■---9-----1	I. BC-312 TELEGRAPH
    2. BC-312 TELEPHONE II/ || /	3. NORMAL
    TRANS	RYI 11(2	KRY4	4. BC-342 TELEPHONE
    K	K	5. BC-342 TELEGRAPH	MICROPHONE
    _____	I1Q7 IIW	SWITCH
    X " 7-------------------------------1------------------------------------H
    TO X “I ||i-„ ■
    TELEPHONE EE-8-C )	| C?q?	1+	v
    INCHEST CH-120	"T" IMF	12V JZ.	101	VT-103
    DC	.Z"" ■'"s.
    O	11	R|05	R|03	N
    REMOTE	? I	A A A_ a a a I_________1
    TELEPHONE	I 3 I	'QC 200M I	/
    9	26 j46	k—y
    k>i I 56	J200	J
    < SW202B	---------------	j । M ANTENNA
    Hi	,w	.13 SHORTING I
    / O |	® "	" ®---"	(X)	20	(X> JUNCTION |	I	3	RELAY |
    / L_	SW205B SW203	V jT jbB?70-Aj	I	[	I
    I -------------. ^_Z_J | I | I |_L_	1--------------1
    MICROPHONE	I I I
    SWITCH	_1_	12V
    — DC
    I------------7
    J~'	—I T-	' — — — — —|।	| RADIO *
    । VIO6	VT-231	|	|	I	.	RECEIVER	.
    ~~l	r~	|	|	V8 |VT-IO7	I	-------------1	SC-342-O	I
    i ZY i i	।	j
    ' Yf V ’ V I I	Zry, !	I antenna I
    I 1	c? C	I 3 SHORTING
    I ——	; i ,#p F Y '	I 7 "£LAY I
    ' 11—?	!	! ~	'
    ! 1 has S'"’	|	---------------’
    1	Ssoon	I	|	sioom	3iomh
    I	i	i	।	1	r	"5V	’
    I________ 1	I	I	1	AC	i
    I SPEECH AMPLIFIER I |	RADIO TRANSMITTER |
    I___BC‘6I"’E _J L -	BC-6I0-E
    _	—------— — ---- —---->	»(. ,44( 5
    Figure 89. Keying relay RYsoo—functional diagram.
    another pair of contacts completes the cathode	155. Receiver Disabling Switches SW200
    circuits of the m-o or crystal-oscillator tube V8	and SW20l (fig. 90)
    and the c-w sidetone oscillator tube Vi06. The Switches SW2oo and SW20i are double-pole, double-C.W. SIDETONE switch SW202Bis also connected throw toggle switches. When these switches are in the cathode circuit of tube Vioej its function is thrown to the ON position and relay RY2Oo is described in paragraph 157.	energized, they perform two functions: One pair
    c. Receiver Disabling Circuits. One pair of of contacts on switches SW200 and SW20i connects
    contacts on relay RY2Oo applies 12 d-c volts (through
    switches SW2Oo and SW20i) to the antenna shorting	receiver
    relays in Radio Receivers BC-312-( ) and	disabling --------------------------
    J	t	.	I-- RADIO RECEIVER BC-3I2-C )
    BC-342-( ). One pair of contacts grounds the	—° / on 6 ,	output
    audio output of Radio Receiver BC-312-( ) q ___________________________________<0_0_000y	—
    through switch SW200; another pair of contacts ry2Oo	° 'antenna'
    ground the audio output of Radio Receiver ()	° 0FF ?	shorting —
    BC-342-( ) through switches SW2Oo and SW20i.
    See paragraph 155 for a functional description of	-------------------
    RECEIVER DISABLING switches SW2Oo and-----------------------------------------------------------------
    SW2oi. Because of the close proximity of the	receiver
    receiving and transmitting antennas, the receiver	____o 0N (5 radio receiver bc-342-o
    input circuits are subjected to large amounts of	____ / - - /
    r-f energy when the receivers are turned to the	°sw2oi	xdQ-ZZL	1
    ky200	------------ I
    transmitter frequency or a harmonic of the trans-	o off o	shorting	____
    mitter frequency. Radio Receivers BC-312-( )	'	relay	°dTa?udio
    and BC-342-( ) are provided with antenna	111111 p"—____________________________
    shorting relays. To prevent damage to the input	—I—	l2v°c Y2oo
    circuits when the transmitter is operating, contacts ".	...	...	,	..	,
    07	r igure 90. Receiver disabling switches—functional
    on these relays ground the receiving antennas.	diagram.
    133
    i\	y
    LOUDSPEAKER	I_______________________________________________■	LOUDSPEAKER
    LS-3	I _____ ___________________________________________ LS-3
    IN CHEST CH-121 I /~^	L—\	IN CHEST CH-120
    r _L	__L_ \]
    5
    RADIO RECEIVER BC-3I2-C)	RADIO RECEIVER 8C-342-O
     OUTPUT	OUTPUT --------
    2D AUDIO	»	2D AUDIO
    0SW2O5A	^^OSA^ 0=
    ----0—R	_	-----------*	-
    C.W.	A203	205	c.w.
    SIDETONE J202 P V °	"	VV\-------4 Y P J204
    J203 p\/-O	O--Y p j205
    	<4 /	8 -NORMAL — HEADSETS BC-312	/ /	— HEADSETS BC-342
    ” OUTPUT A' Y TRANSPOSED
    b 204	Tl 14491
    Figure 91. RECEIVER OUTPUT switch—functional diagram.
    12 d-c volts to the antenna shorting relays; the other pair of contacts grounds the a-f outputs of the two receivers. Switch SW200 (BC—312) disables Radio Receiver BC-312-( ), and switch SW20i (BC-342) disables Radio Receiver BC-342-( ). When these two switches are thrown to the OFF position, the antenna shorting relays are grounded. See paragraph 154 for the functions of relay RY20o. 156 * * * * * * * * * * * * * * * * * * *
    156. Receiver Output Switch SW204 (fig. 91)
    Switch SW204 is a double-pole, double-throw toggle
    switch and it functions as follows: When switch
    SW204 is set to NORMAL, the a-f output of Radio
    Receiver BC-312-( ) is connected to the HEAD-
    SETS jacks mounted toward the left-hand side
    of the junction box and to Loudspeaker LS-3
    located in Chest CH-121. The a-f output of
    Radio Receiver BC-342-( ) is connected to the
    HEADSETS jacks mounted toward the right-hand
    side of the junction box and to Loudspeaker LS-3
    located in Chest CH-120. When switch SW204 is
    set to TRANSPOSE, the a-f output of Radio
    Receiver BC-312-( ) is connected to the right-
    hand HEADSETS jacks and to Loudspeaker LS-3
    located in Chest CH-120. The a-f output of Radio
    Receiver BC-342-( ) is connected to the left-hand
    HEADSETS jacks and to Loudspeaker LS-3
    located in Chest CH-121. By the use of switch
    SW2o4, the operator at Radio Receiver BC-312-( )
    can instantly switch his loudspeaker and headsets to the output of Radio Receiver BC-342-( ), and vice versa. Switch SW204 does not effect the functioning of the RECEIVER DISABLING switches^ The a-f signal applied to the HEADSETS jacks is attenuated an appropriate amount by resistors R2o3 and R205. These resistors also serve to isolate the headsets from the receiver output circuits to prevent grounding the c-w sidetone signal when th6 receivers are disabled.
    157. C.W. Sidetone Switch SW205 (fig. 92)
    Electrically, switch SW20s is a two-section, threey position switch. Its purpose is to complete the cathode circuit of the c-w sidetone oscillator tube V106 and to switch the c-w sidetone signal output of the sidetone amplifier tube Vi08 to either pair of HEADSETS jacks. When switch SW20s is set to position 1 (TO BC-312), the A section applies the sidetone signal to the left-hand HEADSETS jacks of the junction box; when the switch is set to position 3 (TO BC-342), the A section applies the sidetone signal to the right-hand HEADSETS jacks.	i
    - - . i
    158. Start-Stop Switch SW206 (fig. 93)
    Switch SW206 is used to start and stop Power Unit PE-95-( ). When the START button is pressed, current from the 12-volt battery m the power unit hows through the starting relay in the power unit.
    134
    -■V.os i ,	HEADSETS	HEADSETS
    >4-------LvT-231	BC-312	C.W	BC-342	V|08_____*
    Z^Jii	J202^V——O	SWITCH	O ——vjj J204	\
    ' Lzz;	J2O3[t-	...... <:—T205	\Xy
    ‘ j	-- f' sw205A	I----------------------
    -	;	—	5M
    '	1*122-
    I	| 2M
    RI36	|	J	Q2	]3	~
    -----------------mw--------------1-----d d
    500A	|	x^''oSW205B
    POSITION OF	(A .
    SWITCH SW2Q5	I f
    I. TO BC-312	!
    2. OFF-	’ J-------------------------------------,
    a TO BC-342	(A RY	I
    A RY2OO	+|
    i	TLJ4492
    Figure 92. C. W. SIDETONE switch—functional diagram.
    Contacts on the starting relay complete the starting circuit and start the motor of Power Unit PE-95-( ). When the STOP button is pressed,
    POWER UNIT	JUNCTION BOX
    _p£-2^r£ X___	______
    START RELAY	I	*
    rW-------------;------)----1
    LsTART
    ’ SW206A
    12 V DC I I
    —d'H-J-l—j—
    I o\l STOP
    _____	। I sw206B
    -------------1-----
    STOP RELAY	|
    L__________________j l_________________________1
    TL 14486
    Figure 93. ST ART-STOP switch—functional diagram.
    current from the 12-volt battery flows through the stopping relay. Contacts on the stopping relay short-circuit the ignition system and stop the motor of Power Unit PE-95-( ).
    AUXILIARY
    POWER UNIT	BATTERY
    PE-95-1 )	BATTERY	CHEST CH-IO9-A
    f— ----1	SOURCE	I------'
    SWITCH	I	'
    sw207
    I--	■■ ■	ex o--------------'-.
    +	|	PE-95 \ AUX	I +
    12 V "A-	I -A- |2 v
    DC |	! = OC
    -'Ll-----—-------------------------It- I
    l—_□	q_„j
    TO ALL CIRCUITS	“
    REQUIRING 12 VOLTS
    DC FOR THEIR OPERATION	TLI4493
    Figure 94. Battery source switch—functional diagram.
    159.	Battery Source Switch SW2a7 (fig. 34)
    Switch SW207 is a single-pole, double-throw toggle switch. When switch SW207 is set to PE-95, the 12-volt storage battery located in the trailer with Power Unit PR-95-( ) is connected to all circuits requiring 12 d-c volts for their operation. When switch SW207 is set to AUX., the 12-volt d-c circuits are connected to the 12-volt storage battery in Chest CH-109-A. The negative terminals of the storage batteries are grounded and the positive terminals are connected to switch SW207.
    160.	Circuit Breaker CB 200 (fig. 124)
    Circuit breaker CB2oo is designed to break a current in excess of approximately 50 amperes. One side of the 115-volt a-c line from Power Unit PE-95-( ) is common to all equipment. The other side of the line is connected to the equipment through circuit breaker CB2oo. The normal current required by the equipment passes through the circuit breaker without interruption; however, a short circuit on the line, or a load in excess of 50 amperes trips the circuit breaker. The circuit breaker can be reset by pressing the PRESS TO RESET button on the front of the junction box. When switch SW205 is set to position number 1 or 3, the B section grounds the cathode resistor Ri36 of the c-w sidetone oscillator tube V106 through a pair of contacts on relay RY2Oo. When switch SW205 is set to position number 2 (OFF) the c-w sidetone circuits are open.
    161.	Surge Filters
    When the circuit to a coil carrying a current is broken, the magnetic field about the coil collapses. The collapsing magnetic field induces a back emf
    135
    (electromotive force) in the coil that is proportional to the product of the inductance of the coil and the time rate of change of the current through the coil. The current through the coil changes very rapidly at the instant the circuit is broken; accordingly, the voltage induced in the coil may reach extremely high proportions. In a circuit containing
    200	______
    ft™ *	ft00
    / \	T-	(x)SW203
    /	\	±200
    z / 1 iR201	iTZ/ n JACKS
    ecftift200! 342iife	l,oon	R2oft
    If 100 ±C2oo IP	±C2OI	,00n|	'	J20'
    S_____J-0.01 MF h____J-O.OIMF
    '	R204-L
    P.PIMF^
    Ve << I yT-107
    G>ch2 to I MH
    (----j	RY200
    J 0>CH9 ---------6<)-------
    R35> to 10 MH
    (OOM | to
    fl	R 202
    I |------------------------1
    C203	Tt|449»
    0.01 MF	—
    Figure 9'5. Surge filters—functional diagram.
    inductance, a dissipative network is connected across the coil to prevent arcing at the contacts of the switch which breaks the current. This network, sometimes called a surge filter, consists of a resistor in series with a capacitor. In Junction Box JB-70-A there are four of these dissipative networks. (See fig. 95.) The action of a surge filter can best be shown by an example. When the transmitter is keyed for c-w operation, the current through relay RY200 is interrupted in accordance with the dots and dashes to be transmitted. When the current is interrupted, the back emf induced in the coil of relay RY2oo charges capacitor C204 through resistor R2o4. Capacitor C204 then discharges back through resistor R204 and the coil. However, the resistance of the coil together with resistor R204 is high enough that only a few highly damped oscillations occur and the transient voltage dies out in a very short period of time. Thus the back emf, induced in the coil at the instant the current is interrupted, is dissipated in the form of heat in resistor R204 and the resistance of the coil. The antenna shorting relays of Radio Receivers BC-312-( ) and BC-342-( ) are provided with surge filters consisting of resistor R2oo with capacitor C2Oo and resistor R20i with capacitor C20i. Because of the inductance of choke coils CH2, and CH9 in the cathode circuit of oscillator tube V8, a surge filter is required. This filter consists of capacitor C203 and resistor R202.
    Section V. OVER-ALL SYSTEM FUNCTION
    162. General
    Figure 96, an over-all system block diagram, shows the complete function of Radio Sets SCR—399-A and SCR-499-A. The major components of the radio set are: Radio Transmitter BC-610-E, Antenna Tuning Unit BC-939-A, Speech Amplifier BC-614-E, Junction Box JB-70-A, and Radio Receivers BC-312-( ) and BC-342-( ). The signal paths are as shown in figure 96.
    163. C-W Operation
    The transmitter uses a master or crystal oscillator which is keyed for c-w operation. To key the transmitter Key J-37 is connected to either KEY jack of Junction Box JB-70-A. The output of the oscillator is applied successively to the bufferdoubler, the i-p-a, and the p-a stages. The r-f power output of the p-a stage is approximately 400 watts in the 2- to 8-mc range, 300 watts in the 8- to 12-mc range, and 275 watts in the 12- to
    18-mc range. The r-f output of the p-a stage is coupled to the transmitting antenna by means of Antenna Tuning Unit BC-939-A. Plate and screengrid voltage for the oscillator buffer-doubler, and i-p-a tubes is supplied by the exciter power supply; plate voltage for the p-a tube is supplied by the high-voltage power supply; bias voltage for the i-p-a and p-a tubes is supplied by the bias power supply. The sidetone oscillator in the speech amplifier operates when the transmitter is keyed, and the output of the sidetone oscillator is applied to the sidetone amplifier. The output of the sidetone amplifier is connected to the HEADSETS jacks in the junction box through the C.W. SIDETONE switch. Keying the transmitter operates the receiver disabling circuits when the RECEIVER DISABLING switches in the junction box are set to ON. Figure 97 is a functional schematic wiring diagram of the transmitter, speech amplifier, and junction box for c-w operation.
    136
    ANTENNA TUNING UNIT
    .BC-939-A
    r--------------------”--------------------- y...-.-...-...- ~ -- -I- - -------------------------------- "I
    .	I PA	I
    u	I
    |	(VT-IOO)
    I	TWO	.
    j ---------------- ------------------ JAN-807 IN	--------±7-----
    I	MO OR CRYSTAL	BUFFER DOUBLER	dadai i ri	PA
    •	OSCILLATOR	r PARALLEL	Z~^.	______________ |
    I F	(220)	*--*----’ h|oh-voltage
    ( I	\ 115 J	IVT-100)	\.	7	POWER SUPPLY
    ।	\ IOIJ	\	j	x '	x'—x.	1
    JAN^6V6	JAN-6L6	------ JAN-25OTH	( VT-\	|
    .	I	]-	| o	g T	‘	(4 6-A/	.
    ’'	I	•0000000000000000 I
    |	'	'---•---•-----•--J--- •---- •--•-*	°	MODULATOR STAGE	.amLa^a im I
    ,___________|_________o	z^^x	z-—JAN-866A IN I
    EXCITER POWER SUPPLY	rTTs	1	)	(Ch) •----•-- FULL WAVE I
    I	Dino	\ d. I O J	\d\Ol	--
    I	POWERSUPPLY	V_Z	X__Z	/VT-\
    I	__	__ Z------X	Z^X	O< TWO JAN-IOOTH	(	)
    @@@ A ® T 1 LAzLJ 1
    I	--- %___Z	JAN-5Z3	DRIVER STAGE	1
    ’	THREE	IAN-A71	Z~X	Z~X	'
    I	JAN-OD3/ VR -150	1______ ___ /VT-\	/VT-\	1
    I	-------—	---------------- •	* ~	\95 \	(95 )
    TWO JAN-2A3
    | 	RADIO TRANSMITTER BC-6I0-E	----——PUy ~PULL---	-|
    SPEE^H AMPLIFIER	(speech AMPLRl	I	legend:
    °14’ L	POWER SUPPLY	I
    rx	।	-------------- _	-------------- •------•---- PLATE VOLTAGE
    DYNAMIC S\________,	_________ IST A-FAMPLR	(vT-eo) T ATH A-F AMPLR | o	VOLTAGE
    MICROPHONE  VULIA(jt-
    T-50 rf/	I	(VT-IO3)	I ( VT-231 ) I ---------- STAGES COMMON
    \.	1	JAN-80	4 X Z I	T0 CW AND
    I___________----------------------------'to duXTT^ode 1	--- PH0NE operation
    D1	JAN-6SQ.7	'mODULAt’i’oTTIALL JAN-6SN7GT |	--- STAGES USED ONLr
    ^>00000 LIMITER STAGES 1	FOR PHONE OPER-
    ------1---REMOTE----—t	o	---- "* I__________ 1	---- ATION
    I TELEPHONE 2D A-FAMPLR	( 033 )	3D A-FAMPLR AND	--- STAGES USED ONLY
    EE-8-C)	.	X. J	-PHASE INVERTER	FOR C-W OPERATION
    I IST A-F	/ VT-23TX I ---------
    AMP.	(VT-941	JAN-65R7	( DUAL )
    | J)	W y	\TRIODEJ	|
    JAN^6J5 -----*----------*■-- JAN- 6SN7GT .
    I I	----------------“I	|----- LU
    ss. „„	। 3'-™=	1	jss;:0
    OSC	।	O5C	AMPLR
    RADIO	KEYING	Z X	Z^^	.	RADIO
    RECEIVER	CIRCUIT _ I (vT-23l)	---•---	( VT-94)	1	|	RECEIVER
    BC-3I2-O	*“	X.__Z	V /	|	BC-342-O
    OUTPUT	~l	1 DUAL TRIODE	IAM Kle .	___ OUTPUT
    2D AUDI0	I JAN-6SN7GT	____JAN-6J5---	|	2D ^UDIO
    , RECEIVER L2_____________ .RECEIVER ’’	-------------
    DISABLING L_ _ ______	_ ___________ ___________ ___| DISABLING	r
    LOUDSPEAKERl\n	CIRCUIT	.	CIRCUIT -* ,, riZ^l LOUDSPEAKER
    LS-3	[JJ——	L - -	...1---------------------p  pLkj LS-3
    ------------•---------	------------------------- ‘ TELEPHONE
    TO	-----------------4----- JUNCTION BOX --------------------------------- EE-8-C)
    REMOTE <	»	«__________________ JB-70-A	______________________r-	IN
    TELEPHONE	o	O	CHEST
    EE'e“’
    HEADSET	HEADSET
    HS-30 \	HS-30
    Figure 96. Radio Sets SCR-399-A and SCR-499-A—~complete block diagram.
    I SPEECH AMPLIFIER j B+	i |	---------------- TO BUFFER-DOUBLER	i--—--------------—
    |	8C-6I4-E r * I R	j ' V8 VT-|07	AND I PA STAGES	V|6 I VT-2 20
    I	5M<	<5M	I I	/-1— \	TO
    B+ VIO6 5________1	.	I ZTZj	lPA-<-I—---)	CH^ k
    "	IO02MF,.___ VTf23l	I I r~ ,y	STAGE \ X / r	i—O//—i 3 I T-----
    |V|08^^?94 -LCUB------_l_C||7	.| I	XZSZ 12	2.5MH | | I 4->
    /CE\ t/LL d£\ t-oo2mf (	JCH2	---------—Lhz-ANTENN,
    i	i	5—i	v.o.v,,.AnDv,6 T°o2Mrc,aiz	BI p. UNIT
    ।	, "f tom । ,/?<“»	"	4- I_________________LA
    --- SsomT	I I £ Zoom	----------------------------------------------- /"j3’	F'36	1-1-----4---f	SIASTOPOWER-’'360V DC J----1
    y?DETONE?S0°n A |7 A	3URPLV A	L----------"I
    /.VOLUME KC,	-J-.°°6UF	2.5 J	L4
    "-o-vn II —	<	<25m
    I	H	-TZ-U II	l r*l I	V3 JvT-218
    ^=JIOI |	|	Rl2 <500 g|	,^TX
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    I BC'312	I	। *a ।	T? s*------------------t-----
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    OUTPUTS DC SHORTING	1	i	.______P----- V7V1XVT.4(1A
    relays	।	1	r	n	-----———'
    |	I |	ill RY.	-----------------------7------ — —
    I J200	I	I ,	o?	S	T .__________,	EXCITER
    kpyJ -----------------1 '____________II ? ?nv	5 J v ,	, I----^573---*-------•-----STAGES
    KEYS. ||	,,	, , f-------- •	RY	L r	l2ZTX	6H I	I	B +
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    I 11-	„	SW203	I |	I g---- (	<)	r	$ 750,0 kR|O
    i J2oi-X	AT trans-°n । ।	a g	\yry~i—-S	8i65mf I >40M
    I	।	।	_______|	[__ ~a'7MF
    JUNCTION B°x	। | RADIO TRANSMITTER	___________________1________Ta'5MF
    JB-70-A	J ।	BC-6I0-E
    Figure 97. Radio Sets SCR-399-A and SCR-499-A for c-w operation—functional diagram.
    137
    138
    r	R|30	a- -	■—	i
    i-----II "4 -«------VW----► B+	BUFFER DOUBLER _L?i2 2'5rk7^4
    T IIO.OIMF |	5OM	fi	ZH X AND I PA Z^P\ x-p 0 0 1	----*.
    k| ,----1 I v,„	_AAA	I I	( A	A a9a i SjC'TO ANTENNA
    3 £> I	✓—rx 105	rVW—।	—I----I	----) r'V\AA3K tuning unit
    S 3 I______4-X-Yt-223	CHg l00M CH2 \ r-. 7	\/\/ -Lr =4=TOOn 33 t
    3 (gP -----L	--------'	*8	Vl6	C|2 o'oQ2MF .
    3 3	\Jf	Q 2.5MH I MH	-107	VT-220	-----------r <-7
    E/^r MICROPHONE	|	LIMITER CONTROL	0.006MF
    13 T-50	B+ +	R|33 /'POOH ,,R|34	_	_______ ___________________
    nJ	a	L\mh >—t—vw---------------------- z4-x4
    J	RI32> 3meg |cII6 4	500M	Z^E\vT-95	/■L«\vT-2I8
    >rI07	500M> ~IO35MF	c	r—+----(--- )	|-f ■ I----- I
    _______>200M	1------1 RII3	IiOjOIMF____>R* V/V/	K ^P3!- VT-^/is >R"7 >R|IB Z^\V1°< o} C if T, 3 Jo f T3 illg RY3Q
    RIO2 ZJ- X o.OIMfT f /-*■ \00IMfF--f---1 >00M>250M II--|VT'231 3 K 3 £>	=3^	3 3	E=?	3 S I ?1
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    1	..— --------j--------------—M--------------------------—1	nvo >750n	-----"
    < R||0	==Z0	==10	25M
    PLUG PL-68	JI02 ..	T005 f2000 UTA A A A J	---TO----------X ‘	”
    [f^	-f Q J” rrti_______________________________________________________
    3000	JT	■	MODULATOR BIAS L
    SPEECH AMPLIFIER BC-6I4-E	I	V
    —	BIAS TO TUBES EXCITER STAGES
    __________________	_____________ -------- 	 --_______ V|0 V(| AND V|6	B+ __________________________	_____________-	___________—— --- L| 4 , ,_______________RADIO TRANSMITTER BC-6I0-E______. -------------J8 ,-----------,
    ~L	_ ,	___।______________________	3 3	*i2	I-----3	6R >o >=
    L	f	1 r~°	__ ~	3 3	VT-I45/^LX1	T4||/	3	3 fen v x i72	=Ui9 4423	<75w
    LZ__L_________T V VT-746a(^Y---------J	3MF 3MF
    ___I—
    I	-------------------------------------------jniw*
    Figure 98. Radio Sets SCR-399-A and SCR-499-A for phone operation—functional diagram.
    REMOTE. OPERATION CW OR PHONE
    REMOTE + 12 V DC	VIOI | I	| v8
    TELEPHONE	CONTROL	4	VT-IO3 ZTX	.XAtXvT-107
    LINE \	EE-8	_______o	/<—
    \	_____ j T-----------7--0------ "102	/	\	f____\
    ------------ JUNCTION BOX \	*------------------- 	f-A/W------f---(— I	f	I J8-60-A	\	Sw2O2B S ry200-----J 1MEG J----------------------------1S	7/
    Aoi	?——p—A- — ' k. 3	H	5R|01	>rio3 f—'	r—s
    TELEPHONE __________II . I I I ।	~—I	S I MEG <,200 J	J CH^
    rr q , .	II	i ] REMOTE C„n0	1	„	f M > o_	fc> 2
    EE~8 ( ’	IMF	uj | I TELEPHONE _L202  « 	।---o—1—|-SW203 AT	Ci30 R|°4	< RIO6	U |MH
    ________________ | I 1 I TTmF . _________________________ TRANS ON__---------------------'“AAA/-----" A 1,0000	S J30! t n jilt_____________________________UJ SW2O2CpTL _____________ ~ToOO5 YY _L	GCH9  r ------------ o--------------____________________________________________ ■==’■	____ i.ooon----------------S >	3 < PpL-55	"____________________________* 0.006MF ” I
    □	JUNCTION BOX JB-?O-A	SPEECH AMPLIFIER BC-6I4-E	RAOlO TRANSMITTER 1
    3: ,n_____________r	____ BC-6I0-E
    I J-45______________ ___________________________________________________________
    TELEPHONE EE-8-( ) IN CHEST CH-I20-A
    POSITION OF SW2O2 I BC-312 TELEGRAPH	-----------------------
    2 BC-312 TELEPHONE 3 NORMAL	REMOTE OPERATION	---------------
    4 BC-342 TELEPHONE	RECEIVERS TO TELEPHONE RADIO RECEIVER
    5 BC-342 TELEGRAPH	__________________________________________EE-8~( )	BC-3l2-( )
    ------------------------------------------------------- OUTPUT
    -----------------------------------------2D AUDIO
    REMOTE	RECEIVER
    CONTROL	OUTPUT	A
    "1 _ E"EE-8	sw204 r____________________________—/loudspeaker
    TELEPHONE	|02° 61	404	[ LS-3 IN
    LINE	°bw2O2A	I NORMAL	"-----LI CHEST CH-I2I-A
    ------------ JUNCTION BOX \	cl	--------- ■JB~60~A------------------------ 3 I , 202	TRANSPOSE/ \--------------------------RADIO RECEIVER I
    I 11	IT	rtAUIU ntUtlvtn
    ,1 501	? p" II--------------------0--^-r	J J	BC-342-( )
    TFIFPMONF	II	II IMF	I-- lew r203 >	>R2O5
    TELEPHONE	’.n-re	A__ i sw203 5M <	< 5M	OUTPUT
    ■ EE-8-1 )	IMF z I I REMOTE	AT RFC 5 >	? 5	—2D AUDIO
    ----------------1 □ I ; TELEPHONE ____1 TO EE-8 >______________>_________-------------------------------- i______________________I ' p .________---------	_________________, /I LOUDSPEAKER
    ----------------------------—J I J	' •	LS-3 IN -------- --------------------d_	—p	I 	11	------------------LI CHEST CH-I20-A j---------------------------- ’	J2O2 ?	I ?	J204
    TELEPHONE EE-8-( )______________ >	>	>
    —1	J203 cd cd cd tzd J205
    IN CHEST CH-I20-A------------------
    _________________________JUNCTION BOX__JB-70-A_________________________ni«4M
    HEADSETS HEADSETS
    BC-3l2-( )	BC-342-( )
    Figure 99. Radio Sets SCR—399—A and SCR—799—A for remote operation—functional diagram.
    139
    140 ’
    164. Phone Operation	jack of Junction Box JB-60-A. The a-f output
    For phone operation, the transmitter oscillator	°f the Telephone EE-8-( ) is used to modulate
    produces continuous oscillations which are applied	the transmitter for remote phone operation. The
    successively to the buffer-doubler, i-p-a, and p-a	operator at the remote, station can hear signals
    stages. The r-f carrier output of the p-a stage is	received by Radio Receiver BC-312-( ) or BC-
    approximately 300 watts when operating in the	342-( ) when the transmitter control switch SW203
    2-to 8-mc range, 250 watts in the 8-to 12-mc range,	is set EEC .	EE-8. The output of either
    and 200 watts in the 12- to 18-mc range. The r-f	receiver is selected by the REMOTE CONTROL
    carrier is amplitude modulated in the p-a stage	EE-8 switch SW202a. Telephone EE-8, located
    (plate modulation). The transmitter can be modu- Chest CH-120-A, is connected to the telephone lated approximately 90 percent by a carbon Micro- l^e, and provides telephone facilities between the phone T-17 or T-45 or a dynamic Microphone remote station and shelter.
    T-50 connected to the CARBON MIC. 1 and b- Junction Box JB-60-A provides a convenient DYNAMIC MIC. 2 jack and socket, respectively,	means of connecting a remote field Telephone
    of Speech Amplifier BC-614-E. Microphone T-50	EE-8-( ) and Key J-45 to a telephone line. Key
    connects to the input of the first a-f amplifier;	Jack *Eoi is connected across the LINE tormina s.
    Microphone T-17 or T-45 connects to the input	This Jack accommodates Plug PL-55 and is used
    of the second a-f amplifier. The output of Micro-	with key J-45 to key the transmitter. The short
    phones T-17 and T-45 is amplified by the second,	two-conductor rubber-covered cord entering the
    third, and fourth a-f amplifiers; the output of	junction box through a rubber grommet marked
    Microphone T-50 is amplified by the first, second,	EE-8 connects to field	Telephone E 8 ( ).
    third, and fourth a-f amplifier. A portion of the	Capacitor C301 prevents	Telephone EE-8 from
    output of the third a-f amplifier is applied to a	short-circuiting jack J301,	and m addition, serves
    modulation limiter. The modulation limiter pro-	as a low-impedance path	for the telephone ringer
    duces a d-c bias voltage which reduces the gain voltage and voice fiequencies.
    of the second a-f amplifier on extreme voice peaks
    x	x	J i .■ t ,	77,	JUNCTION BOX JB-60-A
    to prevent over modulation of the transmitter.	,------------------------------.
    The speech amplifier power supply furnishes plate	I	|
    and filament voltage for all tubes in the speech	j	0 j0|	LINE
    amplifier, and current for a carbon microphone.	-------1|---------Q
    The output of the fourth a-f amplifier is applied to	I	I MF
    the push-pull driver stage in the transmitter. The To	I_____	J30l
    driver stage develops the a-f voltage and power TELEPHONE ]	O—% Fl key
    required to drive the push-pull Class B modulator. EE-8-( )	----■-----	------U
    The a-f output of the modulator stage is combined
    with the r-f carrier in the p-a stage to produce the	|_________________j_____q
    amplitude-modulated r-f wave which is radiated	।	LINE
    from the transmitting antenna. The microphone
    switches operate the transmitter and the receiver	।______________________________I
    disabling circuits when the RECEIVER DIS- C301 200 V DC	TL 14495
    ABLING switches in the junction box are set to	Jmction Bm JB_e0_A_fmctional '
    ON. Figure 98 is a functional schematic diagram	diagram.
    of the transmitter, speech amplifier, and junction
    box for phone operation.	166. Rectifier RA—63—(*)
    Rectifier RA-63-(*) operates on an input voltage 165. Remote Operation (fig. 99)	of 105 to 125 volts, 50- to 60-cycle alternating
    a. The transmitter can be keyed for c-w opera-	current. The rectifier furnishes a d-c output voltage
    tion or voice modulated for phone operation from	sufficient to charge the 12-volt storage battery in
    a remote station located as far away as 1 mile.	Chest CH-109 at a 5-ampere rate when the battery
    The remote station consists of Telephone EE-8-( )	is in a completely discharged condition. The recti-
    and Junction Box JB-60-A, and is connected to	fier is equipped with a cord and plug ,cor connecting
    the REMOTE TELEPHONE terminals of the	it to Junction Box JB-70-A. A-c voltage is applied
    junction box by means of Wire W-110-B. To key	to the primary winding of transformer T50 0 through
    the transmitter, Key J-45 is connected to the KEY	circuit breaker CB50o and control switch SW2Oo-
    14!
    (See fig. 101.) The circuit breaker protects transformer T5Oo from damage if the secondary circuit is subjected to a short circuit or overload. The circuit breaker can be reset by pressing the red PRESS TO RESET button. The rectifier can be turned on or off and the charging rate can be controlled by switch SWsoo- When the switch is set to TRICKLE, the rectifier provides a trickle charging current of approximately 0.5 amperes into a fully charged battery. When the switch is set to FULL CHARGE, the rectifier furnishes a current of approximately 1.5 to 5 amperes, depending on the condition of the battery
    and the dry disk rectifier RA5Oo. Rectifier unit RA5Oo is connected in a full-wave bridge-type rectifier circuit. The secondary winding of transformer T500 furnishes a-c voltage to rectifier RA500 and relay RY500. When the power is turned on, relay RY5Oo is energized and the relay contacts close. The d-c output of rectifier RA500 is applied to the d-c terminals of plug PL500. When the power is turned off, the relay contacts open and prevent the battery from discharging back through the rectifier.
    r-------—™	1
    ra500	trickle
    !	°	oFFo^^'b—1 sw500	I	pl500
    rC	—	11—i	zfcn
    3	£ CHARGE	I
    y-------------;	1	j rOi
    t500	(k	I
    / cb500> I _
    ry500	TS500
    -------0-p
    j	H-H-J--------
    _____________________________fi-oJ-1-
    j-U-j
    _________________ ,..?l Q-!_■_ I--------------------------J | CD5qq
    j______________T- -.-pr- -____=_____J
    TL 16408
    Figure 101. Rectifier RA-63-(*)—functional diagram.
    142
    Section VI. CHANGES IN EQUIPMENT
    167.	Changes in Radio Transmitter BC-6I0-E
    a.	Rectifier Filament Transformer T2. Beginning with serial number 5191 on Order No. 30204-Phila-43, a change has been made in rectifier filament transformer T2. This change was necessary to prevent break-down caused by arc-over in the transformer. A hermetically sealed transformer with ceramic stand-off terminal insulators (Signal Corps stock No. 2Z9611.144) has been substituted for Stancor type 10P34 (Signal Corps stock No. 2Z9611). The new transformer does not have a secondary center tap and requires connection of the positive high-voltage lead to one of the 2.5-volt filament terminals. For equipments manufactured before the change was made, MWO SIG 11-281-4 applies.
    b.	Plate Power Relay RYi. Beginning with serial number 1353 on Order No. 30203-Phila-43, and serial number 5191 on Order No. 30204-Phila-43, a change has been made in plate power relay RYV This change was necessary to prevent failure of the transmitter due to arcing and sticking of the plate power relay contacts. An industrial contactor type relay, Allen-Bradley type A-209 bearing Hallicrafters part No. 21D056, is used to replace the Leach type 1154 relay.
    c.	Neutralization High-Voltage Isolation Capacitor C29. Beginning with serial No. 5003 on Order No. 30204-Phila-43, capacitor C29 has been changed. This change was necessary to prevent failure of capacitor C29 due to the extremely high r-f potentials to which it is subjected during tuning of the transmitter or during periods of accidental overmodulation. The modification provides a capacitor of higher voltage rating, which prevents flash-over on the adjustable neutralizing capacitor Cis and injury to operating personnel by assuring complete isolation of capacitor Cis from the high-voltage d-c circuit. The original capacitor C29, a Sangamo type HIL 0.001-mf, 2,500 d-c volts (working) Signal Corps stock No. 30A1-80, is replaced with an American War Standard capacitor CM-70-B201-J, 200-mmf, 5,000d-c volts (working), Signal Corps stock No. 3K7020122. For equipments manufactured before the change was made, MWO SIG 11-281-5 applies.
    d.	Filter Choke Li. Beginning with serial number 5191 on Order No. 30204-Phila-43, filter choke Li has been changed. The redesign of choke Li was necessary because of excessive temperature rise. A new filter choke Li Hallicrafters part No. 56C043, is used to replace the original choke Lb
    Hallicrafters part No. 56B018. The new choke has the same base-mounting dimensions but is slightly higher than the original unit. Therefore, it is not interchangeable with the original choke unless switch S Wio is removed, e below.
    e.	Interlock Switches SW2, SWio, SW13, and Circuit Wiring. Beginning with serial number 5191 on Order No. 30204-Phila-43, interlock switches SW2 and SW13 and the circuit wiring to these switches has been changed. Interlock switch SW10 has been removed from the transmitter since it performs no necessary function, and because additional space is required for the new choke coil Li (d above). Interlock switches SW2 and SW10 have been changed to open type contactor switches capable of breaking the primary current to the high-voltage plate supply transformer T6. In addition, these switches have been rewired so that opening of the access doors breaks the primary circuit to the high-voltage plate supply transformer Tg instead of the circuit to the plate power relay RYi. (See fig. 73.) This modification of interlock switch wiring is necessary to prevent injury to operating personnel resulting from failure of relay RYi to open the high-voltage when the relay contacts freeze or stick.
    Figure 102.' Mounting of tubes Ve and Vi before , modification.
    f.	Mounting of Rectifier Tubes VT-46A. When operating Radio Transmitter BC-610-E in dusty localities, large amounts of dust may ac
    143
    cumulate underneath and around the sockets for high-voltage rectifier Tubes VT-46A. This accumulation of dust can absorb moisture and cause flash-over from high-voltage terminals to ground. To facilitate cleaning of the tube sockets and to prevent failure of the transmitter due to flash-over, rectifier Tubes VT-46A can be remounted. Figures 102 and 103 show the original mounting and remounting of rectifier Tubes VT-46A, respectively. For equipments that show symptoms of the above trouble, and have not already been modified, MWO SIG 11-281-2 applies.
    amplifier tube Vios remains connected to the junction of resistors R126 and Rm-
    b. An improved replacement for dual electrolytic capacitors, reference Nos. C108, 109, (Til, 115, and C112, 113 in Speech Amplifier BC-614-E have been procured and are now available for requisition from the field. The improved capacitor, Signal Corps stock No. 3DB8-117, should be requisitioned and installed in place of the original, Signal Corps stock No. 3DB8-35, whenever replacement becomes necessary.
    Figure 103. Mounting of tubes Vs and V? after modification.
    a126	new lead
    --- --------o------WAAAz-------------
    20 M	X
    4	I	ft RI25
    C|||	FORMER	ft	ft	75M
    “T~ 8MF	lEAD	J>	ft	<
    139 ft ft 140 5m	ft	ft 5m
    V|08	VT-94	Vl06	VT-221
    \ I y	x r \P
    ft 138 ft 50M I
    5 *137 ioom
    TL 13808
    A.
    Figure 104. Diagram of change in sidetone oscillator circuit.
    168.	Changes in Speech Amplifier BC-6I4-E
    a. Beginning with serial number 1151 on Order No. 30203-Phila-43, a change has been made in the c-w sidetone circuit. The change increases the available sidetone signal level and compensates for a possible loss in signal level due to circuit element deterioration. The plate-voltage supply connection for tube V106 has been changed from the junction of resistors R126 and Rm to the junction of resistors Ri25andRi26- (See fig. 104.) This change increases the plate-voltage to the sidetone oscillator tube V106. The increased plate voltage results in an increase in output of the sidetone oscillator tube Vio6- Resistor Ri38 has been changed from 100,000 ohms to 50,000 ohms. This change increases the level of the sidetone signal available at the sidetone volume control Rm slightly more than 2 db (decibels). The plate-supply lead for sidetone
    169.	Wiring Change in Junction Box JB-70-A If operation of RECEIVER DISABLING switches SW200 and SW201 does not provide disabling of Radio Receivers BC-312-( ) and BC-342-( ), respectively, regardless of the position of RECEIVER OUTPUT switch SW204, the switches are incorrectly wired. (See fig. 105.) On an incorrectly wired Junction Box JB-70-A, operation of RECEIVER OUTPUT switch SW204 transposes the disabling action as well as the audio output of Radio Receivers BC-312-( ) and BC-342-( ) (except when RECEIVER OUTPUT switch SW204 is in NORMAL position). Such method of operation of these switches is undesirable. Correction in wiring of Junction Box JB-70-A to eliminate this fault was accomplished in production after approximately 200 Radio Sets SCR-399-A had been shipped on Order No. 14153-Phila-43.
    144
    Radio Sets SCR-499-A were shipped with doublet antenna kits (on Order No. 18372-Phila-44) before the coupling coils were changed. These radio sets bear serial numbers 1 to 17 inclusive, 19 to 41 inclusive, and 43 to 87 inclusive. The doublet antenna kits supplied with these 85 radio sets are equipped with Coil Units C-451, C-452, and C-453. These coupling coils are designed to fit inside the p-a tank coils of the transmitter. The desired degree of coupling to the antenna is obtained by moving the coupling coils in or out of the p-a tank coil.
    b. All doublet antenna kits except those mentioned in subparagraph a above are supplied with Coil Units C-387-D, C-388-C, C-389-C, C-390-C, C-447-B, C-448-B, and C-449-B. These coil units have a variable coupling link and replace the fixed link p-a tank coils previously supplied with the transmitter.
    c. As soon as circumstances will permit, Radio Sets SCR-399-A and SCR-499-A will be delivered with the variable link tank coils listed above instead of with the old fixed link tank coils. When the doublet antenna kit is issued for use with such sets, either the oils will be omitted from the kit or, if issued, should be returned to stock.
    Section VII. TROUBLE SHOOTING
    171. General Trouble-Shooting Information
    No matter how well equipment is designed and manufactured, faults occur in service. When such faults occur, the repairman must locate and correct them as rapidly as possible. This section contains general information to aid personnel engaged in the important duty of trouble shooting.
    a. Trouble-shooting Data. Take advantage of the material supplied in this manual to help in the rapid location of faults. Consult the following trouble-shooting data when necessary:
    (1)	Block diagram of Radio Sets SCR-399-A and SCR-499-A. (See fig. 96.)
    (2)	Complete schematic diagrams. (See figs. 120 through 124.)
    (3)	Simplified and partial schematic diagrams. These diagrams are particularly useful in trouble shooting, because the repairman can follow the electrical functioning of the circuits more easily than on the regular schematics, thus speeding trouble location.
    (4)	Voltage and resistance data for all socket connections.
    (5) Illustrations of components. Front, top, and bottom views which aid in locating and identifying parts.
    (6) Pin connections. Pin connections on sockets, plugs, and receptacles are numbered or lettered on the various diagrams.
    (a) Seen from the bottom, pin connections are numbered in a clockwise direction around the sockets. On octal sockets the first pin clockwise from the keyway is the No. 1 pin.
    (5) Plugs and receptacles are numbered on the side to which the associated connector is attached. To avoid confusion, some individual pins are identified by letters which appear directly on the connector.
    b. Trouble-shooting Steps. The first step in servicing a defective radio set is to section-alize the fault. Sectionalization means tracing the fault to the component or circuit responsible for the abnormal operation of the set. The second step is to localize the fault. Localization means tracing the fault to the defective part responsible for the abnormal condition. Some faults such as burned-out resistors, r-f arcing,
    RECEIVER DISABLING
    0N I9	O 10N
    ry2oo -I	U~~~I	7*00
    t—.	sw2oo	sw2oi	r—
    J_ OFF O O ’	O O OFF
    eC-312	BC-342
    I\ /k NORMAL
    TO RADIO -<------------° A°----------“---* T° RAOI°
    RECEIVER	SW204 V \>	RECEIVER
    BC-3l2-(>	° O TRANSPOSED	BC-342C)
    OUTPUT 20 AUDIO	RECEIVER OUTPUT	OUTPUT 20 AUDIO
    RECEIVER DISABLING
    ry °nH l T3°n 200^ J—.J	T—-4 c
    ♦___ SW	SW20l	___f
    1---1 o o200 normal o o
    JL off	a o	off -i
    BC-312 f\-Zl BC-342
    TO RADIO -4---------•—O Y O ♦  ----------► TO RADIO
    RECEIVER	/ \	RECEIVER
    BC-3I2-C1	SW204 O O TRANSPOSED 8C-342-C )
    OUTPUT 2D AUDIO	TRANSPOSED OUTPUT 2D AUD10
    ©RECEIVER OUTPUT
    V tl 13801
    Figure 105. Diagram of change in receiver disabling circuits.
    170. Change in Coupling Coils for
    Doublet Antenna Kit
    a. A change has been made in the coupling coils for the doublet antenna kits supplied with Radio Sets SCR-399-A and SCR-499-A. However, 85
    145
    and shorted transformers can be located by sight, smell, and hearing. The majority of faults, however, must be located by checking voltage and resistance.
    c. Sectionalization. Careful observation of the performance of the radio set while turning the equipment on often sectionalizes the fault to the transmitter or the receiver, and careful observation of the meters on the transmitter front panel often determines the stage or circuit at fault. Additional sectionalizing of the fault will be discussed in paragraphs 178 and 179.
    d. Localization. Paragraphs 178 and 180 through 182 describe the method of localizing faults within the individual components. These paragraphs include trouble-shooting charts which list abnormal symptoms and their probable causes. The charts also give the procedure for determining which of the probable locations of the fault is the exact one. In addition, there are a number of drawings which show the resistance and voltage at every socket pin connection.
    172.	Voltage Measurements
    a.	General. Voltage measurements are an almost indispensable aid to the repairman, because most troubles either result from abnormal voltage or produce abnormal voltages. Voltage measurements are taken easily, because they are always made between two points in a circuit and the circuit need not be interrupted.
    (1)	Unless otherwise specified, the voltages listed on the voltage charts are measured between the indicated points and ground.
    (2)	Always begin by setting the voltmeter on the highest range so that the voltmeter will not be overloaded. Then, if it is necessary to obtain increased accuracy, set the voltmeter to a lower range.
    (3)	In checking cathode voltage, remember that a reading can be obtained when the cathode resistor is actually open. The resistance of the meter may act as a cathode resistor. Thus, the cathode voltage may be approximately normal only as long as the voltmeter is connected between cathode and ground. Before the cathode voltage is measured, make a resistance check with a cold circuit to determine whether the cathode resistor is normal.
    b.	Precautions Against High Voltage. Certain precautions must be followed when
    measuring voltages above a few hundred volts. High voltages are dangerous and can be fatal. When it is necessary to measure high voltages, observe the following rules :
    (1)	Connect the ground lead to the voltmeter.
    (2)	Place one hand in your pocket. This will eliminate the possibility of making accidental contact with either ground or another part of the circuit and causing the electricity to travel from one hand to the other.
    (3)	If the voltage is less than 300 volts, connect the test lead to the hot terminal (which may be either positive or negative with respect to ground).
    (4)	If the voltage is greater than 300 volts, shut off the power, connect to the hot lead, step away from the voltmeter, turn on the power, and note the reading on the voltmeter. Do not touch any part of the voltmeter, particularly when it is necessary to measure the voltage between two points which are above ground.
    c.	Voltmeter Loading. It is essential that the voltmeter resistance be at least 10 times as large as the resistance of the circuit across which the voltage is measured. If the voltmeter resistance is comparable to the circuit resistance, the voltmeter will indicate a voltage lower than the actual voltage present when the voltmeter is removed from the circuit.
    (1)	The resistance of the voltmeter or any range can always be calculated by the following simple rule: Resistance of the voltmeter equals the ohms per volt multiplied by the full-scale range in volts. For example: The resistance of a 1,000-ohm-per-volt meter on the 300-volt range is 300,000 ohms (7? = 1,000 ohms per volt times 300 volts = 300,000 ohms).
    (2)	To minimize the voltmeter loading in high-resistance circuits, use the highest voltmeter range. Although only a small deflection will be obtained (possibly only 5 divisions on a 100-division scale), the accuracy of the voltage measurement will be increased. The decreased loading of the voltmeter will more than compensate for the inaccuracy which results from reading only a small deflection on the scale of the voltmeter.
    (3)	When a voltmeter is loading a circuit, the effect can always be noted by comparing the voltage reading on two successive ranges. If the voltage readings on the two ranges do not agree, voltmeter loading is excessive. The
    146
    reading (not the deflection) on the highest range will be greater than that on the lowest range. If the voltmeter is loading the circuit heavily, the deflection of the pointer will remain nearly the same when the voltmeter is shifted from one range to another.
    (4)	The ohm-per-volt sensitivity of the voltmeter used to obtain the readings recorded on the voltage and resistance charts in this manual is printed on each chart. Use a meter having the same ohm-per-volt sensitivity; otherwise it will be necessary to consider the effect of loading.
    173.	Resistance Measurements
    a.	Normal Resistance Values. When a fault develops in a circuit, its effect will often show up as a change in the resistance values. To assist in the localization of such faults, trouble-shooting data includes the normal resistance values as pleasured at the tube sockets and at key terminal points. These values are measured between the indicated points and ground, unless otherwise stated. Often it is desirable to measure the resistance from other points in the circuit to determine whether the particular points in the circuit are normal. The ■normal resistance values at any point can be determined by referring to the resistance values shown in the schematic diagram, or by use of the resistor color code. (See fig. 154.)
    b.	Precautions. (1) Before making any resistance measurements, turn off the power. An ohmmeter is essentially a low-range voltmeter and battery. If the ohmmeter is connected to a circuit which already has voltages in it, the needle will be knocked off scale and the voltmeter movement may be burned out.
    (2)	Capacitors must always be discharged before resistance measurements are made. This is very important when checking power supplies that are disconnected from their load. The discharge of the capacitor through the meter will burn out its movement, and in some cases may endanger life.
    c.	Correct Use of Low and High Ranges. It- is important to know when to use the low-resistance range and when to use the high-resistance range of an ohmmeter. When checking the circuit continuity, the ohmmeter should be set on the lowest range. If a medium or high range is used, the pointer may indicate zero ohms, even if the resistance is as high as 500
    ohms. When checking high resistances or measuring the leakage resistance of capacitors or cables, the highest range should be used. If a low range is used, the pointer will indicate infinite ohms, even though the actual resistance is less than a megohm.
    d.	Parallel Resistance Connections. In a parallel circuit the total resistance is less than the smallest resistance in the circuit. This is important to remember when trouble shooting with the aid of a schematic diagram.
    (1) When a resistance is measured and the value is found to be less than expected, make a careful study of the schematic to be certain that there are no resistances in parallel with the one that has been measured. Before replacing a resistor because its resistance measures too low, disconnect one terminal from the circuit and measure its resistance again to make sure that the low reading does not occur because some part of the circuit is in parallel with the resistor.
    (2) In some cases it will be impossible to check a resistor because it has a low-voltage transformer winding connected across it. If the resistor must be checked, disconnect one terminal from the circuit before measuring its resistance.
    e. Checking Grid Resistance. When grid resistance is checked, a false reading may be obtained if the tube is still warm and the cathode is emitting electrons. Allow the tube to cool, or reverse the ohmmeter test leads so that the negative ohmmeter test lead is applied to the grid.
    f. Tolerance Values for Resistance Measurements. Tolerance means the normal difference that is expected between the rated value of the resistor and its actual value.
    (1)	Most resistors that 'are used in radio circuits have a tolerance of at least 20 percent. For example, the grid resistor of a stage might have a rated value of 1 megohm. If the resistor were measured and found to have a value between 0.8 and 1.2 megohms, it would be considered normal. As a rule, the ordinary resistors used in circuits are not replaced unless their values are off more than 20 percent. However, in some cases precision resistors and potentiometers are used. When a resistor is used whose value must be very close to its rated value, the tolerance is usually stated on the diagram or the maintenance parts list.
    (2)	The tolerance values for transformer
    147
    windings are generally between 1 and 5 percent. As a rule, suspect a transformer which shows a resistance deviating more than 5 percent from its rated value. Allow the transformer to cool off before the resistance test is made.
    g. High-resistance Measurements. Many leakages will not show up when measured at low voltages. Most ohmmeters use a maximum test voltage of 15 volts on the highest resistance range. Where it is necessary to measure resistance above a few megohms or the leakage resistance between conductors of a cable, the test should be made using an applied voltage of 100 volts or more. If it is possible to ground one end of the resistance being checked, one of the low-voltage power supplies in the equipment can be used to provide about 300 volts for making these high-resistance measurements. The manner in which such measurements are made is indicated in figure 106. This method should be used only when the resistance being measured is very high. Be careful not to handle the meter after the circuit has been completed. The meter used should have an ohm-per-volt sensitivity of 1,000 ohms or more. The resistance of the meter is equal to the ohm-per-volt sensitivity multiplied by the range to which the meter is set. The derivation of the formula Rx = 3002?m is
    V
    shown below. Rx is the unknown resistance, Rm is the meter resistance, and V is the voltmeter reading.
    7^ = 300-7
    Rm V
    If Rx is very large, V will be small in comparison to 300. Assuming that 300-V can be re-
    + 300 VOLTS
    POWER SUPPLY
    VOLTMETER
    RESISTANCE BEING CHECKED
    Rx = ^Rm (APPROX.)
    EXAMPLE
    V=5 VOLTS. THE METER IS USED ON ITS 300 VOLT RANGE AND HAS A RESISTANCE OF 1,000 OHMS-PER-VOLT.
    RM = 300 X 1,000= 300,000 OHMS.
    Rx:	X 300,000 =18 MEGOHMS.
    □
    TL3553O
    Figure 106. Measurement of high resistance.
    placed by 300, the formula Rx — 300 is obtained.
    X ~V~
    When solved for Rx this gives Rx = 30QRm.
    V
    When making the measurement, the meter should first be put on the 300-volt scale to protect it in case Rx is very low. If the voltage used is not 300 volts, the correct value should be inserted in the formula in place of 300.
    174.	Capacitor Tests
    Capacitors which are leaky or shorted can be found by resistance checks of the stage. A capacitor which is suspected of being open can best be checked by shunting a good capacitor across it. In i-f (intermediate-frequency) circuits, keep the lead to the capacitor as short as the original capacitor leads. In 1-f (low-frequency) circuits (less than 1 megacycle), the test capacitor leads may be several inches long. A capacitor color code is shown in figures 152 and 153 for checking the capacitor value against the value shown on the circuit diagram.
    175.	Current Measurements
    Current measurements, other than those indicated by panel meters, are not ordinarily required in trouble shooting in the radio set. Under special circumstances, where the voltage and resistance measurements by themselves are not sufficient to localize the trouble, a current measurement can be made by opening the circuit and connecting an ammeter to measure the current. This procedure is not recommended except in very difficult cases.
    a.	When the meter is inserted in a circuit to measure current, it should always be inserted away from the r-f end of the resistance. For example, when measuring plate current, do not insert the meter next to the plate of a tube, but insert it next to the end of the resistor which connects to the power. This precaution is necessary to keep the meter from upsetting the r-f voltages.
    Caution: A meter has least protection against damage when it is used to measure current. Always set the current range to the highest value. Then if necessary, decrease the range to give a more accurate reading. Avoid working close to full-scale reading because this increases the danger of overload.
    b.	In most cases, the current to be measured flows through a resistance which is either known or can be measured with an ohmmeter.
    148
    The current flowing in the circuit can be determined by dividing the voltage drop across the resistor by its resistance value. The drop across the cathode resistor is a convenient method of determining the cathode current.
    176.	Tube Checking
    Tube checkers are used to check the emission of electrons from the cathode and to test for shorted elements. Tube checkers will not test the performance of high-voltage tubes, rectifiers, or some special tubes in the modulator and rectifier. Tube checkers are useful, however, for checking receiving-type tubes used in the various components.
    a.	Results obtained from a tube checker are not always conclusive, because the conditions are not the same as those under which the tube operates in the set. For this reason, the final test of a tube must be its replacement with a tube which is known to be good. In many cases it is quicker and more reliable to replace a suspected tube with a good one than to check it with the tube checker.
    b.	An operating chart and an instruction book or technical manual are provided with the tube checker. This chart indicates the setting of the tube checker for each tube type. The number of controls, their arrangement, and their settings vary with different types of tube checkers.
    177.	Analyzer BC-1052-E
    a.	General. Analyzer BC-1052-E is packed in Chest CH-89-A. Directions for setting the analyzer will be found on the chart in the cover of the chest. This equipment can be used for the following purposes:
    (1)	Voltage measurements, both direct and alternating, from less than 1 to 3,000 volts.
    (2)	Continuity tests.
    (3)	Determining values of resistors, 0 to 10 megohms.
    (4)	D-c measurements from 0.1 ma to 15 amperes.
    b.	Resistance Measurements. To test any resistor—
    (1)	Set the analyzer switches and make test prod connections as indicated in the chart for the range into which the resistor falls.
    (2)	Short the test prods and adjust the meter for full-scale deflection (zero ohms) by use of OHMS ADJUST knob.
    (3)	Touch the test prods to the ends of the resistor, at least one end of which should be disconnected from the circuit.
    (4)	Read the ohms on the OHMS scale, and multiply that reading by the value indicated on the ohms range on the rotary selector switch. Note. The ohms adjustment must be made every time the range switch is changed from one range to another.
    c.	Measurement of Alternating and Direct Voltages.
    Caution: Whenever the approximate voltage, current, or db level is unknown, always begin measurements with the highest range to prevent damaging the instrument by an overload.
    (1)	Refer to the chart for correct settings of controls, switches, jacks, and test prods before making any measurements.
    (2)	The DECIBEL calibration is for use across 500-ohm lines and loads. The scale is read directly in db.
    (3)	The OUTPUT jacks are for measuring the voltage or db level of any a-c or audio voltage. Internal circuits are made through a 0.1-mf isolating capacitor inside the instrument, and in such cases alternating current or audio superimposed on a d-c voltage may be read without harm to the analyzer.
    d.	High-voltage Measurements.
    Warning: It is extremely dangerous to make this measurement. Contact with the high voltage in Radio Transmitter BC-610-E may be fatal. Do not make this measurement except as a last resort, and then always arrange to have someone else present. The recommended procedure for measuring the high voltage is as follows :
    (1)	Insulate the analyzer well above ground by placing it on dry boards or other insulating material at least 1 inch thick.
    (2)	Set analyzer controls to proper positions for measuring 3,000 volts as indicated on the analyzer chart.
    (3)	Remove coil unit L7.
    (4)	Place red (positive) test lead prod into center jack of the jack bar of the coil unit.
    (5)	Connect black (negative) test lead to any convenient ground on the transmitter frame.
    (6)	Open right-hand cover door (over tuning units) to open its interlock switch. (This switch will be used to close the circuit (13) below).
    (7)	Fasten down the interlock switch at the left-hand cover door so that it is closed.
    149
    (8)	See that the back screen is in place so that its interlock is closed.
    (9)	Arrange the red (positive) test prod and cord so that the cord is extremely well insulated. The cord should be carefully supported so that it is free and clear of the door and frame of the transmitter and any components.
    (10)	Stand clear of the red (positive) test lead and see that no one comes in contact with it when voltage is on.
    (11)	Set PLATE POWER switch of the transmitter at ON.
    (12)	Put your left hand in your pocket.
    (13)	With your right hand, turn on the high voltage by pressing the interlock switch at the right-hand cover door.
    (14)	Read the voltage indication on the analyzer and release the interlock switch.
    (15)	Set PLATE POWER switch to OFF and remove fastening from left-hand cover interlock when finished.
    e.	Internal Batteries. The self-contained batteries of the analyzer consist of two 714-volt C batteries (Batteries BA-34), one 1^-volt heavy-duty dry cell (Batteries BA-34), and one 11/2-volt heavy-duty dry cell (Battery BA-30). These may be replaced by removing the four screws from the front panel. Remove the batteries by loosening the screws holding the brackets which hold the batteries in place. Be sure to observe the polarity when replacing batteries. The 1^-volt battery is held in place by spring clamps. Be sure to cut out a section of the battery paper cover to permit a good connection to the zinc shell.
    178.	Trouble-Shooting Procedures
    Caution: Do not change fuses or make repairs with the high voltages on, for under this condition a potential of 2,000 to 2,500 d-c volts is present on all three decks of the transmitter.
    a.	Failure of this equipment to operate properly will usually be caused by one or more of the following faults.
    (1)	Improperly connected power cable between Power Unit PE-95-( ) and Shelter HO-17-A.
    (2)	Worn, broken, or disconnected cords or plugs.
    (3)	Defective fuses.
    (4)	Burned relay contacts due to overloads.
    (5)	Wires broken from excessive vibration.
    (6)	Defective tubes.
    (7)	Inactive (dirty or cracked) crystal.
    b.	When failure is encountered and the cause is not immediately apparent, check the above items before starting a detailed examination of the component parts of the system.
    c.	Check fuses at an early stage in trouble shooting. Do not continue to burn out fuses before looking elsewhere to determine the basic source of the trouble. Insertion of an electric lamp in place of a fuse will often prove helpful in tracing the source of the trouble if fuses continue to burn out.
    d.	The cause of the trouble can usually be traced to the component at fault by means of the meters and controls on the equipment itself. The use of the schematic diagrams and a logical system of reasoning will almost always isolate the fault. For example: If the transmitter cannot be keyed from either KEY jack or Junction Box JB-70-A, the trouble might be in the 12-volt power supply, relay RY200, switch SW203, the cording from the junction box to the speech amplifier, the cord from the speech amplifier to the transmitter, or the transmitter itself. To isolate the trouble proceed as follows:
    (1	) Switch the BATTERY SOURCE switch on Junction Box JB-70-A to the other 12-volt source.- If this does not clear the trouble, the 12-volt supply is probably not at fault.
    (2	) Plug the key into the KEY jack on the speech amplifier and try to key the set. If the transmitter cannot be keyed, the trouble is in the junction box or the connecting cord. If the transmitter still cannot be keyed, the trouble is in the cord from the speech amplifier to the transmitter or in the transmitter.
    (3	) Throw the EXCITER PLATE POWER switch on the transmitter to ON. If no excitation is indicated on the EXCITATION METER the trouble is in the transmitter.
    179.	Trouble-Shooting Charfs
    The accompanying trouble-shooting charts, if properly used, simplify trouble shooting. There are four charts. The first chart covers the sec-tionalization of trouble in Radio Sets SCR-399-A and SCR-499-A. This chart lists the various symptoms which may be recognized easily by the operator, and gives the probable location for the existing trouble as well as the recommended correction. It tells the operator whether the trouble is in the transmitter, the receivers, the speech amplifier, the junction box, or the power supply. By proper use of this chart, the operator can isolate the trouble to
    150
    one particular component of the equipment, and thus save time that might otherwise be lost in checking components that are free of trouble. The second chart shows the localization of trouble in Radio Transmitter BC-610-E. This chart will aid in determining which stage in the transmitter is at fault, and will aid in localizing the trouble to the individual part in the circuit which is causing the abnormal condition.
    The third and fourth charts are similar to the second, except that they deal with localizing the trouble in Speech Amplifier BC-614-E and Junction Box JB-70-A respectively. Therefore, the first chart will be used mainly by the operator, whereas the last three, covering trouble shooting within the various components, will be used by the repairman.
    151
    180. Sec+ionalizing Trouble in Radio Sets SCR-399-A and SCR-499-A
    Symptoms	Probable trouble	Corrections
    1.	Power Unit PE-95-( ) fails to start when START button is pressed 2.	Power unit starts, but no power is available at Radio Set SCR-399-A or SCR-499-A 3.	No filament power when FILAMENT POWER switch is set to ON 4.	Low or zero reading on ANTENNA CURRENT meter 5.	No grid excitation indicated when EXCITATION METER switch is set to P.A. GRID position (assuming intermediate amplifier is operating properly) 6.	No plate current indicated on P.A. PLATE meter. Necessary grid current present. HIGH VOLTAGE PROTECT switch set to HIGH VOLTAGE PROTECT 7.	Excessive plate current indicated on P.A. PLATE meter 8.	PLATE POWER switch thrown to OFF. P.A. PLATE meter indicates plate current still flowing 9.	No excitation indicated by EXCITATION METER when EXCITER PLATE POWER switch is set to ON position 10.	Transmitter functioning normally. Radio Receivers BG-312-( ) and BC-342-( ) fail to disable during transmission	1.	Discharged battery in power unit might operate start relay, but fails to turn over the engine Broken wire in power cord or bad connection at plug START and STOP leads interchanged or disconnected either at Junction Box JB-70-A or at trailer terminal board 2.	Loose socket connection. Circuit breaker defective or circuit breaker nob closed 3.	Fuse FSi, FS2, or FS4 open. FILAMENT POWER switch, defective Damaged Cord CD-763 or poor plug connections Filament resistor Ris defective 4.	Incorrect control setting on Antenna Tuning Unit BC-939-A. Sections of transmitting antenna missing Insufficient antenna coupling 5.	Tube V1 e defective or, improperly inserted Open r-f choke CIIg2 Adjustable resistor Ru defective 6.	TRANS. ON-OFF switch on Junction Box JB-70-A not thrown to TRANS. ON position Reset necessary on overload relay Open fuse FS3 Interlock switches not closed Short in high-voltage circuit continually tripping overload relay Rectifier tube Ve or V7 defective Missing or improperly installed coil unit on jack bar Resistor R19 defective, or loose in socket 7.	Improper tuning of tank circuit Wrong coil unit Failure to use vacuum capacitor C28 when operating below 2.5 me Excessive antenna coupling No bias voltage due to open fuse FS5 or tube V 5 defective 8.	Contacts on relay RY 1 sticking because of severe overload 9.	Tuning unit improperly seated in socket Tube V8 or V9 defective EXCITER PLATE POWER switch defective BAND SWITCH not set to proper channel r 10.	RECEIVER DISABLING switches not turned to ON position Junction Box JB-70-A not functioning properly	1.	Start power unit with hand crank See TM 11-904 Repair cord or connection Connect leads properly 2.	Tighten connection. Replace or close circuit breaker 3.	Replace open fuse. Replace switch Repair cor<| or connection 4.	Set control according to tuning chart Replace missing sections Increase antenna coupling 5.	Replace tube or insert tube properly 6.	Throw switch to ON Press OVERLOAD RESET switch Replace fuse Close panels on top of transmitter tightly Check high-voltage circuit Replace defective tube Install coil unit properly Replace resistor R19, or tighten 7.	Tune tank circuit according to tuning chart Use proper coil unit Install capacitor C28 Reduce coupling Replace fuse FS5 or tube V5 8.	Clean contacts of relay RYi Caution: Leave plug out of socket SOo when working on this relay 9.	Insert tuning unit firmly in socket Replace tube Set switch to proper channel 10.	Turn switch to ON position See paragraph 182.
    152
    181. Localizing Trouble in Radio Transmitter BC-6I0-E
    Symptoms	Probable trouble	Corrections
    1.	FILAMENT POWER switch thrown to ON position. Green lamp does not light. FIL. VOLTAGE meter indicates filament voltage 2.	FILAMENT POWER switch thrown to ON position. Green lamp does not light. No voltage indicated by FIL. VOLTAGE meter 3.	FILAMENT POWER switch at ON position. Green lamp lights. No voltage indicated on FIL. VOLTAGE meter 4.	FILAMENT POWER switch at ON position. Green lamp lights. FIL. VOLTAGE meter indicated filament power present. Tubes Vi, V2, and V5 not lighted 5.	EXCITER PLATE POWER switch at ON position. No intermediateamplifier grid current indicated when EXCITATION METER SWITCH is at INT. AMP. GRID position. Tuning unit set according to tuning chart. M.O.-XTAL switch and BAND SWITCH at proper positions	1.	Lamp LM3 burned out 2.	Fuse FSi, FS2 or FS4 burned out FILAMENT POWER switch defective Damaged power Cord CD-763, or poor contacts at sockets SO201 or SO6 3.	Tube V13, V14, or V15 not in sockets Filament resistor Ris defective 4.	Fuse FS5 open 5.	Switch SW3 defective . Tube Vs or V9 defective Defective rectifier tube V12 Open resistor Rs or choke CH7	1.	Replace lamp 2.	Replace fuse Replace switch Repair cord or sockets 3.	Place tubes in sockets Replace resistor Ris 4.	Replace fuse FS5 5.	Replace switch Replace defective tube Replace defective tube Replace defective part
    153
    182. Localizing Trouble in Junction Box JB-70-A
    Symptoms
    1.	TRANS. ON-OFF switch at the TRANS. OFF position during c-w operation. No plate current indicated on P.A. PLATE meter when transmitter is keyed
    2.	Press-to-talk switch is depressed during phone operation. No plate current indicated on P.A. PLATE meter
    3.	Transmitter functioning normally on both c-w and phone operation. Radio Receivers BC-312-( ) and BC-342-( ) fail to disable during transmissions
    4.	Transmitter operating normally. Sidetone is not being received at Radio Receivers BC-312-( ) and BC-342-( )
    5.	Transmitter cannot be keyed during c-w operation from a remote position
    6.	Transmitter cannot be modulated from a remote position
    7.	During remote operation the telephone is not being fed reception from Radio Receiver BC-312-( ) or BC-342-( )
    Probable trouble
    1.	Contacts of switch SW203 closing circuit of relay RYi fail to close
    Relay RY200 fails to function
    Wiring from SW203 to PL200 defective
    Contacts of relay RY200 in circuit of the cathode of oscillator tube Vs fail to close
    2.	Relay RY200 fails to function Press-to-talk switch defective
    12-volt power supply for energizing relay RY200 lacking
    Contacts of relay RY200 in the circuit of relay RYi fail to operate
    3.	RECEIVER DISABLING switch SW200 or SW201 not turned to ON position
    Switches SW200 and SW201 defective
    4.	C.W.-SIDETONE switch SW205 at OFF position
    Relay contacts of RY200 in circuit of switch SW205B fail to close
    5.	REMOTE CONTROL EE-8 switch SW202 at incorrect position. (Also see 1 above)
    6.	Capacitor C202 defective. TRANS. ON-OFF switch SW203 at incorrect position
    7.	TRANS. ON-OFF switch SW203 at an incorrect position
    REMOTE CONTROL EE-8 switch SW 202 at incorrect position
    Corrections
    1.	Repair, adjust, and clean contacts
    12-volt power supply lacking
    Repair relay RY200
    Repair wiring
    Repair, clean, or adjust contacts
    2.	Repair or replace relay RY200
    Repair or replace switch, or replace microphone
    Repair 12-volt power supply from
    Power Unit PE-95-( )
    Switch to auxiliary battery supply
    Repair, clean, or adjust contacts of relay RY200
    3.	Turn switch to ON position
    Repair or replace switches SW200 and SW201
    4.	Turn C.W.-SIDETONE switch to TO BC-312 or to TO BC-342 position
    Clean, adjust, or repair contacts of relay RY200
    5.	Place switch SW202 at correct position
    6.	Replace defective capacitor C202 Place TRANS. ON-OFF switch at TRANS. ON position
    7.	Place TRANS. ON-OFF switch at REC. TO EE-8 position
    Turn REMOTE CONTROL EE-8 switch to correct position
    154
    183. Localizing Trouble in Speech Amplifier BC-6I4-E
    Symptoms	Probable trouble	Corrections
    1.	FILAMENT POWER switch on transmitter power panel closed. Red lamp fails to light 2.	FILAMENT POWER switch at ON position, filament voltage present at all tubes, plate voltage lacking 3.	Transmitter can be modulated by a dynamic microphone or Telephone EE-8-( ), but not by a carbon microphone 4.	Transmitter can be modulated by a carbon microphone, but not by a dynamic microphone or Telephone EE-8-( ) 5.	Transmitter can be modulated by carbon or dynamic microphone, but not by Telephone EE-8-( ) 6.	Filament voltage and plate power supplied to all tubes. Transmitter can be modulated. Sidetone lacking during c-w operation 7.	Filament voltage and plate power supplied to all tubes. Transmitter can be modulated. Speech limiter fails to limit speech peaks.	1.	Fuse FSs open, lamp LMioi burned out 2.	Rectifier tube V107 defective Secondary 250-volt winding of transformer T103 burned out Shorted filter capacitor Cios or C109 Open filter choke CH 101 3.	Resistor Rno or R123 defective Transformer T101 defective Shorted capacitor C120 or Cno 4.	Tube V101 defective Resistor R102 or R103 defective 5.	Resistor Rios defective 6.	Oscillator tube Vine defective Resistor R139, R140, Rise, R138, or R137 defective Amplifier tube Vios defective Resistor R122 or R141 defective • Capacitor C117 or Cm defective 7.	LIMITER CONTROL R134 defective Speech limiter tube V105 defective Transformer T104 defective Capacitor Cue defective Capacitor Cm defective Resistor R109 defective	1.	Replace fuse FS5, replace lamp LM101 2.	Replace tube V107 Replace transformer T103 Replace shorted capacitor Replace defective choke 3.	Replace defective resistor Replace transformer Replace capacitor 4.	Replace defective tube Replace defective resistor 5.	Replace defective resistor 6.	Replace defective tube Replace defective resistor Replace defective tube Replace defective resistor Replace defective capacitor 7.	Replace resistor Replace tube Replace transformer Replace capacitor Replace capacitor Replace resistor
    Section VIII. REPAIRS
    184.	Replacement of Parts
    Careless replacement of parts often make new faults inevitable. Note the following points:
    a.	Before a part is unsoldered, note the position of the leads. If the part (such as a transformer) has a number of connections to it, tag each of the leads.
    b.	Be careful not to damage other leads by pulling or pushing them out of the way.
    c.	Do not allow drops of solder to fall into the set, since they may cause short circuits.
    d.	A carelessly soldered connection may create a new fault. Be very careful to make well-soldered joints, since a poorly soldered joint is one of the most difficult faults to find.
    e.	When a part is replaced in r-f or i-f circuits, place it exactly as the original one was placed. A part which has the same electrical value but different physical size may cause trouble in h-f (high-frequency) circuits. Give
    particular attention to proper grounding when replacing a part. Use the same ground point as in the original wiring. Failure to observe these precautions may result in decreased gain, or in oscillation of the circuit.
    185.	Replacement of Tubes
    a.	Tube V16 is removed as follows:
    (1)	Open the doors in the top of the transmitter over the plate coil and the tuning units.
    (2)	Take out the tuning units and remove tubes V8 and Vo from their sockets.
    (3)	Remove the grid lead from the grid cap on the side of tube V16 and the plate lead from the plate cap on top.
    (4)	Turn the tube counterclockwise until it can be lifted out of its socket.
    (5)	Remove the tube through the door over the tuning unit side of the transmitter.
    155
    b.	Modulator tubes V3 and V4 are removed as follows:
    (1)	Remove the back screen.
    (2)	Take off the plate and grid leads from the caps.
    (3)	Turn the tube counterclockwise and lift it out of the socket.
    c.	High-voltage rectifier tubes V6 and V7 are removed as follows:
    (1)	Remove the back screen.
    (2)	Disconnect the plate lead from the cap.
    (3)	Turn the tube counterclockwise and lift it out of the socket.
    d.	To remove tubes V10, Vu, and V12, proceed as follows:
    (1)	Lift up the two doors in the top cover.
    (2)	Remove the tuning units.
    (3)	Loosen the clamp around the base of the tube with a screwdriver by reaching in through the door over the plate coil.
    (4)	Pull the tube straight up, gently rocking it from side to side.
    186.	Removal of Antenna Tuning Unit BC-939-A
    To remove the antenna tuning unit proceed as follows:
    a.	Disconnect the antenna and ground leads.
    b.	Disconnect the coaxial cable leading from the transmitter.
    c.	Take off the four wingnuts holding the tuning unit to the top of the transmitter.
    d.	Lift the unit up and forward.
    187.	Removal of Top of Transmitter Cabinet The top of the transmitter cabinet should be taken off when extensive work is to be done in the r-f section. Remove the antenna tuning unit first (par. 186) ; then proceed as follows:
    a.	Remove the eight bolts holding the top to the mounting straps.
    b.	Unscrew the four wing-head screws which secure the top to the cabinet.
    c.	Disconnect the two leads which are plugged in terminal strip TSg on the exciter deck.
    d.	Lift the cover clear from the cabinet.
    188.	Removal of R-F Section
    The r-f section may be removed from the transmitter as follows:
    a.	Remove all tubes for safekeeping.
    b.	Disconnect the leads from terminals 1 and 3 on terminal strip TSX on the exciter chassis apron.
    c.	Disconnect the two leads to the coil of re
    lay RY4, and release thqm from the clamp on the side of the cabinet.
    d.	Disconnect the leads to meter M2, and clear them from the bracket under the meter.
    e.	Disconnect the black lead to capacitor C12.
    f.	Pull out plugs PLX and PL2 from their sockets on the modulator deck, and release the laced cable from its bracket on the modulator chassis.
    g.	Remove the eight bolts which hold the r-f section to the straps of the cradle.
    h.	Remove the 14 bolts which fasten the r-f section to the modulator section.
    i.	Lift the r-f section off.
    189.	Removal of Chests From Shelter
    Whenever it is necessary to remove any of the major components of Radio Set SCR-399-A from Shelter H0-17-A, move the truck in such a position as to jack-knife Trailer K-52-( ), so that the rear of the truck will become more readily accessible. If possible, disconnect the trailer.
    a.	Removal of Chest CH-89-A (Seat Bench) . Two men are required to remove Chest CH-89-A from the shelter.
    (1)	Unscrew the six wing-head bolts holding the chest to the floor.
    (2)	Lower the chest from the floor of the truck to the ground, holding it by its handles.
    b.	Removal of Chest CH-88-A (Wall). Two men are required to remove Chest CH-88-A from the shelter.
    (1)	Remove cotter pins from trunk clamps.
    (2)	Unclasp all four trunk clamps.
    (3)	Remove chest by its handles.
    c.	Removal of Chest CH-119-A. Two men are required to remove Chest CH-119-A from the shelter.
    (1)	Remove Chests GH-88-A and CH-89-A.
    (2)	Remove Tool Equipment TE-48 and Cord CD-652 from Chest CH-119-A to lighten weight.
    (3)	Unclasp the four trunk clamps.
    (4)	Slide chest to the door and lower to ground.
    d.	Removal of Chest CH-120-E. Four men are required to remove Chest CH-120-E from the shelter.
    (1)	Disconnect all cords connecting Chest CH-121-A to Chest CH-120-A and close the cover of the latter.
    (2)	Disconnect Cord CD-659 from Chest CH-109-A.
    156
    (3)	Disconnect all cords from the bottom of Junction Box JB-70-A.
    (4)	Disconnect ground straps from bottom of chest.
    (5)	Disconnect Cord CD-764 from front of Speech Amplifier BC-614-E, and remove cord.
    (6)	Loosen turnbuckles holding Chest CH-120-A to table frame after removing safety wires.
    (7)	Remove chest from table frame and lower to ground.
    190.	Removal of Radio Transmitter BC-610—E Four men are required to remove Radio Transmitter BC-610-E from the shelter.
    a.	Remove Chest CH-89-A as described in paragraph 189.
    b.	Disconnect Cords CD-763 and CD-764 from their sockets on the rear of the transmitter.
    c.	Remove Antenna Tuning Unit BC-939-A from the top of the transmitter as described in paragraph 186.
    d.	Unscrew the four long wrench nuts holding the cradle of the transmitter to the floor of the shelter.
    e.	Move the transmitter and its cradle directly toward the right wall to the center of uhe shelter.
    f.	Move the transmitter around into the center aisle and toward the rear of the truck, (it will now be necessary to have three of the men on the ground to assist in lowering the transmitter from the floor of the shelter to the ground.)
    g.	Lower the transmitter directly to the ground by the four handles.
    191.	Replacement of Switches in Radio Transmitter BC-6I0-E
    a.	General. The method of removal and replacement of the majority of the switches in the transmitter is apparent upon inspection. It is important, however, that all leads to the switch be tagged before they are disconnected from the lugs or terminals.
    b.	Removal of Band Switch SW8. First remove the r-f section as described in paragraph 188. Rest the r-f section on its top, and remove bank switch SW8 as follows:
    (1)	Disconnect all leads to the switch; tag each one.
    (2)	Remove the knob from the shaft by loosening the two setscrews.
    (3)	Remove the nut and washer from the shaft on the front of the panel.
    (4)	Remove the switch from the bottom of the exciter deck by unscrewing the five nuts which secure it to the deck.
    (5)	Replace in reverse order. When replacing the knob, see that the setscrew in the side of the handle engages the flat side of the shaft.
    192.	Replacement of Parts in Speech Amplifier BC-6I4-E
    The parts of Speech Amplifier BC-614-E are easily accessible when the chassis is removed from the cabinet. To remove the chassis, disconnect the three cords from the front panel. Release the four winged panel locks and pull the chassis straight out of the cabinet.
    a.	Limiter Control R134. To replace the limiter control, first loosen the resistor mounting strip just behind the control by unscrewing the two nuts holding the strip to its mounting. Move the strip to the rear. Unsolder the three leads to the control, and tag each. Unscrew the two nuts holding the control to the front of the chassis, and remove the control. Replace in reverse order.
    b.	Microphone Gain Controls. To replace either microphone gain control, first disconnect the leads to the control. Remove the knob by loosening the setscrew holding it on the shaft. Remove the nut and washer securing the control to the panel, and take the control off the panel. Replace in reverse order.
    193.	Removal of Junction Box JB-70-A
    To remove Junction Box JB-70-A from the cabinet, first disconnect all cords from the right side, front panel, and bottom of the chassis. Disconnect the grounding braid from the bottom of the chassis with a screw driver. Disconnect the remote telephone line,. if connected. Disconnect the cord which connects the junction box to the speech amplifier from its socket on the panel of the speech amplifier. Release the four panel locks and pull the chassis forward. With a screw driver, disconnect the leads from terminal 9, 10, 11, and 12 on TS200 ; and pull the cord through the rubber grommet in the right side of the junction box. Pull the chassis all the way out of the cabinet.
    194.	Rustproofing and Repainting
    When the finish on the cabinets or panels of any of the components of Radio Set SCR-399-A or
    157
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    169
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    |[ _f 7	,.	I	____ 7-AuOlO
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    H'32	T331	|2M	• _, ’TOP.N2 "	VT’80
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    "—------------------------------— ------1 •	002 t	2Z^'
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    4-	TUBE SOCKET CONNECTIONS	’	8?v	,1-1 \l
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    BOTTOM VIEW OF SOCKETS	'	T 103
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    CAPACITORS
    REF SYMBOL	WORKING VOLTS		REF SYMBOL	WORKING VOLTS
    cIOi CIO2 CIO3 C|04 CIO5 Cl06 ClOT C|08 C|09 Clio Cl n C|,2 Cl 13 C| 14 C| 15	600 V DC 600 V DC 600 V DC 25 V DC 600 V DC 600 V DC 25 V DC 475 V DC 475 V DC 25 V DC 475 V DC 475 V DC 475 V DC 600 V DC 475 V DC		C| 16 C| 17 C| IB C119 C|20 C|2l CI22 C|23 C,24 CI25 C|26 C|27 C|28 CI29 C, 30	400 V DC 600 V DC 600 V DC 600 V DC 25 V DC 600 V DC 600 V DC 600 V DC 400 V DC 600 V DC 600 V DC 500 V DC 600 V DC 500 V DC 500 V DC
    RESISTORS
    REF SYMBOL	WATTS		REF SYMBOL	WATTS
    RIOI	1/2		ri2 1	l
    rI02	1/2		rI22	1/2
    rI03	1/2		R124
    rI04	1/2		rI25	2
    rI05	1/2		Rl 26	2
    RlO6	1/2		R|27	1
    rI07	1/2		Rl 26	l
    rI08	1/2		rI29	1/2	•
    ri09	1/2		ri30	1/2
    ri 10	1/2		Rl 31	1/2
    Rl 1 2	1/2		rI32	1/2
    Rl 1 3	i/Z		rI33	1/2
    R| 14	V2		rI35	1/2
    R| 15	1		rI36	1/2
    Rl 16	1/2		rI38	1/2
    Rl 17	1/2		Rl 39	1/2
    Rl 18	1/2		rI40	1/2
    R| 19	1/2		rI4 1	1/2
    rI20	1/2		R|42	1/2
    TL-848IA
    Figure 123. Speech Amplifier BC-614-E—schematic diagram.
    MO ___
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    * - 1- — - - —— - -*- - - - —----X___________ LX	CURRENT Z" ------------
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    Figure 120. Radio Sets SCR—399—A and SCR—499—A—simplified schematic diagram.
    CAPACITORS
    REF. SYMBOL	WORKING VOLTS	REF. SYMBOL	WORKING VOLTS
    Cl	600 V DC	C 1 5	2,500 V DC
    C2	600 V DC	C 1 6	1,000 V DC
    C3	600 V DC	C 17	1,000 V DC
    c4	600 V DC	C 1 9	4,000 V DC
    ^5	600 V DC	C20	600 V DC
    C6	600 V DC	c21	600 V DC
    	600 V DC	C23	600 V DC
    C8	500 V DC	C21j	1,000 V DC
    C9	600 V DC	C25	600 V DC
    c 10	600 V DC	^26	600 V DC
    C | |	6000 V DC	- c27	100 V DC
    CI3	500 V DC	C28	20, 000 V RMS TEST
    CI1	2500 V DC	C29	5, 000 V DC
    RESISTORS
    REF. SYMBOL	WATTS	REF. SYMBOL	MATTS
    Rl	1/2	RI5	1/2
    r2	20	RI6	2
    R3	20	RI7	2
    R4	1	RI8	75
    R5	20	R 19	600
    R6	2	R20	10
    R7	2	R2I	1/2
    R8	2	R22	1/2
    R9	20	R23	1
    RIO	20	R24	10
    R 1 1	100	R25	2
    R 12	50	R28	1/2
    R 1 3	200	R34	10
    Rm	1/2	R35	1/2
    I	‘----------------------	| XJ7 ANTENNA L6	2 I0MC
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    Figure 124. Junction Box JB-70-A—schematic diagram.
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    175
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    Figure 126. Radio Transmitter BC-610—E, exciter deck—practical wiring diagram.
    176
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    Figure 128. Antenna Tuning Unit BC—939—A—practical wiring diagram.
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    \ c*e	*	\ ° o /	rO □ Eh
    \	- 200 V DC	\	Y /
    >l-2grio	SEOVOC g~HAsVAC J /	'	!	D T
    VT-220	VT-145	M50 V DC 4480 V DC	lOOVAC
    O I	।--------------------Z-o	O~\----5VAC ----1	6 3 V AC
    \ o 7	u
    L- 870 V AC---------O	0-7-------------1
    ----5V AC-----	*“
    PC'7 q qCI6
    48ov dc —I	T T A
    450 V DC '	X480 V DC
    SOCKET VIEWS ARE BOTTOM VIEWS
    NOTE ALL VOLTAGES MEASURED WITH 1,000 OHM PER VOLT VOLTMETER IN ANALYZER BC-IO52-E SUPPLIED WITH RADIO SET SCR-399-A
    VOLTAGES MEASURED TO GROUND UNLESS OTHERWISE INDICATED
    TL l«40?
    Figure 132. Radio Transmitter BC-610-E, exciter deck3 voltages at tube sockets and terminal strips.
    179
    _ *________________________________________erqnt edge of modulator chassis___________________
    117 V AC	——
    -«ovoc —।	-fl I®	,\~IT5 V D.C \~T~435 v AC __pJ5vAC
    C2j c20	=1 5s/) A I’ T h Ci C	°=
    '	J 7 I’	“I fle kl [2	05 a“ | T’
    x'-" Aso/ *	j j" > p D?
    2	« S“ ' -9OVDC	SOj	so_	ro	435 v AC
    "»	I
    - 380 VDC -.	r -380 V DC	*	l~360 V DC
    Q a 0 G *• ?)
    E-90V.DC	-400 VDC	-360-'SC	.J-300 V DC
    ■ITS VDC-	PHONE	PHONE	-300 VDC ______,	7	500 VAC
    *'______-40VDC--	Tt>	40 VDC	T3	300 VOC ______T| ^OOVAC
    50-6 OC	I-1
    □	Q -360 VDC -------OF------------------360 VDC □	□	□	SrA , |-> rj
    CW	G	C	CW	ST 100	115	«LI m Ln Ll Li-
    on	He -360 V DC  Q^-— -360 VDC	Lg o - g
    C-360 V DC *3S0VDC	' -	\	PHONE---------------------------PHONE	rd X	S □	-7VDC-□	□	□	TV DC	O	O	\ I /	\__/	/	\
    I	\o-,	J/	\<5	r«/ I	L	\	\Q	q/
    2-5 VAC	X1 J	V	V	|tL_2.5VDC \	\
    \	/	\	/	---------'	-------L-5VAC
    \	/	\	/	VT-218	V7-2.«
    \_y	W	VT-145
    VT-95	VT-95
    SOCKET VEWS ARE BOTTOM VIEWS
    NOTE: ALL VOLTAGES MEASURED WITH 1,000 OHM PER VOLT VOLTMETER IN ANALYZER BC-IO52-E SUPPLIED WITH RADIO SET SCR-399-A VOLTAGES MEASURED TO GROUND UNLESS OTHERWISE INDICATED	TL 16411
    Figure 133. Radio Transmitter BC-610-E, modulator deck, voltages at tube sockets and transformer^
    180
    FRONT EDGE; OF POWER SUPPLY CHASSIS
    BOTTOM VIEW OF POWER SUPPLY
    NOTE! ALL VOLTAGES MEASURED WITH 1,000 OHM PER VOLTMETER IN ANALYZER BC-IO52-E SUPPLIED WITH RADIO SET SCR’399 “ A
    VOLTAGES MEASURED TO GROUND UNLESS OTHERWISE INDICATED
    Figure 134- Radio Transmitter BC-610--E, power-supply deck, voltages at tube sockets and transformers.
    2000 V DC PHONE
    O	25CO V DC	CW
    2160 V DC PHONE
    O	2600 V DC C
    2160 V DC PHONE
    26 00 V DC CW |-------------------100 VAC-----------
    --------------------------(k
    os	EH----------------------------
    ----25 V AC--------------O	S ?□
    2160 V DC PHONE	2160 V DC PHONE
    —~^2600 V DC CW	"—--^ 2600 V DC CW
    2 5V AC j | j—2 5 V AC
    /Z
    ।	। i r	।
    \ r a '
    .... ' — ----------------------------------'_________
    VT-46A	VT-46A
    J83
    VT- 94	VT-231	VT- 80
    ____ O45VOC^.	76 V DC .	_____,240V0C	_____
    6VDC TI64	I-------Z)o\
    fO	\	VT-231	/Q)	O 0>~r  ---------
    Zp ,Q/	\ /O Q\ 240 V DC Zp oQ/\ O	J/
    \	\	U"> rJ	"Ls.3VAcX * *0 *0 ’Q -^265 V DC
    22.5VDC -s	L63VAC J	V/-30VDC	_____-___________
    z^6j VAC —F~~7^ - 1.2 V o C
    250 V DC -- -----------265 V DC
    TIOI	TIO2	CMlOl
    □s ’□	D3 ’□
    □ □ □
    VT-231	VT-233
    8.7 V DC	25 V DC	-\
    □« >□	D' 40 Fax
    50 V DC -x/\O o) '■6 sdcV	(q Oyle.SVAcX
    "Zp	Tp 2p>/
    8 7 V DC	----15 0 V DC	----
    SOCKET VIEWS ARE BOTTOM VIEWS
    NOTE all VOLTAGES MEASURED WITH 1,000 OHM PER VOLT VOLTMETER IN ANALYZER BC-IO52-E SUPPLIED WITH RADIO SET SCR-399 A
    VOLTAGES MEASURED TO GROUND UNLESS OTHERWISE INDICATED	TL 16412
    »
    Figure 135. Speech Amplifier BC-614-E, voltages from tube sockets to chassis.
    182
    AP	PENDIX I
    MAINTENANCE PARTS LIST
    For maintenance parts information, see appropriate sections of Army Service Forces Catalogs SIG-7 SCR-399 and SIG-7 SCR-499, Organizational Spare Parts, and SIG-8 SCR-299, SCR-399, SCR-499, Higher Echelon Spare Parts.
    183
    APPENDIX II
    REFERENCES
    I. Parts List
    SIG 1
    SIG 2
    SIG 3
    SIG 4-1
    SIG 4-2
    SIG 5
    SIG 6
    SIG 7
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SIG 8
    SB 11-8
    SB 11-10
    Introduction to ASF Signal Supply Catalog (when published).
    Complete Index to ASF Signal Supply Catalog (when published).
    List of Items for Troop Issue.
    Allowances of Expendable Supplies.
    Allowances of Expendable Supplies for Schools, Training Centers, and Boards.
    Stock List of all Items.
    Sets (when published).
    Organizational Spare Parts.
    Higher Echelon Spare Parts for Radio Sets SCR-399-A and SCR-499-A.
    Higher Echelon Spare Parts for Radio Receivers BC-312-( ) and BC-342-( ).
    Higher Echelon Spare Parts for Radio Transmitter BC-610.
    Higher Echelon Spare Parts for Speech Amplifier BC-614-( ).
    Higher Echelon Spare Parts for Antenna Tuning Unit BC-939-A.
    Higher Echelon Spare Parts for Telephones EE-8-( ).
    Higher Echelon Spare Parts for Headset HS-30- ( ).
    Higher Echelon Spare Parts for Shelter HO-17.
    Higher Echelon Spare Parts for Junction Box JB-70-A.
    Higher Echelon Spare Parts for Power Unit PE-95-A, B, C, D.
    Higher Echelon Spare Parts for Frequency Meter Set SCR-211-( ).
    Higher Echelon Spare Parts for Microphone T-30- ( ).
    Chests for Running Spares.
    Signal Corps Kit and Materials for Moisture and Fungi-Resistant Treatment.
    2. Technical Manuals on Auxiliary Equipment and Test Equipment
    TM	11-300	Frequency Meter Sets SCR-211-A, SCR-211-B, and SCR-211-C
    TM	11-303	Test Sets I-56-C, I-56-D, I-56-H, and I-56-J.
    TM	11-307	Signal Generators I-72-G, I-72-H, and I-72-J.
    TM	11-321	Test Set I-56-E.
    TM	11-2613	Voltommeter 1-166.
    TM	11-2626	Test Unit 1-176.
    TM	11-2627	Tube Tester 1-177.
    TM	11-472	Repair and Calibration of Electrical Measuring Instruments.
    3. Painting, Preserving, and Lubrication
    SB 11-10 Signal Corps Kit and Materials for Moisture and Fungi-Resistant Treatment.
    4. Shipping Instructions
    U. S. Army Army-Navy General Specification for Packaging and Packing for Oversea Spec No. Shipment.
    100-14A
    5. Decontamination
    TM 3-220
    6. Demolition
    FM 5-25
    Decontamination.
    Explosives and Demolitions.
    7. Camouflage
    FM 5-20
    Camouflage, Basic Principles.
    184
    8.	Other Technical Publications
    FM 21-6	List of Publications for Training.
    FM 21-7	List of War Department Films, Film Strips, and Recognition Film Slides.
    FM 21-8	Military Training Aids.
    FM 21-40	Defense Against Chemical Attack.
    FM 24-6 Radio Operator’s Manual, Army Ground Forces.
    FM 24-11	Combined Operating Signals.
    FM 24-18	Radio Communication.
    TB SIG 5	Defense Against Radio Jamming.
    TB	SIG	13	Moistureproofing and Fungiproofing Signal Corps Equipment.
    TB	SIG	25	Preventive Maintenance of Power Cords.
    TB	SIG	66	Winter Maintenance of Ground Signal Equipment.
    TB	SIG	69	Lubrication of Ground Signal Equipment.
    TB SIG 72 Tropical Maintenance of Ground Signal Equipment.
    TB	SIG	75	Desert Maintenance of Ground Signal Equipment.
    TB	SIG	143	Installation Instructions for Vehicular Radio Sets.
    TM 1-455 Electrical Fundamentals.
    TM 11-227 Signal Communication Equipment Directory, Radio Communication Equipment.
    TM 11-300 Frequency Meter Set SCR-211-( ).
    TM 11-310 Schematic Diagrams for Maintenance of Ground Radio Communication Sets.
    TM 11-314 - Antennas and Antenna Systems.
    TM 11-333 Telephones EE-8, EE-8-A and EE-8-B.
    TM 11-430 Batteries for Signal Communication Except those Pertaining to Aircraft.
    TM	11-453	Shop Work.
    TM	11-454	The Radio Operator.
    TM	11-455	Radio Fundamentals.
    TM	11-462	Signal Corps Reference Data.
    TM 11-483 Suppression of Radio Noises (when published).
    TM 11-496 Training Text and Applicatory Exercises for Amplitude-modulated Radio Sets.
    TM 11-499 Radio Propagation .Handbook.
    TM 11-904-H Power Units PE-95-G and PE-95-H.
    TM 11-850-N Radio Receivers BC-312-N, BC-312-NX, BC-342-N, BC-314-G, and BC-344-D.
    TM 11-2737 Installation of Radio and Interphone Equipment in Shelter HO-17 (when published).
    TM 38-250 Basic Maintenance Manual.
    9.	Forms
    Unsatisfactory Equipment Report. (See fig. 151.)
    10.	List of Abbreviations
    a-c....................................................... alternating-current
    a-f....................................................... audio-frequency
    a-v-c .................................................... automatic-volume-control
    BFO ...................................................... beat-frequency-oscillator
    cps....................................................... cycles per second
    c-w ...................................................... continuous-wave
    db ....................................................... decibel (s)
    d-c....................................................... direct current
    h-f....................................................... high-frequency
    i-f ...................................................... intermediate-frequency
    i-p-a .................................................. intermediate-power-amplifier
    kc........................................................ kilocycle (s)
    1-f ...................................................... low-frequency
    ma........................................................ milliampere(s)
    me........................................................ megacycle (s)
    mmf ...................................................... micromicrofarad (s)
    m-o ...................................................... master-oscillator
    m-v-c................................... ................. manual-volume-control
    185
    „_a	................................................. power-amplifier
    \	............... ,............... radio-frequency
    I I. Glossary
    See glossary, TM 11-455.
    186
    Table VIII. Continuity checks for cables and terminal strips
    a. Radio Transmitter BC-610-E
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohms)

    Plug PLi (in modulator)	PL!	7 8	Remove plug PLi from socket SOi Remove plug PLi from socket SOi	Terminal 1 of terminal strip TSi ' Terminal 3 of terminal	0 0
    		9	Remove plug PLi from socket SOi	strip TSi Terminal 4 of terminal	0
    		11	Remove plug PLi from socket SOi	strip TSi Terminal 5 of terminal	0
    				strip TSi
    Plug PL2 (in modulator)	pl2	7 8	Remove plug PL2 from socket SO2 Remove plug PL2 from socket SO2	Terminal 7 of terminal strip TSi Terminal 8 of terminal	0 0
    		10	Remove plug PL2 from socket SO2	strip TSi Terminal 10 of terminal	0
    		11	Remove plug PL2 from socket SO2	strip TSi Terminal 9 of terminal	0
    		12	Remove plug PL2 from socket SO2	strip TSi Terminal 11 of terminal	0
    				strip TSi
    Plug PL3 'in Modulator)	pl3	1	Fuse FS5 in operating condition. Remove plug PL3 from socket SO3	Terminal 5 of terminal strip TS3	0
    		1	Fuse FS.5 in operating condition. Remove plug PL3 from socket SO3	Terminal 5 of plug PL3	0
    		1	Fuse FS5 in operating condition; lamp LM3 in its socket. Remove plug PL3 from socket SO3	Terminal 6 of plug PL3 Note. Setting of potentiometer Bis varies resistance reading.	9-21
    		1	Fuses FSi and FS5 in operating condition; lamp LM3 in its socket; switch SWi at ON. Remove plug PL3 from socket SO3	Terminal 3 of plug PL3 Note. Setting of potentiometer Ris varies resistance reading.	9-21
    		1	Fuse FSs in operating condition; lamp LM3 in its socket; switch SW6 at ON. Remove plug PL3 from socket SO3 and plug PL4 from socket SO4	Terminal 11 of plug PL4 Note. Setting of potenti-ometer Ris varies resistance reading.	9-21
    		1	Fuse FSs in operating condition; lamp LM3 in its socket; switch SW3 at ON. Remove plug PL3 from socket SO3 and plug PL4 from socket SO<	Terminal 12 of plug PL4 Note. Setting of potentiometer Ris varies resistance reading.	9-21
    		1	Switch SW7 at PHONE; fuse FSs in operating condition. Remove plug PL3 from socket SO3	Terminal 2 of plug PL3	0
    		4		Terminal 4 of terminal	0
    		4 4	Switch SW12 closed. Remove plug PL3 from socket SO3 Potentiometer Ri8 full counterclockwise. Remove plug PL3 from socket SO3	strip TS3 Terminal 6 of terminal strip TS3 Terminal 6 of plug PL3	0 15
    		5	Fuses FS2 and FS4 in operating condition. Remove plug PL3 from socket SO3	Terminal 7 of plug PL3	0
    		7	Fuses FS2 and FS3 in operating condition; lamp LMi in its socket. Remove plug PL3 from socket SO3 and plug PLi from socket SO4	Terminal 7 of plug PL.»	340
    		7	Fuses FS2 and FS3 in operating condition; lamp LM4 in its socket; switch SWi at NORMAL. Remove plug PL3 from	Terminal 8 of plug PL4	.1
    			socket SO3; remove plug PL< from socket SO 4
    		7	Fuses FS2 and FS3 in operating condition; lamp LMi in its socket; switch SW4 at NORMAL. Remove plug PL3 from socket SO3	Terminal 1 of terminal strip TS3	.1
    		7	Fuses FS2 and FS3 in operating condition; switch SW7 at C.W. Remove plug PL3 from socket SO3	Terminal 2 of terminal strip TS3	0
    		7	Fuses FS2 and FS3 in operating condition; switch SW7 at PHONE. Remove plug PL3 from socket SO4	Terminal 3 of terminal strip TS3	0
    		8	Remove plug PL3 from socket SO3	Terminal 7 of terminal	0
    				strip TS3
    187
    a. Radio Transmitter BC-610-E (Contd.)
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohins)
    Plug PL4 (in modulator)	PL4	9 9	Remove plug PL4 from socket SO 4 Potentiometer R12 full clockwise. Remove plug PL4 from socket SO4	Ground or chassis Terminal 10 of plug PL4	500 500
    Plug PLn (on meter panel)	•	1 2 3 4 G 7 8	Remove plug PLn from socket SOu Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove’plug PLn from socket SOn	Terminal 5 of terminal strip TS2 Terminal 8 of terminal strip TS2 Terminal 6 of terminal strip TS2 Terminal 9 of terminal strip TS2 Terminal 7 of terminal strip TS2 Terminal 10 of terminal strip TS2 . Terminal 12 of terminal strip TS2 Terminal 11 of terminal strip TS2	0 0 0 0 0 0 0 0
    Socket SO 1 (in modu-	SOt	7	Remove plug PLi from socket SOi	Ground or chassis	0
    lator)		8 9	Remove plug PLi from socket SOi Remove plug PLi from socket SOi	Terminal 2 of socket SO 5 Terminal 11 of socket SO 1	0 85
    Socket SO2 (in modulator)	SO2	7 7 7 10 11	Remove plug PL2 from socket SO2; remove plug PL3 from socket SO3 Remove plug PL2 from socket SO2 Remove plug PL2 from socket SO2; remove plug PL3 from socket SO3 Remove plug PL2 from socket SO2; remove plug PL4 from socket SO4 Remove plug PL2 from socket SO2	Terminal 4 of socket SO3 Terminal 8 of socket SO2 Terminal 5 of socket SO3 Terminal 11 of socket SO 4 Tap on resistor Ri 1	0 3 3 0 0
    Socket SO3 (in modu-	SO3	1	Remove plug PL3 from socket SO3	Terminal 6 of socket SO3	1.5
    lator)		1 1 2 3 7	Remove plug PL3 from socket SO3 Remove plug PL3 from socket SO3 Remove plug PL3 from socket SO3 Remove plug PL3 from socket SO3 Remove plug PL3 from socket SO3	Terminal 1 of socket SO 5 Terminal 3 of socket SO 5 Terminal 6 of socket SO3 One side of socket SOo Other side of socket SOo	0 1.5 280 0 0
    Socket SO4 (in modulator)	SO4	7 9 10 11	Remove plug PL4 from socket SO4 Remove plug PL4 from socket SO4 Remove plug PL 4 from socket SO 4 Switch SW5 closed. Remove plug PL3 from socket SO3; remove plug PLi from socket SO 4	Terminal 8 of socket SO4 Terminal CT of transformer Ti (2.5-volt winding). An open bias voltage contact on relay RY3 Terminal 8 of socket SO 3	10 3,200 0 80
    Socket SO5 (in modulator)	SO 5	8 6 5 4	Remove plug PL4 from Socket SO4	Ground or chassis Terminal 7 of socket St) 5 Terminal 8 of socket SO 5, ground, or chassis Terminal 11 of socket SO 4	0 37 180 0
    Sockets SO7, SO8, * and SO9 (in tuning	SO7	1	Switch SWn at position 1	Terminal 5 of tube Vs (JAN-6V6)	0
    unit)	SO7	1	Switch SWi i at position 2 or 3	Ground or chassis	0
    	SOs	1	Switch SWn at position 2	Terminal 5 of tube Vs (JAN-6V6)	0
    	so8	1	Switch SWn at position 1 or 3	Ground or chassis	0
    	SO9	1	Switch SWn at position 3	Terminal 5 of tube Vs (JAN-6V6)	0
    	SO9	1	Switch SWn at position 1 or 2	Ground or chassis	0
    	SO-)				 . 	 . 	 	 • 				 			■		 						—		—- - —>•
    	SO8 SO9J	2		Ground or chassis	0
    188
    a. Radio Transmitter BC-610-E (Contd.)
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohms)
    Socket SO7, SO8, ?nd SO9 (in tuning unit) (Contd.) Socket SO 11 (on upper control panel) Terminal strip TSi	SO7 so8 so9 so7) so8 SO9J SO7 SO7 so8 so8 so9 SO9 SO7) so8 SO9 SO7 SO8) SO9J SO7 so8 so9 SO7 SO8 so9 SOu TSi	4 4 4 7 8 8 8 8 8 8 10 11 11 11 11 12 12 12 1 2 2 3 7 8 1 1 1 1 1 1 3 4 5	Switch SW11 at position 1 Switch SWn at position 2 Switch SWn at position 3 Switch SWn at position 1 Switch SWn at position 2 or 3 Switch SWn at position 2 Switch SWn at position 1 or 3 Switch SWn at position 3 Switch SW11 at position 1 or 2 Switch SWn at position 2 or 3 Switch SWn at position 1 or 3 Switch SWn at position 1 or 2 Switch SWn at position 1 Switch SWn at position 2 Switch SWn at position 3 Meter switch SW8 at DOUBLER PLATE. Remove plug PLn from socket SOn Meter switch SW8 at DOUBLER PLATE. Remove plug PLn from socket SOn Meter switch SW8 at DOUBLER PLATE. Remove plug PLn from socket SOn Meter switch SW8 at DOUBLER PLATE. Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove plug PLn from socket SOn Remove tube Vie from its socket Remove tube Vie from its socket Remove lamp LM2 from its socket. Remove plug PLn from socket SOn	One side only of capacitor Ci One side only of capacitor C1. One side only of capacitor Ci Terminal 9 of terminal strip TS2 Terminal 3 of socket for tube V9 (JAN-6L6) Terminal 7 of sockets SO8 and SO9 Terminal 3 of socket for tube V9 (JAN-6L6) Terminal 7 of sockets SO7 and SO9 Terminal 3 of socket for tube V9 (JAN-6L6) Terminal 7 of sockets SO7 and SO8 Ground or chassis Terminal 10 of terminal strip TS2 Terminal 12 of socket SO7 Terminal 12 of socket SO8 Terminal 12 of socket SO9 Plate caps of tubes V10 and V11 Plate caps of tubes V10 and V11 Plate caps of tubes V10 and V11 Terminal 3 of socket SOn Terminal 4 of socket SOn Terminal 6 of socket SOn Terminal 5 of socket SOn Ground or chassis One side of socket for lamp LMi Ground or chassis Terminal 8 of terminal strip TS2 Terminal 12 of terminal strip TS2 Terminal 3 of terminal strip TS2 Terminal 4 of terminal strip TS2 Terminal 11 of terminal strip TS2 Terminal 8 of socket for tube V8 (JAN-6V6) Terminal 2 or 3 of socket for tube V12 (JAN-5Z3) Terminal 2 or 3 of socket for tube V12 (JAN-5Z3)	0 0 0 20 0 0 0 0 0 0 0 20 0 0 0 0 0 0 .6 .6 .4 500 0 0 0 35,000 0 0 0 4 0 70 0 0
    189
    a.	Radio Transmitter BC-610-E (Contd.)
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohms)
    Terminal strip TSi (Contd.) Terminal strip TS2	TS2'	7 9 10 3 4 5 7 9 10 12	Tubes V13, V14, V15 in their sockets Switches SW2, *SWio, SW13 closed	Terminal 8 of terminal strip TSi Terminal 6 of terminal strip TS2 Terminal 11 of terminal strip TSi One side of meter M3 Other side of meter M3 Grid connection of tube V16 Terminal 3 of sockets for tubes V10 and Vn Terminal 4 of socket for tube V9 Terminal 2 of sockets for tubes V10 and V11 Ground or chassis	1.0 0 0 0 0 20 5,000 50,000 20,000 0
    Terminal strip TS3	ts3	1 2 3 4 4 6 8 8 9	Relay RY2 at normal	Terminal 0 of transformer t6 Terminal 2600 of transformer Te Terminal 2000 of transformer Te Terminal 5 of terminal strip TS3 Terminal 7 of terminal strip TS3 An open contact on relays RY2 and RY5 Ground or chassis Aside of meter M2 Ground or chassis	0 0 0 1 3 775 75,000 0 0
    * SWio was omitted on models beginning with Serial No. 5191 on Signal Corps Order No. 30204-P-44 and on all transmitters thereafter.
    b.	Speech Amplifier BC-614-E
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohms)
    Socket SO101 (marked DYNAMIC MIC. 8)	SO101	1 2		Ground or chassis Terminal 4 of socket SO102	0 0
    -		2 3	* .	Tip contact of jack J102 Terminal 3 of socket SO102	0 500,000
    Socket SO 102	SO102	1 2 2 5 6 7 7		Terminal 3 or 6 of tube V106 (JAN-6N7) Tip contact of jack J101 Terminal 2 of socket SO103 Ground or chassis - Terminal 4 of socket SO103 Terminal 3 of socket SO103 Terminal 1 of socket SO 103	500 0 0 7,000 0 0 16
    		•8		Ground or chassis	0
    Socket SO103	SO 103	5 6 6 8		Positive terminal of meter M101 Ground or chassis Terminal 7 of socket SO103 Ground or chassis	0 35 35 0
    Transformer Tjos	T103	CT CT	Insert dummy phone plug in Jack J102	Ground or chassis Ground or chassis	311 511 *375
    * This reading applied on all Signal Corps orders except Signal Corps Order No. 14153-P-43.
    190
    c. Junction Box JB-70-A
    Measured from	Ref symbol	Term or lead No.	Action or condition	Measured to	Resistance (in ohms)
    Terminal strip TS2eo Note. Disconnect all in Plug PL200 Plug PL201 (to Loudspeaker LS-3 in Chest CH-20) Plug PL202 (to BC-342 PHONE 2ND AUDIO) Socket SO200 (power input)	TS200 erconnectin PL200 PL201 PL202 SO200	1 3 3 6 6 8 12 12 12 g cables wh 1 2 3 4 5 6 7 8 Tip Sleeve Tip Sleeve 1 2 2 2 3 3 3 3 3 3 3 3 3	Switch SW203 at TRANS. ON Switch SW205 at TO BC-312 or TO BC-342 Hold relay RY200 closed Switch SW202 at position 1, 3, or 5 Switch SW202 at position 2, or 4; switch SW203 at TRANS. ON en making the following checks except connections to Receiver output transpose switch in NORMAL position Press STOP button to close switch SW206A Switch SW207 at PE-95 Switch SW207 at PE-95 Switch SW207 at PE-95; switch SW200 at BC-312 ON. Hold relay RY2oo closed Switch SW207 at PE-95; switch SW201 at BC-342 ON. Hold relay RY200 closed Switch SW207 at PE-95; switch SW200 at ON. Hold relay RY200 closed Switch SW207 at PE-95; switch SW201 at ON. Hold relay RY200 closed Switch SW207 at PE-95; switch SW203 at TRANS. ON Switch SW207 at PE-95; switch SW203 at TRANS. ON. Switch SW202 at position 1 or 5 Switch SW207 at PE-95; switch SW203 at TRANS ON; switch SW202 at position 2 or 4	Terminal 2 of terminal strip TS200 Terminal 4 of terminal strip TS200 Ground or chassis Ground or chassis Terminal 11 of terminal strip TS200 Terminal 12 of terminal strip TS200 Other side of EE-8 in chest CH-120 Sleeves of jacks J200, J201, J202, J203, J204, and J205 Ground or chassis terminal strip TS200. Terminal 4 of terminal strip TS200 Terminal 3 of terminal strip TS200 Terminal 6 of terminal strip TS200 Terminal 7 of terminal strip TS200 Terminal 5 of terminal strip TS200 Terminal 2 of terminal strip TS200 Terminal 1 of terminal strip TS200 Terminal 8 of terminal strip TS200 Terminal 9 of terminal strip TS200 Terminal 12 of terminal strip TS200 Terminal 9 of terminal strip TS200 Terminal 12 of terminal strip TS200 Terminal 4 of socket SO200 One side of sockets SO201 and. SO202 One side of sockets SO207, SO208, and SO209 A-c contact of socket SO203 Terminal 4 of socket SO204 Terminal 7 of terminal strip TS200 Terminal 2 of socket SO204 Terminal 2 of socket SO205 Terminal 2 of socket SO204 Terminal 2 of socket SO205 Tip contact of jacks J200 and J201 One side of the remote line Ground or chassis	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 200 0 0 0 0 100 100 100
    191
    c.	Junction Box JB-70-A (Contd.)
    Measured from	Ref symbol	Term or lead No.	Action or condition		Measured to	Resistance (in ohms)
    Socket SO200 (power input) (Contd.)		4 5			Ground or chassis One side of sockets SO201	0 0
    		5 5			and SO202 One side of duplex sockets SO207, SO208, and SO209 One a-c terminal of	0 0
    		6	Press START button to close	switch	socket SO203 Terminal 4 of socket	0
    			SW206A		SO200
    Socket SO203 (on Rectifier RA-63-(*) )	SO203	+ 12V	Switch SW207 at AUX		Terminal 4 of socket SO204	0
    Socket SO204	SO204	1			One side of the remote	0
    					line
    		1			Ground or chassis	0
    		3			Ground or chassis	0
    Socket SO205	SO205	1			Ground or chassis	0
    		3			Ground or chassis	0
    Socket SO206 (duplex spare)	SO206	Either GND terminal			Ground or chassis	0
    Socket SO210 (audio cord)	SO210	1 ' ■ 1	Switch SW205 at TO BC-312		Tip contact of jacks J202 and J203 Terminal 5 of terminal	5,000 5,000
    		1	Switch SW204 at NORMAL		strip TS200 Terminal 2 of socket	0
    		1	Switch SW204 at TRANSPOSE		SO210 Terminal 10 of terminal	0
    		2	Switch SW204 at TRANSPOSE		strip TS200 Terminal 9 of terminal	0
    		2	Switch SW204 at TRANSPOSE		strip TS200 Tip contact of jacks J204	5,000
    		2	Switch SW205 at TO BC-342;	switch	and J205 Terminal 5 of terminal	5,000
    		3	SW204 at TRANSPOSE		strip TS200 Ground or chassis	0
    		4			Ground or chassis	0
    		_
    192
    Table IX. Data for checking transformers, chokes, and inductors
    Note. Resistances of less than 1 ohm are given as 0. All measurements are made with windings disconnected from the associated circuit.
    a.	Radio Transmitter BC-610-E and Antenna Tuning Unit BC-939-A.
    		Ref	Windings	D-c	Inductance
    Component		symbol	or	resistance	(in
    			terminals	(in ohms)	microhenries)
    R-f choke		CHi		20	1,000
    R-f choke		CH2		20	1,000
    R-f choke		CH 3		32	2,500
    R-f choke		ch4		8.5	2,500
    R-f choke		ch5		20	1,000
    R-f choke		ch6		20	1,000
    R-f choke		ch7		20	1,000
    R-f choke		ch8		20	1,000
    R-f choke		ch9		42	10,000
    Filter choke		Li		90	6 x 106
    Filter choke		l2		125	6 x 10°
    Filter choke		L3		125	6 x 106
    Filter choke		l4		58	11 x 106
    Antenna coupling coil		L5			1.8
    Antenna loading coil		Le			100
    Coil Unit C-387-B		L7			58
    Cod Unit C-388-A		L7			32
    Coil Unit C-389-A		l7			18
    Coil Unit C-390-A		l7			12
    Coil Unit C-447		l7			5.9
    Coil Unit C-448		l7			3.5
    Coil Unit C-449		l7			2
    Antenna loading coil		l44			14
    Tuning unit
    M-o grid coil	TU-47	l8			89
    M-o grid coil	TU-48	l9			55.5
    M-o grid coil	TU-49	Lio			41.0
    M-o grid coil	TU-50	Li 1			21.4
    M-o grid coil	TU-51	L12			14.1
    M-o grid coil	TU-52	L13			7.4
    Crystal-oscillator cathode coil	TU-47	Li4			37
    Crystal-oscillator cathode coil	TU-48	L15			19
    Crystal-oscillator cathode coil	TU-49	Lie			9.2
    Crystal-oscillator cathode coil	TU-50	L17			66.0
    Crystal-oscillator cathode coil	TU-51	Lis			22.8
    Crystal-oscillator cathode coil	TU-52	L19			18.0
    Buffer-doubler plate coil	TU-47	L2q			40
    Buffer-doubler plate coil	TU-48	L2i			30.8
    Buffer-doubler plate coil	TU-49	l22			20.6
    Buffer-doubler plate coil	TU-50	L23			12.6
    Buffer-doubler plate coil	TU-51	l24			8.6
    Buffer-doubler plate coil	TU-52	L25			5.66
    Intermediate-amplifier plate coil	TU-47	L26			40
    Intermediate-amplifier plate coil	TU-48	l27			30.8
    Intermediate-amplifier plate coil	TU-49	L28			20.6
    Intermediate-amplifier plate coil	TU-50	l29			12.6
    Intermediate-amplifier plate coil	TU-51	L30			8.6
    Intermediate-amplifier plate coil	TU-52	L31			5.66
    M-o grid coil	TU-53	L32			7.5
    Buffer-doubler plate coil	TU-53	L33			2.56
    Intermediate-amplifier plate coil	TU-53	l34			2.56
    M-o grid coil	TU-54	L35			12.7
    Buffer-doubler plate coil	TU-54	L36			4.84
    Intermediate-amplifier plate coil	TU-54	L37			1.15
    Crystal-oscillator cathode coil	TU-53	L41			8.0
    Crystal-oscillator cathode coil	TU-54	L42			14.2
    Power transformer		Ti	500-0-500-volt secondary;	135
    			117-volt primary;	1.5
    			2.5-volt, 5.0-amp secondary.	0
    			5.0-volt, 3.0-amp secondary	0
    Filament transformer		t2	117-volt primary;	11
    			100-volt primary;	10
    			2.5-volt 10-amp secondary	0
    Filament transformer		t3	100-volt primary;	3
    			5-volt, 16-amp secondary	0
    Power transformer		t4	100-volt primary;	2.0
    			5-volt, 10.5-amp secondary	0
    193
    a. Radio Transmitter BC-610-E and Antenna Tuning Unit BC-939-A (Contd.).
    Component	Ref symbol	Windings or terminals	D-c resistance (in ohms)	Inductance (in microhenries)
    Power transformer (Contd.)		6.3-volt, 3.5 amp secondary;	0
    		5-volt, 3-amp secondary	0
    Power transformer	t5	115-volt primary;	1.5
    		435-0-435 secondary	85
    Power transformer	t6	2,000-volt primary tap;	0
    		2,600-volt primary tap;	0
    		total secondary	140
    Audio transformer	T'z	500 line primary;	35
    		G to G secondary;	950
    		G to CT secondary	475
    Audio transformer	t8	P to P primary;	250
    		P to CT primary;	125
    		G to G secondary;	170
    		G to CT secondary	85
    Modulation transformer	t9	P to P primary;	300
    		P to B primary;	150
    		P to B + secondary	135
    Relay winding	RYi*		540
    Relay winding	RYi		97
    Relay winding	ry2		780
    Relay winding	ry3		280
    Relay winding	RY 4		480
    Relay winding	RY 5		6
    * Supplied with Signal Corps Orders Nc. 14153—Phila—43 and 30204—Phila—43 only.
    b.	Speech Amplifier BC-614-E.
    Component	Ref symbol	Windings or terminals	D-c resistance (in ohms)	Inductance (in microhenries)
    Audio transformer	Tioi	1 to 2;	11
    		3 to 4	13.5
    Audio transformer	T102	1 to 3; 2 to 3; or	660
    		1 to 2;	330
    		4 to 5	35
    Power transformer	T103	115-volt primary;	16
    		6.3-volt, 2-amp secondary;	0
    		5-volt, 2-amp secondary;	0
    		250-250 secondary	600
    Audio transformer	T104	2 to 3;	3,750
    		8 to 5; 8 to 7; or	8,500
    		6 to 5	4,500
    Filter choke	CHj		700	29
    c.	Junction Box JB-70-A.
    Component	Ref symbol	Windings or terminals	D-c resistance (in ohms)	Inductance (in microhenries)
    Relay winding	.RY2oo		200	1.5
    194
    Table X. Performance Characteristics
    Description	Indicating meter	Meter switch position	Normal	Limits
    				Maximum	Minimum
    Line voltage (a-c) Filament voltage Buffer-doubler plate current Intermediate-amplifier grid current Intermediate-amplifier plate current P-a grid current (PLATE POWER OFF) P-a grid current (PLATE POWER ON) P-a plate current (PHONE) P-a plate current (C.W.) Modulator plate current (no modulation) Modulator plate current (100% modulation) Power output (voice) (4 me) Power output (c-w)	FIL. VOLTAGE EXCITATION METER EXCITATION METER EXCITATION METER EXCITATION METER EXCITATION METER P. A. PLATE P. A. PLATE MODULATOR PLATE MODULATOR PLATE	DOUBLER PLATE INT. AMP. GRID INT. AMP. PLATE P. A. GRID P. A. GRID	115 volts 5.0 volts 35 ma 2 ma 150 ma 75-100 ma 65- 80 ma 250 ma 290 ma 40 ma 200 ma 320 watts 500 watts	125 volts 5.3 volts 8 ma 175 ma 260 ma 300 ma 50 ma	105 volts 4.9 volts 25 ma 1 ma 60 ma 50 ma 200 ma 200 ma 35 ma 210 watts 325 watts
    Table XI. Characteristics of vacuum tubes
    Signal Corps Tube	VT-46A	VT-80	VT-94	VT-95	VT-100	VT-103	VT-107	VT—115	VT-139	VT—145	VT—218	VT-220	VT-231	VT-233
    JAN type	866A/866	80	6J5	2A3	807	. 6SQ7	6V6	6L6	OD3/ VR-150	5Z3	100-TH	250-TH	• 6SN-7GT	6SR7
    Description	Mercury vapor half-wave rectifier	High vacuum full-wave rectifier	Triode	Triode	Beam power	Duplex diode triode	Beam power	Beam power	Voltage regulator	High vacuum full-wave rectifier	Triode	Triode	Twin triode	Duplex - diode triode
    A-c filament voltage A-c filament current (amp) D-c plate voltage D-c screen voltage D-c grid-bias voltage Max a-c voltage per plate Max inverse peak voltage D-c plate current (ma) D-c screen current (ma) D-c grid current (ma) Max d-c output current (ma) Plate dissipation (watts) Approx grid driving power (watts) Approx output power (watts) Plate resistance (ohms) Transconductance (microohms) Amplification factor Load resistance (ohms)	2.5 5.0 10,000 250	5.0 2.0 400 1,400 110	6.3 0.3 250 -8.0 -9.0 7,700 2,600 20	2.5 2.5 300 -62 40 15 800 5,250 4.2 3,000	6.3 0.9 600 250 -50 100 9.0 3.0 25 0.22 37.5	6.3 0.3 250 -2.0 0.8 91,000 1,100 100	6.3 0.45 300 150 -25 35 5 3.0 12	6.3 0.9 375 200 -35 88 9 3.5 20 0.18 17 f	150 30	5.0 3.0 500 1,400 250	5.0 6.5 2,000 225 100 380 30 16,000	5.0 10.5 2,500 -220 290 70 250 42 600 32	6.3 0.6 250 -8.0 9.0 7,700 2,600 20	6.3 0.3 250 -9.0 9.5 0.3 8,500 1,900 16 10,000
    195
    j--------------- 83 *------------4
    WEIGHT = 4300 LB LOADED	TLI645I
    Figure 136. Shelter H0-17-A—dimensional outline sketch.
    196
    1	!	[1 I'
    M	J.	•	. =■ s
    I I
    4-.- ■	H—	!► ; _
    ■* l£------------— 55^’----------- . r
    “’4
    h---------------------------------J L---,4---j
    WEIGHT = I65 LB LOADED TLI6457
    Figut e 137. Chest CH—88—A—dimensional outline sketch.
    197
    J/,s
    CHEST CH-88-A
    LAYOUT OF CONTENTS
    y	y	y	y	y	y	y	y
    COIL UNIT C-387-3 COIL UNIT C-388-A COIL UNIT C-389-A COIL UNIT C-39O-A COIL UNIT C-447 COIL UNIT C-448 COIL UNIT C-449 CAPACITOR C2g 2.0-3.5 MC.	3.5-45 MC.	4 5-57MC	5.7-8 MC.	8-11 MC,	11-14 MC.	14-18 MC.	OR C30
    QUANTITY 2	QUANTITY 2	QUANTITY 2	QUANTITY 2	QUANTITY 2	QUANTITY 2	QUANTITY 2	kammc
    □ U M fwr
    QUANTITY 2
    ~y y y y y y y y
    TU-47	TU-47	TU-51	TU-51	-	MICROPHONE T-50 CAPACITOR C2g
    RELAY RY,	°UANT'TY '	,2MMF
    1	CARTON	QUANTITY I
    —i------------1------------1------------t---------- PLATE POWER SPARE FUSES	SPARE
    V	V	y	QUANT)TY (	QUANTITY I	PILOT LAMPS
    TU-48	TU-48	TU-52	TU-52
    ~y	y	y	y	~y	y	y	y
    TU-49	TU-49	TU-53	TU-53	TU-47	TU-49	TU-51	TU-53
    y	y	~y	y	y	y	~y	~y
    TU-50	TU-50	TU-54	TU-54	TU-48	TU-50	TU-52	TU-54
    ----—----------—-------------------------------------11 “---------------------------------------------------
    TLI6462
    Figure 138. Chest CH-88-A—lay-out of contents.
    198
    ll*"'	--II ■■ ~ "..[ "1BI-'*- - \	r-T-^s— ~ay —•err-'  ~	~ I	- r	" * -	I	-■ J ■	—
    o o ~© o ©	© ^r~~ °	°	)
    ------—.—---------------------------CJ_.—“ ...	----------xU":—	^"1.
    -|vp	into
    v	2
    I |____________________________________________________________________________________________________[I ____________	. ;	♦ ..."~'j"
    L________________________________________________________.78±-l_________________________________________J	k-6i-4-------6j-|‘
    F*	78 2 C-C MTG HOLES	“ C-C MTG HOLES 8	1
    -------------------------------------------------------eo‘------------------------------------------------
    I " ---------18 ±.--------
    WEIGHT--300 LB LOADED	TLI6458
    Figure 139. Chest CH—89—A—dimensional outline
    199
    ____________________________________________________________________________________I ______________________________________________________________________________________
    CHEST CH-89-A CONTENTS CHART
    HINGE______________ HINGE	HINGE	HINGE
    A	HYDROMETER ~ 25/
    VT-22O	VT-2IB	VT-218	TUBE	Quantity-'|L	VT-2I8	2-GROUND STRAPS (B7A2O8)	MAST BASE RING FOR MP-47
    —	FOR SH E LT E R B	»■ ■ * utitv ■
    SPARES ___________________ 2-GROUND CLAMPS(76BI17)	QUANTITY- I
    r OR |4 J	FOR TRUCK BODY	co
    OUANTITY-I QUANTITY-1 QUANTITY-1 SPEECH AMP > CA«BON	QUANTITY-1	CAPACITOR	T	MAST BASE SPR.NG
    AND	TETRA - CH LORIDE	Q.q C?X
    RADIO TRANS. QUANTITY-1	jMFp 4Q00V	1	ASSEMBLY FOR MP-47
    , )	- 1	„ 1	—t-------------------,---—---- quantity-ieach	§
    -J	y	y 'y CAPACITOR	____________________ “■	CORD CO-314
    5	Clft C17	2'-7	.	CORD CO-316
    = OPERATING OPERATING OPERATING	n a - a a MFn nnnv	5
    «	u	85 8-5MFO IOOOV SPARE	ANALYZER BC-IO52-E	®	«
    - SPARES	SPARES	SPARES	QUANTITY-1	QUANTITY-1	J	QUANTITY - I EACH	g
    ° CARTON I	CARTON 2	CARTON 3	--------- REC ANTENNA FOR TRANS	2 « J	f
    ©	X-,,, .taoo GUY ASSEM8LV	L *“	?	STAKE ASSEMBLY GP’B	°
    “	INSULATORS,	QUANTITY-2	STRAP ST-I9-A	P z P-5	OU4NTITY-2	K
    “• ___________ GASKETS AND	3 SI IS A	£ u. 5	OUANTHY 2	<
    T7	f)	~7)	BUSHING 777	H---------- QUANTITY-3	J o a. g uj	£
    FOR MP-47 S REC ANTENNA -S	© £ 5	-	IOO FT ANT WIRE
    TROUBLE	GUY ASSEMBLY	" 1	, o UJ r> 1
    LAMP SMALL TCOLS SPARE 77}-------------------- OUANTITY-2 MAST BASE ^COUNTERPOISE CP-I5-B " 2 ? « j >
    WITH	AND	LAMP	._________________ BRACKET	„„„„ „„	 r °: Q
    = s_	= r W
    lli	Io	T I (a) • i
    1	i	i A i
    . T) , AT I L-ZZl WEIGHT = 87.5 LB LOADED TLI6460
    Figure Hl. Chest CH—10&-A—dimensional outline sketch.
    ’ 201
    ,	 BOX BX-34-B	QUAN.2 IIO V TROUBLE LAMPS	SPARE TUBES FOR TRANS.	|7 TOOL BOX TE-48
    		^7
    	47 FREQUENCY METER SCR-2II
    TYPEWRITER
    		VT-22O QUAN.2		VT-218 QUAN. 2	VT-218 QUAN, MISC.TRANS.TUBE	MISC. TRANS. TUBES
    TLI6464
    Figure llj.3. Chest CH-119—( )—lay-out of contents.
    Is	<»	»	a	s I	J1
    | si	a	a	a	 /Of	XX/ld.
    TO	/7 (Next superior headquarters)	(Station)	(Technical service)
    cOMPLlETEMAJ^^ITEM	~ ~
    NOM FNOATlfRF	“	XXfy
    73g ~ a=> / o — E Xy
    MODEL	MANUFACTURER -
    e	xxx	XX^yo^A-
    U. S. A. REG. NO.	SERIAL NO.	7/	DATE RECEIVED ~if
    £Xde^ ~X. /4153-XXjd -4-5'0/	GZ8	2 XXa 44
    EQUIPMENT WITH WHICH USED (if applicable)	::	~.
    (Xyccdd XXt SO.E' -399- C ) XX^ /-/O-//_________________________________________________________________________
    NOMENCLATURE OF DEFECTIVE COMPONENT
    DART NO. -	TYPE
    3D68-34	C Jo) /vy'jLdtf 6 a*/f - /o + fojb, GGou.d.Q.
    MANUFACTURER	“	"	"	U *	~~9	DATE INSTALLED
    ____________________________/4 XXr 44
    V * LENGTH OP SERVICE
    DATE OF INITIAL TROUBLE	TOTAL PERIOD OF OPERATION BEFORE FAILURE (FILL IN WHERE APPLICABLE)’
    7ZO X'-Jr 44	Y E A RS	MONTHS	DAYS	HOURS	MILES	ROUNDS
    TOTAL YEARS MONTHS DAYS
    TIME	z*)	A	C	~	-	-	-
    INSTALLED	L>	O	Co
    DESCRIPTION OF TROUBLE AND PROBABLE CAUSE
    GIVE TYPE OF FAILURE. MECHANICAL. ELECTRICAL. WORKMANSHIP. MATERIAL. DESIGN
    C JO Xld-Ze/CE Cred/		i^ 44
    RECOMMENDATIONS	* '	f	(/ /Y	* ——£/	{.
    ___________ ft- isXnd.
    OFFICE	STATION	DATE	SIGNATURE	~
    ______________________________________________
    (Technical service)	NAME
    TO CHIEF	/9.C EL A. Wt L SO74
    NAME	f	V	f	‘	RANK AND TITLE	/J
    Ca&tr.j	C.
    STATION	ijanK	ORGANIZATION
    ______________________________________________________________________________________S7± dLl ■	&
    INSTRUCTIONS___________________________________________________________ft '
    1	• h *s imperative that the Chief of Technical Service concerned be advised	5. It will not be practicable or desirable in all cases to fill all blank spaces
    at the earliest practical moment of any constructional, design, or operational	of the report. However, the report should be as complete as possible in order
    defect in materiel. This form is designed to facilitate such reports and to provide	to expedite necessary corrective action. Additional peHirent information not
    a uniform method of submitting the required data.	provided for in the blank spaces should be submitted as inclosures to the form.
    2.	This form will be used for reporting manufacturing, design or operational	Photographs, sketches or other illustrative material are highly desirable.
    defects in materiel with a view to improving and correcting such defects, and for	6.. When cases arise where it is necessary to communicate with a chief cf
    use in recommending modifications of materiel.	'	service in order to assure safety to personnel, more expeditious means of coir.-
    3.	This form wiU not be used for reporting failures, isolated material defects or L„U“Cah°n QWauthor“ed- This fom	be u6ed to confiTm	madi
    malfunctions of materiel resulting from fair-wear-and-tear or accidental damage	e^e o.Y8, meailj' . .	. ,. j f
    nor for the replacement, repair, or the issue of parts and equipment. It does not	7J T?1S f,or”	m°de °a‘	U81n? V =?nnc.S ONJamzations and forward^,
    replace currently authorized operational or performance records	“ duplicate through command channels to the cmef of technical service Tho
    .	j	office of the chief of technical service receiving the report will forward an iniorma-
    4.	neports ot malfunctions and accidents involving ammunition will continue	tion copy to the Commanding General, Army Ground Forces or Army Air F jees,
    N '	as directed in the manner described in AR 750-10 (Change whichever is applicable, and to the Commanding General, Army Service lorces.
    5?r‘	8- Necessity for usinw this form will be determined by the using or service troops.
    W. D., A. O. O. Form No. 468
    1 December 1943	16-37786-1 u. s. covebnuemt raixTmeorrics
    TLI534O
    Figure 151. WD AGO Form f68.
    COLOR	SIGNIFICANT FIGURE	MULTIPLIER		VOLTAGE RATING (VOLTS)	CHARACTERISTIC (AWS MICADIELECTRIC)
    		RMA MICA- AND CERAMIC-DIELECTRIC AWS MICA- AND PAPER-DIELECTRIC	AWS CERAMICDIELECTRIC
    BLACK	0	1	1		A
    BROWN	1	10	10	100	B
    RED	2	100	100	200	C
    ORANGE	3	1000	1000	300	D
    YELLOW	4	10,000		400	E
    GREEN	5	100,000		500	F
    BLUE	6	1,000,000		600	G
    VIOLET	7	10,000,000		700
    GRAY	8	100,000,000	0.01	800
    WHITE	9	1,000,000,000	0 1	900
    GOLD		0 1		1000
    SILVER		0.01		2000
    NO COLOR				500	TLI34I7-I
    Figure 152. Capacitor color codes.
    207
    RMA 6-DOT COLOR CODE FOR MICA-DIELECTRIC CAPACITORS
    -H~	p	SIGNIFICANT FIGURES
    S	W	FIRST SECOND THIRD
    1 CAPACnun I rW-ft
    | MiQRcifej
    V?ALIiNrE CAPACITANCE MULTIPLIER RATING TOLERANCE
    RMA 3-DOT COLOR CODE FOR	AWS 6-DOT COLOR CODE FOR
    MICA-DIELtCTRIC CAPACITORS	PAPER-DIELECTRIC CAPACITORS
    ARE ALWAYS SIGNIFICANT FIGURES
    wnc mlvvmio piper SECOND
    SIGNIFICANT FIGURES	SILVER a , 1	/
    FIRST SECOND	J\ 2	/
    ______fW /
    9 9 9	=	\	=
    T-T toito
    \	OPERATING	'
    MULTIPLIER	TEMPERATURE	MULTIPLIER
    MULTIPLIER	RANGE
    The silver dots serve to identify this marking. The ___________.__________________ sixth dot shows whether the capacitor has a maxi-
    Capacitors marked with this code have a voltage mum operating temperature of 167°F (black) or rating of 500 volts.	185°F (brown)
    CAPACITANCE TOLERANCE				TEMPERATURE COEFFICIENT OF CAPACITANCE xlO’6 mmf/mmf/°c
    RMA & AWS MICA-AND PAPERDIELECTRIC (PERCENT)	RMA CERAMICDIELECTRIC (PERCENT)	AWS CERAMICDIELECTRIC GREATER THAN 10 MMF (PERCENT)	AWS CERAMICDIELECTRIC LESS THAN 10 MMF (MMF)
    20	20	20	2.0	0
    1	1	1		- 30
    2	2	2		— 80
    3	3	2.5	0.25	-150
    4	4			-220
    5	5	5	0.5	-330
    6	6			-470
    7	7			-750
    8	2.5			4- 30
    9	10	10	1.0	Not specified
    5
    10
    20				TLI347-2
    Figure 153. Capacitor color codes.
    208
    AWS 6-DOT COLOR CODE FOR	AWS COLOR CODE FOR TUBULAR
    MICA-DIELECTRIC CAPACITORS	CERAMIC-DIELECTRIC CAPACITORS
    J™ significant figures	significant figures
    blaVk first second	first second
    DLAU\
    =1111 Ik—1= q o> q	timix *
    P O Q	c™EUntE	ToZnce"
    characteristic capacitance multiplier	OQOu	‘
    TOLERANCE	Ljy---______________
    The black dot serves to identify the AWS marking.	ciI^Vakit5
    Capacitors marked with this code are rated at 500	SIGNIFICANT FIGURES
    volts, except the following AWS type CM35 capaci- -----——_________________________________
    tors with capacitances of 6,800, 7,500, and 8.200 Capacitors marked with this code have a voltage micromicrofarads, and AWS type CM40 capacitors rating of 500 volts, with capacitances of 9,100 and 10,000 micromicrofarads are rated at 300 volts.
    RMA COLOR CODE FOR TUBULAR
    CERAMIC-DIELECTRIC CAPACITORS
    -----------------------------------------------------------------------------------
    I	I
    ►	RMA: Radio Manufacturers Association <	CAPACITANCE SIGNIFICANT FIGURES
    >	aia/c a ■	j	<	TOLERANCE FIRST SECOND THIRD
    J	AWS: American War Standard	<	\	\	I
    >	(American Standards Association]	<	\	\	|	S
    i--------------------------------------I	=—C' BlHwBll—
    >	NOTE: These color codes give all capacit- |	r	Kvl Lvw J
    >	ances in micromicrofarads.	1	/
    ►	<	TEMPERATURE mii.tidiicd
    L______________________________________COEFFICIENT MULTIPLIER
    Capacitors marked with this code have a voltage rating of 500 volts.
    209
    [*rkSoR I
    H	a a n F O	AWS COLOR CODE F0R
    5 11 II 11	» FIXED COMPOSITION RESISTORS
    FIXED COMPOSITION RESISTORS	tolerance multiplier significant figures’
    _____________________________________	\	( FIRST SECOND
    \ , j / .......... /
    SIGNIFICANT FIGURES	V7/,T
    FIRST (BODY) SECOND (TIP	O	O	O'
    EImA “-------------------------------------------------T
    significant figures |	[|	FIRST SECOND
    U MULTIPLIER U	\,.	/ ~...
    =1 | 11 u=
    reii-------------	iOLMlJ____________'
    => / \
    V& Y/^Y/X	MULTIPLIER TOLERANCE
    FIRST ^COND^^-ANCE
    SIGNIFICANT FIGURES MULTIPLIER	--------—---------.------------
    The exterior body color of insulated resistors may ______________________________________be any color except black. The usual color is natural
    Insulated fixed composition resistors with axial tan. The exterior body color of uninsulated resistors leads are designated by a	natural tan	background	with axial leads may be either black or white. The
    color Non-insulated fixed composition resistors with	exterior body color of uninsulated resistors with
    axial leads are designated	by a black	background	radial leads may be black or it may be the color pf
    color	the first significant figure of the resistance value.
    SIGNIFICANT	TOLERANCE
    COLOR	FIGURE	MULTIPLIER (PERCENT)
    BLACK	0	1
    BROWN	1	10
    RED	2	100
    ORANGE	3	1000
    YELLOW	4	10,000
    GREEN	5	100,000	►	j
    >	4
    BLUE	6	1,000,000►	RMA:	Radio Manufacturers Association	j
    VIOLET 7 10,000,000,	AWS	American War Standard	4
    GRAY	8	100 000 000	>	(American Standards Association) <
    _________________________'	'____________________________>	4
    WHITE	9	1,000,000,000	►	<
    GOLD	0 1	5
    SILVER	0.01	10
    NO COLOR	20
    ———J____________________ -	n !34I8
    Figure 157. Resistor color codes.
    210
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    21 i
    TUNING CHART OF RADIO TRANSMITTER BC610-E'I f TUNING CHART OF RADIO TRANSMITTER BC-610-E
    for	for
    Tuning Unit TU-47	Tuning Unit TU-48
    NOTE Ule v C 50	Frequency Range 2.0-2.5 M C	Frequency Range 2.5-3 2 M C
    On 2-2.5 MC
    APPROXIMATE DIAL SETTINGS	APPROXIMATE DIAL SETTINGS
    * Tuurur rnuToni c	ANTENNA TUNING	nnrn.nur rnvrT.>	TIIMtur fONTOni 9	ANTENNA TUNING
    OPERATING CRYSTAL	TUKIHG CONTROLS	UH|1 3(.?39.A	OPERATING CRYSTAL	TUNING CONTROLS	0f.939.A
    FREQUENCY FREQUENCY <011 ---- ------—----------•	FREQUENCY FREQUENCY COIL ---- (? .-------------
    IM IF	INI TuM.lr BflM0	IM IF UNIT	INT riLiLr BAND
    KILOCYCLES USED	*° D0US X T G SWITCH ^P11"6 L0A0IMG	KILOCYCLES USED	*0 DOUB ' TUHIMG SWITCH COUPLING LOADING
    POSITION	____ I —	POSITION
    2000	2000	O387 D ]]	2.4	4.7	20	2-10 4.9	4.6	2500	2500 C'387 D 10	07	2 8	7	210	43 226
    2550	2550 O387 D 18	1.7	3.4	12.5 2 10 4.3 23.9
    2050	2050	C-387-D 22	3.2	5.2	3 0	2-10 4.9	7.1	2600	26fl0 c.3g7.D 26	? Jfl 4 3 25Q
    2100	2100 C 387 D 32	3.8	5.5	3 9	2-10	5.1	9.4	2650	2650 C 387 D 33	3.1	4.4	21.5 2 10 4.2 26.2
    r„	2700	2700 C 387 D 40	3.7	4.9	25.5 210 4.2 27.3
    2150	2150	C387-D	41	4.3	5.9	47.5	2-10	4.9	11.4
    2750	2750	0387-D	46	4.1	5.3	29.0	210	4.2	28.3
    2200	2230	03870	49	4.8	6.3	56.5	2-10	4.8	13.3	2800	2800	C.337-D	52	45	5 g	33q	210	4.2	29.3
    2250	2250	0387 D	57	5.2	6.7	6 3.5	210	4 .7	1 5.1	2850	2850	O387 D	58	4.9	6.1	365	210	4.2	30.2
    290S	2900	C-387 D	63	5.2	6.5	405	210	4.5	31.0
    2300	2300	C 387 D	63	5.6	7.0	70	2-10	4.6	16.8
    2950	2950	O387 D	68	5.6	6.8	435	210	4.1	32.0
    2350	2350	0387-0	69	6.0	7.4	77	2-10	4.5	18.3	3^	3000	C387-D	73	5.9	7.2	4 7 0	2	10	4.1	32.7
    2400	2400	C 387 D	75	6.3	7.7	83	2-10	4.5	19.8	3050	3050	0387-0	78	6.1	7.4	50.0	2	10	4.1	33.5
    3150	31G0	C-387-D	82	6.4	7.7	53.0	210	4.1	34.2
    2450	2450	0387 0	81	6.7	8.0	88	2-10	4.6	21.3
    3150	3150	03870	87	6.6	7.9	55.5	210	4 2	35.0
    2500	2500	C387-D	85	[ 7.0	8.2	94 | 2-10	4.6	22.6	3200	3200	0387-0	90	6.8	8.0	58.5	210	4.2	35.6
    HOTI-FOO EXACT M.O. SETTUI5, USE FREQUENCY METER SET SCR-211-()	MOTE-FOR EXACT M.O. SETTING, USE FREQUENCY METER SET SCR-211-()
    PART HO. 9M1QS	J	___________________________________PART WO. 92B105_
    NOTE: VIEW ABOVE SHOWS BOTH FACES OF CHART. FACES COMBINE BACK TO BACK	TL1668I
    TO MAKE ONE CHART.
    Figure 156. Timing chart, Tuning Units TU-47 and TU-48.
    212
    TUNING CHART OF RADIO TRANSMITTER BC-61O-E( TUNING CHART OF RADIO TRANSMITTER BC-610-E
    lor	for
    Tuning Unit TU-49	Tuning Unit TU-5O
    Frequency Range 3.2-4.0 MC	Frequency Range 4.0-5.0 M C
    APPROXIMATE DIAL SETTINGS	APPROXIMATE DIAL SETTINGS
    OPERATING CRYSTAL	TUNING CONTROLS	&UNIT K wT	OPERATING CRYSTAL	TUNING CONTROLS	NA ™^G
    FREQUENCY FREQUENCY COIL ----- „	—------------- FREQUENCY FREQUENCY COIL ———___________ P 4 _ , B( 939 4_
    IN	IF UNIT	|NT ^ATE BAND	IN	If UH|T	PLATE BAND
    KILOCYCLES USED	*0 DOUB w HG SWIKH COUPLING LOADING	KILOCYCLES USED	M.O. D0U8.	TUNING SWITCH COUPLING LOADING
    _____				POSITION 	___	 	4MP	POSITION 3200_3200	C-387 D	25	3.4	5.8	58.5	210	4.2_35.6_4000	20G0	C 388 C	7	2.2	3.5	48	210	4.0	43 2
    3250	3250	C387 D	30	3.8	&.]	61.0	210	4.3	36.3	4^°	2825	C’388 C	13	2 5	3 9	50	210	4 0	43 7
    M	.	4100	2050 C 388 C 19	2.9	4.3	52	2 10	4.0 44 0
    4300	3300	C 387 D	35	4.2	6.3	63.0	2	10	4.3	37.0	4150	2075	C-388 C	24	3.2	4.6	54.5	210	3.9	44 3
    3350	3350	C387-D	40	4.6	6.5	65.5	2	10	4.5	3 7.5	4200	2100	03880	29	3.5	5.0	56.5	210	3.9	44 6
    3400	3400	C 387 D	45	4.9	6.7	670	210	4.6	38.2	4250	2125	0388 0	34	3.8	5.3	58.5	2 10	3.9	4 4 9
    3450	3450	O387 D	50	5.3	6.9	6 9 5	2	10	4.7	38.7	4300	2150	0388 0	39	4.1	5.6	60.5	2 10	4.0	4 5 2
    qcnn -Knn r-»fl7-n « c a 7 1 7m Tin c .	4350	2,75 C’388 C 44	4.4	5.9	62.5 2 10	4.0 45.5
    3500	3500	0388D	55	56	7.1	21	2-10	3.4	38.9	4400	2200	O388 C	48	4.6	6.1 '	63.5	2 10	4.0	45.8
    3550	3550	C-388C	59	5.9	7.3	235	2~IO	3 5	39.5	4450	2225	0388 0	52	4.8	6.4	65 5	210	4.0	46.1
    3600	3600	C-388 C	64	6.1	7.5	265	210	3.5	39.9	4500	2250	0388 0	56	5.1	6.6	67	210	4.0	463
    3650	3650	0388 C	68	6.4	7.7	29.5	210	3.6	40.4	4550	2275	C389-C	60	5.3	6 8	155	2-10	2J	46.4
    3700	3700	O3S8C	72	6.6	7.9	3 2	210	3.7 4 0.9	^00	O389 C	64	5.6	7.0	17.5	210	2.9	46.7
    4650	2325	0389 c	67	5.8	7.2	20	210	2.9	46.9
    3750	3750	0388 C	75	6.8	8.1	35	2-10	3B	41.3	4700	2350	O389	C	71	6.0	7.3	22	210	2.8	47.2
    3800	3800	O388 C	79	7.0	8.3	3 7.5	2 10	3.9	41.7	4750	2375	O389	C	74	6.2	7.5	2 4.5	2 10	2.9	4 7.4
    3850	3850	C383 C	82	7.2	8.5	40.5	210	3.9	42.2	4800	2400	C 389	C	78	6.4	7.7	2 6.5	2 10	2.9	4 7 6
    3900	3900	C-388 C	85	7.4	8.7	4 3	2 10	4.0	42.5	4850	2425	C‘389	c	81	6 6	7 8	29	2 10	2 9	479
    4900	2450	C’389 0	84	6.8	8 0	31	2 10	2 9	4 8 1
    3950	3950	G388-C	80	7.6	8.8	45	210	4.0	42.9	w0	„„	„	?|)
    4000	4000	C-388-C	91	7.8	8.9	4 8	2 10	4.0	4 3.2	5000	2500	C389C 91	7.1	8.4	355 210	2.8 48.5
    NOTE-FOR EXACT M.O. SETTING, USE FREQUENCY METER SET SCR-211-()	MOTE-FOR EXACT M O. SETTING, USE FREQUENCY METER SET SCR-211-( )
    L— ---------------------------------------------	-----------------------------—----------------—J
    __________________________PART NO. 92S106	PART NO. 92B106 N0TE:VIEW ABOVE SHOWS B°TH FACES OF CHART. FACES COMBINE BACK TO BACK	tL 15950
    ' O MAKE ONE CHART.
    Figure 157. Tuning chart, Tuning Units TU-49 andTU-50.
    213
    TUNING CHART OF RADIO TRANSMITTER BC-610-E	TUNING CHART OF RADIO TRANSMITTER BC-61O-E
    f°r	for
    Tuning Unit TU-51	Tuning Unit TU-52
    Frequency Range 5-6 35 MC	Frequency Range 6.35-8.0 M C
    APPROXIMATE DIAL SETTINGS	APPROXIMATE DIAL SETTINGS
    ANTENNA TUNING	ANTENNA TUNING
    OPERATING CRYSTAL	TUNING CONTROLS . .	UNIT BC-939-A	OPERATING CRYSTAL	TUMINv CONTROLS	BC 939-A
    FREQUENCY FREQUENCY COIL ----- !*„ ~ a^n --------- • f'f»Y	COIL ------------- 17 -----T" -------
    IN	IF unit	INT PLATE BAND	III	n UNIT	iut	BAND
    KILOCYCLES USED	M °' 00UB AMP TUNI* SW,T(H t0(MI>!G lOflOIW	'KILOCYCLES USED	MO. MU» "L IUMIHG SWITCH COUPLING LOADING
    	’	POSITION	________	POSITION 5000	2500	C389 C 5	2.5	4.0_35 5_210	2.8	48.5_,................... ......
    5050	2525	(-389	0	10	2.8	4.3	3 7 5	2 10	2.8	48.7	6350	3175	G390C	8	4.4	2.8	43.5	210	2.3	52.5
    5100	2550	C-389	C	15	3.1	4.6	39.5	210	2.8	4&9	6400	3200	0390 0	10	4.6	3.3	45	210	2 2	52.7
    5150	2575	C 389C	19	3.4	4.8	41.5	2 10	2 8	49.1
    5200	2600	C 389 C	23	3.7	5.1	43	210	2.8	49.3	6500	3250	C390-C	17	5.0	3.8	47.5	2 10	2.2	53.0
    5250	2625	C 389 C	27	3 9	5.3	4 5	2 10	2 8	4 9 5	6600	3300	(-39Q-C	23	5 4	4 2	5 0 5	2 10	2 2	53 1
    5300	2650	C 389 C	31	4.2	5.6	47	210	2.8	49.6	v jtu u	J n.a ju.o z iu t.t jj.i
    5350	2675	C 339 C	34 i 4.4	5.8	48.5	2-18	2.8	49.8	6700	3350	C 390 C	29	5.8	4.7	5 3	2 10	2.2	53.4
    54CO 2700 C 389 C 38	4.6	6.0	50-5	23	50.0	lAfsQ f-lon-C	Al c i rc	o Q R
    5450	2725	( 389 C 41	4 8	6.2	52	2-1®	2.8	50.1	- 3408 C 398 C 35	6 1 5J 55	2 10	2 Z 53 6
    5500	2750	C-3S9-C	44	5.0	6.4	54	2 IS	2.8	50.4	6900	3450	C’390’C	41	6.4	5.6	53 '	210	2.2	517
    5550	2775 C. 389 C 48	5.2	6.6	5 5-5	2-10	2.8	50.5	tsusw	r ann n Al a l l. a	*> in no ex n
    5600	2800	0389 0	51	5.4	6.7	57	2 10	2.8	5Q7	7000	3508	0390’0	47	6.6	6.0	oC.5	2 10	2.2	54.0
    5650	2825	( 389 C	55	5.5	6.9	58.5	2 18	2.8	50.9	7100	3550	C’390’0	52	6.9	6.4	6 3	2 10	2.2	54.2
    5700	2850	(-M9-C	58	5.7	7.1	60	2 10	2.8	51.0	-,„n~	z	,,	, ,	. o	r„ „
    57Q0	285p 0-3%-c	»	5 7	7.1	2-10	2.2	50.9	7200	3600 C’390’C	57	7.1	6.8	6 5	2-10	2.2	54.4
    5750	237S-	0’390'0	5.9	7.2	23	2’10	2.2	5L0
    5323	2900	C 390-0	64	6.1	7.4	?5	210	2 3	51.2	7300	3650	C’390’C	62	7.3	7.1	67	210	2.2	54.5
    5850	2925 C 390-C	66	6.2	7.5	265	2 10	2.2	51.3	, ,	, , . nn n nn
    5980	2950	( 395-C	6?	6.4	7.7	28.5	2 10	2.2	51.4	7400	3700	C’390 C	67	7.5	7.4	69	2'10	2.2	54.7
    5950	2975	C-390-C	72	6.5	7.8	2*5	2 10	2.3	51.5	7500	375g	C390C	7]	77	77	7|	2'10	2.2	54.9
    6000	3K9	C353-C	74	6.7	8.0	315	2 19	2.3	51.7	~	,,
    6050	3025	C 390-C	77	6.8	8.1	33 5	21®	2.3	51.9	76©0	C’390’C 75	7.9	0.9	72.5 2'19	2.2	55.1
    3450	79	70	82	«	21S	5,n	77fl®	3850 C390-C 79	8.1	8.2	7 4.5 2*19	2.2	55.2
    6150	3075	C39O-C	82	7.1	8.4	365	M 0	2.3	52.0
    62^0	3129	C-390-C	84	7.2	8.5	38 5	M®	2.3	52.2	7800	3900	G390C	83	8J	8.4	76	2'13	2.1	55-4
    six e£c e n u t!'. ” S	7,M 3,50	87 8'4 “	7Z5 2"> 2J 555
    6350	3175	C399-C	99	7.5	8.9	435	210	2.3	52 5	8000	4000	C'390’C	91	83	8.8	78.5	2'10	2.1	55.7
    MOTf-FO« EXACT M.0. SETTWS, USE FREQUENCY METER SET SCR-211-()	MOTE - FOR EXACT M.0. SETTIHG, USE FREQUENCY METER SET SCR-2l1-()
    ___________________________________PART «O 928107	J	_________________________________PART NO. 92BI07_j NOTE’ VIEW ABOVE SHOWS BOTH FACES OF CHART. FACES COMBINE BACK TO BACK________________________TLI5948
    TO MAKE ONE CHART.
    Figure 158. Tuning chart, Tuning Units TU-51 and TU-52.
    214
    TUNING CHART OF RADIO TRANSMITTER BC-610-E( TUNING CHART OF RADIO TRANSMITTER BC-610-E
    for	for
    Tuning Unit TU-53	Tuning Unj} w.53
    Frequency Range 8.0-12.0 MC	Frequency Range 8.0-12.0 MC
    APPROXIMATE DIAL SETTINGS	APPROXIMATE DIAL SETTINGS
    OFERATIMG CRYSTAL	TUNING CONTROLS	AJF|T "r( 939 A	OPERATING CRYSTAL	TUNING CONTROLS	ANTENNA TUNING
    IN	IF UM|T	imt t	BAND	.r	Cull	PLATE ramh
    usio	■» oou.	s«m» touMt	m	sou, «r _ ,„,t
    	0W				 POSITION 8000	4000	£-44743	6	1.5	1.5	20.5	210	1.5	55.5_10,000________5000	£-447.3	61_5.7	5 7'	64	5	10 18	1 1	*2 5
    8100	4050	£-447-B|	9	1.8	1.8	2 3 5	2	10	1.5	55.7	10,100	5050	C-447-B	63	5.8	5.8	655	1018	1.1	*2.7
    8200	4100	C-447-B	13	2.0	2.0	26.	210	1.5	559	10,200	5100	0447-0	65	6.0	6.0	67	1018	1.1	*3.0
    8300	4150	£-447-8	16	2.3	2.3	2 8 5	2	10	1.5	56.1	10,300	5150	£-447-9	67	6.2	6.2	685	1018	1.1	*3.4
    8400	42G0	C-447-B	19	2.6	2.6	31	2	10	1 5	56.1	10,400	5200	£-447.9	68	6.3	6 3	70	10-18	1 1	*3 7
    8500	4250	C-447-81	23	2.8	2.8	3 3 5	2 10	1.5	56.2	10,500	5250	£-447-B	70	6.4	6.4	71.5	10 18	1 1’	*4’0
    8600	4300	£-4476	26	3.1	3.1	36	2	10	1.5	56.4	10,600	5300	C-447-B	72	6.6	6.6	72.5	10-18	1.1	*45
    8700	4350	C447 B	29	3.3	3.3	385	270	1.5	56.5	10,700	5350	£-44743	73	6.7	6.7	74	10 18	1.1	*4.7
    8300	4400	£-4478	32	3.6	3.6	41	2	10	1.5	56.7	10,800	5400	£-4476	75	6.8	6.8	75	1018	l.l	*5.0
    8900	4450	C-447B	35	3.8	3.8	43	2	10	1.5	5GB	10,900	5450	£-447B	76	7.0	7.0	76.5	10 18	1.1	*5 3
    9000	4500	£-4473	38	4.0	4.0	455	2	10	1.5	57.1	11,000	5500	£-447 6	78	7 1	7 1	77.5	10-18	11	*5 7
    9100	4550	£-4478	41	4.2	4.2	47.5	2 10	1.5	57.3	>’.000	5500	C-448-B	78	71	7.1	37	10-18	1.2	*56
    «00	4650	C«B 43	4.3	4.3	49.5	2 10	1.5	57 4	II^S C’^	J,9	%	72	3^ I0H8	1.2	.&»
    9300	4650	£-4478	46	4.5	4.5	52	2	10	1.5	57.5	11,300	5650	0448-8	82	7.4	7.4	425	1018	12	*65
    9400	4700	C447B	49	4.7	4.7	53.5	2	10	t.5	57.7	n,4QQ	5700	£-44^	M	75	|75	445	1(Hg	]2	*67
    9500	4750	C-447B	51	4.9	4.9	55.5	2	10	1.5	57.7	11/500	5750	C-448B	M	7.6	I	7.6	4s'	10-18	12	*70
    9600	4800	C-447S	53	5.1	5.1	57.5	2	10	1.5	57.8	11,603	5800	C448-B	85	7.7	:	7.7	48	1Q-18	1.2	*7 1
    9700	4850	C4476	55	5.3	5.3	59	2	10	1.5	58.0	11#700	5850	£-4486	86	78	78	495	]fl.18	, 2	*74
    9800	4900	57	54	54	695	210	1.4	58.3	<11,800	5900	C-4486	87	7.9	7.9	51	10 18	1.2	*7.7
    9900	4950	C-447B 59	5.6	5.6	6 3	2-10	1.4	58.4	11 900	5950	C-4486 ga 8n on 52=; in IS 12	*7Q
    10,000,1 5000 C-447Bj 61	57	57 J 64.5 2-10 1,4 [58.5	“ 87	87	545 1078 1.2 *8 f
    ' NOTE - FOR EXACT M.O SETTING, USE FREQUENCY METER SET SCR-211-()	MOTE - FOR EXACT M.O. SETTING, USE FREQUENCY METER SET SCR-211-()
    •	*S«t L.F. loading Coil at 30
    »	PART NO. 92B1C3	_J	________________PART MO. 9?81®e
    NOTE- VIEW ABOVE SHOWS BOTH FACES OF CHART. FACES COMBINE BACK TO SACK	Ti 16980
    TO MAKE ONE CHART	'
    Figure 159. Tuning chart, Tuning Unit TU-53.
    215
    TUNING (HART OF RADIO TRANSMITTER BC-61O-E U	TUNING CHART OF RADIO TRANSMITTER BC-610-E
    for	for
    Tuning Unit TU-54	Tuning Unit TU-54
    Frequency Range 12-18 MC	Frequency Range 12-18 MC
    APPROXIMATE DIAL SETTINGS	APPROXIMATE DIAL SETTINGS
    OPERATING CRYSTAL	TUNING CONTROLS	o«"!G	OPERATING CRYSTAL	TUNING CONTROLS	AuLEn *BC 939'flG
    FREQUENCY FREQUENCY (OIL ---- f ‘ ---“"'J-K-W/- FREQUENCY FREQUENCY COIL _____________ Lrf --- ।	----
    IN IE UNIT	imt	*AND	IN IF UM|T	|MT	BAND
    KILOCYCLES USED	M 0 DOUB *„ IUN,MG $W|TCH COUPLING LOADING	KILOCYCLES USED	*0 DOM	SWIICH COUPLING LOADING
    __________________________AMP_____POSITION________________________________________________POSITION______
    14,000	3500	C-449B	46	3.2	4.6	37.5	10-18	|.|	»l2.0
    12,000	3000	C-4486	6	.3	1.1	54.5	10-18	1.2	*8.1	14,200	3550	C-4496	49	3.4	4.8	40.5	10*18	1.1	*12.3
    12,100	3025	C-4486	9	.4	1.4	55.5	10-18	1.2	* 8.4	14,400	3600	04496	52	3.6	5.1	43	10*18	l.l	*12.4
    12,200	3050	04486	12	.6	1.6	57	10-18	1 I	*8.6	14,600	3650	C449B	55	3.8	5.3	46	10*18	I	I	*126
    12,300	3075	C-4486	14	.8	1.8	5 85	10-18	1.1	*8.8	14,800	3700	C-449-B	58	3.9	5.5	48.5	10*18	I	I	*13.0
    12,400	3100	04486	17	1.0	2.1	60	10-18	1.1	*9.0	15,000	3750	04496	61	4.1	5.7	52.5	10 18	I	I	*13.2
    12,500 - 3125	C-448-B	19	1.2	2.3	61	10-18	1.1	*9.2	15 200	3800	04496	63	4.3	5.8	545	10-18	l.l	*13 6
    12,600	3150	04486	21	1.4	2.5	625	10-18	1.1	*9.5	15,400	3850	C449.J	65	45	6 1	57	10 18	। 0	*138
    J^an o! 15	8	15,600 3900 C’449B 68 4 7	6 2	59 1018	10 *142
    S ™ Z	:	66.5 10-18 H :.oo	™	™ « - 615 r 10 ■"■2
    3250	C-4-M 29	1.9	3.2	67.5 10-18	13	iS°“ 4000	72	5 °	66	63	,H8	10 ?44
    13,100	3275	C-4486	31	2.1	3.3	69	10-18	l.l	*10.4	, 6'200	4050	C449’B|	74	57	67	65	1018	10	146
    13,200	3300	0448-B	33	2.2	3.5	70	10-18	1 I	*10.7	16'400	4100	C'449B	76	5 3	68	67	1018	09	’,47
    13,300	3325	C-4486	35	2.4	3.7	71	10-18	l.l	*10.8	16,600	4150	C449‘B	78	55	69	69	10‘18	09	*147
    13,400	3350	C-448-B	37	2.5	3.8	72	10-18	l.l	*11.0	16,800	4200	C-4496	80	5.6	7.1	71	10 18	0.8	*14.9
    13,500	3375	C*4486	38	2.6	4.0	73	10*18	l.l	*11.2	17,000	4250	C-4496	82	5.7	7.2	73	10*18	0.8	*15.1
    13,600	3400	C-4486	40	2.7	4.1	745	10-18	l.l	*11.3	17,200	4300	C-4496	84	5.8	7.4	7 5	10*18	0.8	‘15.4
    13,700	3425	04486	41	2.8	4.3	7 5	10-18	l.l	*116	17,400	4350	04496	E5	5.9	7.5	76.5	10*18	0.7	’154
    13,800	3450	04486	43	3.0	4.4	76.5	10-18	l.l	*11.6	17,600	4400	04496	87	6.1	7.7	7 7	10 18	0.5	*156
    13,900	3475	04486	45	3.1	4.5	7 7	10-18	1.0	*11.8	17,800	4450	04496	89	6.2	7.9	80	10*18	0.4	*16.0
    14,000	3500	C-448 6	46	3.2	4.6	7 8	10-18	1.0	*119	18 000	45Q0	(-4496	91	6.3	8.1	82	10*18	0.4	*163
    MOTE—FOR EXACT M.O. SETTING, USE FREQUENCY METER SET SCR-211-()	MOTE —FOR EXACT M.O. SETTING, USE FREQUENCY METER SET SCR-211-( )
    _____’5ft 1 F lood'n9 Co11 °’ 30_-Set I F Loading Coil at 30	____________	 __________________________________PART NO. 9?BW9_PART NO. 92B109 NOTE- VIEW ABOVE SHOWS BOTH FACES OF CHART. FACES COMBINE BACK TO BACK______________________TLI5949
    TO MAKE ONE CHART.
    Figure 160. Tuning chart, Tuning Unit TU-54.
    UNT LIBRARIES DENTON TX 76203
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