[Radio Receivers Bc-312-(*), Bc-312-(*)x, Bc-342-(*), Bc-314-(*) and Bc-344-(*)]
[From the U.S. Government Publishing Office, www.gpo.gov]
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WAR DEPARTMENT TECHNICAL MANUAL
NON-CIRCULATING
RADIO RECEIVERS BC-312-D, BC-312-(*)X, BC-342-D, BC-314-(*) and BC-344-D-
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WAR DEPARTMENT • 1 5 MARCH 1944
TM 11-850
*c i
TECHNICAL MANUAL
RADIO RECEIVERS BC-312-C), BC-312-(*)X, BC-342-C), BC-314-C) and BC-344-C)
Changes! WAR DEPARTMENT
No. 1 J Washington 25, D. C., 21 February 1945
TM 11-850, 15 March 1944, is changed as follows:
2. Differences In Models.—
* * * * * * *
*This change supersedes TB SIG 11-850-1.
AGO 372C—Feb. 622703°—45
AGO 372C
c. Table Showing Characteristics oj Different Models.— m External Input Oscillator Noise Crystal Weisht
Model Range «•,?* Voltage Power Compart. Balancing Filter Pou“ds Remarks
KC Bands Supply (Watt8) Heaters System Circuit * » «»♦**«» * BC-314-E " " " " " " " 56 Both phone jacks con- Antenna disabling relay
nected to the output also grounds 1st audio of 2d a-f stage. grid.
BC-314-F __ " " " " I " " " 56 Refer to remarks for BC-314-E.
■ • I______:_______• _______________________:_______________ .
to
* * * * * * *
5. Weight and Dimensions.—
The weight of the receiver * * * 18 x 10% x 9 inches. The weight of Radio Receiver BC-312-M including Mounting FT-162 is 56 pounds.
8. Initial Procedure (Superseded).—
Radio Receivers BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*), and BC-344-(*) are shipped in crates 28^ x 18 x 17i/2 inches, packed one to a crate. The total weight of the packed crate is 120 pounds. Unpack the equipment carefully and check the components thoroughly for any damage sustained in shipping. If necessary, clean with a soft brush or blower before installation. Refer to the list of components for checking, or to the packing slip that accompanies the equipment.
11. Operation.—
a. Panel Controls.—
*
(12) Panel Jacks.—
*
*
*
NOTE: In sets BC-312 * *
correct output
impedance.
The 250—ohm tap is connection point No. 5 of the transformer.
To change the output impedance, remove a phone tip from the 4,000-ohm jack and insert it into the 250-ohm jack on the terminal strip located on the underside of the chassis adjacent to the first detector coil unit assembly. This circuit change connects the speaker and both phone jacks for the impedance indicated on the chassis below the terminal strip. The output transformers of Radio Receivers BC-314-F and BC-312-M are
wired for an output impedance of 4,000 ohms. If an output impedance of 250 ohms is required, have the wire which is attached to terminal 4 removed and connected to terminal 5.
Figure 6.—Functional circuit diagram * * * see figure 10. (For Radio Receiver BC—312—M, the connections to the secondary of first detector transformer L->s are as shown in figure 6.1.)
16. Antenna Circuit (figs. 6, 7, and 8).—
The ALIGN INPUT * * * antenna and ground. Neon lamp LMi has been omitted from later production models of Radio Receivers BC-312-M, BC-312-N, BC-314-G, BC-342-N, and BC—344—D.
21. Second Detector and Audio Amplifier (figs. 6, 7, and 11).—
A duplex-diode triode * * * into these jacks. In later model receivers output transformer T2 has been provided with a 250-
AGO 372C
3
ohm tap. Thus, the secondary of the transformer can match either a 250- or a 4,000-ohm load.
1ST DET 1ST I.E
VT-87 L28 VT-86
r-——ir~r~ t ;■ R:
--\te==/ j ■ Ht=zZZ,
J RI4 >R48 Jr50 Jri5 >RI7 S 063 C59
C47 C48 S C49 S S S S 054 1 1 ।-
j 1 [___,, >R52 RI9 S
— — | TL152I8 |
Figure 6.1.—Radio Receiver BC-312-M, revised wiring diagram for first detector transformer Las.
Figure 12.—Schematic diagram, Receiver BC-312-(*). (For Radio Receiver BC—312—M, the connections to the first detector transformer are as shown in figure 12.1. The audio-output connections are as shown in figure 12.2.)
|—lb 1 II T T---------
C95 ■= C94 J
_____ a S R18
L28^
o—|l_^o j C63J- 1ST I.E
1ST DET ! । C54 S ’T’ VT-86
VT-87 jHF---->R52 v,°°
(ri7 / । -L I —"—A-
-----1 *~~~ *) T—♦ > ~ I “■■■“—]— y/---------------------------------/RI5-\l ’"T/
° 1 nC48 | [C49 | R50 ■
C76 T PHONES
,----o _]_C74 2D AUD|0
R„ > I
AUDIO
VT-66 T2
r-----------r~t----------0
^7-^ G SPEAKER
/ \ Uri|||ie3|-=^"'"*^ Clean and coat teeth, remove eiceti
\ fePr_
'JjUU fcu1 ~ PS Tuning Control* Gear Shaft i or 2 dropr
BOTTOM VIEW
LUBRICANTS.
PS - OIL, LUBRICATING, PRESERVATIVE, SPECIAL U.S. ARMY SPEC NO. 2*120.
GL- GREASE, LUBRICATING, SPECIAL, ORDNANCE DEPARTMENT SPEC AXS*637.
TLI7538
Figure 23.1.—Lubrication chart for Radio Receivers BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*), and BC-344-(*).
AGO 372C 7
1). Dynamtotors DM-17 and DM-%1.—
The end bearings are the only points on the dynamotors which require lubrication. To lubricate them, remove the end plugs, then knead lubricant into the space between inner and outer races. Wipe off excess lubricant and reinstall plugs. If the air temperature is above 0° F., use Grease, General Purpose, WB No. 2, U. S. Army Spec. No. 2-108. If the air temperature is below 0° F., use Grease, Lubricating, Special, Ordnance Department Spec. No. AXS-637.
CAUTION: WHEN CHANGING TYPE OF LUBRICANT, WASH BEARINGS WITH DRY-CLEANING SOLVENT OR FUEL OIL, AND ALLOW THE PARTS TO DRY THOROUGHLY. WASH EACH BEARING, WITH DYNAMOTOR INVERTED, TO PREVENT THE WASHING FLUID FROM FLOWING INTO THE CASE. DO NOT ALLOAV FLUID TO GET ON COMMUTATOR, BRUSHES, OR ELECTRICAL CONTACTS.
29.1. Preventive Maintenance Techniques (Added).—
Preventive maintenance is a systematic series of operations performed at regular intervals on equipment to eliminate major breakdowns 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 and repair is to locate and correct existing defects. The importance of preventive maintenance cannot be overemphasized. The entire system of radio communication depends upon each set’s being on the air when it is needed and upon its operating efficiency. It is vitally important that radio operators and repairmen maintain their radio sets properly.
29.2. Description of Preventive Maintenance Techniques (Added).—
a. General.—
Most of the electrical parts used in Radio Receivers BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*), and BC-344-(*) require 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 contains these specific instructions and serves as a guide
8
AGO 372C
for personnel assigned to perforin the six basic maintenance operations: Feel, Inspect, Tighten, Clean, Adjust, and Lubricate. Throughout this change, the lettering system for the six operations will be as follows:
F—Feel
I—Inspect
T—Tighten
C—Clean
A—Adjust
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, equipment becomes undependable and subject to break-down when the equipment is most needed.
b. Feel.—
The feel operation is used most often to check rotating machinery, such as blower motors, drive motors, etc., and to determine if 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 trouble. 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
AGO 372C
9
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 compounds; and oxidation of metal contact surfaces.
(2) Placement, by observing that all leads and cabling 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 in performing them are given wherever necessary throughout this manual.
CAUTION: SCREWS, BOLTS, AND NUTS SHOULD NOT BE TIGHTENED CARELESSLY. FITTINGS TIGHTENED BEYOND THE PRESSURE FOR WHICH THEY ARE DESIGNED WILL BE DAMAGED OR BROKEN.
Whenever a loose connection is tightened, it should be moisture-proofed and fungiproofed again by applying the varnish with a small brush. See paragraph 39.1 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.
29.3. Preparation for Preventive Maintenance (Added).—
a. General.—
For ease and efficiency of performance, preventive maintenance on Radio Receivers BC-312-(*), BC-312-(*) X, BC-342-(*), BC-314-(*), and BC-344-(*) will 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
10
AGO 372C
are discussed in paragraph 29.2. These general instructions are not repeated in this paragraph. When performing preventive maintenance, refer to paragraph 29.2 if more information is required for the -items in following paragraphs. All work is to be performed with the power removed from the equipment. After preventive maintenance has been performed on a given day, the equipment should be put into operation and checked for satisfactory performance.
b. Common Materials Needed.—
The following materials will be needed in performing preventive maintenance:
Common hand tools (TE-41 or equivalent).
Camel’s-hair brush.
Clean cloth.
#0000 sandpaper.
Crocus cloth.
Fine file or relay burnishing tool.
OE, oil, engine, SAE No. 10, U. S. Army Specifications No. 2-104B.
Solvent, Dry-cleaning, Federal Specification P-S-661a.
NOTE : Gasoline will not be used as a cleaning fluid for any purpose. Solvent, Dry-cleaning, Federal Specification P-S-661a, as 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. Carbon tetrachloride, or fire-extinguishing liquid (carbon tetrachloride base), will be used, if necessary, only on contact parts of electronic equipment.
29.4. Item 1, Exterior of Radio Receiver (Added).—
a. Operations.—
The operations of preventive maintenance are indicated by means of the letters of the word FITCAL. For example in the list shown below if the letters ITC are placed beside the part or parts to be checked, that particular part of the receiver must be inspected (I), tightened (T), and cleaned (C).
ITC Cabinet.
1TCA Panel control knobs and knob assemblies.
IT Switch controls.
IT Jacks.
ITC Pilot lamps.
ITC Jack cover assemblies.
ITC Binding posts.
ITC Fuses and fuse holders.
ITC Panel locks.
ITC Power socket.
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11
b. Remarks.—
(1) Inspect.—
Inspection consists of carefully examining the parts indicated for color, scratches, breaks, dents, blisters, state of cleanliness, etc., and watching for indications of possible trouble. Discoloration or blistering of a part is evidence of overheating. Inspect the equipment for dust, corrosion, mildew, rust, fungus growth, and other foreign matter.
(2) Tighten.—
Do not tighten parts indiscriminately. Tighten them only when definitely known to be loose.
(3) Clean.—
Remove all dirt, dust, fungi, or other foreign matter. Use dry-cleaning solvent on exposed metal parts. On painted parts use a damp cloth.
(4) Adjust.—
Adjust the position of the knobs and align the arrows with the markings on the front panel.
29.5. Item 2, Interior of Radio Receiver, Top of Chassis (Added).—
a. Operations.—
ITC Tubes and tube sockets.
ITC Transformer shields and tube shields.
ITCL Tuning capacitor and gear assembly.
ITC Crystal unit.
ITC Neon lamp.
ITC Volume control.
b. Remarks.—
(1) Inspect.—
Check the general physical condition of the top of the chassis. Make sure there are no dents and breaks in the chassis or mounted parts. Also check for loose connections and broken leads. Each dial light assembly should be firmly clipped to its bracket and the lamp secured in the socket. Make certain all shields are securely mounted. Inspect all mounting nuts and locknuts for tightness. Check the gears for badly worn or broken teeth. The springs in the antibacklash gears must be tight and in good physical condition. Make certain the crystal unit is held firmly in place by its clamps.
(2) Tighten.—
Tighten all nuts and screws when necessary.
CAUTION: DO NOT TOUCH ADJUSTING SCREWS ON ANY OF THE TRANSFORMERS.
12
AGO 372C
(3) Clean.—
Remove all dust, lint, etc., with a soft brush. Remove oil and grease with a soft cloth dampened with dry-cleaning solvent. Clean all tubes, tube shields, transformer shields, power socket pins, volume control, and other-parts mounted on the chassis.
(4) Lubricate.—
For details on lubrication see paragraph 29.
29.6. Item 3, Bottom of Chassis (Added).—
a. Operations.—
FIC Resistors and capacitors.
ITC Soldering terminal boards and lugs.
ITC Tube sockets.
I Wiring.
IC Switches.
ITCL Band change assembly and drive gears.
b. Remarks.—
(1) Teel —
Feel resistors and capacitors immediately after equipment shutdown and check for overheating.
(2) Inspect.—
Make a genera] over-all inspection of the chassis. Check carefully for loose or broken leads and poorly soldered connections to solder lugs.
(3) Clean.—
Remove all dirt and other foreign matter from parts under the chassis and from the chassis proper, using a camel’shair brush. In smaller spaces a cloth dampened with dry-cleaning solvent and wound around a thin screwdriver can be used.
29.7. Item 4, Dynamotors DM-17 and DM-21 (Added).—
a. Operations.—
FITCL Dynamotor unit.
b. Remarks.-—
(1) Feel.—
See paragraph 29.2A
(2) Inspect.—
Make an over-all check of the dynamotor unit, bearings, commutator, etc.
(3) Tighten.—
See that the dynamotor is securely fastened to the receiver chassis.
(4) Clean.—
Wipe off excess lubricant, grit, dirt, and other foreign matter.
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13
(5) Lubricate.—
See paragraph 29.
29.8. Item 5, Rectifier RA-20 (Added).—
a. Operations.—
ITC Transformer, tube, fuse, capacitors, choke, and switch.
IC Resistor, terminal board, power socket, and wiring.
b. Remarks.—
(1) Inspect.—
Check the rectifier components for possible defects. See that the parts are securely fastened, clean, and in good physical condition.
(2) Tighten.—
Tighten all nuts that are found to be loose.
(3) Clean.—
Remove dirt, rust, etc., from all parts above and below the rectifier chassis.
29.9. Preventive Maintenance Check List (Added).—
The following check list is a summary of the preventive maintenance operations which will be performed on Radio Receivers BC—312—('*'), BC-312-(*)X, BC-314-(*), BC-342-(*), and BC-344-(*). The time intervals shown on the check list may be varied at any time by the local commander. However, for best performance of the equipment, the operations will be performed at least as frequently as called for in the check list. The echelon column indicates which operations are considered first echelon maintenance and which operations are considered second echelon maintenance.
When performed
Item „ tx Si 3 Eche-
No. °Peratlons Item £ Ion
•2 03 ~ S § §
m O S a t*
1 ITCA Exterior of radio receiver__________X------------------- 1st
2 ITC Top of chassis__________________________ X-------------- 1st
2 L Top of chassis______________________________X----------- 2d
3 FITC Bottom of chassis_______________________X--------------- 2d
4 FITC Dynamotor DM-21-f*)1________________________X----------- 2d
4 L Dynamotor DM-21-(*)1-------------------------------------------X 2d
5 ITC Rectifier RA-20 2 * 4____________________________X--------------- 2d
i Used in Radio Receivers BC-312-(*) and BC-314-(*).
2 Used in Radio Receivers BC-342-(*) and BC-344-(*).
F I
Feel Inspect
T
Tighten
c A L
Clean Adjust Lubricate
14
AGO 372C
39.1. Moistureproofing and Fungiproofing (Added).______
a. 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:
(1) Resistors, capacitors, coils, chokes, transformer windings, etc., fail.
(2) Electrolytic action takes place in resistors, coils, chokes, transformer windings, etc., causing eventual break-down.
(3) Hook-up wire and cable insulation break-down. Fungus growth accelerates deterioration.
(4) Moisture forms electrical leakage paths on terminal boards and insulating strips, causing flash-overs and crosstalk.
A 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. This treatment involves the use of a moisture- and fungi-resistant varnish applied with a spray gun or brush. Refer to TB SIG 13, Moistureproofing and Fungiproofing Signal Corps Equipment, for a detailed description of the varnish-spray method of moistureproofing and fungiproofing.
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.
c. Step-by-step Instructions For Treating Radio Receivers BC-312-BC-34£-(*\ and BC-344~(*).—
(1) Preparation.—■
Make all repairs and adjustments necessary for proper operation of the equipment.
(2) Disassembly of Radio Receivers BC-312-(*) and BC-314-(*).—
(a) Loosen the panel locks holding the receiver chassis to the case, and remove the chassis.
(S) Remove four screws holding Dynamotor DM-21 to the receiver chassis.
() Unsolder six leads from the terminal strip adjacent to Rectifier RA-20.
(c) Remove four screws holding Rectifier RA-20 to the receiver chassis, and remove the rectifier.
(1) Unsolder the switch wire from the fuse holder.
(2) Remove two screws holding the line plug to the case, and remove the line plug.
(3) Remove the lockout holding the line switch to the case, and remove the line switch.
(4) Remove the seven screws holding the chassis to the case, and remove the chassis.
(tZ) Follow steps ( 'f' I IH
Wjy ... Jyi
TUBE SOCKETflk /d'l / /
ASSEMBLY W fJBrf Li/ Z
:| s b / / J
W|r W / /
Figure 41.—Radio Receivers BC-312-(*), BC-314-(*), BC-342-(*), or BC-344-(*)—top rear view of chassis showing components covered with masking tape.
AGO 372C
17
18
AGO 372C
• ' '■ DRIVE GEARS FOR
'—Z 1 TUNING ASSEMBLY
..—
’’W JR # ZtU- ’ JMMrW' JcY jacks xv " -’ ■ fl MZ
' ' z'4 * ' '"■ too7 \< >Ljk
' ^z # ■ , . ’ , • ,_•
x' t;" x '* •* ■ ■* *
■ # * - - jr* - JSwt - •-/
/z Wl*- --> * - fJli
/ w~.. *<» ♦• « ‘^ii
DRIVE GEARS FOR V*V BAND CHANGE ASSEMBLY^MB^EMBjjl^-vWY>lGW7
''^ ■
Wr ^‘i; ; z-Z***/ ■
^F fW/ i
IW .
. '‘•,“95!
Figure 42.—Radio Receivers BC-312-(*), BC-314-(*), B(’-342-(*), or BC-344-(*)—bottom view of receiver showing components covered with masking tape.
i LINE PLUG CONTACTS
\
HL
■■■ •'■•
® z i Wv ® dig
l ^^y^S8|jart3M«bA. * *-'• .-»a
? ! INTER-UNIT WIRING ''
wli I Wk
\ ^IBwl4 Jr^ikw I
<: zll^^^--"'
■ ;
TLI31MI
Figure 43.—Rectifier RA-20, part of Radio Receivers BC-342-(*), and BC-344-(*)—top view of rectifier showing components covered with masking tape.
AGO 372C 19
(2) Crystal phasing capacitor (fig. 41).
(3) Tuning capacitor gang assembly (fig. 41).
(4) Five jacks along edge of panel (fig. 42).
(5) Drive gears of tuning assembly (fig. 42).
(6) Drive gears of band change assembly (fig. 42).
(7) Interunit wiring (fig. 43).
(8) Line plug contacts (fig. 43).
e. Drying.—
Place equipment in oven or under heat lamps and dry for 3 or 4 hours at 140° F.
CAUTION: DO NOT EXCEED 140° F. IF WAX BEGINS TO MELT IN ANY OF THE COMPONENTS, DECREASE THE TEMPERATURE AND INCREASE THE BAKING TIME APPROXIMATELY 1 HOUR FOR EACH 10° F. DROP IN TEMPERATURE.
/. Varnishing.—
(1) Apply three coats of moisture proofing and fungiproofing varnish (Lacquer, Fungus-resistant, Spec. No. 71-2202 (Stock No. 6G1005.3), or equal, to all equipment to be treated, except the first r-f, second r-f, first detector, and oscillator sections. Allow a 15- to 20-minute drying period after each coat.
(2) Using a brush, apply varnish to the coil forms and wires in the first r-f, second r-f, first detector, and oscillator sections. Be careful not to get varnish on the plates of the variable capacitors or on the switch contacts.
(3) Using a brush, apply varnish to any portions of sprayed equipment not reached by the spray gun. Make sure that all components are adequately protected by varnish.
g. Reassembly.—
(1) Remove the masking tape.
(2) Clean all contacts with varnish remover, and burnish the contacts.
(3) Reassemble the set and test its operation.
h. Marking*—
Mark the letters MFP and the date of treatment near the most conspicuous or most important nameplate on the equipment and in such a location that the marking will not become obliterated or rubbed off. In the absence of a nameplate, place the marking where it can be read easily and is not subject to wear.
EXAMPLE: MFP—8 June 1944.
20
AGO 372C
40.1 . Maintenance Parts List for Radio Receivers BC-312-(*)> BC—312—(*)X, BC—342—(*), BC-314-(*), and BC-344-(*) (Added).—
For maintenance parts information refer to the appropriate sections of the Army Service Forces Catalog SIG 7 BC-312, SIG 8-BC-312, SIG 7-BC-314, SIG 8-BC-314, SIG 7-BC-342, SIG 8-BC-342, SIG 7-BC-344, and SIG 8-BC-344.
[AG 300.7 (1 Nov 44) ]
By order of the Secretary of War:
Official:
J. A. ULIO
Major General
The Adjutant General
G. C. MARSHALL
Chief of Staff
Distribution :
AAF (5) ; AGF (5) ; ASF (2) ; T of Opn (5) ; Dept (5) ■ Def Cornel (2) ; Base Comd (5); AAF Comd (2) ; Arm & Sv Bd (2) ; S Div ASF (1) ; Tech Sv (2) ; SvC (5) ; Area ASvC (2) ; NDGS 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 (20) ; ROTC (5) ; Lab 11 (2) ; Sig AS (2) ; Rep Shop 11 (2) ; A (5);D (2); AF (2)
Five (5) copies to each of the following: T/O & E 1-27; 1-37; 1-67; 1-113; 1-117; 1-127; 1-137; 1-147; 1-167; 1-252; 1-267; 1-277S; 1-300-1; 1-310-1; 1-312; 1-317; 1-412; 1-452T; 1-487S; 1-637; 1-757; 1-759; 1-767; 1-768; 1-777S; 1-779; 1-977; 4-37; 5-512S; 5-526S; 6-10-1; 6-12; 6-20-1; 6-26; 6-36 ; 6-50-1; 6-56; 6-76; 11-7; 11-16; 11-18; 11-47; 11-87S; 11-97; 11-107; 11-127; 11-147S; 11-217; 11-237; 11-247; 11-257; 11-267; 11-287; 11-297; 11-460-1S; 11-477S; 11-517S; 11-537S; 11-587; 11-592; 11-597; 11-677S; 17-20-1; 17-26; 17-29; 17-60-1; 44-7; 44-10-1; 44-12; 44-16; 44-26; 44-116; 44-126; 44-136; 44-226S
For explanation of symbols, see FM 21-6.
U. S. GOVERNMENT PRINTING OFFICE: 1945
AGO 372C
21
WAR DEPARTMENT TECHNICAL MANUAL
T M 11-850
This Technical Manual supersedes TM 11-850, 4 June 42 and TM 11-85ON, 4 Feb. 43.
RADIO RECEIVERS BC-312-D. BC-312-OX, BC-342-D, BC-314-(‘) and BC-344-(*).
H7AR DEPARTMENT • 15 MARCH 1944
For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. Price, 25 cents (paper cover)
WAR DEPARTMENT
Washington 25, D. C., 15 March 1944
TM 11-850, War Department Technical Manual, Radio Receivers BC-312-(*), BC-312(*)X, BC-342(*), BC-314-(*) and BC-344-(*), is published for the information and guidance of all concerned.
[A. G. 300.7 (24 Aug. 43)]
By order of the Secretary of War:
G. G MARSHALL, Chief of Staff
Official:
J. A. ULIO,
Major General,
The Adjutant General
Distribution:
Bn and H 1, 2, 4-7, 11, 17, 19(6); IC 1, 2, 4, 6, 7, 11, 17(5), 19(2).
(For explanation of symbols, see FM 21-6.)
II
TABLE OF CONTENTS
Paragraph Page Section I. DESCRIPTION.
General .................................... 1 5
Differences in models ...................... 2 5
Construction ............................... 3 7
Mounting ................................... 4 7
Weight and dimensions ...................... 5 7
Frequency ranges .........................' 6 It
List of main components .................... 7 13
IL INSTALLATION AND OPERATION.
Initial procedure .......................... 8 15
Installation ............................... 9 15
Preparation for use......................... 10 16
Operation .................................. 11 17
Precautions during operation................ 12 24
Field maintenance .......................... 13 24
Accessory equipment ........................ 14 25
III. FUNCTIONING OF PARTS.
General circuit ............................ 15 28
Antenna circuit ............................ 16 32
Radio-frequency circuits ................... 17 33
Radio-frequency oscillator ................. 18 35
Crystal filter ............................. 19 3g
Intermediate-frequency amplifier ........... 20 38
Second detector and audio amplifier ........ 21 40
Continuous-wave oscillator ................. 22 41
Volume control ............................ 23 41
Dial lamp circuit........................... 24 42
Heater circuits ............................ 25 49
Dynamotor DM-21-(*) ........................ 26 50
Dynamotor DM-21-CX ......................... 27 51
Rectifier RA-20 ............................ 28 51
1
Paragraph Page
IV. MAINTENANCE.
Lubrication 29
Inspection . 30
Tube socket voltage measurements 31 55
Procedure in case of failure 32 55
Locating trouble . 33 61
Trouble shooting 34 62
Repairs 35
Chassis layout illustrations 36 66
Continuity test tables 37 66
Removal and assembly of parts 38 84
Alignment 39 25
V. SUPPLEMENTARY DATA.
Table of replaceable parts 40 97
LIST OF ILLUSTRATIONS
Fig- No. Title page
1. Radio Receiver BC-312-(*), front panel view.t..... 8
2. Radio Receiver BC-342-(*), front panel view....... 9
3. Radio Receiver BC-314-(*)- Receiver BC-344-(*) is identical in physical appearance. ................. 10
4. Radio Receiver BC-312-(*) removed from cabinet .. 12
5. Outline dimensions of all models ................ 14
6. Functional circuit diagram of BC-312-(*), BC-312-(*)X, and BC-342-(*), MVC operation ........ 29
7. Functional circuit diagram of BC-314-(*) and BC-344-(*) .................................... 30
8. Antenna circuit, all models
9. Antenna noise-suppression circuit as used in BC-312, BC-312-A, BC-312-C, BC-342 and BC-342-C ..................... 82
10. Circuit diagram, crystal filter circuit ................. 37
11. Functional diagram, second detector, manual and automatic volume control, all models 39
12. Schematic diagram, Receiver BC-312-(*) ................. 43
13. Schematic diagram, Receiver BC-312-(*)X ................ 44
14. Schematic diagram, Receiver BC-314-(*) ................. 45
15. Schematic diagram, Receiver BC-342-(*) ................. 46
16. Schematic diagram, Receiver BC-344-(*) ................. 47
2
Fig. No. Title Pag*
17. Tube heater circuits in BC-312-(*), BC-314-(*), BC-342-(*) and BC-344-(*) ................................. 48
18. Oscillator compartment heaters in BC-312 and BC-342 .... 48
19. Tube heater circuits in BC-312-(*)X .................... 49
20. Dynamotor DM-21-(*) as used in BC-312-(*) and BC-314-(*) ................................................. 50
21. Dynamotor DM-21-(*), schematic diagram ................. 51
22. Rectifier RA-20, inside view, as used in BC-342-(*) and BC-344-(*) .................................... 52
23. Rectifier RA-20, schematic diagram ..................... 52
24. Tube socket voltage measurements for BC-312-(*) using adapter with Test Set 1-56- series ................... 56
25. Tube socket voltage measurements for BC-312-(*)X using adapter with Test Set 1-56- series ................... 57
26. Tube socket voltage measurements for BC-314-(*) using adapter with Test Set 1-56- series ................... 58
27. Tube socket voltage measurements for BC-342-(*) using adapter with Test Set 1-56- series ................... 59
28. Tube socket voltage measurements for BC-344-(*) using adapter with Test Set 1-56- series ................... 60
29. Chassis layout, high-frequency models, no crystal filters, top view........................................... 67
30. Chassis layout, high-frequency models, with crystal filter, top view ........................................... 68
31. Chassis layout, medium-frequency models, top view ...... 69
32. Chassis layout, high-frequency models, bottom view ..... 70
33. Chassis layout, medium-frequency models, bottom view ... 71
34. Chassis layout, high-frequency models, shields and
power supply removed, rear view ...................... 72
35. Chassis layout, medium-frequency models, shields and power supply removed, rear view ........................ 73
36. Chassis layout, rear view, BC-312-(*) showing Dynamotor DM-21-B or DM-21-CX ................................ 74
37. Chassis layout, rear view, BC-342-(*), showing Rectifier RA-20 ............................................ 75
38. Location of terminals on volume control ................ 81
39. Location of terminals on OFF-MVC-AVC switch ............ 81
40. Set-up of receiver and test equipment for receiver alignment ................................................. 86
3
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, etc.
2. Cut — Use axes, handaxes, machetes, etc.
3. Burn — Use gasoline, kerosene, oil, flame throwers, incendiary grenades, etc.
4. Explosives — Use firearms, grenades, TNT, etc.
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 — Tubes
Resistors Capacitors Coils Switches Tuning dials Dynamotors Crystals Chassis
2. Cut — Chassis wiring Connecting Cordage
3. Burn — All diagrams Instruction books Technical manuals
4. Bury or scatter — Any or all of the above pieces after breaking.
DESTROY EVERYTHING
SAFETY NOTICE
CAUTION: THIS EQUIPMENT EMPLOYS HIGH VOLTAGES WHICH ARE DANGEROUS AND MAY BE FATAL IF CONTACTED BY OPERATING PERSONNEL. WHEN WORKING ON THIS EQUIPMENT, ALWAYS GROUND EVERY PART BEFORE TOUCHING IT.
4
This Technical Manual supersedes TM 11-850, 4 June 42 and TM 11-85ON, 4 Feb. 45.
SECTION I DESCRIPTION
Paragraph
General ................................................. j
Differences in Models ..................................... 2
Construction .............................................. 3
Mounting ................................................. 4
Weight and Dimensions ..................................... 5
Frequency Ranges .......................................... 6
List of Main Components ................................... 7
1. General.—
The radio receivers described in this manual are of the superheterodyne type. They are built ruggedly and are suitable for vehicular, portable, or fixed operation. They are highly sensitive and selective and are designed for the reception of voice, tone, or continuous-wave signals from transmitting stations using amplitudetype modulation. These receivers are identical in size, in general external and internal construction and appearance, and in the fundamental arrangement of their electrical circuits. They are divided into two main groups. The first covers the frequency range of 1500 to 18000 kilocycles in six bands; the second covers the range from 150 to 1500 kilocycles in four bands. For purposes of identification in this manual, the first group is referred to as the high-frequency (h-f) group, and the second group as the mediumfrequency group (m-f). Within each group are models for operation on either storage batteries or alternating-current power sources.
2. Differences In Models.—
a. It is advisable for all using personnel to become thoroughly familiar with the differences in the various models. Much confusion in the requisitioning of complete receivers and replacement parts for them arises from the fact that more than a dozen similar type numbers are listed for receivers that look alike. The following description is organized according to the frequency ranges and power requirements mentioned in paragraph 1. (See Sec. Ill for a detailed description of the actual circuits.)
b. It will be noted that some identical receivers within a series have type numbers with different suffix letters. These numbers identify equipment made to the same specifications but on different orders, either by one or several manufacturers.
S
TM 11-850
2 SIGNAL CORPS
c. Table Showing Characteristics Of Different Models.—
Freq. No. External Input Oscillator Noise Crystal Weight
Model Range of Voltage Power Compart. Balancing Filter Pounds Remarks
KC Bands Supply (Watts) Heaters System Circuit
BC-312 1500-18000 6 12-14v D.C. 90-100____Yes_____Yes_____Yes_____58 Uses DM-17-A Dynamotor.______________
BC-312-A ” ” ” 50- 60 No ” ” 56 This and subsequent D. C. models employ DM-21-(*)
BC-312-C " ’’ ” ” ” ” ” 56
BC-312-D ” ” ” ” ” No ” 56
BC-312-E_____2______” ■____”________"_________"_______”______________56________________________________________
BC-312-F_____”_______”_____”_________2________”________”_____’’______66_____________________________
BC-312-G " ” ” ” " " ” 56
BC-312-J " ” " ” ” ’’ ” 56
All Phone VT-134 Antenna Relay
BC-312-HX ” *' 24-28v D.C. 25- 35 " ’’ ” 48 Jacks 2d instead Also Disables
Audio of VT-66. 1st Audio
Osc Compart.
BC-312-NX " ” ” ’’ ” ” No 48 ” ” ” Heat Insulator
Removed
BC-312-L " " 12-14v D.C. 50- 60 ” “ ” 56 ~
BC-312-M ” ” " " " " " 56 ” ~ ”
BC-312-N ” " " " " » ” 56 ”
BC-342 ” M 110-120V A.C. 100 Yes Yes Yes 61,5
Refer to remarks for BC-312 with same suffix
BC-342-C ” " ” 75 No ” ” 61.5 letter for circuit changes.__________
BC-342-D ’’ ” ” ’• ” No ” 61.5
BC-342-F ” " " " » " •• 61.5
BC-342-J *' ” ” ” ” ” ” 61.5 ~~~
BC-342-L " " " " ” ” ” 6D5
BC-342-N ’61.5
SELECT. CONTROL (variable selectivity 1st I-F)
BC-314____150-1500__4 12-14v D.C. 50- 60___Yes______" No 58 knob on front panel. This model only._
BC-314-C ” " ” " No " ” 56
BC-314-D_____"______“______2________"_________2_______"_______’’_______________________________________________
Both phone jacks con- Antenna disabling re-
BC-314-E ’* ” ’’ ” ” ” ” 56 nected to the output lay also grounds 1st
_____________________________________________ of 2d a-f stage._____________audio grid. BC-314-G_56 ”_____________________”
SELECT. CONTROL (variable selectivity 1st I-F)
BC-344_______”______” 11Q-120V A.C. 75_______Yes ” ” 61.5____knob on front panel. This model only.
Antenna disabling relay All jacks to
BC-344-D_____»______"_____”_________” _____No________"______"______61.5 also disables 1st audio. 2nd audio.
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 2-5
BC-342-C*), BC-314-C*) AND BC-344-(*)
d. Throughout this manual, where descriptive matter applies equally to all receivers of a series, the suffix letter is omitted and the symbol (*) is used instead; for example, Radio Receiver BC-312-(*). The full type number is used when a particular model must be identified for any reason. The table on page 6 shows the difference between models.
3. Construction.—
The cabinet, the panel, and the inside chassis are made of metal. The internal parts of the receiver are thoroughly shielded by means of metal inclosures as shown in figure 4. The various compartments and cans are clearly marked and are easily identified. Aluminum was used in early models but substitutes have been used in later models. The outside surfaces of the cabinet and the front of the panel are finished in black. The whole panel-chassis assembly slides in and out of the cabinet readily and is locked firmly in place by means of five knurled locking screws of the captive type. Convenient handles are located on the vertical sides of the panel. The over-all dimensions of the receivers are 18 by 9 by 9 inches. (Figures 1, 2, and 3 show front views of Radio Receivers BC-312-(*), BC-342-(*), and BC-314-(*) respectively. Due to minor variations in design, certain models may vary slightly in appearance from those shown. The front panel of BC-344-(*) is identical in appearance to that of BC-314-(*).)
4. Mounting.—
Mounting FT-162 (shown under receivers in figs. 1, 2, and 3) consists of a metal-alloy plate provided with holes for fastening in a vehicle or on a fixed table or bench. Mounted on soft rubber pads in the four corners of the plate are short studs which engage holes in the bottom of the receiver cabinet. The latter is held on the mounting by slides, which can be pulled forward to release the cabinet. The mounting minimizes the transmission of vibration and shock to the receiver.
5. Weight and Dimensions.—
The weight of the receiver including Mounting FT-162 is 46 pounds in the models using aluminum. The weight of the steel model is 58 pounds for battery types, 61.5 pounds for a-c types. The dimensions of all models are approx. 18 x 10^4 x9 inches.
7
TM 11-850
5
SIGNAL CORPS
Figure 1.—Radio Receiver BC-312-(*), front panel view. (Certain models of this receiver will vary slightly in appearance due to modification in design.)
8
TM 11-850
5
RADIO RECEIVERS BC-312-C*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
Figure 2.—Radio Receiver BC-342-(*), front panel view. (Certain models will vary slightly in appearance due to modification in design.)
9
TM 11-850
5
SIGNAL CORPS
Figure 3.—Radio Receiver BC-314-(*). Receiver BC-344-(*) is identical in physical appearance.
10
TM 11-850
RADIO RECEIVERS BC-312-C), BC-312-(*)X, 6
BC-342-(*), BC-314-C) AND BC-344-(*)
6. Frequency Ranges.—
a. High Frequency Models.—
In these models, the frequency range of 1500 to 18000 kilocycles is covered in six bands, which are selected by means of a positive, rotary switch on the front panel marked BAND CHANGE.
The bands are as follows:
Band Frequency range (kc)
A....................... 1500 - 3000
B ...................... 3000 - 5000
C................<...... 5000 - 8000
D....................... 8000 - 11000
E...................... 11000 - 14000
F...................... 14000 - 18000
b. Medium Frequency Models.—
In these models, the frequency range of 150 to 1500 kilocycles is covered in four bands, as follows:
Band Frequency range (kc)
A ....................... 150 - 260
B ....................... 260 - 450
C ....................... 450 - 820
D ....................... 820 - 1500
c. Overlap.—
There is sufficient overlap between bands to provide complete coverage.
d. Tuning Dial.—
The band switch is geared to a shutter on the tuning dial marked FREQUENCY in such a manner that a calibrated scale appears in the dial window for each position of the band switch marked BAND CHANGE. In addition, a uniform scale of 45 divisions remains in view at all times at the bottom of the tuning dial. The tuning capacitor and the dial are geared so that the former goes from one extreme position to the other in 12 revolutions of the knob marked FAST TUNING. Also a part of the tuning gear system is a smaller knob marked VERNIER, which has a calibrated scale of 100 divisions. One revolution of this knob is equal to one of the 45 divisions on the uniform scale of the tuning dial. Very accurate records can therefore be kept of the dial settings for particular frequencies or stations.
11
TM 11-850
6
SIGNAL CORPS
^-l»T I.F. TUBE y-SHIELD BEHIND TUBE SHELF °I.F.TUBE-\ jC —s OSCILLATOR
\lxkJ \ \7 / SECTION
Tai --/ 11 iil_ ' z
JMI-----IB^n ---BAND
. |G" ....■Xm~| CHANGE SWITCH
9 ' © DRiVE GEARS
DYNAMOTOR■ |© 0 0 MOUNTING ---' ■ ^y -^--.-X.r-^--p-^?—' *
H|N6ES l_Z—. XL^__ -.—J
©x ©\ ©--l8T R.F. STAGE
©\ x-----2ND R.F. STAGE
GRP. 6 TERM. BD.~’ * ©----18T DET. STAGE
X CM
Figure 4.—Radio Receiver BC-312-(*) removed from cabinet. (The BC-312-(*)X, BC-342-(*), BC-314-(*)> and BC-344-(*) are similar in appearance.)
12
TM 11-850
7
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-C) AND BC-344-(*)
7. List of Main Components.—
Each receiver is issued with the necessary vacuum tubes mounted in place. In addition, a complete receiver includes the following:
Radio Receiver BC-312-(*)
1-Dynamotor DM-21- (*) or equivalent.
3-Fuses FU-21-A, 2 installed, 1 spare.
2-Lamps LM-27.
1-Mounting FT-162.
Radio Receiver BC-312-(*)X
1-Dynamotor DM-21-CX or equivelant.
3-Fuses FU-25-A; 2 installed, 1 spare.
2-Lamps LM-42.
1-Mounting FT-162.
Radio Receiver BC-342-(*)
3-Fuses FU-21-A; 2 installed, 1 spare.
2-Lamps LM-27.
1-Mounting FT-162.
1-Rectifier RA-20 (including Fuse FU-27).
Radio Receiver BC-314-(*)
1-Dynamotor DM-21-(*) or equivalent.
3-Fuses FU-21-A; 2 installed, 1 spare.
2-Lamps LM-27.
1-Mounting FT-162.
Radio Receiver BC-344-(*)
3-Fuses FU-21-A; 2 installed, 1 spare.
2-Lamps LM-27.
1-Mounting FT-162.
1-Rectifier RA-20 (including Fuse FU-27).
(See par. 14 for accessory equipment.)
13
TM 11-850
7
SIGNAL CORPS
Figure 5.—Outline dimensions of all models.
14
TM 11-850
8-9
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-C*) AND BC-344-C)
SECTION II
INSTALLATION AND OPERATION
Paragraph
Initial Procedure ............................................ 8
Installation ................................................. 9
Preparation For Use .......................................... 10
•Operation ................................................... 11
Precautions During Operation ................................. 12
Field Maintenance ............................................ 13
Accessory Equipment .......................................... 14
8. Initial Procedure.—
Be careful in unpacking and handling these receivers. After removal from shipping box, examine equipment for damage that may have occured during shipment. If necessary, clean with a soft brush or blower before installation.
9. Installation.—
a. Procedure.—
Install Mounting FT-162 on a substantial support. Add Mounting FT-178 to prevent excessive horizontal movement of .receiver on its mounting if it is installed in a vehicle. If a shielded
LOOSENESS
\VTh here“ <----------------7
meanspoor rm
U SIGNALS
AdliEMr A A 'Ax
W-H. \ s'* \
IBC-46 _ *
— .... w A
INSERT PLUGS OF THE PL-114 TYPE FULLY BEFORE YOU TIGHTEN THE KNURLED RING
antenna lead is used, connect it to the shielded antenna binding post. When the antenna lead is not shielded, the ALT-SIG-ANT post may be used. In Receivers BC-312-(*), BC-312-(*)X and BC-314-(*) insert the power cord plug in Socket SO-94 located on the lower right of the front panel. Be sure that the plug is
51)4330 0—44—
15
TM 11-850
9-10
SIGNAL CORPS
pushed in all the way before tightening the knurled ring. In Receivers BC-342-(*) and BC-344-(*) insert the power plug into the receptacle of the rectifier at the back of the cabinet. This receptacle normally is covered with a plate held .by two screws. The plate can be removed and refastened to the case next to the power receptacle by means of the two screws. Insert a headset plug in either of the jacks marked PHONES.
b. Final Check.—
Before applying power to the receiver, carefully check cording and wiring and study paragraph 11, OPERATION.
10. Preparation For Use.—
a. Pilot Lamps.—
In Receivers BC-312-(*), BC-342-(*), BC-314-(*) and BC-344- (*) install two pilot Lamps LM-27 in the sockets underneath the reflector. In Receiver BC-312-(*)X install two pilot Lamps LM-42 in the sockets. The reflector is part of the assembly on the front panel of the receivers which contains the dial window. The two pilot lamps may be inspected after removing the four screws holding the reflector to the front panel.
b. Vacuum Tubes.—
(1) These receivers are ordinarily issued with tested radio tubes installed. The tubes should not be interchanged or removed unless they become defective; changing them may cause misalignment. Except for the radio-frequency and continuous-wave oscillator, all tube sockets are accessible when the receiver chassis has been removed from its cabinet.
(2) To reach the continuous-wave oscillator tube socket, remove the screw at the top of the continuous-wave oscillator compartment and the screw about halfway down the center of the right side of the oscillator compartment. Loosen, but do not remove, the screw at the bottom of the rear and halfway down the left side of this compartment. Lift off the compartment cover.
(3) To reach the tube socket in the radio-frequency oscillator compartment, loosen the two screws near the top of the right side of this compartment, then lift the hinged cover occupying the rear third of the top of this compartment. Check the tubes with tube checker such as the one in the Test Set 1-56 series.
c. Line Voltage Compensation (On BC-342-(*) and BC-344-(*) only).—
Remove the receiver from the cabinet and turn it upside down
16
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 10-11
BC-342-(*), BC-314-(*) AND BC-344-(*)
so that the terminal strip near the rectifier is accessible. If prevailing line voltage, measured across terminals 1 and 4 of the terminal strip, is below 115 volts, change the input lead to the rectifier unit. Loosen, but do not remove, the two screws on opposite sides of the rectifier cover; remove the two screws at the outside edge of the rectifier unit, and remove the cover. This will expose the rectifier terminal board and the line-voltage compensating taps. Unsolder wire attached to the compensating tap marked 120V, and solder it to that marked 110V. After making this change, replace rectifier cover.
d. Fuses.—
The fuses marked LAMPS and DYN-FIL on the front panel of Radio Receivers BC-312-(*), BC-314-(*), BC-342-(*) and BC-344-(*) are Fuses FU-21-A. Check for continuity and for proper rating (10 amperes) before installation. Fuses FU-25-A are used in these positions in Receiver BC-3 1 2- (*)X only and are rated at 5 amperes. Fuse FU-27, in Rectifier RA-20 of Receivers BC-342-(*) and BC-344-(*), can be reached from the rear of the receiver cabinet. Check for continuity and for proper rating (2 amperes).
11. Operation.—
a. Panel Controls.—
(1) Radio Frequency Tuning.—
On high frequency models the main tuning dial is of the flat disk type parrying seven scales, six of which are calibrated in kilocycles and one in 45 equal divisions. On medium-frequency models, the main tuning dial is also of the flat disk type but carries five scales, four of which are calibrated in kilocycles and one calibrated in 45 equal divisions. The dials in these radio receivers can be revolved through an arc of about 300° by either of two controls on the front panel. FAST TUNING control provides for a 25 to 1 reduction. VERNIER control provides for a 90 to 1 reduction and carries a scale marked with 100 equal divisions which can be used to interpolate the 0-45 scale of the main dial. Two dial lights illuminate the main dial. A masking plate rotates with the band changing mechanism and covers all portions of the dial, except the 0-45 scale and the scale of the particular frequency band selected.
(2) Band Changing.—
The BAND CHANGE control operates switches located in
17
TM 11-850
11 SIGNAL CORPS
the radio-frequency oscillator, first radio-frequency stage, second radio-frequency stage, and first detector (mixer) stage compartments. It also operates the masking plate mentioned above. All unused coils are short-circuited.
(3) OFF-MVC-AVC Switch________
The OFF-MVC-AVC switch permits the use of manual or automatic volume control. This control also serves as the power ON-OFF switch when the control switch in Rectifier RA-20 of Receivers BC-342- (*) and BC-344- (*) is on, and is the only ON-OFF switch on Receivers BC-312-(*), BC-312-(*)X, and BC-314-(*).
(4) Antenna Alignment Control.—
The ALIGN INPUT control permits tuning a 50 to 200-p.^.f antenna to resonance in high-frequency models. In medium-frequency models, it permits tuning a 250 to 1000-/x/xf antenna to resonance.
(5) Continuous-wave Oscillator Control.—
The CW-OSC OFF-ON switch controls the use of the continuous-wave oscillator. Another control, CW-OSC ADJUST, allows-variation in the pitch of the received signal.
(6) Crystal Filter Control.—
CRYSTAL PHASING control which permits the use of a crystal filter is incorporated in Receivers BC-342-(*), BC-312 to BC-312-J inclusive, and BC-312-HX. The filter is in the circuit at all settings of this control except at OUT. The purpose of the crystal filter is to increase the selectivity of the receiver.
(7) Volume Control.—
The VOL knob operates a dual potentiometer for control of volume. Using MVC it controls the receiver sensitivity; using AVC it controls audio-frequency gain.
(8) Input Binding Posts.—
In order to connect the antenna to the receiver, all sets have two antenna binding posts, one marked SIG ANT and the other ALT SIG ANT, except for BC-312 which has three, SIG ANT, ALT SIG ANT, and NOISE ANT. One of these posts, SIG ANT, is shielded and is used when the antenna is connected to the receiver through a shield lead. All sets have a ground post marked GND. This should be connected to a good ground (six foot metal stake driven in damp earth or to frame of vehicle in which set is installed) .
18
TM 11-850
11
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
(9) Pilot Lamp Dimmer Control.—
Receivers BC-312-L-M-N and NX have controls which adjust the brightness of the pilot lamps LM-27 and LM-42. These controls are located in the same position as the CRYSTAL PHASING control on the panel of receivers equipped with the crystal filter. Turning this knob (marked DIAL LIGHT) to the left dims the pilot lamps.
(10) Send-receive Switch.—
When the receivers are used with a transmitter and associated cording (as in Radio Set SCR-245- series), the REC-SEND switch at SEND position connects a relay through the key jack. This relay short circuits the antenna and grid of the first audio tube to ground when the key is depressed. (In Receivers BC-312 to BC-312-J, BC-342 to BC-342-J and in Receivers BC-314 to BC-314-D and BC-344 the audio grid is not grounded.)
(11) Fuses.—
Fuse holders are mounted on the front panel so that the fuses may be easily replaced. The LAMPS fuse protects the circuit of the dial lamps. The DYN-FIL fuse protects the circuit supplying the filaments and power to the dynamotor. The SPARE fuse replaces either of the other two fuses when necessary. In addition to the above, there is a 2-ampere, 250-volt fuse in Rectifier RA-20, which can be reached from the rear of the cabinet in Receivers BC-342-(*) and BC-344-(*).
(12) Panel Jacks.—
The jacks on the front panel are as follows:
(a) KEY - To connect a telegraph key when the receiver is used with a transmitter (as in Radio Set SCR-245- series).
(6) MICRO - To connect a microphone for voice transmission when the receiver is used with a transmitter (as in Radio Set SCR-245- series).
(c) SPEAKER 2D AUDIO - To connect a permanentmagnet type loudspeaker.
(d) PHONES 2D AUDIO - To use a headset with the receiver, insert a headset plug into jack.
(e) PHONES 2D AUDIO - This jack is connected in parallel with the jack above it and is used for the same purpose.
NOTE: In sets BC-3 12 to and including BC-312-J, BC-342 to and including BC-342-J, BC-314 to BC-314-D and BC-344, this
19
TM 11-850
11 SIGNAL CORPS ’
jack is marked PHONES 1ST AUDIO and connects headsets to output on first audio stage. In later model receivers of all types, provisions have been made for connecting headsets having an impedance of either 4000 or 250 ohms by a wiring change to the phone jacks. This change in wiring is to be made by operating personnel. A reversible tag indicates the correct output impedance.
(13) Power Socket.—
For Receivers BC-312-(*), BC-312-(*)X, and BC-314-(*) connections to the d-c source of the proper potential are made as follows: Connect the proper power cord terminated by Plug PL-114 to Socket SO-94, mounted on the front panel of the receiver. Push the plug all the way into the socket before tightening the knurled ring. (On Receivers BC-342-(*) and BC-344-(*) this socket has a cap which may be removed if necessary. For power connections of these receivers, see paragraph 11 j.)
(14) Panel Locks.—
Panel locks are provided to secure the chassis of the receivers in the cabinet. By turning the five straight knurled knobs clockwise, the receiver panel is pressed firmly against the rubber gasket. To remove the receiver from its cabinet, these lock-knobs must be turned counter-clockwise as far as they will go.
(15) Noise-balancing Control.—
(a) In Receivers BC-312, BC-312-A, BC-312-C, BC-342, and BC-342-C, a noise-balancing system is provided. This operates only on the 1500-3000 and 3000-5000 kilocycle bands. It is intended to reduce ignition interference when the receiver is part of an installation in a vehicle; it is not used when the receiver is part of a portable or semifixed radio set. This system is rather critical in adjustment. On later procurements the noise balancing feature has been eliminated.
(b) If the receiver is in a vehicle and ignition noise is troublesome, proceed as follows: Turn the BAND CHANGE knob to either of the above-mentioned frequency ranges. With the regular set antenna connected, but with the NOISE ANT post idle, turn the VOL knob to about 6. Adjust the control marked NOISE ADJUST for maximum noise output. Disconnect the signal antenna. A special noise antenna is required. This consists merely of a length of shielded wire. Connect one end to the NOISE ANT post on the receiver. Leave the other end open with one foot of the shielding removed and hang it in the engine compartment of
20
TM 11-850
11
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
the vehicle without touching any live part of the ignition wiring. Adjust the NOISE BALANCE control for maximum noise output. This should be equal to the noise received with the signal antenna. If the noise outputs are not equal, relocate the pick-up end of the noise antenna until they are. Connect both antennas. Adjust the NOISE ADJUST and NOISE BALANCE controls until the minimum noise output is secured.
(c) If repeated trials with the noise antenna in different locations do not effect a noticeable reduction of noise, remove the antenna and discontinue the experiments.
b. Source of Power.—
(1) In Receivers BC-312-(*) and BC-314-(*) a 12 to 14 volt battery is required. Receivers BC-312-(*)X requires a 24 to 28 volt battery. A power cord fitted with Plug PL-114 is required. Plug PL-114 fits into panel Socket SO-94 (SOi), and the cord must be long enough to reach the battery. The only connections that must be made are to the heavy prongs of the plug-socket combination; the other prongs are used for control purposes. When the receiver is part of radio set installation, consult the cording diagram of the particular radio set to determine the exact hook-up. This will be found in the technical manual or instruction book for the set. In the case of the a-c receivers (BC-342-(*) and BC-344-(*) ), connect the a-c cord to a 110-volt outlet. Disregard the Socket SO-94 (SOi) since in a-c receivers its connections are used only for control purposes.
(2) The a-c receivers of this series are designed to operate on 110- to 120-volt, 50 to 60 cycle, a-c power. They will be damaged if used on higher voltages or on 25-cycle, a-c power. The primary of the power transformer of Rectifier RA-20 has taps for 110 and 120 volts. Check the line voltage with an a-c voltmeter. Use the 110 volt tap for voltages below 115 volts and the 120 volt tap for voltages above 115 volts. Seldom is trouble found from excessively high voltages; usually the voltage is likely to be low, especially at night. If the voltage does run consistently high, connect a dropping variable resistor in the line and adjust it to the correct value. A suitable unit for this purpose is a 250 ohm, 200 watt, ceramic core wire wound resistor.
(3) The a-c receivers cannot be used on 25-cycle power, generated in some large industrial areas and in the Panama Canal Zone.
NOTE: Be certain that the correct source of power of proper voltage is applied to the receiver being used.
21
TM 11-850
11
SIGNAL CORPS
c. To Turn On Receivers.—
(1) To turn on power in Receivers BC-342-(*) and BC-344- (*), plug in the power cord and throw the a-c power switch at the rear of the cabinet to ON. Now turn the OFF-MVC-AVC switch to either MVC or A VC.
(2) To turn on power in Receivers BC-312-(*), BC-312-(*)X, and BC-314-(*) turn OFF-MVC-AVC switch to either MVC or AVC.
d. To Turn Off Receivers.—
Turn the OFF-MVC-AVC switch to OFF.
e. To Select Different Modes of Operation.—
With receivers operating, use the following procedure:
(1) Continuous-wave (c-w).—
Turn the OFF-MVC-AVC switch to MVC. Throw the CW-OSC OFF-ON switch to ON.
(2) Tone or Voice.—
Tyirn the OFF-MVC-AVC switch to AVC. Throw the CW-OSC OFF-ON switch to OFF.
f. To Tune in a Signal.—
Use BAND CHANGE control to select the frequency band which covers the frequency of the signal to be received. Using FAST TUNING control, tune to the approximate frequency of the signal. Adjust ALIGN INPUT control for maximum noise level. This assures maximum receiver sensitivity. Use the control marked VERNIER to tune in the signal. Adjust VOL control for desired volume level. Turning this control to the right increases the volume; placing OFF-MVC-AVC switch at AVC tends to maintain volume at a constant level as determined by the setting of VOL. AVC is used primarily for reception of voice signals. The proper setting of this control is therefore determined by the character of the signal received.
g. To Change Frequency.—
To change frequencies it is necessary to tune to the new frequency in the manner described in paragraph Ilf. Advance VOL control and rotate the tuning dial slowly to avoid passing over a weak signal without hearing it.
h. To Control Sensitivity.—
The sensitivity of the receiver is affected by controls ALIGN
22
TM 11-850
11
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, BC-342-C*), BC-314-C*) AND BC-344-(*)
INPUT, VOL., CRYSTAL PHASING (on receivers so equipped), and OFF-MVC-AVC. To obtain maximum sensitivity, adjust the control marked ALIGN INPUT to secure the maximum noise output from the receiver, turn the control marked VOL as far as possible to the right. When reception is particularly noisy, weak signals may be read more easily if VOL is rotated to a lower setting. CRYSTAL PHASING control (on receivers so equipped) should be at OUT and OFF-MVC-AVC control at MVC.
i. To Control Selectivity.—
• Receivers BC-312 to BC-312-J and BC-342-(*) use a crystal filter in the intermediate-frequency amplifier circuit. Turn the CRYSTAL PHASING control away from OUT to increase the selectivity of the receiver. (The operation of this control also decreases sensitivity.) The CRYSTAL PHASING control is intended for use primarily in reception of continuous-wave signals. When tuning voice signals, it may increase the selectivity of the receiver to such a degree as to distort them. However, in receiving a voice signal with very heavy background noise, or a voice signal which is very much distorted, it may be found that proper operation of CRYSTAL PHASING control will improve the clarity of the signal. Experiment with the use of this control on various types of signals in order to determine what may be expected from its dperation.
j. To Change The Pitch Of A Continuous-wave Signal.—
The pitch of a continuous-wave signal may be changed either by operating VERNIER control (which changes the tuning of the receiver) or by operating the CW-OSC ADJUST control. The latter control permits a change in pitch of the signal without changing the tuning of the receiver. Once a signal has been satisfactorily tuned in, it will usually be better to make desired changes in signal pitch by means of CW-OSC ADJUST control.
k. Power Connection and Control of Receivers BC-342-(*) ana BC-344-(*).—
(1) A-C Power Socket.—
A-C power connections are made to a receptacle located in Rectifier RA-20 which is accessible from the rear of the receiver chassis.
(2) A-C Power Switch—
This switch is located in Rectifier RA-20 and is accessible from the rear of the receiver. It controls the power input to the receiver.
23
TM 11-850
11-13
SIGNAL CORPS
After this switch is closed the receiver power is controlled entirely by the OFF-MVC-AVC switch located on the front panel.
I. Power Units For Various Receivers.—
Receiver
BC-312-(*)
BC-312-(*)X BC-314-(*)
BC-342-(*)
BC-344- (♦)
Power Unit
DM-21-(*) DM-21-CX DM-21-(*) RA-20 RA-20
Primary Power
12-14 v. d.c.
24-28 v. d.c.
12-14 v. d.c.
110-120 v. 60-cycle a.c.
110-120 v. 60-cycle a.c.
12. Precautions During Operation.—
a. General.—
BE CAREFUL WHEN HANDLING CONTROLS OF THESE RADIO RECEIVERS. MOST OF THE CONTROLS ARE EQUIPPED WITH STOPS TO LIMIT THE EXTENT TO WHICH THEY MAY BE TURNED. FORCING ANY CONTROL BEYOND ITS NORMAL STOP WILL CAUSE SERIOUS DAMAGE. THIS CAUTION APPLIES PARTICULARLY TO THE CONTROLS MARKED BAND CHANGE AND CRYSTAL PHASING.
b. Power Cords.—
Before removing the receiver chassis from the cabinet, always disconnect the power cord from the power source.
c. Band Change.—
In changing frequency bands, the band change switch may be accidentally stopped between connection points. Make certain that this control is turned until it positively engages the contact point for the desired band.
13. Field Maintenance.—
Servicing this equipment in the field consists, almost entirely, of the replacing of tubes, pilot light bulbs and fuses, and making minor'repairs. Alignment and major adjustment or repair will be done only by authorized Signal Corps repair units of trained personnel, who are adequately supplied with the necessary tools and equipment.
2DM-17-A is interchangeable with this unit and was issued with earlier models.
24
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 14
BC-342-(*), BC-314-O AND BC-344-(*)
14. Accessory Equipment.—
a. The following items, not necessarily included as parts of the receivers, are required to operate them:
(1) Receiver BC-312-(*).—
1 Power Cord with Plug PL-114
1 Headset HS-30- series and cords CD-604 and CD-307-A, or cord CD-6053
2 Tubes VT-65
1 Tube VT-66
4 Tubes VT-86
1 Tube VT-87
1 Tube VT-88
Antenna
Source of Power (12-14 volts d-c)
( 2) Receiver BC-312-(* )X.—
1 Power Cord with Plug PL-114
1 Headset HS-30- series and cords CD-604 and CD-307-A, or cord CD-6053
2 Tubes VT-65
4 Tubes VT-86
1 Tube VT-87
1 Tube VT-88
1 Tube VT-134
Antenna
Source of Power (24 - 28 volts d-c)
(3) Receiver BC-314-(*).—
1 Power Cord with Plug PL-114
1 Headset HS-30- series and cords CD-604 and CD-307-A, or cord CD-6053
2 Tubes VT-65
1 Tube VT-66
4 Tubes VT-86
1 Tube VT-87
1 -Tube VT-88
Antenna
Source of Power (12-14 volt d-c)
3If Headset HS-30- series with proper eords or cord is not available, Headset P-19 may be used.
25
TM 11-850
14
SIGNAL CORPS
(4) Receiver BC-342-(*).—
1 Cord CD-370, or equivalent (a-c input)
1 Headset HS-30- series and cords CD-604 and CD-307-A, or cord CD-6058
2 Tubes VT-65
1 Tube VT-66
4 Tubes VT-86
1 Tube VT-87
1 Tube VT-88
1 Tube VT-97 Antenna
Source of Power (110-120 volts a-c)
(5) Receiver BC-344- (*) .—
1 Cord CD-370, or equivalent (a-c input)
1 Headset HS-30- series and cords CD-604 and CD-307-A, or cord CD-6053
2 Tubes VT-65
1 Tube VT-66
4 Tubes VT-86
1 Tube VT-87
1 Tube VT-88
1 Tube VT-97 Antenna
Source of Power (110-120 volts a-c)
b. Antenna.—
(1) T ypes.—
When an antenna is not included as part of the equipment the following antennas can be used. For optimum high-frequency reception (from 10 me and higher) use an antenna about 50 feet long, including lead-in. For optimum medium-frequency reception use an antenna about 100 feet long, including lead-in. For optimum low-frequency reception (BC-314-(*) and BC-344-(*) ) use an antenna about 50 feet long including lead-in.
NOTE: The above antennas can be installed either indoors or outdoors, but outdoors is preferable. The knob on panel ALIGN INPUT (Capacitors C26 or Ci, par. 16) permits tuning the an-
3If Headset HS-30- series with proper cords or cord is not available, Headset P-19 may be used.
26
TM 11-850
TIADIO RECEIVERS BC-312-(*), BC-312-(*)X, 14
BC-342-(*), BC-314-(*) AND BC-344-(*>
tenna to resonance at various frequencies. See paragraphs Ila (4) and Ilf.
(2) Antenna installation precautions.—
Install antenna as high as possible. Keep away from power and telephone lines, metal and metal-roofed buildings, trees, heavy foliage, electric motors and devices, etc. Insulate each end of the antenna.
27
TM 11-850
15
SIGNAL CORPS
SECTION III FUNCTIONING OF PARTS
Paragraph
General Circuit ............................................ 15
Antenna Circuit .......................................... 16
Radio-frequency Circuits .................................. 17
Radio-frequency Oscillator ................................ 18
Crystal Filter ...............................:.........*... 19
Intermediate-frequency Amplifier ........................... 20
Second Detector and Audio Amplifier ........................ 21
Continuous-wave Oscillator ............................. 22
Volume Cdntrol ............................................. 23
Dial Lamp Circuit .......................................... 24
Tube Heater Circuits ....................................... 25
Dynamotor DM-21-( ) ..............................-......... 26
Dynamotor DM-21-CX ......................................... 27
Rectifier RA-20 ............................................ 28
15. General Circuit.—
Receivers BC-312- (♦), BC-312- (*) X, BC-314- (*), BC-342-(♦) and BC-344-(*) are of the multi-band, integral-coil, superheterodyne type. Metal tubes are used throughout, although “GT” type tubes may be used in the first intermediate-frequency amplifier, second intermediate-frequency amplifier and second detector-first audio amplifier stages.Figure 6 shows a functional circuit diagram of Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) ; figure 7 is a functional circuit diagram of Receivers BC-314-(♦) and BC-344-(*) showing the connections set up by the BAND CHANGE switch to receive a signal in one particular frequency band. (The crystal filter circuit used in some models is shown in figure 10.) In these functional diagrams the BAND CHANGE switch and all coils and capacitors not essential to the operation on that band are omitted for the sake of clarity. These receivers employ two stages of pentode radio-frequency amplification, a first detector (pentagrid mixer) stage, and a separate triode radio-frequency oscillator (H.F.O.) ; they also employ two stages of pentode intermediate-frequency amplification; a duplex diode-triode second detector, AVC rectifier, first stage of audio frequency; a separate stage of pentode audio-frequency. A separate triode oscillator (B.F.O.) is provided to produce a beat note for continuous-wave reception.
The two radio-frequency stages provide selectivity and high sensitivity and tend to reduce possible interference from
28
TM 11-850
15
RADIO RECEIVERS BC-312-C), BC-312-(*)X,
BC-342-(*)» BC-314-C) AND BG-344-(*)
ii——— —___________r-H—I*
O i /rk\ 9 - / ■ 1 i I b 1 _1
< i
ir
'rT tMBUMf—t X' „ 1 -* 5;
I • --'ISIWWT-----* ■ || > »” ,- I ’* F »»
r------------- —Wi -------o0 vwA 6
s nfti) r-F~ - - ===~11 Twk>TtTl)
_ . ---VWV—►
। "*Sk
M k-k- Pp
k , ‘ LT J
-----------------ss---------------HI-> -------------------------a jki ih>-+1
r>
\ - »s -
x --W^—U->3
. \ rrHjF'k i • , rX> j?
_r~— L- kw^ * ---------------—'VW- «’
1 ’ ^i!pq Tjx^rr^ 1 -h=—-i
\ L—। SP 0^"’
o " “f ■ * '/'AM---- _,-
\ pA/wi
;®PSk____________________I
-------------^£vV/v^£—^-V'/'A/-
. r
Figure 6.—Functional circuit diagram of BC-312-(*), BC-312-(*)X, and BC-342-(*)» MVC operation. For crystal filter diagram see figure 10.
29
TM 11-850
15
SIGNAL CORPS
—WRW-----r--------------rIHl'- • ,
I -HHl"
a^LZlihfj H”], w ___
w > r HWi
I , _T . 'll—
I u± AHI--
g 2 /jTrA 1 ____"21i H1'' ahmmhiiz-
-------nf+pi"’ ------------------Hr-*
|L_____5 UT «s H s T 8 ~7
IJ , “Il I * z
-==?^
•S sf-HWWH -zww-i > J
---------Ln -W / ?,
___t—S—-----------JUh-
X. UUf , .4
rD'i'LLp!!^,. .. r,7
N I p----J----/waa-Uv&V-—-HH"
- jWmtt $
?Sffipr-iiv o
--------■*-^]|—1 —.----l|-||i- e
nn-^—frrn --------------5---------
a r / । s
~n| »{*!![j Iyy!iv vVWV ' i'W 'll1, <5
j > ^^223222227_fi------------!——MimusvhH’ p
। |W | ^TOHW--Jih,
1?lHl" S J z—X
^HH-e—-------------I o2 Zi • r\
—i . 4xT
i 4^
-^"1 7------------- 1
-Mk-> Io- i X'
-Wav-HH'' s i j,
--------fZJJDJJp-j-AAW-t|H||.
rz-ivvw—Uh..
, eiH ■? s
1 S 8 ?
ji AI i i i 14 4-zwvsa------->
J’ [|?
>----------------------J—
Figure 7.—Functional circuit diagram of BC-314-(*) and BC-344-(*).
30
TM 11-850
15
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-C*) AND BC-344-(*)
signals occuring at either the intermediate frequency or at the image frequency. The mixer tube circuit with its associate oscillator converts the frequency of the received signal to that at which the intermediate-frequency amplifier is tuned. The intermediatefrequency stages provide additional selectivity and amplification. The second detector stage demodulates the amplified signal to audibility. The audio-frequency stage provide additional amplification. The c-w oscillator, generates a signal slightly different in frequency from that to which the intermediate-frequency stages are tuned. When these signals are mixed they produce an audible signal adjustable in pitch for receiving continuous wave signals.
BAND A CIRCUIT REFERENCES SHOWN ISTRF
BAND B AND C FUNCTIONS IDENTICAL VT-86
8AND D CIRCdlT REFERENCES SHOWN ISTRF
BAND E AND F FUNCTIONS IDENTICAL VT’86
HIGH FREQUENCY MODELS
BAND A CIRCUIT REFERENCES SHOWN IST.R.F
BAND B, C AND D FUNCTIONS IDENTICAL VT-86
MEDIUM FREQUENCY MODELS
Figure 8.—Antenna circuit, all models.
594330 o—44-----3
31
TM 11-850
16 SIGNAL CORPS
16. Antenna Circuit (figs. 6, 7, and 8).—
The ALIGN INPUT knob on the front panel controls capacitor C26 in Receivers BC-312-(*), BC-312-(*)X, and BC-342-
NOISE ANT. SIGNAL ANT. BANDA CIRCUIT REFERENCES SHOWN
BAND B FUNCTIONS IDENTICAL
NOISE° ' SJSIGNAL c o I L ] gL* COIL
------J'iPLZe ,________________ , ||C|01 f ..
. SW2l 4=C25
COCUOILl'NG'§ (h*-M( SL| Z-C| M/C28 |R53I
II—L------T—It—f
C27 CIO2
J- i xr AVC
BAND C CIRCUIT REFERENCES SHOWN NOISE ANT. SIGNAL ANT.
l;|_|_________..co.
♦XL ^c»L-£ , SW2| leas11 j p
L2'S ©«. jsL! yCi I
'C27 T (C,02
X X X AVC
NOSE ANT. SIGNAL ANT. BAND 0 CIRCUIT REFERENCES SHOWN
XT7 XV BANOS ED F FUNCTIONS IDENTICAL
. L26
L25 . 5
“3 if______________. c1?.
Xi—£ Ls**! 4=c” J-if.
-a X, '
1 c27 C102
AVC
Figure 9.—Antenna noise-suppression circuit as used in BC-312, BC-312-A, BC-312-C, BC-342, and BC-342-C.
(♦) and capacitor Ci in Receivers BC-314-(*) and BC-344-(*). These capacitors permit tuning the antenna circuit to resonance with an incoming signal. The neon lamp LMi, which is connected
32
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 16-17
BC-342-C), BC-314-C) AND BC-344-(*)
between the antenna and ground, normally has a very high resistance. When a certain threshold voltage is exceeded, the lamp becomes a conductor by ionization and prevents further rise in voltage by by-passing the current to ground. It is used in this circuit to protect the receivers from any excessive voltage which might be applied to the antenna. In Receiver BC-312, BC-312-A, BC-312-C, BC-342, and BC-342-C, a noise-suppression circuit is included in the antenna circuit (figure 9.) In the noise-suppression circuit there are three coils L05, Loe,, and L27, which when properly adjusted, tend to reduce motor ignition interference. L2g is coupled to L26, an electrostatic shield being provided to insure that this coupling is entirely magnetic. This coupling is also adjustable. The coupling between L26 and L27 is primarily electrostatic; the necessary magnetic shield is provided to insure that this type of coupling is secured. The coupling between L26 and L27 is also adjustable. An adjustment on the front panel marked NOISE BALANCE controls the coupling between L26 and L25 and serves to adjust the amount of noise introduced into the receiver circuits from the noise antenna. The coupling between L27 and L26 is controlled by the NOISE ADJUST control and determines the phase relationship of the resultant noise voltage introduced into the receiver. The coupling between L25 and L26 is adjusted to produce minimum noise (not always zero). L27 is then varied to reduce the noise to zero, thereby insuring that the phase of the noise fed by the separate antennas results in cancellation. L27 also acts as a radiofrequency choke between antenna and ground.
17. Radio-Frequency Circuits (figs. 6 and 7).—
a. Receivers BC-3I2-(*), BC-312-(*)X and BC-342-(*).
In Receivers BC-312-(*), BC-312-(*)X, and BC-342-(*), the circuits of the first radio-frequency amplifier, second radiofrequency amplifier, and mixer stages are very nearly identical. They are designed to permit tuning with three sections of a four gang capacitor. The screen voltages for the tubes in the aforementioned stages are provided by voltage dividers connected between B4~ and ground. Resistors R2 and R3, Rs and R9, and R48, Ris4 and R5o4 form these voltage dividers. Each of the three screens is separately bypassed to ground by its own capacitor C30, C36, and C49 respectively. For MVC operation, cathode bias for the two e ______________
d 4These two resistors are in parallel.
33
TM 11-850
17
SIGNAL CORPS
radio-frequency tubes is partly fixed and partly variable. The fixed bias is derived from the drop across Ri and R7. The variable bias value is provided by means of a voltage divider formed by R36 and variable resistor R35. These latter resistors are connected between B-|- and ground, so that a change in the value of R35 will cause a change in the cathode bias. R35 is shorted to ground for automatic volume control (AVC) operation so that the cathode biases of the first radio-frequency and second radio-frequency tubes are provided entirely by the drop across Ri and R7. The cathode bias for the mixer tube is derived from the drop across Ru and is not variable. The injector grid bias for the mixer tube is secured by means of resistors Ri3 and R14. All cathodes have their own separate bypass capacitors, C29, C35 and C48. Capacitors C33 and C45 keep the d-c voltages from being impressed on the grids of the second radio-frequency and mixer tubes. There is a blocking capacitor C101 in the first radio-frequency stage to make the grid circuit identical with those of the two succeeding stages. Coils Li, L7, and Li3 are the tank inductances for the grid circuits of the first radio-frequency, second radio-frequency, and mixer stages respectively. These tank inductances are tuned by a ganged capacitor consisting of C28, C34, and C46. In series with these sections are three capacitors, C25, Cioo> and C38, across each of which is placed a shorting switch, SW2, SW4, and SW6 respectively, operating with the band change mechanism. These shorting switches permit the series capacitors to be used in the three highest frequency bands to obtain greater frequency spread on the dial, and short them in the three lowest frequency bands. Trimmer capacitors Ci, C7, and C13 are provided to permit individual alignment of the three circuits. Radio-frequency blocking capacitors C32 and C39 are used to prevent shorting the plate supplies of the first and second radio-frequency tubes to ground. AVC circuits (par. 23 b) contain resistor-capacitor network filters. Decoupling networks, consisting of resistors and capacitors, are inserted in all plate supply leads to remove any radio-frequency which might be fed back into the power supply.
b. Receivers BC-314-(*) and BC-344-(*).—
In Receivers BC-314-(*) and BC-344-(*) the first radio-frequency amplifier, second radio-frequency amplifier, and mixer stages also are designed to permit tuning with three sections of a four-gang capacitor. The screen voltages for the tubes in the above
34
TM 11-850
17-18
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
mentioned stages are provided by voltage dividers connected between B-f- and ground. Resistors R3 and R4, R9 and Rio, Ri«’3, R-,33 and R45 form these voltage dividers. Each screen is separately bypassed to ground by its own capacitor, either C9, Ci8 or C49. For MVC operation, cathode bias for the two radio-frequency tubes is partly fixed and partly variable. The fixed bias is derived from the voltage drop across R2 and R8. The variable bias value is provided by a voltage drop across R44 and variable resistor R3o-Any change in the setting of R30 will change the bias applied to the cathodes of these two tubes. R30 is shorted to ground for AVC operation so that the cathode biases are provided entirely by the drop across resistors R2 and R8. The cathode bias for the mixer tube is derived from the drop across Ri5 and is not variable. The injector grid bias for the mixer tube is secured by means of resistors R14 and R15. Each cathode has its own cathode bypass capacitor C8, C17 or C48. Coils Li, L5 and L6: and L13 and L44 are the inductances for the grid and plate circuits of the first radio-frequency, second radio-frequency, and mixer stages. These tank inductances are tuned by a ganged capacitor consisting of C7, Ci« and C46. Trimmer capacitors C2, Ci4, and C27 are provided to permit individual alignment of the three circuits. In order to isolate each stage, decoupling resistors R(i and Rn are located in the B-j-lead of the first radio-frequency and second radio-frequency amplifier stages. These decoupling resistors are bypassed to ground by capacitors C76 and C8i. Also, all AVC circuits contain resistorcapacitor network filters for decoupling purposes.
18. Radio-Frequency Oscillator (figs. 6 and 7).—
a. Receivers BC-312-(★), BC-312-(*)X and BC-342-(*)..
The radio-frequency oscillator in Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) employs a modified Hartley circuit. The tank circuit consists of an inductance Lm which is tuned by one section of the ganged capacitor C82. Fixed capacitor C4o is used in series with the tuning capacitor on the three highest frequency bands. Shorting switch SW8 is ganged with the shorting switches already mentioned. Trimmer capacitor C19 is used to align the oscillator tank circuit so it will track with the other tuned radio-frequency stages in the receivers. The resistor R4i serves to reduce the plate voltage supplied by the power supply to the proper
BThese two resistors are in parallel.
35
TM 11-850
18-19
SIGNAL CORPS
value. The oscillator plate is bypassed by C83 directly to ground which forms the plate return to the radio-frequency grounded end of the tank coil; C88 serves as a grid blocking capacitor and R42 as a grid bias resistor. The radio-frequency voltage occurring between the cathode of the oscillator tube and ground is impressed on the injector grid of the mixer tube (first detector) through the coupling capacitor C47. The heterodyne action of the mixer and oscillator on the received signal produces an output signal (at 470 kc, the intermediate frequency) which has the same modulation as the signal received on the antenna.
b. Receivers BC-314-(*) and BC-344-(*) .—
In Receivers BC-314-(*) and BC-344- (*) the radio-frequency oscillator is of the plate feed-back type. The tank circuit consists of transformer L2i and L22, fixed capacitor C28, and one section of ganged capacitor C«7. Trimmer capacitor C23 is used to align the oscillator tank circuit so it will track with the other tuned radio-frequency stages. Resistor Ri3 serves to reduce the plate voltage supplied by the power supply to the proper value. Capacitor C72 is used to bypass the oscillator plate return to ground; capacitor C66 serves as the grid blocking capacitor, and resistor R38 as the grid bias resistor. The radio-frequency voltage impressed on the injector grid of the mixer tube is secured from the oscillator tank circuit. The heterodyne action of the mixer and oscillator on the received signal produces an output signal (at 92.5 kc, the intermediate frequency) which has the same modulation as the signal received on the antenna.
19. Crystal Filter (fig. 10).—
A crystal filter is incorporated in Receivers BC-312 to BC-312-J, BC-312-HX and BC-342-(*). The output of the mixer stage is coupled to the grid circuit of the first intermediate-frequency stage through the first detector transformer L28. Capacitor C53 and the primary coil of the intermediate-frequency transformer are wired in parallel to form a resonant circuit which is tuned to 470 kc by an iron core within the transformer coil. The secondary of this transformer and both coils in the first intermediatefrequency and second intermediate-frequency transformers, L29 and L3o, are tuned in a similar manner. In the secondary side of the first detector transformer L28, there is a bridge circuit consisting of capacitors C94, C95 and C5i, and a crystal CX which is
36
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 19
BC-342-(*)» BC-314-(*) AND BC-344-(*>
provided with a shorting switch SWi0- When this switch is closed, one-half of the available voltage across the secondary winding of the first detector transformer L28 is impressed on the grid of the
1ST DET. 1ST IF.
VT-87 VT-86
I---------------------------------------------1
CRYSTAL-.
„ 28(, 800 MMF ZUSW|°
I 0 '*-& (to-----r r ।
I 53 / °52 100 MMF |
I 400 » St Sf < CX >______________I l-i>
I MMF j? I ~V. A11 >100000
I ....... TV TT-------c—5 <
I 95 4-50 MMF> r
( 800 MMF > 18
. 1 1,000
1 i 54 s* l7 i 63-
J1 MF > 1ST. DET. TRANS - Jf' MF J , ’ FORMER C-282 ~ < D
L_________________________________
I' 8+ AVC I
Figure 10.—Circuit diagram, crystal filter circuit.
first intermediate-frequency tube through a blocking capacitor C52. When the switch is open (the CRYSTAL PHASING control turned away from OUT), the signal is impressed on the grid of the first intermediate-frequency tube through the crystal CX and blocking capacitor C52. This crystal, which behaves as a sharply tuned resonant circuit, resonates at the intermediate-frequency of 470 kc. 'The crystal with its holder is one element of a bridge circuit also containing capacitors C94, C95 and C51. Capacitor C5i, which is operated by the CRYSTAL PHASING knob, makes it possible to adjust this bridge circuit so that the capacitance of the crystal CX is balanced out and undesired signals which are close to, and interfering with, the desired signal are discriminated against. The control is referred to as CRYSTAL PHASING, since its operation tunes the bridge circuit arid consequently adjusts the phase relations of the voltages and currents. The sharpness of resonance of this crystal bridge greatly increases the effective selectivity of the receiver when the crystal is in the circuit.
37
TM 11-850
20
SIGNAL CORPS
20. Intermediate-frequency Amplifier (figs. 6 and 7).—
a. Receivers BC-312-(*), BC-312-(*)X and BC-342-(*).
In Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) resistor R52 provides a high impedance, d-c grid return for the first intermediate-frequency amplifier tube and provides for the introduction of A VC voltage. The intermediate-frequency stages are coupled to each other inductively by the first and second intermediate-frequency transformers, L29 and L30. Both sides of these transformers form circuits which are made resonant to the intermediate-frequency by a capacitor in parallel with each winding. These transformers are tuned by a movable iron core. Cathode bias for the first intermediate-frequency amplifier tube is derived from the voltage drop across Ri9 and the same voltage divider system as for the first and second radio-frequency amplifier tubes. Cathode bias for the second intermediate-frequency amplifier tube is secured from the voltage drop across the resistor R24. The screen voltages for the two intermediate-frequency amplifier tubes are provided by voltage dividers consisting of R20 and R2i for the first intermediate-frequency amplifier tube, and R25 and R26 for the second intermediate-frequency amplifier tube. These voltage dividers are connected between B-f- and ground. Each screen is separately bypassed to ground by its own capacitor, either C60 or C69.
b. Receivers BC-314-(*) and BC-344-(*).—
In Receivers BC-314-(*) and BC-344-(*) the first detector transformer is made resonant by means of the two capacitors, C34 and C32, connected in parallel with coils L29 and L30 which in turn are tuned by movable iron cores. The A VC voltage is introduced through resistor R18 and bypassed by capacitor C33. Cathode bias for the first intermediate-frequency amplifier tube is secured from the voltage drop across R19, R30 and R44. Capacitor C5i is the cathode bypass for this tube. The first intermediate-frequency transformer is an impedance coupling device made up of the tuned circuit L3x and C36 and the coupling capacitor C38. Resistor Ri provides a high-impedance, d-c grid return for the second intermediatefrequency amplifier tube. Cathode bias is secured by the drop across resistor R24 which is bypassed by capacitor C34. The screen and plate circuits of the intermediate-frequency amplifier tubes are filtered by decoupling resistor-capacitor networks made up of R21, r22, R26- R27> C52, C37, C55 and C42. A VC is introduced into the second intermediate-frequency amplifier tube through resistors Rx and R23
38
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 20
BC-342-C*), BC-314-(*) AND BC-344-(*>
1ST RF 2NO. R F 1ST OCT 1ST IF 2ND I F 2ND DET
<500-rv. <500^v- <550^. < 500^- < JOO
LiL_i it
„ “-S3"" -
-----------------------------------i
MAMML VOLUME CONTROL _ 05 MF JL I MCG <
C75 *30$_|
l*TRF 2»RF |U DET |U | F 2»IF 2® DET
[9 [9 [9 A [Fkrff
SJ0O.A. S»»«A S JOO a. < 800 .A. T| f-o
YvV^-X-AMA-, *** <. nCgH_
pu ■» “pztr
..... --------------------------------------------W.-____1I AUTOMATIC VOLUMC CONTROL------------S ! *• * ' V **'• ’*• S
1ST R F 2N0. R F 1ST DET 1ST I F 2ND I. F 2W DET
r© r© r© r© r©
II TO TNO
I I c«5 AUWO
<350^- <350^- <500^- < 500 < 500
>R2 > *8 $*15 < Rl» <*2« U32 l35
• | • 34 .
, '-k-----------------------*—I 50,CXR^| *°° “*
SOpOO^v. .1 MEG.- «T\
r
-------------------------- U I i MANUAL VOLUME CONTROL----I I °J **-▼ >
VKF 2«RF <“«T l« U wir 2" °ET
fp [9 if* [9
r r |s‘ r k 5«i"
Wn w-L
——J——L ' J [
AUTOMATIC VOLUMC CONTROL -R •„ < |
Figure 11.—Functional diagram, second detector, manual and automatic volume control, all models.
39
TM 11-850
20-21
SIGNAL CORPS
bypassed by capacitor C39. The second intermediate-frequency transformer is made up of coils L32 and L33 and capacitors C40 and C4i.
21. Second Detector and Audio Amplifier (figs. 6, 7, and 11).—
A duplex-diode triode is used as a second-detector-AVC-lst audio amplifier tube. One diode section serves as the second detector. The other diode section provides AVC voltage. The triode portion of the tube serves as the first audio-frequency amplifier. In Receivers ,BC-312-(*), BC-312-(*)X and BC-342-(*), resistors R49 and R34 comprise the diode load resistance. In Radio Receivers BC-314-(*) and BC-344-(*), the load resistors are R28 and R29. Radio-frequency bypass capacitors C71 annd C72 in the high-frequency receivers and C75 and C80 in the medium-frequency receivers are used to filter any remaining radio frequency out of the detector diode load circuit. Bias for the second detector, AVC, first audio amplifier tube is secured by resistor R28 and bypassed by capacitor C73 in the high-frequency receivers and by R37 and C58 in the medium-frequency receivers. The grid of the first audiofrequency amplifier tube receives its excitation through coupling capacitor C8i for the high-frequency group and C94 in the mediumfrequency group of radio receivers in series with the MVC-AVC switch arm. This excitation consists of the voltage drop across the entire resistance of R34 (h-f group) or R29 (m-f group) for MVC operation, and the drop across a section of the same resistance for AVC operation. The output of the first audio-frequency amplifier tube is coupled by C76 (h-f group) or C43 (m-f group) to the second audio-frequency amplifier tube grid. The primary of transformer Tj in the first audio-frequency amplifier tube plate circuit acts as an impedance coupling element. The B-|- is bypassed to ground by capacitor C74 (h-f group) or C57 (m-f group) to keep radio frequency out of the plate power supply. Cathode bias for the second audio-frequency amplifier tube is provided by the drop across the parallel-connected resistors R3i-and R54 in the high-frequency group and R33 and R52 in the mediumfrequency group. The resistors are bypassed by C98 (h-f group) or C60 (m-f group). The output of the first audio-frequency amplifier tube is coupled through transformer Ti to jack and the output of the second audio-frequency amplifier tube is coupled through transformer T2 to jacks J2 and J3 which are connected in
40
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, . 21-23
BC-342-(*), BC-314-(*) AND BC-344-(*)
parallel in receivers BC-312 through BC-312-J, excepting BC-312-HX, BC-342 through BC-342-J, BC-314 to BC-314-D and BC-344. In receivers BC-312-(*)X, BC-312-L, BC-312-N, BC-342-L, BC-342-N. BC-314-E, BC-314-G and BC-344-D, the output of the second audio-frequency amplifier tube is coupled through transformer T2 to jacks Ji, J2 and J3, which are connected in parallel. Headset or a speaker may be plugged into these jacks.
22. Continuous-wave Oscillator.—
a. High-frequency Group (fig. 6).—
A modified Hartley oscillator circuit is used. The tank circuit of this oscillator consists of coil L3i and capacitors C84 and C85 connected in parallel. A grid blocking capacitor C86 is used in conjunction with a grid bias resistor R43. The plate supply to this oscillator tube is connected through voltage-dropping resistor R37-Switch SWn in the plate supply lead permits turning the continuous-wave oscillator on or off at will. The radio-frequency plate circuit is completed through capacitor C87 from plate to ground. A portion of the voltage drop across tank coil L3i is impressed on the plate end of the second detector tank circuit through a low-pass filter consisting of coil L32, resistor R51, and capacitors C96 and C97; and through the coupling capacitor C4i. The purpose of this filter is to prevent the introduction of harmonics of the continuous-wave oscillator frequency into the detector circuit of the receiver.
b. Low-frequency Group (fig. 7)-—
A modified Hartley oscillator circuit is used in these radio receivers. The tank circuit of the oscillator consists of coil L34 and capacitors C82, Ces, and Ceo connected in parallel. Capacitor C74 is the grid-blocking capacitor and resistor R39 is the grid bias resistor. Resistor R36 is the plate voltage-dropping resistor connected in series with switch SW10, which permits switching the continuous-wave oscillator on or off. Capacitor Css completes the radiofrequency circuit from plate to ground. The radio-frequency voltage appearing across coil L34 is injected into the second detector tube through capacitor C44.
23. Volume Control.—
a. Manual Volume Control Action (figs. 6, 7 and 11)-
When operating on manual volume control (MVC), the cathodes of the first and second radio-frequency amplifier tubes and
41
TM 11-850
23-24 SIGNAL CORPS
the first intermediate-frequency amplifier tube are returned to the-voltage divider consisting of resistors R35 and R36 in the high-frequency group and resistors R30 and R44 in the medium-frequency group. This voltage divider is connected between B-|- and ground so that, by operating the VOL control on the front panel, the grid bias on these tubes is changed, thus varying the amplification of the tubes. In this mode of operation, the AVC bus is shorted to ground, and that portion of the audio-frequency signal which appears across R34 (h-f group) and R2<) (m-f group) is available at the input of the first audio-frequency amplifier tube.
b. Automatic Volume Control Action (figs. 6, 1 and 11).—
In AVC operation, the control grids of the first and second radio-frequency amplifier tubes, the mixer tube, and the first- and second intermediate-frequency amplifier tubes are returned to ground through the AVC diode resistor R30 (h-f group) and resistor R32 (m-f group). A change in voltage across this load resistor affects the bias, thus changing the amplification of these tubes. The AVC system is designed to bias these tubes more negatively as the signal increases, thus reducing their amplification and tending to maintain a constant input to the second detector. The AVC diode plate of the second detector tube is coupled through C37 (h-f group) or C45 (m-f group) to the plate circuit of the second intermediate-frequency stage, providing an intermediate-frequency voltage which is rectified by the AVC diode circuit. Rectification takes place in the AVC diode circuit when the peak value of the intermediate-frequency voltage impressed is greater than the d-c voltage drop across the second detector bias resistor in the cathode circuit of this tube. The magnitude of the AVC voltage is therefore dependent upon the strength of the received signal in excess of the voltage drop across the bias resistor.
24. Dial Lamp Circuit (figs. 12, 13, 14, 15 and 16).—
In Receivers BC-312-(*), BC-314-(*), BC-342-(*) and BC-344-(*) two digl Lamps LM-27 are connected in series. In Receivers BC-312-(*) and BC-314-(*) the source of power is the 12-volt, d-c supply; and in Radio Receivers BC-342-(*) and BC-344-(*) it is supplied by a separate 1 2-volt, a-c winding of power transformer T3. In Receiver BC-312-(*)X, two lamps LM-42 are connected in series across the 24-volt, d-c supply. A dial light dimmer-rheostat R56 (R55 on BC-312-L and BC-312-
42
TM 11-850
24
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-C), BC-314-(*) AND BC-344-(*)
■ n O _ „ o I 8 „ I
■I- -- _Z_ mg ? ~ f_5 o PL* -L_> a
rrfPn . 11
f II T TV—00 SF S S |l lj|
IT 5 >5 5* • «_i_ HI_।__
L_uk--------■ - /03070iH’Ti 1
X 3 Ht: <00-0 ;
r^-ATvVV~i o’ । ।
stf SS&gf
«i wj
85 bH> 0 >8
os==L—---------------4q».
5-< ---I fl’ MW*!, I1jz
» I' *« ^yv i VOLUME | C7Z| T I 33 * PHONES
,' L ——i avc1—^YT~?r— ’ 2N0 AU0'°
, —rJfc-n „ ,^_^nTTc» 4^v4‘>s^i’»LU%
r-n— ci --- 11 r~~!i T“ ---*rkF * ® ! orr ml --------------- t,
IM|?5au«N*c -■ S£ luJ. I! * C '” ” 'r»« il'-AVC ill AUDIO n-----— 2±..s,£
+ 13 --xwm"mHlsn h .-Juu-^’tri ■—I Y , 11 yiw.; _____
j,1] I—-m’i—ih, «w. i1 ’"ii' r—'s»!,r-TmM« 't’8‘ *’’■•* Foff Z-c >A iv111*? n.
»«yM ym I J 'm? |j^K i ..““A1' '"a"’ l"4 LM5 m | F (m-1 )t T _____’
3* 2a i' w,j| 7v7»« I rtr''~9- xj *✓ TCao i ।
A rKyi ----------E=Z!:^r?/y rT^i 1 ^=^7 ,-+ 33° y>oorF Fs mmf ’ 1--------------c°'A
▼''COMMON CHASSIS OR BUSS CONNECTIONS ___ I— ■ ^~ - / ' VT-154 P I T "Ol? ? »l~[c > *5* Rl"2
R-- AUDIO ------© 1 1981 JjSEND
__LP—-7-4_____________S.FF T3J_-_~______ pZ.Fc
oM-ei-cx Il 11 r
i terminal1 r9o_zp—zzzz.: । —_r-_---—— i n
|00000000| '*3° ' I---------—? i ।—zlJZ ,, |Tmicrophone
! ------------tP______0\T
। f|? , ~ . (iE H N ucdJ TYPICAL PLUG CONNECT.ONS O C OPERATION
I “ /TYsi- 1 A^P T~I. I \ F V / O F.LAMENT-24V
( <>. JW I? । I H’ \O K < oy-T Fl LA ME NT+24 v FlrOMMOM
| PktJJz I FL i ____l—o2 1 KO O y E MIC RING &S-COMMON
I | L-1 . I----------- ., . J । p H SIDE TONE VI
| --------1 ---L°‘ --------' 3 SEND REC RELAY s)
1------------"J CONNECTION STRIP y m}00***0*
Figure 13.—Schematic diagram, Receiver BC-312-NX.
Receiver BC-312-HX incorporates crystal filter, see figure 10.
44
TM 11-850
24
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-C*) AND BC-344-(*)
• ANT. ALT ANT. -------------------7—------------- 4000/1 250/1____n , ■
। ?________________________________________________p —1 pf r 7g;
~ —-— Alfa?—, Laim/—-f^J3
©LM| b b SEND \ receive_____________________________ ] r/W5\- • --1 •
GJ------------------------------------------------cj’ .. TT31 si'h. tc«
_ I----Ce, ----- --------[---cM„, " — I —2 2ND "1
I ST. PjdVT-8fe I' II Ls 2ND.RE]vT-8fc It .— 1ST. DET. VT- 87 ~ IST.LFlVT-aS 2MD.I.FVT-06 DET. VT-88^ AUDIO VT-6fe
-A rS|l -fib ’ fflgl -fWb W] Oi P® LW boT , bcTT” r^jr^- ] -f L( iT b-----------------
sw2 , rrj :( s"4 _,io!o4 . 1: i s sis sws -.om^2- 21* G —5a_,"n •"] ,e>g >” 1 .'2? *21'34 .. _ >aJ>»;l °» |
<<■_ I'W fite Pr fite: WrWW m 51 ® [r8! \.L1»U> - ixsf ’ « _1 L/Pl 7-«• u,_ _L_ »IS S|8 i «j, 2^1 i rfelS’P51I U +
5-1 rf=3 JnySHM
,'-----rl» Li=-rrin _________________________IE______* « 4>£^a~,
c’ is 4 X ‘“131 T R>o / <
SWj_^ " T p L- 5 ■' — ” -^2- BF 5 X C W OSC IVT-45 p-j T -J
Ok- =Ll IOiittEEE=!] I&l —=0 —E?"3 h - ^I=ip_ u.lSp7 gwJ r7
gndp (gbouno all chassis J. X‘ s 38 -=• .. Jz . < > ' r^l
1 + connections) x^o xc„ n«wF—-| KTlTayj TMI == = z=i:==s^z4J
U1-^1
<■ Ljj vta86 ?''s — ------j—° u
|| 2ND.R.F. IST.DET M y( N I I 0Js
5'“® C c» VT- 84 VT-OS I ‘f-V8 ° Tl 4 “T - --4
7g=sd , “ ir A A VeI45 J ^-cypca —
(LL«m -viMir- 1 T I ST. R.F R.F. OSC I u / I I I L— SHIELD
^pJUlLr^ ~lh VT-66 VT-8S
^o-fVr
( —n|Ml£L- VT-T65 CONNECTIQn ITIjZ- TYPICAL PLUG CONNECTIONS'.-
a-Lj^cs. ifoVoWfoj S-.^iSSX
________. 4- A A H J- SEND-REC. RELAY
-/\ /\ 1—-----1 N- KEY; SEND -REC. RELAY
»—W/----- 1ST. IF 2 ND. IF ____( u- MIC. TIP
; ;c72 B|s । /[" e "• 1 ®1 not used
SW9fi — , rtk (7^4= SA! I m' AND T ARE COMMON .
------ .] B^U I G.^F^S, ANDY ARE COMMON. ------~=U i pavfihi ।
i ______DM j
Figure 14.—Schematic diagram, Receiver BC-314-(*).
45
TM 11.850
24
SIGNAL CORPS
2ND. R E ..,CI3 ^CRYSTAL PHASING
K L vr.86.d5r---- , r-*=-Li T .(n cxi •■ ■—| ----------
* • Z“^\ c39 SW >.0UT 8 lc„ c64
---------25"^; (/-——) 2^755 s*l0|-. -3^i AT
rl, ,..j^ *“f »>|K ‘Y I , 29./Sg£- sOffinrf
':2jttbuf 1 ’Bkk L "A1®^ 1 pT „ j>.C63T 1ST. IF p? ||°»~ ZN0 IF It l|C“—
rsI_l_ f vTeV J^*^Jr52l VT'86/4X r-fr— VT'6X4>J -v-i
- JutrA-fl ,, "2JV"1 r____1 Z®\ M ■ /^"N (Hfc— ^7
r-^T^o pE * =F« l F=n I tr , Fl^-^-dr rf-rz^A-,7 “
5 C r ~ ftg Uf~' I O c f I|X T 36 1 _1 1 R,J —-4r—rl ——fr—rl
caj^lW/ *~l H=E=====-------- T- II^wxtunwg I rTTFN I sw I „ 1 ■■- r
L X p-BANO CHANGE 1r4i X 32 X / II R36 I F 2WD. DET, f]
_J4 11 c r T97 >1 p7 L’ I! ^lllllfil
C,7tT JtC| 1* tM RF r5 " rA 1-^-lA REOSC. [TC93 SSl c.w.oscJ'V87 c^Tb~'1Z____ I ' PH0NES
4«3 ' vt'6>±\ 7^r- [ TPS8 I •’•• "-“ bm2 lm5 sw ; OFF __L3-q )T '° v—£=dlJ3
77 36 m.ac6I oGf pr\ "4/ । if Annn N nW aWt 2*° 0ET AW>,° zcn 4 1 q Fi \ ~~~~1 /-^c T
8, _____iilgmip ArT“ n~ t] B
^orf 7±T______ is--.1 <■<.„ A. n _£?!Z52_I|51 ,h0 ’
'ST a^lVT-86 f""'L's INDB-Fhr-tfc [ It i_--| 1ST DET. VT- 8T ’ 1ST.id VT-86 2ND.IF VT-86 PET VT-8&X. AUDIO VT-Sfc
”T—LXiT uxT rfiiBH kX XT rin XT
ppJJttb— 'xT’/ -\ilHjr- y __ ---------------------------X. J XT’/
|X_ , X" r^' < mr? ] ,( ( y i m m______________________________________y
s"2 „mC5- li'Te ^atLcd-1 v, « '”.._'» «» »» 1 “sa
rw xx tRROOnUlftnU anx rti £| jf*'C|* ~ 1 jr^11 41 i r*^ I lc**i 1 ? r>i|csi| [ ? lCs*ICs5r 5 ? [ c**f T8i ? > ? r“r
"] m -aSm-4 Lm \uuJr— +"*’ *“ r* ■>2' ..■?*“ **4 +
L^’ I X" |l JXiTflnk—-
aSII ]grpl IjrjM JSRTI
—J ^b5 L—|_ _ L—X___ _j_-----jcM | xC/ LM cgl _p)LM* F
GNDo (gbovnb all chassis C STT J..* ’*» i (L L T/< [(—, ~ xrxix
4- 4- connections) Yck> yci9 l2i - S&|ZX> I c,
+ + JJJJmiVf] T»y w#»|
, T‘ T r ^4 E ~ ~f ”
rau#* 'A4'
” J. VT-86 VT- 86 U .....1
------- A A___________________| - ------- --- WV*- I ST. I F 2 ND. IF_I--I-ZTZi
Sc71 R13 ---— I yT I X- I
S", --I ” ¥4 Pn_§
Ze/*3--- \ /\ / 120V -SO; I
»■ ^1 . fTi>l
I J_j
TM 11-850
24 SIGNAL CORPS
M) is incorporated in Receivers BC-312-N and BC-312-NX. The dial lamps are connected1 so as to receive current through fuse F2 or F5 (F5 on BC-312-(*)X only) and are turned on or off by the OFF-MVC-AVC switch in all models.
ISTDET 2n2rF
' RMOSCl istrf '
° ISTAF 2NDJF °
2ND.DET.
" O> ° AUDIO ’
cw OSO.
R47 ON HF. GROUP
R43 ON M.F. GROUP
----------------12 VOLTS-------------------
Figure 17.—Tube heater circuits in BC-312-(*), BC-314-(*), BC-342-(*) and BC-344-(*).
TO TUBE HEATERS I I
----1 1-------------------V—---------• J •-----------•
I
lm2 lm3
© © I’"'2
n n
I 5WI3 I NOT A PART OF
| ---o-----------------I j BC-312-C
r38
| R39
R40 c
I ±C89 ,, |
| _|C9O ? T THSI ।
i
Figure 18.—Oscillator compartment heaters in BC-312, and BC-342.
48
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 25
BC-342-C*), BC-314-(*) AND BC-344-C*)
25. Heater Circuits (figs. 17, 18 and 19).—
Either metal or GT type tubes are employed in these receivers. All tubes except Tube VT-134 in Receiver BC-312-(*)X and Tube VT-97 in Receivers BC-342-(*) and BC-344-(*) require a heater voltage of approximately 6 volts per tube. Tube VT-134 requires 12.6 volts and Tube VT-97 requires 5 volts. To permit operation from a 12 or 24 volt power supply system, the tubes
I ST.DET.2NDR.E
IST.R.F R.EOSC.
2NDJ.F. ISTLF |
C.W.OSC. 2ND.DET.
R55 /k
H VW\A/ ^jD10
-----------24 VOLTS-------------
Figure 19.—Tube heater circuits in BC-312-(*)X,
in the receiver proper are connected in series-parallel (fig. 17). In Radio Receiver BC-312-(*)X (fig. 19) resistor R55 is used as a (ilament-dtopping resistor, in series with the heater of Tube VT-134. In Radio Receivers BC-312- (*), BC-314- (*), BC-342-(*) , and BC-344-(*) (fig. 17) a resistor is connected in parallel with Tubes VT-88 and VT-65 to reduce the current flowing through the beater of these tubes to the correct value. Tube VT-97 is used in Rectifier RA-20} and its filament power is supplied by a separate winding on power transformer T3. Tube heaters in the receivers are bypassed to ground through capacitors. In Receivers BC-312 and BC-342 the temperature of the oscillator compartment is thermostatically controlled by means of heaters (fig. 18)*
49
TM 11-850
26
SIGNAL CORPS
26. Dynamotor DM-21-(*) (figs. 20 and 21).—
Dynamotor DM-21-(*) as used in Receivers BC-312-(*) and BC-314-(*) (DM-17-A6 in BC-312) operates on a d-c input of between 12 and 14 volts, producing the necessary plate voltage for the receivers. This dynamotor is secured to the underside of the
To a chassis------—i--------g —Grd. screw
fermirtai strip a |
f Ji
z; ; \ proash
a lag*
Gr -eon y
to 2 ——gMFWH
in ' 1 ikv
’ ~ K
;,:■ ■' - I
W' s
i ft®
2/b [ J
Figure 20.—Dynamotor DM-21-(*) as used in BC-312-(*) and BC-314-(*).
chassis of the receiver. Under full load conditions, the dynamotor draws about 2.7 amperes at 14 volts direct current with a d-c output of approximately 85 milliamperes at 230 volts. Filter FL-6-B is inclosed within the dynamotor to prevent the transfer of radio-frequency interference and commutator ripple into the voltage supply circuits of the receiver.
•DM-17-A is interchangeable with DM-21-(*).
50
TM 11-850
27-28
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, BC-342-C*), BC-314-(*) AND BC-344-C*)
27. Dynamotor DM-21-CX (figs. 20 and 21).—
Dynamotor DM-21-CX is used in Receiver BC-312-(*)X and operates on a d-c input of between 24 and 28 volts, producing the
DYNAMOTOR DM-2I-B r----------;T4-----------1
--------f-pPrrr----• A+!
|RED' ■{ j b+1
iV"O f i
! [GREEN 2 . . . _ „ |
I i----u-----B-|
i :i ? i I
J DYNAMOTOR | I FILTER FL-6:B | I----------lJ____________!
Figure 21.—Dynamotor DM-21-(*), schematic diagram.
necessary plate voltage for the receiver. This unit is identical in appearance to DM-21-(*) (figs. 20 and 21). This dynamotor is secured to the underside of the chassis of the receiver in the same way as Dynamotor DM-21-(*). Under full load conditions, the dynamotor draws about 1.6 amperes at 28 volts direct current with a d-c output of approximately 82 milliamperes at 245 volts. Filter FL-6-CX is inclosed in the dynamotor case and prevents the transfer of radio-frequency interference and commutator ripple.
28. Rectifier RA-20 (figs. 22 and 23).—
Rectifier RA-20 is used in Receivers BC-342-(*) and BC-344-(*). Operating on an a-c input of 110-120 volts, 50-60 cycles, it supplies the necessary plate voltage for the receivers. This rectifier is secured to the underside of the chassis in the same manner as the dynamotor in battery-powered receivers. Under full load conditions, the rectifier draws approximately 0.7 ampere at 120 volts alternating current with a d-c output of approximately 95 milliamperes at 260 volts. The power transformer used in this rectifier has one primary winding and four secondary windings. The primary winding is tapped to provide for an input of 110-120 volts, 50-60 cycles. The high-voltage secondary winding delivers approximately 300 volts alternating current to each side of the center
51
TM 11-850
28
SIGNAL CORPS
Figure 22.—Rectifier RA-20, inside view, as used in BC-342-(*)
and BC-344-(*).
VTS7
i— r-yrory—t———7—Ti
I == 1 Term/nal
J- J. | Board
i I -^l“OZ?k 6 j ww tmT|' \ r71;
r3 proron —To!
---------j C07777770/7 y-------- ■ I oaFh
Rect/fierV^S---------1 \,/Oy:
RA-20 Mg 1—.....--1
To Rad/o Receiver
Cs!), C!H, — 8-microfarad Capacitor CA-329
F3 — 2-ampere Fuse FU-27.
L35 — 14-henry choke Coil C-227.
R40 — 65,000-ohm bleeder Resistor RS-220.
SO2 — A-c power socket.
SWj3 — Line Switch SW-105.
T3 — Power Transformer C-228.
Figure 23.—Rectifier RA-20, schematic diagram.
52
TM 11-850
28
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, BC-342-(*), BC-314-C*) AND BC-344-C*)
tap, under load. The rectifier filament winding delivers 2 amperes at 5 volts for Tube VT-97; the receiver tube filament winding delivers 2 amperes at 12 volts: and the auxiliary filament winding, which supplies voltage to the pilot Lamps LM-27, delivers .3 amperes at 12 volts. The rectifier Tube VT-97 is of the high-vacuum, full-wave metal type. A filter is provided in the rectifier supply which is made up of two 8-microfarad electrolytic capacitors and 14.5-henry, 85-milliampere choke coil. A bleeder resistor R4o is connected directly across the output of the rectifier filter to protect the filter capacitors. A 2-ampere fuse is placed in series with the primary of the transformer T3 for overload protection.
53
TM 11-850
29-30
SIGNAL CORPS
SECTION IV
MAINTENANCE
Paragraph
Lubrication ................................................ 29
Inspection ............................................■..... 30
Tube Socket Voltage Measurements ............................ 31
Procedure In Case Of Failure ................................ 32
Locating Trouble ............................................ 33
Trouble Shooting .............,............................. 34
Repairs ..................................................... 35
Chassis Layout Illustrations ................................ 36
Continuity Test Tables ...................................... 37
Removal and Assembly Of Parts ............................... 38
Alignment ................................................... 39
29. Lubrication.—
a. General.—-
The various gears and bearings of the receiver chassis are lubricated by the manufacturer with sufficient lubricant to last the life of the equipment. Unless operated under abnormal conditions, they should never require further lubrication. In the event that such lubrication becomes necessary, petrolatum should be.used very sparingly.
b. Dynamotors DM-17-A, DM-2 !-(*) and DM-21 -CX.—
The bearings of these dynamotors are of the sealed, ball-bearing type, and are packed with grease at the time of manufacture. They will require one drop of light lubricating oil at each bearing after 500 hours of operation. Any oil above this amount will do more harm than good. To remove the cover of the dynamotor compartment, loosen the two knurled thumb screws on the left-hand side (facing the rear of set) and the flat-head screws on the righthand side of the dynamotor.
30. Inspection.—
The receiver should be given a thorough examination before each use and before being returned to storage. A careful inspection should be carried out to make sure that the equipment is left in good operating condition and thus ready for use at any time. This inspection should include examination of the power cord to see that the plug is securely fastened, and that it has not been damaged. All accessible components should be examined and, if dirty, should be cleaned.
54
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 31-32
BC-342-(*), BC-314-(*) AND BC-344-(*)
31. Tube Socket Voltage Measurements.—
a. Figures 24, 25 and 27 show tube socket voltage measurements for high-frequency units, and figures 26 and 28 those for medium-frequency units, made with Test Set 1-56- series. These voltages are not critical, and considerable variation may be expected from receiver to receiver. However, if voltages vary greatly from those indicated, further tests should be made to locate the cause and remedy it. The input voltage to the 12 to 14 volt units should be adjusted to 14 volts; in the 24 to 28 volt units to 28 volts; and in receivers using 110 to 120 volt, 50 to 60 cycle alternating current, to either 110 or 120 volts, depending on the adjustment described in paragraph 10c. Socket voltages will vary depending on actual input voltages.
32. Procedure In Case Of Failure.—
a. Failure of these receivers to operate properly may be due to external causes, such as a disconnected or grounded antenna, failure of the power source, or a damaged headset. Check all these possibilities before removing the receiver chassis from the cabinet. The receiver itself may now be checked by setting all controls for maximum sensitivity and noting the noise level. Lack of normal noise output, or no response when the antenna terminal is touched with a metallic object, indicates trouble within the receiver. The trouble, if actually within the receiver, will most frequently be a blown-out fuse, a loose or defective tube, or a defective power unit.
55
TM 11-850
32
SIGNAL CORPS
R.F OSC. 1ST. R.F 2ND. R.F 1ST. DET 1ST? I.F co
-VT-65 .VT-86 VT-86 VT-87 VT-86 r&8l L8'8
r--sr—i / nr6-8i / I—I r70i \—lr6-6i / n /40
7|° z^V —4.3 nSb)4-—^ND. I.F
fl f>4.2 (fl WO P 225^5^^86
-----wooz/ xxQ9z/ /vX°z/ 95 -Z ytK -----* 225^90 z225^90 z225l95
||[ TITT I H] Z^3§^^110 C.W.OSC.
________ —M—M—-------n o—-------------------vies j—______=r ti 220 ■ —r
---------------------P Jo v225
LI 68 (O)> «.8
J U p /7oz-^y\ 1 O
/ 7\ \ \oCzq) ) 6.8
2ND. AUDIO . fzS-7 \ I 2ND. DET
VT-66 / 235J /L7-2 1ST. AUDIO
------------- L VT-88 l------------■■ ~ ___Li
* R.FOSC.CATHODE TO GROUND R.F OSC. PLATE TO GROUND NOTE:-
BAND"ZV 28 BAND"D" 0 BAND X 105 BAND "D" 80 MVC POSITION .VOLUME
BAND"B"2O BANDY' 0 BAND"B" 110 BAND "E" 90 CONTROL MAXIMUM.
BAND 0 12 BAND F 0 BAND 0 105 BAND F 95
NOTE:-
ALL VOLTAGES SHOWN ARE TO GROUND FROM THE POINTS INDICATED, EXCEPT HEATER
VOLTAGE WHICH IS BETWEEN POINTS INDICATED.
Figure 24.—Tube socket voltage measurements for BC-312-(*) using-adapter with Test Set 1-56- series.
56
TM 11-850
32
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
R.F OSC. 1ST R.F 2ND. R.F 1ST. DET 1ST. I.F CQ_
VT-65 VT-86 VT-86 VT-87 VTz86 pH
, . , / Inm ।—i r7Qi /1—I'6-9 /n /40
6 8 ti/ J lfofo-4.1 fol 2ND. I.E
/Z6&\\ 235^1\po57 235—AxpozA-— VT~86
(fol (foB 4.2 43(fofo--3.7 fol7 v
_______* 236 95 '43(?96 240404 ________
||[ W W H] fofoV"'110 C.W.OSC.
-----LJ LJ LJ n r_____________0—Boffo-------------vf65_ J----1_lb fo fo fofo
1 l5|° (ffo)) 6.8^
J fofo fol) 6-8
2ND. AUDIO /2327 \ i 2ND-DET
VT-134/ 2453 AT 7.2 ' I I ST. AUDIO
________ /________________________________________________ VT-88 ___________:_____i______________~ i * R.FOSC.CATHODE TO GROUND______T R.F OSC. PLATE TO GROUND NOTE-
BANDX 24.5 BAND"D" 0 BAND X 112 BAND "D" 69.0 MVC POSITION,VOLUME
BAND"B" 16.0 BAND"E" 0 BAND “bT 15 BAND "E" 79.0 CONTROL MAXIMUM.
BAND"0" 10.4 BAND"F“ 0 BAND "0" 105 BAND "F" 83.5
NOTE>
ALL VOLTAGES SHOWN ARE TO GROUND FROM THE POINTS INDICATED, EXCEPT HEATER
VOLTAGE WHICH IS BETWEEN POINTS INDICATED.
Figure 25.—Tube socket voltage measurements for BC-312-(*)X using adapter with Test Set 1-56- series.
57
TM 11-850
32
SIGNAL CORPS
R.F. OSC. 1ST. R.F. 2ND. R.F. 1ST. DET. 1ST. I.F.
VT-65 VT-86 VT-86 VT-87 VT-86 70 70
ioo^_ I ln68i fa i68i Zon / n Im zsTl /* /AA fteC®) --45 L&CW- ^ND.I.F.
EL «-3.6»F48 235%^fc^tg6
\J-%z । jSSvy \x®o// 95
____________ z2354)8 z23?98 z235428--------------- ■ -- ■ --— ----------------------\
m30 c.w.osc.
—
7i° (Q) jHL_
vVoGw) 7.0
2ND. AUDIO .Z235-7 \ I 2ND. DET
VT-66 zZ 240j /: 8.0 1ST. AUDIO
------------ Z_________________________________________________________VT-88
1 . 5
ALL VOLTAGES SHOWN ARE TO GROUND FROM THE POINTS INDICATED, EXCEPT HEATER VOLTAGE WHICH IS BETWEEN POINTS INDICATED. MVC POSITION. VOLUME CONTROL MAXIMUM.
Figure 26.—Tube socket voltage measurements for BC-314-( adapter with Test Set 1-56- series.
) using
58
TM 11-850
32
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-C) AND BC-344-(*)
R.F OSC. 1ST R.F 2ND. RE 1ST. DET. 1ST. I.F VT-65 VT-86 VT-86 VT~87 VT~86
H o Ld
i .
_____/____________________n co J
‘---tn l-wA. ^Z>O
r > cm —
i Q “\
o - \-------------
in \ o
cm V-L z mOin
<0 Zzo^X--> . 13 CD 01 O>
« (O) 3 gs>34-
■----- %OQ
____
3 JM —
/ \ in ---
8 " Z cn^A0
CM Q \ O O QQ
1 m . \ I., zzz
L^SJ gj
I---1
> । Hl i Z
II
■—ZZo\\ to ----LI----
cm ’ = -—j r
IS) \«5OqA/--j
I .
J --------J
■—VtZcZ O q
% —j 1 o°°
-—YYsZ' o ■- H
—J VTSr... tn orci’LiJU-
____I O=Q=Q=Q
2 co ■---------'\ ___, p z z z
X st 1— -r-7ZJ |-- <1 5 / Vvogz/ \xq_ox/ 95-/ 96^
_____1— ' z255l98 z 25098 2265LI28
— ... - _____________ • -----------------
‘------ I 1 IT I /pF/v^""'30 C.W.OSC.
_______ LULU LU n _____________ 0-----------------V-65
j 1----------------p h U°LU '
-------------------P L V250
6.5 (lYni gcj A~
u [_____WooW /7^\----1
u u uw/ (PrWT
2ND. AUDIO 245J \ I 2ND.DET.
VT-66^ z 265-* r^8.0 1ST AUDIO
----------- L__________________________________________________VT-88
■ - - J
ALL VOLTAGES SHOWN ARE TO GROUND FROM THE POINTS INDICATED, EXCEPT HEATER VOLTAGE WHICH IS BETWEEN POINTS INDICATED. MVC POSITION, VOLUME CONTROL MAXIMUM.
Figure 28.—Tube socket voltage measurements for BC-344-(*) using adapter with Test Set 1-56- series.
60
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 32-33
BC-342-(*), BC-314-(*) AND BC-344-(*)
b. One of the most frequent causes of trouble or poor results in the receivers is a partly charged storage battery. Check terminal voltage, level of the electrolyte and its specific gravity. Clean terminals and see that they are tight. Cleanliness of the case should be checked at least daily. (For technical data on storage batteries, see TM 10-580 and TM 11-430.) In vehicular installations, in addition to the above servicing, inspect the charging generator and see that it delivers current to the battery when the engine is slightly raced. Reversed polarity of battery connecting wires is another common cause of trouble.
33. Locating Trouble.—
The following possible causes of trouble are suggested in the event that detailed examination of the receiver becomes necessary:
■ SYMPTOM CAUSE
No filament voltage. Open power lead Short-circuited power lead Poor plug contact Burned-out fuse in panel Burned-out fuse in rectifier NOTE:— The first five causes should be checked before the receiver chassis is removed from the cabinet. Burned-out tube filament Damaged by-pass capacitor C78 or C79 Loose connection inside the receiver
No plate voltage. Open or shorted cord Poor plug contact Burned-out fuse in panel Burned-out fuse in rectifier NOTE:— The first four causes should be checked before the receiver chassis is removed from the cabinet. Defective filter (FL-6-(*) ) Loose connection inside receiver Shorted by-pass capacitor C50. C6i, C74, or C80. Open resistor
- Defective dynamotor
61
TM 11-850
33-34
SIGNAL CORPS
SYMPTOM CAUSE
No audio-frequency output. Headset plug not completely inserted in jack Defective headset, headset plug, or cord NOTE:— The first two causes should be checked before the receiver chassis is removed from the cabinet. Defective tube NOTE:— Test the tubes with a tube checker of Test Set I-56-series. If found serviceable, they should be replaced in the sockets of the receiver from which they were removed. Loose connection inside receiver Damaged capacitor C8i Defective transformer (Tx or T2) Defective jack insulation Breakdown on radio-frequency coils, leads, or switches Defective band-change switch
Erratic noise in receiver. Defective headset or headset cord NOTE:— This cause should be checked before the receiver chassis is removed from the cabinet. Dust or dirt in the receiver Loose connection in the receiver Chattering relay Defective capacitor or resistor in the receiver Defective dynamotor or filter unit Noisy volume control (R34 and R35)
34. Trouble Shooting.—
a. General.—
The simple tests described above will reveal the cause of the trouble in most cases of inoperative receivers. In cases where they do not, it is necessary to adopt a definite procedure. A competent repair man can readily find the “dead” stage by starting at the
62
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 34
BC-342-(*), BC-314-C*) AND BC-344-C*)
output end of the receiver and working progressively back toward the antenna. A Signal Generator 1-72-(*), or equivalent, is used as the signal source during the tracing process.
b. Checking Audio Amplifier.—
After the receiver and the signal generator have warmed up, turn the output switch of the latter so that a 400-cycle output from the modulator section becomes available at the output cord. Ground the shielded side of the cord directly to the chassis of the receiver. Plug phones into 2nd audio phone jack. Connect the “hot” end, by means of the test clip, to the triode plate of the second-detector tube, and listen in the headphones. If a good signal is heard, the final or second audio stage is operating satisfactorily. To check the operation of the triode audio-amplifier or first audio section of VT-88, clip the generator output to the center lug of the outer volume-control potentiometer, with the receiver set for automatic volume control, and turn volume control on full. The signal should be louder than before.
c. Checking Second Detector.—
Adjust the signal generator to give 470-kc7, 400-cycle modulated output. Connect the “hot” end to the signal diode plate of VT-88 (pin No. 4). If the diode detector is operating, the 400-cycle tone will be heard in the phones.
d. Checking Intermediate-frequency Amplifier.—
Adjust the signal generator for a modulated 470-kc7 output Turn the receiver to manual volume control. Connect a 300-ohm resistor in the “hot” output lead of the generator to act as a dummy antenna. Remove the grid clip of the .second intermediate-frequency tube and fasten the dummy antenna to the tube grid cap. If the second intermediate-frequency stage is working, the tone will again be heard in the headset. Use the minimum output from the generator that gives a comfortable signal. Work back to the grid of the first intermediate frequency tube, and then to the first detector. When testing the latter, turn the CRYSTAL PHASING knob (if the set has a crystal filter) to OUT. Reduce the output of the generator as more stages come into action. Each time the generator output is connected to an intermediate-frequency grid, rock the frequency dial of the generator very slightly and note if the
594.5.U) 0—44 —
63
TM 11-850
34
SIGNAL CORPS
volume of the signal goes up. If maximum volume is obtained at frequencies above or below 470 kc7, the adjusting screws of the intermediate-frequency transformers probably have been moved. Do not undertake realignment. This will be done after it has been definitely determined that the circuit components themselves are in good order.
e. Checking Radio-frequency Oscillator.—
(1) Check the plate voltage against the values shown in figures 24, 25, 26, 27 or 28. This oscillator is dependable and rarely gives trouble. However, to be absolutely sure of the check, remove the first detector tube from its socket and twist a bare end of an insulated wire, 2 to 3 feet long, around the injector grid pin of the tube. Be careful not to short the bare end to another pin. This is pin No. 5 counting clockwise from the key of the locating pin when looking at the bottom of the tube. Reinsert the tube in its socket, leaving off the grid cap, and place the wire on the bench near the Frequency Meter SCR-211- series. For each position of the receiver band change switch, set the frequency meter to a frequency about the center of that band. Turn the receiver tuning knob and listen for heterodyne signals in the frequency meter. These indicate that radio frequency oscillator output is present. Remove the wire and replace the grid cap before proceeding.
(2) There is a quicker alternate method for checking the radio frequency oscillator. With the oscillator Tube VT-65, in the socket, tap the grid terminal with the point of a lead pencil-The oscillator is functioning if a popping noise is heard each time the grid is tapped with a pencil point.
f. Checking Radio-frequency Amplifier.—
Replace the 300 ohm resistor by a 100 p.p.f capacitor. Leave on the 400-cyde modulation. Adjust the generator to any frequency falling within the tuning range of each position of the band switch. Leave the grid clips in place, and connect the new dummy antenna successively to the first detector, second radio-frequency, and first radio-frequency grids, and to the antenna post. Vary the generator or receiver tuning until a signal is heard in the headset, and use the minimum generator output for a comfortable indication. If no signal is heard with the signal injected at any tube, check the components of the stage immediately following.
7Use 470 kc for all of the high-frequency receivers, and 92.5 kc for the low-frequency models.
64
TM 11-850
35
RADIO RECEIVERS BC-312-O, BC-312-(*)X,
BC-342-(*), BC-314-C*) AND BC-344-(*)
35. Repairs.—
a. General.—
Insert the tubes firmly all the way into their proper sockets and make firm grid cap connections. The chassis should be securely locked into its box by means of the five locking screws on the front panel. Repair service of this equipment in the field consists, almost entirely, of replacing tubes, pilot light bulbs, and fuses, and making minor repairs. Alignment and major adjustment or repair of these receivers are to be done only by authorized Signal Corps repair units of trained personnel, supplied with the necessary tools and instruments.
b. Cords.—
Should a cord be found defective, examine and repair the connections to the plugs. If the cord is damaged internally, temporary repairs, may be made, all joints being thoroughly insulated. Install a new cord as soon as possible.
c. Headset.—
When a headset fails to operate properly, the trouble usually is due to a defective headset cord or plug. If the damage is within the phones proper, a new headset must be secured and the defective units shipped to the proper agency for repair.
d. Dynamotors DM-17-A, DM-21-(*) and DM-21-CX.—
Normally, if these dynamotors are defective, they should be replaced. The replacement of brushes, turning down of commutators, freeing of bearings, and all repairing of defective receiver dynamotors is done at Signal Corps repair shops or at Signal Corps radio sections at air depots. Only when a replacement dynamotor cannot be obtained, or when an emergency arises, are local repairs permitted. When repairs are made locally, careful sanding in of new brushes to fit the commutator, proper spring adjustment and a running-in period are necessary to insure quiet receiver operation. If results following such local replacement of brushes are unsatisfactory, return the dynamotor to a depot for overhauling. Commutators that are not worn excessively may be cleaned by using a fine grade of sandpaper (never use emery cloth) and/or by wiping off thoroughly with carbon tetrachloride. If the bearings are not damaged but merely need freeing, add a drop of light
65
TM 11-850
35-37
SIGNAL CORPS
oil to each. Replace the dynamotor if the trouble is caused by "an open or short-circuited winding, scored commutators, or some other serious defect.
e. Rectifier RA-20.—
Rectifier RA-20 may appear to be defective or show a low-voltage output because of a short circuit in the receiver. Disconnect the high-voltage orB-j- lead to the receiver at point 7 of the connection strip, and measure the rectifier output voltage. This should be considerably higher than the normal voltage at the plate of the tube, as given in paragraph 31. If the rectifier unit appears to be defective, remove it for checking. Make individual checks of the electrolytic capacitor, the filter choke, Fuse F3, Tube VT-97, and the power transformer, if measurements indicate the power supply to be at fault. If the rectifier is found defective, return it to an authorized Signal Corps repair station, together with the two supporting brackets.
f. Other repairs.—
Repairs other than the foregoing will not be attempted by using personnel unless specifically authorized by the provisions of appendix C, Signal Corps General Catalog.
36. Chassis Layout Illustrations.—
Chassis layout illustrations for Radio Receivers BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*) and BC-344-(*) are shown in figures 29 to 37.
37. Continuity Test Tables.—
a. Group 1 Terminal Board.—
(See fig. 32 for h-f receivers, and fig. 33 for Radio Receivers BC-314-(*) and BC-344-(*).) Measurements are made using the ohmmeter of Test Set 1-56- series. The receivers are turned OFF during these measurements and the volume control is set at maximum. (NOTE: All measurements may vary -]----------20%.) On
Receivers BC-.342-(*) and BC-344-(*) disconnect the red wire coming from Rectifier RA-20 from the number 7 terminal of the group 6 terminal board.
66
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-C)
TM 11-850
37
Figure 29.—Chassis layout, high-frequency models, no crystal filter^ top view.
r 1ST DETECTOR TRANSFORMER TUNING
VIST. R.F TUBE /
\ vTUBE SHELF / r-|ST I. F. TUBE
\ \ y2ND- r f tube /
\ \\ T-IST. DETECTOR TUBE / V~1ST , F TRANS. TUNING HfNGED SEC. OF -x \ \ \ / \ r~ 2ND. I F TUBE
R.F. OSC. SHIELD \ — / \ |
(R F. OSC. TUBE INSIDE \ L/" ''g"''""L L A ‘
shield) JyiQ
DC C\C n fl' ,z''***
RF OSC —wHBf IRBr .-j:2ND if TRANS
SHIELD * frlfe" / TUNING
*>>4-M la
I /—2ND. DET.
ANTENNA ot t ■r*Z,X TUBE
ALIGNMENT ' f|*“ !|MeZ,£wY 3p ■ J XWfi WIt*—vYntWl irir\ ■■■■" i ( (tube fl Wp*..* 'rl ~,NSlDE)
/ i / r* lllidM ©MBb\
/ /CRYSTAL PHASINg\ \ \ X-2ND- AU0|0 TUBE
NEON TUBE LM. / / CAPACITOR SHAFT \ VVOLUME CONTROL
/ ^TUNING CAPACITOR, AND \ GRP. 4 TERM. BD. UNDER VOL. CONT GANG TUNING CAPACITOR D,AL DR,VE GEARS '-AU0|O TRANSFORMER K
Figure 30.—Chassis layout high-frequency models, with crystal filter top view.
68
TM 11-850
37
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
x~IST R.F. TUBE p-l ST DETECTOR TRANSFORMER TUNING
X. vTUBE SHELF I Y~,ST- LF TuBE
\ \ y-2ND. R.F. TUBE I \xdST. I.F. TRANS. TUNING
' Nl \ . \ 1ST. DETECTOR TUBEy I V\. 2ND. ,F TUBE-
HINGED SEC.-^J7~
of r.f. osc.
SHIELD » ' J ; '
INSIDE SHIELD) _J ^|j ' TRANS..
—U--,—TUNING
R.F. OSC.--- fhw»rW«Q MR . I '
SHIELD I
JB WiIRWrRWwiBuW WWl■* 4-^ 2nd. det A^-rr-L.^.- —-----IMhI CaISw ’"* 'oCflt-IST. AUDIO
ANTENNA ngl If'^j^TUBE
ALIGNMENT .U|! wjwir
CAPACITOR ■ di k. ilk lC.W. OSC.
VATAUIIVH ZjWMBMmMMS, - \-*\ 5 BMME/ (TUBE INSIDE)
1 ly...
NEON TUBE CAPACITOR, AN^\^\ '\-2ND. AUDIO TUBE
/ DIAL DRIVE GEARS \ \-vOLUME CONTROL
/ \ GRP 4 TERM.BD.UNDER VOL.CONT.
GANG TUNING CAPACITOR-Z \-AUDIO TRANSFORMER Tg
Figure 31.—Chassis layout, medium-frequency models, top view.
69
TM 11-850
37
SIGNAL CORPS
1ST. I.F. TRANSFORMER TUNING r-IST DETECTOR STAGE
\ A1ST. I.F. TUBE SOCKET f /—2ND R.F. STAGE
2ND. LF. TUBE\ \GRP-2 TERM. BD^ / / plST. R.F. STAGE
socket \ XfoV 7 / - -y
TRANSFORMERI ' ■ s ®^-BANDSW. TlJNING p F R ^"""' shaft
LJI & SLEEVE
GRP. I TERM. BD. W V J WEflkx/* \ ' « Si
2ND.- DETECTOR
TUBE SOCKET-^^^F|^MM^mL \ BM
*7-OSCILLATOR
1 \ l.Z " ‘ja* « SECTION
** /<8Si ■ \ N *•
GRP. 6 TERM. BdT \ \ -1ST. DET. TRANSFORMER TUNING
\ 4—2ND. AUDIO TUBE SOCKET
— OFF-M.V.C.-A V.C. SWITCH
Figure 32.—Chassis layout, high-frequency models, bottom view.
70
TM 11-850
37
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
X—1ST I F. TUBE SOCKET .—1ST. DETECTOR UNIT ASS'Y
\ GRP. 2 TERM 8D.-y / r—2ND. R.F. UNIT ASS'Y
2ND. I.F. TUBE—< \ / / / r—1ST. R.F. UNIT ASS’Y
SOCKET \ \ / / /
\ z-------.................—x
2ND.I.F. ujrtiF D’ SSE e
TRANSFORMER—\ V t'XiWGeisS j
TUH1N0 IR-j iiWP- -7 j ” 'R J GRR! TERM.BD.-^A^-^X® 7 \ / ’ I SHftFT
i tSy.C* -• v WRIH \ sleeve
2ND. DETECTOR j\ u> a -4
TUBE SOCKET-2? \ 07
IBi; ----------OSCILLATOR
< \ .« -fern J> section
GRP. 6 TERM. BD. X. |ST. DET TRANSFORMER TUNING
\ ©-—2ND. AUDIO TUBE SOCKET
0 OFF-M.V.C.-A.V.C. SWITCH
Figure 33.—Chassis layout, medium-frequency models, bottom view.
71
TM 11-850
37
SIGNAL CORPS
vIST. I.E TUBE 5-SHIELD BEHIND TUBE SHELF
-ND. I F. TUBEbfrWffc I------------------------------------------OSCILLATOR
1% | s9fi j \ SECTION
i __, i a & z v
WHMWRffBWFEy "r1 a r ur M BrW^IR>JmMEm - q
■ li 4M®Awi^S HTT5-------band ghg.
SWITCH
RECTI Fl ER Q DRIVE GEARS
mounting t—l-A
HINGES / 7 ---4 5t A ^L-_.... .......,
/ 1ST. DET. STAGE^ / ^LOCK NUT A LTRIMMER ADJUSTMENT GRP. 6 TERM. BdU 2ND. R.F. STAGE-' Ljsr R.F> STAGE
4-(*).—
Measurements are made using the ohmmeter of Test Set 1-56 series. The receivers are turned OFF during these measurements, and Plug PL-114 is removed from Socket SO-94. Resistance values -are between indicated terminal and ground.
78
TM 11-850
37
RADIO RECEIVERS BC-312-(*). BC-312-(*)X,
BC-342-(*), BC-314-C) AND BC-344-(*)
Terminal Meter Setting Meter Reading Probable Cause if Reading is Incorrect
D r x 1 0 Ground terminal inside dynamotor
not grounded
G r x 1 0 Open wiring
M r x 1,000 Infinity- Shorted wiring
T r x 1,000 Infinity Shorted wiring
U r x 1,000 Infinity Shorted wiring or short in Jack J4
V r x 1 0 Open wiring
S r x 100 17,000 Open circuit in dynamotor or open
wiring
K r x 1,000 Infinity K should not be wired into receiver
F r x 1,000 Infinity F should not be wired into receiver
E r x 1,000 Infinity Shorted wiring or short in Jack J4
H r x 1 650 Open secondary in transformer T,
or open wiring
N r x 1,000 Infinity Shorted wiring or short in Jack J-
R r x 1,000 Infinity R should net be wired into receiver
J r x 1,000 Infinity Shorted wiring
h. Socket SO-94 for Receivers BC-342-(*) and BC-344-(*).
Measurements are made using the ohmmeter of Test Set 1-56 series. The receiver is turned OFF during these measurements, and Cord CD-370 is removed from Rectifier RA-20. Resistance values
are between terminal ' indicated and ground.
Meter Meter Probable Cause if
Terminal Setting Reading Reading is Incorrect
D r x 1 0 Open filament winding on power
transformer or open wiring
G r x 1 0 Open wiring
M r x 1 0 Open auxiliary 12 v. winding on
power transformer or open wiring
T r x 1 0 Open filament winding on power
transformer or open wiring
U r x 1,000 Infinity Shorted wiring or short in J4
V r x 1 0 Open wiring
S r x 1 0 Open wiring
K r x 1,000 Infinity K should not be wired into receiver
F r x 1,000 Infinity F should not be wired into receiver
E r x 1,000 Infinity Shorted wiring or short in jack J4
H r x 1 650 Open secondary in transformer Tr
or open wiring
N r x 1,000 Infinity Shorted wiring or short in jack J-
R r x 1,000 Infinity R should not be wired into receiver
J r x 1,000 Infinity Shorted wiring
.'!M33O ()—14------(i
79
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SIGNAL CORPS
i. Jacks Ji, J*, J3, J4, and for Receivers BC-312- (*), BC-312-(*)X, BC-3~42-(*), BC-314-(*) and BC-344-(*).—
Measurements are made using the ohmmeter of Test Set 1-56-series. The receivers are turned OFF during these measurements. Plug PL-114 and Cord CD-370 are removed from the receiver. Resistance values are between indicated terminal and ground.
Terminal Meter Setting Meter Reading Probable Cause if Reading is Incorrect
Jj tip r x 1 6001 Open secondary in T22, open or
shorted wiring, shorted J2 or J3
J] sleeve r x 1 0 Open wiring
J., tip r x 1 600 Open secondary in T22, open or
shorted wiring, shorted «J\ or J3
J., sleeve r x 1 0 Open wiring
J3 tip r x 1 600 Open secondary in T2, open or
shorted wiring, shorted J4 or J,
J3 sleeve r x 1 0 Open wiring
J3 ring «r x 1,000 Infinity Shorted J3
J4 tip r x 1,000 Infinity Shorted wiring or shorted J4
J4 ring r x 1,000 Infinity Shorted wiring or shorted J4
J4 sleeve r x 1 0 Open wiring
J5 tip r x 1,000 Infinity Shorted wiring
J- sleeve r x 1 0 Open wiring
j. Volume Control for Receivers BC-312- (*), BC-312- (*) X BC-342-(*), BC-314- (*) and BC-344-(*).—
Measurements are made using the ohmmeter of Test Set 1-56 series. The receivers are turned OFF during these measurements and volume control is set at maximum. Resistance values are between indicated terminal and ground.
1650 in BC-312 to BC-312-J, BC-342- to BC-342-J, BC-314 to BC-314-F, and BC-344.
2TX in BC-312 to BC-312-J, BC-342 to BC-342-J and BC-344.
80
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
z 2 , REAR VIEW 5
Front or r-f section Rear or audio section
Figure 38.—Location of terminals on volume control.
Terminal Meter Meter Probable Cause if
Setting Reading Reading is Incorrect
1 r x 1,000 50,000 ohms Open volume control
2 r x 1 0 Open wiring
3 i- x 1 5 to 25 ohms Open or shorted volume control or wiring
4 r x 1 750 ohms Open or shorted wiring, shorted volume control or capacitor
5 r x 1,000 .5 megohm Open or shorted volume control or wiring
6 r x 1,000 .5 megohm Open or shorted volume control or wiring
k. OFF-MVC-AVC Switch.—
Measurements are made using the ohmmeter of Test Set 1-56 The receiver is turned OFF during these measurements, he volume control and the dial light dimmer-rheostat
RE4R VIEW
Ot \
\ \ X.
Front section id id die section Rear section &
Figure 39.—Location of terminals on OFF-MVC-AVC switch.
PI*1 mS N, and NX) are both set at maximum. Plug
p . 4 or Cord CD-370 must not be attached to the receiver, esistance values are between indicated terminal and ground.
81
TM 11-850
37
TM 11-850
37
SIGNAL CORPS
(1) For Receivers BC-312-(*) and BC-314-(*).—
Meter Meter Probable Cause if
Terminal Setting Reading ' Reading is Incorrect
1 r x 1 5 to 25 ohms Open or shorted volume control or wiring, defective switch
2 r x 1,000 1 megohm Open or shorted wiring or defective switch
3 r x 1 0 Open wiring
4 r x 1,000 .5 megohm Open or shorted volume control or wiring
5 r x 1,000 .5 megohm Open or shorted volume control or wiring
6 r x 1,000 Infinity Shorted capacitor or defective switch
7 r x 1,000 Infinity Shorted wiring
8 r x 1 30 ohms Pilot lights burned out or defective wiring
9 r x 1,000 Infinity Shorted wiring
10 (2) r x 1 0.5 ohm Tube filament open, open or short circuit in dynamotor or wiring For Receiver BC-312-(*)X— Meter Meter Probable Cause if
Terminal Setting Reading Reading is Incorrect
1 r x 1 5 to 25 ohms Open or shorted volume control or wiring, defective switch
2 r x 1,000 1 megohm Open or shorted wiring or defective switch
3 r x 1 0 Open wiring
4 r x 1,000 .5 megohm Open or shorted volume control or wiring
5 r x 1,000 .5 megohm Open or shorted volume control or wiring
6 r x 1,000 Infinity Shorted capacitoi’ or defective switch
7 r x 1,000 Infinity Shorted wiring
8 r x 1 100 ohms Pilot lights burned out or defective wiring
9 r x 1,000 Infinity Shorted wiring
10 r x 1 3.5 ohms Tube filament open, open or
short circuit in dynamotor or wiring
82
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
(3) For Receivers BC-342-(*) and BC-344-(*).
Meter Meter Probable Cause if
Terminal Setting Reading Reading is Incorrect
1 r x 1 5 to 25 ohms Open or shorted volume control or wiring, defective switch
2 r x 1,000 1 megohm Open or shorted wiring, defective switch
3 r x 1 0 Open wiring
4 r x 1,000 .5 megohm Open or shorted volume control or wiring
5 r x 1,000 .5 megohm Open or shorted volume control or wiring
6 r x 1,000 Infinity Shorted capacitor or defective switch
7 r x 1 0 Open auxiliary 12 v. winding on power transformer or open wiring
8 T X 1 30 ohms Pilot light burned out, shorted or open wiring
9 r x 1,000 Infinity Shorted wiring
10 r x 1,000 Infinity Short in wiring or switch
1. Tube Socket Resistance Tables for High-frequency Receivers.—
Measurements are made using the ohmmeter of Test Set 1-56 series. The OFF-MVC-AVC switch is at OFF during these measurements, except where AVC is indicated, the volume control is set at maximum, the continuous-wave oscillator is turned ON, the BAND CHANGE switch is set on Band A (1500-3000 kc). Plug PL-114, or Cord CD-370, is not connected to the receiver being measured. On Receiver BC-342-(*), disconnect the red wire coming from Rectifier RA-20 from the number 7 terminal of the group 6 terminal board. Resistance values are between the terminal indicated and ground, and are expressed in ohms.
Tubes Cathode Plate Screen Grid (AVC)
1st r-f VT-86 500 17,750 25,000 3.35 meg
2d r-f VT-86 500 17,750 25,000 3.35 meg
1st detector VT-87 350 17,750 20,000 3.35 meg
1st i-f VT-86 500 17,750 25,000 1.26 meg
2d i-f VT-86 500 17,750 25,000 1.35 meg
2d detector VT-88 750 17,750 250,000
2d audio VT-66 or
VT-134 1,000 17,500 16,750 50,000
R-f oscillator VT-65 7,500 46,750 - - _ - 37,500
C-w oscillator VT-65 0 117,250 - - - - 200,000
83
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TM 11-850
37-38
SIGNAL CORPS
■m. Tube Socket Resistance Tables for Medium-frequency Receivers.—
Measurements are made using the ohmmeter of Test Set 1-56 series. The receivers are turned OFF during these measurements, except where AVC is indicated, the volume control is set at maximum. the continuous-wave oscillator is turned ON, and the BAND CHANGE switch is set on Band A (150 to 260 kc). Plug PL-114 or Cord CD-370 is not connected to the receiver being measured. On Radio Receiver BC-344-D, disconnect the red wire coming from Rectifier RA-20 from the number 7 terminal of the Group 6 terminal board. Resistance values are between indicated terminal and ground and are expressed in ohms.
Grid
Tubes Cathode Plate Screen (AVC)
1st r-f VT-86 350 19,000 36,000 1.35 meg
2d r-f VT-86 350 19,000 36,000 1.35 meg
1st detector VT-87 500 19,000 26,000 1.35 meg
1st i-f VT-86 500 19,000 34,000 1.35 meg
2d i-f VT-86 500 19,000 32,000 2.35 meg
2d detector VT-88 750 19,000 - - - - .25 meg
2d a-f VT-66 1,000 19,000 19,000 .25 meg
R-f oscillator VT-65 0 54,000 - - - - 50,000
C-w oscillator VT-65 0 300,000 . - - _ - .2 meg
38. Removal and Assembly of Parts.—
a. .Replacement of Radio-frequency Unit Assembly.—
Turn the BAND CHANGE knob to Band A and remove the set screw in the switch shaft sleeve (see figures 34 and 35). Then remove the single plug in the side of the r-f oscillator cover at the end of the receiver. By means of long nose pliers, draw the switch shaft through the hole. Remove the shield behind the tube shelf. Remove the shield behind the coil boxes and remove both round-head screws at the front, and the two spacer studs at the rear corners of the tube shelf. Raise the tube shelf as far off the mounting shelf as it will go. Make certain that the gang-tuning capacitor is closed; then unsolder the connections to the radiofrequency units and remove the screws which hold the units to the mounting shelf. Tag each wire so it will be replaced correctly. The unit may now be removed. When replacing the unit, be sure that the switches in the unit are in position for Band A before replace
84
TM 11-850
38-39
RADIO RECEIVERS BC-312-(*), BC-312-(*)X,
BC-342-(*), BC-314-(*) AND BC-344-(*)
ment. Be sure all connections are made correctly before resoldering the wires.
b. Replacement of Radio-frequency Oscillator Unit Assembly.
Remove the screws holding the outer cover, which incloses the upper and lower compartments. Then remove the outer cover. Unsolder the four leads from the terminal panel below the tube socket. Tag each wire so it will be replaced correctly. Remove the four screws holding the unit to the bottom of the shield compartment. The unit may now be withdrawn from the chassis without removing the band switch shaft. When replacing the unit, make sure the switches in the unit are in the same position as the switch shaft.
c. Replacement of Rectifier RA-20 and Dynamotors DM-21-(*) and DM-21-CX.—
Unsolder the connections to the power unit at the connection strip and remove them in a group. The connections should be noted or tagged so that they will be replaced correctly. Remove the two screws adjacent to the 1st and 2nd intermediate-frequency tube sockets which secure the two mounting-support posts at the back of the power unit. Remove the two stud bolts which holds the hinge sections together, or remove the six screws holding the power unit hinges to the front panel.
39. Alignment.—
a. Apparatus Set-up.—
Figure 40 shows a typical set-up for an alignment job. Note especially that the receiver is standing upright. In this position, all the adjusting screws and controls are readily accessible. The illustration shows the most usual combination of apparatus available under field conditions, as listed in paragraph 39c.
b. Dynamotor or Rectifier Support.—
The primary adjusting screws of the three intermediate-frequency transformers are on the under side of the chassis. In order to reach them, it is necessary to remove one mounting stud of the dynamotor or rectifier and to swing the latter up on its outer hinge. Before touching the receiver, cut a piece of scrap wood 6 inches Jong and about 1 inch by % or ^4” inch in cross section. Stand
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TM 11-850
39
SIGNAL CORPS
the receiver on its oscillator-compartment end. Find the two small cap screws close to the first and second intermediate-frequency tubes and remove them; the studs or collars through which these screws pass will fall out. Loosen and then pull out the long screw passing through the inner hinge of the dynamotor or rectifier.
7°
Phones 2^ Audio
Jack
Dynamotor or pect/fier
l?adio
block of Wood.
To Chassis
Figure 40.—Set-up of receivers and test equipment for receiver alignment.
GrJdCUp „
"Dummy "Antenna Ci
Shielded___
Signal Generate
(When the receiver is upright, this will be the louder hinge.) The unit is now loose. Raise it slowly, making sure that the connecting wires are free, and prop it upright by means of the wood block. The unit is heavy, and will keep the block in place rather securely.
c. Equipment.
The following equipment will be required for proper receiver alignment:
( 1) Signal Generator 1-72 series, or equal.
(2) Headset or loudspeaker.
(3) Dummy antennas (50-/x/xf capacitor for radio-frequency alignment for 1500 kc and above; 250-/i/xf capacitor for alignment below 1500 kc; 300-ohm resistor for intermediate-frequency alignment).
(4) Frequency Meter SCR-211 series.
(5) Test Set 1-56 series.
(6) Alignment tools.
(7) Special battery cord and battery.
(8) Plug PL-55 (or equal) for output meter.
86
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 39
BC-342-C*), BC-314-(*) AND BC-344-(*)
d. Precautions Prior to Alignment.—
Before an attempt is made to align or calibrate a receiver, it is essential that all components be operating satisfactorily. It is assumed that all the tubes have average constants. The receiver must be warmed up for about an hour prior to alignment. This is to permit stabilization of the radio-frequency circuits and other circuit elements. The signal generator and frequency meter also must have about an hour warm-up before an alignment is attempted. In connecting the receiver for alignment and calibration, be very careful that the sensitive meter located in the signal generator is not shorted to ground by the power supply employed in the receiver. Attenuators and meters of certain signal generators burn out very easily if improperly grounded. Check to ascertain that the same side of the power line is grounded in both signal generator and receiver in the case of the a-c operated receivers. Since no fuses are provided in the output circuits of signal generators, it is impossible to provide protection against this source of trouble. BE VERY CAREFUL IN HANDLING THIS EQUIPMENT. The signal generator must be placed as close to the receiver as possible to enable the use of short leads. Long leads serve no useful purpose and often cause the equipment to operate erratically. Some of the alignment screws for the i-f transformers cannot be reached unless the dynamotor unit is removed. Instructions for the removal of components are given in paragraph 39b. Note the locking arrangement on the i-f alignment screws. IT IS IMPERATIVE THAT THE LOCKING NUT BE RELEASED BEFORE THE ADJUSTING SCREW IS TURNED. Be very careful when manipulating the alignment screws.
e. Receiver markings.—
(1) Radio-frequency letter markings.—
Receivers BC-314-(*) and BC-344-C*) have four band posi-, tions. The trifnmer capacitor adjustment screws associated with each band are similarly marked by letters A through D, inclusive. The BC-312-(*), BC-312-(*)X, and BC-342-(*), having six band positions, are marked by letters A through F.
(2) Radio-frequency capacitance markings.—
The trimmer capacitor adjustment screws, in addition to the band letter markings, show the relative value of capacitance included in the circuit. A red dot is located on one side of the screw
87
TM 11-850
39
SIGNAL CORPS
driver slot in the end of the screw. The capacitor is of the airpadded type composed of a stator and a rotor. The rotor can be rotated through 360 degrees; at the completion of one revolution, the initial capacitance value is repeated. When the receiver is setting in a normal position, the stator plates are located below the center line (screw driver slot). Capacitance is at a minimum when the red dot is above the center line, and at a maximum when the red dot is below the center line.
(3) Intermediate-frequency markings.—
Each intermediate-frequency transformer is marked on top of the container with its functional purpose. For Receivers BC-3 14-(*) and BC-344-(*) the markings are: 1ST DET TRANS and C-292, 1ST IF TRANS and C-293, and 2D IF TRANS and C-294. An adjustment screw is located on the top of each transformer. Adjustment screws on the under side of the chassis are for 1ST DET TRANS and 2D IF TRANS. There is no under side adjustment for the 1ST IF TRANS. For Receivers BC-312-(*)\ BC-312-(*)X1 and BC-342-(*) the markings are: 1ST DET TRANS and C-2821, 1ST IF TRANS and C-283, and 2D IF TRANS and C-284. Each of these transformers has a top and bottom adjustment screw. The 1ST DET TRANS2 also contains the crystal phasing circuit equipped with a crystal. For all types of receivers, the adjustment screws on the intermediate-frequency transformers vary the position of the iron cores as a means of tuning. Each adjusting screw is locked by means of a lock nut.
f. Alignment frequencies.—
(1) Receivers BC-312-(*), BC-312(*)X, and BC-342-(*) use an intermediate frequency of 470 kc. The radio-frequency alignment frequencies for the different bands are:
Band A B C D E F Alignment Frequency 2900 kc 4900 kc 7850 kc 11000 kc 13750 kc 17700 kc
1lst DET TRANS and C-412 in Receivers BC-312-N, and BC-312-NX. 1st DET TRANS and C-422 in Receivers BC-312-L and BC-312-M.
*Not on Receivers BC-312-L, BC-312-M, BC-312-N and BC-312-NX.
88
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RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 39
BC-342-(*), BC-314-(*) AND BC-344-(*)
(2) On bands, A, B, and C the radio-frequency oscillator operates at a frequency 470 kc above the radio-frequency signal being received. For bands D, E, and F the radio-frequency oscillator operates 470 kc below the radio-frequency signal being received.
(3) On bands A, B, and C set the radio-frequency oscillator trimmer capacitors for the minimum capacitance for which the radio-frequency oscillator can be peaked. Set the radio-frequency oscillator trimmer of bands D, E, and F for the maximum capa-tance for which the radio-frequency oscillator can be peaked. This automatically avoids setting the radio-frequency oscillator at an image frequency.
(4) Receivers BC-314-(*) and BC-344- (♦) use an intermediate-frequency of 92.5 kc. The radio-frequency alignment frequencies for the different bands are:
Band
A B C D
Alignment Frequency
255 kc
440 kc
800 kc
1450 kc
(5) In Receivers BC-3 14-(*) and BC-344-(*), the radiofrequency oscillator operates at a frequency 92.5 kc above the radio-frequency signal being received.
(6) For Receivers BC-314-(*) and BC-344-(*), set the radio-frequency oscillator trimmer capacitors for the minimum capacitance that will peak the oscillator circuit.
(7) If a signal generator capable of generating a frequency of 92.5 kc for the alignment of the i-f of Receivers BC-314-(*) and BC-344-(*) type is not available, a substitute will have to be used. See g (4) (b) below.
g. Alignment Procedure.—
(1) General.—
This alignment procedure applies to Radio Receivers BC-312-(*), BC-312-(*)X, BC-314-(*), BC-342-(*) and BC-344-(*). 7he following panel control settings are made before the alignment is begun, and are left in these positions unless otherwise stated:
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SIGNAL CORPS
(a) Set OFF-MVC-AVC switch to MVC.
(b} Set CRYSTAL PHASING control to OUT (if receiver is equipped with crystal) .
(c) Set CW-OSC OFF-ON switch to OFF (except for CW-OSC alignment.)
(d) Set VOL control for maximum output.
(e) Plug output meter into PHONES 2D AUDIO.
(2) Calibration of Test Equipment.—
Frequency Meter Set SCR-211-(*) can be used to check the frequency and stability of the signal generator used. This is done by coupling (inductively or capacitively - not directly) the output of the signal generator to the antenna of the frequency meter. Set the signal generator at the test frequency to be used, and adjust the output so that a satisfactory heterodyne note is heard in the phones which are plugged into the frequency meter. When this is accomplished adjust the frequency meter for zero beat with the signal generator. Check the frequency by reading the setting of the frequency meter, and make the necessary readjustments of the signal generator to keep it on frequency (using the frequency meter as the standard).
(3) Order of Stage Alignment.—
An over-all receiver alignment is accomplished by adjusting the various stages in the following order:
(a) Second intermediate-frequency transformer
(Z?) First intermediate-frequency transformer
(c) First detector output transformer
(d) Continuous-wave oscillator
(e) Crystal filter (when employed in the receiver)
(f) Radio-frequency oscillator
(g~) Grid circuit of the first detector
(/?) Grid circuit of the preceding radio-frequency stages (z) Antenna alignment capacitors
(4) Intermediate-frequency Alignment.-—
(a) With receiver controls set as instructed in paragraph 39114330 ()—44—
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SIGNAL CORPS
(2) Set the CRYSTAL PHASING control for minimum background noise.
(3) Vary the signal generator frequency above and below 470 kc by means of the fine frequency control adjustment, so as to bring the signal generator frequency to exact coincidence with the natural frequency of the crystal at the above mentioned setting of the phasing control.
(4) Readjust the top core trimmer screw (located at the top of the 1st detector output transformer) for maximum output.
(5) Repeat the operations of (2) and (3) again. Do not change the setting of the crystal phasing control during operations indicated in (2), (3), (4) and (5).
(6) The receiver now will have a considerably higher crystal selectivity and sensitivity than before, but when the crystal operation is removed, sensitivity will be slightly less.
96
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, BC-342-(*)» BC-314-C*) AND BC-344-(*)
TM 11-850
40
SECTION V SUPPLEMENTARY DATA
Paragraph
Table of Replaceable. Parts .................................................. 40
40. Table of Replaceable Parts.—
a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) .— NOTE: Unless otherwise indicated, parts as listed apply to all equipments covered by this manual. Order replacement parts by stock number, name and description, and receiver model. No? ^quip" Stock* Number Name and Description of Part Function Dra"wing°No!
Cj 4 3D289 CAPACITOR CA--89; variable, air, 3-25 ggf, Band A trimmer, 1st r-f SC-A-1728
7 plates, 0.008" minimum spacing between rotor and stator plates, isolantite base, overall length 1-9/32", screwdriver adjustment, special contact spider, plates and wiper contacts silver or nickel plated. (Same as C7,
C19.)
C2 8 3D291 CAPACITOR CA-291; variable, air, 6-100 /z/zf, Band B trimmer, 1st r-f SC-A-1728
27 plates, 0.008" minimum spacing between rotor and stator plates, isolantite base, overall length 1%", screwdriver adjustment, special contact spider, plates and wiper contacts silver or nickel plated, all other parts nickel plated. (Same as C3, Cs, C9, C14, C15,
C._>0, C21.)
C3 — — CAPACITOR CA-291; (Same as C2.) Band C trimmer, 1st r-f —
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SIGNAL CORPS
98
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).—
Order replacement ^arts by stock number, name and description, and receiver model.
n'Z C40, C100.)______________
99
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40 SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).—-Order replacement parts by stock number, name and description, and receiver model. No/ QEq£pn Stock^Number Name and Description of Part Function DrTwing°No'
G2g 1 3D293 CAPACITOR CA-293; variable, air, 10-210 Antenna alignment SC-D-2580
isolantite base, overall length 3-9/16" x 1-9/32" high, plates, studs and shaft silver plated.
C27 7 3D284 CAPACITOR CA-284; fixed, 0.05 yf ±10%, 1st r-f bypass SC-D-1995
400 v. d.c. working, pajjer, pigtail leads.
(Same as C92, C99, C92, C87, C99, C;92.) — 1 3D292 CAPACITOR CA-292; variable, air, 13-226 Tuning gang SC-D-2568
mmL 4 sections. (C28, Q34’ C46> CS2.) C28 — —• One section of CA-292; (See preceding item). 1st r-f tuning —
— 3 3D195 CAPACITOR CA-195; fixed, 3 section, each SC-D-512
0.05 yf -|-14% —6%, 300 v. d.c. working, paper, oil impregnated, 3 terminals, sealed in metal case 1.738" long x 1-1/16" high x 9/16" wide, 2.125". between centers of mounting brackets. (C29, C30, C31, C35, C3(;
C37, C48’ C49, C50.)
G29 — — One section of CA-195; (See preceding item). 1st r-f cathode bypass —
C30 — — One section of CA-195; (Same as C29.) 1st r-f screen bypass r—
Q31 — — One section of CA-195; (Same as C29.) 1st r-f “B” supply bypass —
C32 —______22_________ CAPACITOR CA-284; (Same as C27.) 1st r-f plate bypass —
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TM 11-850
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RADIO RECEIVERS BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*) AND BC-344-C*)
Par. 40 a. Radio Receivers BC-312- (*), BC-312-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan, in Signal Corps Z , _ 7~~. ~~ ———————
No. Equip. Stock Number Name and Description of Part Function Signal Corps
--------------------------------------------------------------- Drawing No. 03 6 3D266 CAPACITOR CA-266; fixed, 100 n/if + 14% 2d r-f grid coupling SC-D-1993
—6%, 250 v. d.c. working, mica, pigtail leads.
(Same as C45, C47, C86, C101.)
04 — — One section of CA-292; (Same as C28.) 2d r-f tuning —
05 One section of CA-195; (Same as C2!).) 2d r-f cathode bypass —
3,i One section of CA-195; (Same as C29.) 2d r-f screen bypass __
07 — — One section of CA-195; (Same as C2 Cc3, C66, C76.) (Except BC-312, BC-312-A, N, NX, BC-342, BC-342-N.) CAPACITOR CA-281; fixed, 0.01 ±10%, 400 v. d.c. working, paper. (Used in BC-312, BC-312-A, N, NX, BC-342, BC-342-N only.) CAPACITOR CA-344; (Same as C53.) (Except BC-312, BC-312-A, BC-342.) CAPACITOR CA-295; fixed, 50 ^f ±2%, 300 v. d.c. working, mica, %" x %" x (Used in BC-312, BC-312-A, BC-342 only. CAPACITOR CA-371; (Same as C54.) (Except BC-312, BC-312-A, N, NX, BC-342, BC- 342-N.) CAPACITOR CA-281; (Same as C54.) (Used in BC-312, BC-312-A, N, NX, BC-342, BC- 342-N .only.)
Signal Corps Stock Number — A y A i
Quan, in Equip. 1 1 1
Ref. No. W O w w w O O O
fPart of an assembly, not a replaceable part.
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40
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).—
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan.in Signal Corps XT . . x. . n „ Sitrnnl
No. Equip. Stock Number Name and Description of Part Function Drawing No.
t CAPACITOR CA-344; (Same as C53.) (Ex- ]
cept BC-312, BC-312-A, BC-342.) " I
O57 j t CAPACITOR CA-295; (Same as C55.) (Used J-lst i-f transformer _______
in BC-312, BC-312-A, BC-342 only.) | primary tuning
t CAPACITOR CA-371; (Same as C54.) (Ex- )
cept BC-312, BC-312-A, NX, BC-342.) (Re- | C58 — places CA-281 in all models.) list i-f plate bypass __
t CAPACITOR CA-281; (Same as C54.) (Used
[ in BC-312, BC-312-A, NX, BC-342.)
1 3D302 CAPACITOR CA-302; fixed, 3 sections, each — SC-D-2567
0.05 pf +14%—6%, 300 v. d.c. working, paper, oil impregnated, 3 terminals, sealed in metal case, 1.738" long x 1-1/16" high x 9/16" wide, one mounting bracket at side, other bracket at front. (C59, C60, C61.) C59 — — One section of CA-302; (See preceding item) 1st i-f cathode bypass _
One section of CA-302; (Same as C59.) 1st i-f screen bypass —
C»i One section of CA-302; (Same as C59.) 1st i-f “B” supply bypass —
C02______________________ CAPACITOR CA-284; (Same as C27.) 1st detector AVC bypass —
+Part of an assembly, not a replaceable part.
104
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d) ._
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. SC-D-1993
Function c/2 ct5 « c » P. g .5 2 « <2 5 Sc £ g c §5 . < i Sc — ■y 'C n ~ cl «M c •- *2 V .§ T ,. q> "" C cn "O to -Q & .q ' CM CM CM
Name and Description of Part CAPACITOR CA-371; (Same as C-4.) (Except BC-312, BC-312-A, N, NX, BC-342, BC- 342-N.) CAPACITOR CA-281; (Same as C-4.) (Used in BC-312, BC-312-A, N, NX, BC-342-N only.) CAPACITOR CA-296; (Same as C53.) (Used in BC-342 only.) CAPACITOR CA-342; fixed, 100 nA ±2%, 400 v. d.c. working, silver mica, pigtail leads. (Except BC-312, BC-342.) CAPACITOR CA-295; (Same as C-5.) (Used in BC-312, BC-342 only.) CAPACITOR CA-342; (Same as C64.) (Except BC-312, BC-342.) CAPACITOR CA-295; (Same as C5V) (Used in BC-312, BC-342 only.) CAPACITOR CA-371; (Same as C54.) (Except BC-312,, BC-312-A, N, NX, BC-342 and BC-342-N.) CAPACITOR CA-281; (Same as C54.) (Used in BC-312, BC-312-A, N, NX, and BC-342-N.) CAPACITOR CA-296; (Same as C53.) (Used BC-342 only.)
Signal Corps Stock Number 4- 4- 4— 4- 4-4-4- 4- 4-4-
Quan.in Equip. I III
Ref. No. co -r cs
fPart of an assembly, not a replaceable part.
105
TM 11-850
SIGNAL CORPS
40
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan.in Signal Corps n _ Signal Corps
No. Equip. Stock Number Name and Description of Part Function Drawing No.
C„7 1 3D279 CAPACITOR CA-279; fixed, 10 + 14% — Diode AVC coupling SC-D-1993
6f/r, 400 v. d.c. working, mica, pigtail terminals. (Use to replace 10 Erie type
NPO-K in BC-312-L, M.)
— 2 3D301 CAPACITOR CA-301; fixed, 3 sections, each — SC-D-2567
0.05 /zf + 14.%—6%,300v. d.c.working, paper, oil impregnated, 3 terminals, sealed in metal case, 1.738" long x 9/16" wide x 1-1/16" high, mounting brackets at right angles.
(Cfi8, C69, C70, C73, C74, C75.)
C,i8 — — One section of CA-301; (See preceding item.) 2d i-f cathode bypass —
C(!!) — — One section of CA-301; (Same as C68.) 2d i-f screen bypass —
C70 — — One section of CA-301; (Same as C68.) 2d i-f plate supply —
bypass
C71 1 3D218 CAPACITOR CA-218; fixed, 150 wf +14% '
—6%, 250 v. d.c. working, mica, closed type
terminals.
C72 1 3D193 CAPACITOR CA-193; fixed, 500 /x^f + 14% >2d detector output filter SC-D-1993
—6%, 250 v. d.c. working, mica, closed type |
terminals.
C73 — — One section of CA-301; (Same as C68.) 2d detector cathode
bypass
C74 — — One section of CA-301; (Same as Cfi8.) 1st audio ”B” supply
bypass
C75 — — One section of CA-301; (Same as C68.) AVC filter
106
TM 11-850
40
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, BC-342-C*), BC-314-C*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-3 12-4*), BC-312-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
N\f ^Equip” sToc^Number Name and Description of Part Function Signal Corps
v. oiuch iNuiuut;! Drawing No
f — CAPACITOR CA-371; (Same as C54.) (Ex- '
cept BC-312, BC-312-A, BC-342.) (Replaces
CA-281 in all models.) C7(i — j — CAPACITOR CA-281; (Same as C-4.) (Used 2d audio grid coupling —
in BC-312, BC-312-A only.)
— CAPACITOR CA-296; (Same as C-3.) (Used
in BC-342 only.) — 1 3D276 CAPACITOR CA-276; fixed, 3 sections, each — SC-D-512
0.1 /zf + 14% —6%, 400 v. d.c. working, paper, oil impregnated, 3 terminals, sealed in metal case, 1-27/32" long x 1" high x 13/16" wide, 2%" between centers of mounting brackets. (C78, C79, C80.) C7s — — One section of CA-276; (See preceding item.) —“A” supply bypass —
C79 — — One section of CA-276; (Same as C78.) +“A” supply bypass —
C8o — — One section of CA-276; (Same as C78.) 2d audio “B” supply —
bypass
Csi — — CAPACITOR CA-281; (Same as C-)4.) 1st audio grid coupling —
C82 — — One section of CA-292; (Same as C28.) R-f oscillator tuning —
Qss 1 3D277 CAPACITOR CA-277; fixed, 0.1 nt ±10%, R-f oscillator plate SC-D-1995
_______________________ 400 v. d.c. working, paper, pigtail leads. bypass
107
TM 11-850
40
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-C*), BC-3 1 2-(*) X and BC-342-C*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model.
Nof.‘ ^Equip? Stock3Number Name and Description of Part Function Drawto^N?.
3D280 CAPACITOR CA-280; variable, air, 10 /z/zf.
(Used in BC-312, BC-312-A, C, BC-342-C
only.)
3D383 CAPACITOR CA-383; variable, air, 1-10
C84 1 0.008" minimum spacing between rotor and l-C-w oscillator control SC-A-1728
stator plates, assembly 1-11/16" long, special spider plate, shaft and studs all silver or nickel plated. (Except BC-312, BC-312-A,
C and BC-342-C.)
Cs.-, 1 3D253 CAPACITOR CA-253; variable, air, 4-75 /z/zf, C-w oscillator trimmer SC-A-1728
20 plates, 0.008" minimum spacing between stator and rotor plates, overall length 1-15/32", screwdriver adjustment, special contact spider, plates and wiper contacts silver or nickel plated, all other parts nickel
plated.
Cs<; — — CAPACITOR CA-266; (Same as C33.) C-w oscillator grid —
coupling
C87 — — CAPACITOR CA-284; (Same as C27.) C-w oscillator plate —
bypass
C8s — — CAPACITOR CA-266; (Same as C33.) R-f oscillator grid —
_______________________ coupling
108
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 40
BC-342-C*), BC-314-(*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-3 12-(*), BC-312-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Nof’ ^Equip" Stocka,Number Name and Description of Part Function Drawit^No.
CS!) 2 3D211 CAPACITOR CA-211; fixed, 0.002 rf, 250 v.
d.c. working, 7/8" x 7/8" x 5/16". (Used |
in BC-312, BC-312-A and BC-342 only.) {.Thermostat contact SC-D-1993
C!M( — — CAPACITOR CA-211; (Same as Cs9.) (Used bypass
in BC-312, BC-312-A and BC-342 only.)
— 1 3D329 CAPACITOR CA-329; electrolytic, 2 sections, — SC-A-1490
each 8 /zf, 450 v. d.c. working, capable of
withstanding continuous operation at 85° C.
(Cs9» C90.)
C8<| — — One section of CA-329; (See preceding item.) 1
(Used in BC-342-C, D, F, J, L, M, N only.) |
c9o — — One section of CA-329; (Same as C8<).) (Used }.“B” power supply filter —
in BC-342-C, D, F, J, L, M, N only.) |
02 t CAPACITOR CA-295; (Same as C35.) (Used 2d i-f transformer
in BC-312, BC-312-A, BC-342 only.) secondary tuning
O<»3 t CAPA.CITOR CA-295; (Same as C33.) (Used 2d i-f transformer
in BC-312, BC-312-A, BC-342 only.) primary tuning
C.,4 — t CAPACITOR CA-298; fixed, 800 wf ±2%, ]
250 v. d.c. working, silver mica, pigtail leads. | (Except BC-312-N, NX.) {.1st detector transformer SC-D-1993
O95 — t CAPACITOR CA-298; (Same as C<)4.) (Ex- I tuning
_____________________________cept BC-312-N, NX.)
fPart of an assembly, not a replaceable part.
109
TM 11-850
40
©
SIGNAL CORPS
110
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. Nof.‘ StLckaNumber Name and Description of Part Function Draw^VgNm
C9G 2 3D286 CAPACITOR CA-286; fixed, 75 ppi +14% ]
—6%, 250 v. d.c. working, pigtail leads. J.C-W oscillator output SC-D-1993
C97 — — CAPACITOR CA-286; (Same as C9((.) J filter
C9S 1 3D275 CAPACITOR CA-275; fixed, 4 pf +14% 2d audio cathode bypass SC-D-512
—6%, 50 v. d.c. working, 2 terminals, sealed
in. metal case, 2" long x 2" high x 1" wide,
2%" between centers of mounting brackets.
C99 — —■ CAPACITOR CA-284; (Same as C27.) 2d r-f AVC bypass —
Ctoo — CAPACITOR CA-294; (Same as C25.) 2d r-f padder —
Cioi — — CAPACITOR CA-266; (Same as C33.) 1st r-f grid coupling —
C1O2 — — CAPACITOR CA-284; (Same as C27.) 1st r-f AVC bypass —
Cio3 — — CAPACITOR CA-344; (Same as C-)3.) (Used 1st detector transformer —
in BC-312-N, NX only.) ' tuning
(2Z3501-6A CRYSTAL pC-6-A; quartz, 470 kc. (Except Crystal filter SC-D-2972
BC-312, BC-312-A, L, M, N, NX, BC-342.)
CX 1
2Z3501-6 CRYSTAL DC-6; quartz, 470 kc. (Used in Crystal filter SC-A-1994
BC-312, BC-312-A, BC-342 only.)
DM 1 3H1621-( ) DYNAMOTOR DM-21-(*); 235 v. d.c. out- Plate power supply SC-D-2723
put at 90 ma, 12-14 v. d.c. input, 50° C rise, enclosed in metal case 5-15/16" long x 5-7/16" wide x 3%" deep. (Not used in BC-342-(*).) (DM-21-(*) may be used to replace DM-17-A in BC-312 by requisitioning
__________________________ Bracket Set, Stock No. 2C4312/B50.)
TM 11-850
RADIO RECEIVERS BC-312-C), BC-312-(*)X, 40
BC-342-(*), BC-314-C*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-3J2-(*), BC-3 12-(*)X and BC-342-(*) (Cont’d) _
Order replacement parts by stock number, name and description, and receiver model.
No. Quan.in Signal Corps i n .. .. c;.... i r-
Ref. Equip. Stock Number i Name and Description ot Part Function Signal Corps
___________________________________________________ Drawing No. pi 2 3Z1921A____. FUSE FU-21-A; cartridge type, 10 amperes, Dynamotor and filament
25 volts, lb" long x 11 ” dia. (Except BC- circuit 312(*)X.)
USE FU-21-A; (Same as Fp) Dial light circuit
U 1 3Z1927 FUSE B’V-27; cartridge type, 2 amperes, 250 A-c line
volts, 1 U " long x Li " dia. (Except BC-312-
(*) and BC-342.) 2 3Z1925A FUSE FU-25-A; 5 amperes, 25 volts, 1%" Dynamotor and filament
long x dia. (T sed in BC-312-( )X only.) circuit
F.-> — B USE BU-25-A, (Same as B 4.) Dial light circuit
1 3Z1890-6( ) FILTER FL-6-(*); contains chokes and ca- Dynamotor filter unit SC-D-1866
pacitors, sealed in metal case 2" high x wide x 5" long, 5-3/16" between mount-
ing centers. Ji 3 . 2Z5534A JACK JK-34-A; open circuit for Vs" panel gist audio phone jack SC-D-2339
max, brass sleeve threaded %-32, complete with phenolic ring, washer, locating plate, brass washers, nut, pin. Beryllium contact, cadmium plated.
JACK JK-34-A; (Same as Jr) 2d audio phone jack —
2 2Z5533A JACK JK-33-A; 3 circuit, for %" panel max, Speaker jack SC-D-2332
brass sleeve threaded %-32, complete with brass nut, pin, washer, terminal, phenolic washer ring, locating plate. 2 beryllium cop-___________________________ per contacts, cadimum plated.
M, N.
§2d audio in BC-312-NX, L, M, N and BC-342-L,
5!m:;:!oo 44
111
TM 11-850
SIGNAL CORPS
40
Par. 40 a. Radio Receivers BC-3 1 2-(* ), BC-312-(*)X and BC-342-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. Ikel’ Q“an;’n c^*K|,aVz°,kS Name and Description of Part Function D^vin^Nn8
No. Equip. Stock Number H Drawing No.
J4 — — JACK JK-33-A; (Same as J3.) Microphone jack —
J- — — JACK JK-34-A; (Same as Jr) Key jack —-
— 1 2C4342N/A2 First r-f unit assembly consisting of: 1st r-f tuning unit SC-D-2553
CAPACITORS: CA-289, (3) CA.290, (2) Fain., 2538-37
CA-291, CA-294; 2 switches, 6 coils and terminal board assembly, overall assembly mounted in aluminum box. (Used in BC—
312-F, HX, N, NX, BC-342-F, N.)
—- 2C4312M.1/T2 First r-f unit assembly consisting of: 1st r-f tuning unit RCA,T-
CAPACITORS: CA-289, (3) CA-290, (2) 621254-502
CA-291, CA-294; 2 switches, 6 coils and terminal board assembly, overall assembly mounted in aluminum box 4.937" x 5.390" x 2.061". (Used in BC-312-J, L, M, BC-342-
J, L, M, only.)
|L, 1 3C1083 COIL 1st r-f, Band A
XL., 1 3C1083-3 COIL 1st r-f, Band B
+L~ 1 3C1083-6 COIL 1st r-f, Band C
JL, 1 3C1083-9 COIL 1st r-f, Band D
JL- 1 3C1083-12 COIL 1st r-f, Band E
XL,;______1 3C1083-15______COIL________________________________1st r-f. Band F________________
JBC-312-A uses coils made in accordance with RCA dwg. KX-289494. :j:BC-312-C uses coils made in accordance with RCA dwg. KX380082 or TX-262208. XBC-312-D uses coils made in accordance with RCA dwg. T-620350 except that oscillator coils are made in accordance
with RCA dwg. TX-262208.
j:For BC-312-F, HX, N and NX and BC-342-F and N use Farnsworth dwg. 2556. iFtor BC-312-J, L, M and BC-342-J, L, M use RCA dwg. TX-262208 and T-620350.
112
TM 11-850
40
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, BC-342-C), BC-314-C*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-/*) /Cont’d)._
Order replacement parts by stock number, name and description, and receiver model. Ref. Quan.in I Signal Corps KT , ——— _____-------
No. Equip. Stock Number Marne and Description of Part Function ’ Signal Corps
——___________________________________________/ Drawing No. 1 2C4342N/A3 Second r-f unit assembly consisting of: 2d r-f tuning unit SC-D-?553
CAPACITORS: CA-289, (3) CA-290, (2) ” irarn okqq.-q
CA-291, CA-294; 2 switches, 6 coils and terminal board assembly, overall assembly mounted in aluminum box. (Used in BC-312-
F, RX, N, NX, BC-342-F, N.)
2C4312M.1/T3 Second r-f unit assembly consisting of: 2d r-f tuning uni RCA T-
CAPACITORS: CA-289, (3) CA-290, (2) 621254-503
CA-291, CA-294; 2 switches, 6 coils and terminal boarc. assembly, overall assembly mounted in aluminum box 4.937" x 5.390" x 2.061". (Used in BC-312-J, L, M, BC-342-
J, L, M only.)
1 3C1083-1 COIL o i -pt, , A
1 3C1083-4 COIL 2d B“d B
•X 1 3C1083-7 COIL 2d r f Band C
tL>« 1 3C1083-10 COIL 2d - f Bard D
tL„ 1 3C1083-13 COIL 2d i-L Band E
■J—12.----J----3C1083-16_____COIL_____________________________ 2d r-f, Band F
IrToioT Uses C°ills made in accordance with RCA dwg. KX-289494 tRrl 9 n USeS C01hS maT m accordance with RCA dwg. KX380082 or TX-262208 1 withi RCA dwg' TX.a262208a“°rdanCe "ith RCA dWg' T-620350 ‘hat oscillator coils are made in accordance ♦For RC 312 T ’ tHXmN Tnoi?? BC-342-F and N use Farnsworth dwg. 2556. +Foi BC-312-J, L, M and BC-342-J, L, M use RCA dwg. TX-262208 and T-620350.
113
TM 11-850
40
SIGNAL CORI’S
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont'd).— Order replacement parts by stock number, name and description, and receiver model. Ref. Quan.in Signal Corps KT j • .• „ , I Signal Corps
No. Equip. Stock Number Name and Description of Part Function j Drawing No.
1 2C4342N/A1 First detector unit assembly consisting- of: 1st detector tuning’ unit SC-D-2533
CAPACITORS: CA-289, (3) CA-290, (2) Farm, 2538-36
CA-291, CA-294; 2 switches, 6 coils and terminal board assembly, overall assembly mounted in aluminum box. (Used in BC-312-
F, HX, N, NX, BC-342-F, N.) — 2C4312M.1/T4 First detector unit assembly consisting of: 1st detector tuning unit : RCA. T-
CAPACITORS: CA-289, (3) CA-290, (2) 621254-504
CA-291, CA-294; 2 switches, 6 coils and terminal board assembly, overall assembly mounted in aluminum box 4.937" x 5.390" x 2.061". (Used in BC-312-J, L, M, BC-342-J,
L, M only.)
1 3C390 COIL 1st detector, Band A
1 3C390-1 COIL 1st detector, Band B
jL|- 1 3C390-2 COIL 1st detector, Band C
tL1(; 1 3C390-3 COIL 1st detector, Band D
1 3C390-4 COIL 1st detector, Band E
_______ 1 3C390-5 COIL 1st detector, Band F jBC-312-A uses coils made in accordance with RCA dwg. KX-289494. jEU-312-C uses coils made in accordance with RCA dwg. KX380082 or TX-262208. <£>C-J12-D uses coils made in accordance with RCA dwg. T-620350 except that oscillator coils are made in accordance
W;Jr RCA dwg. TX-262208.
vFot BC-312-F, HA, N and NX and BC-342-F and N use Farnsworth dwg. 2556. ■(For BC-312-J, L, M and BC-342-J, L, M use RCA dwg. TX-262208 and T-620350.
114
Par. 40 a. Radio Receivers BC-312-(*), BC-3 12-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. RADIO RECEIVERS BC-312-(*), BC-312-(*)> BC-342-(*), BC-314-C*) AND BC-344-(») Ci co cn 00 ° S £5 LfT) £ H 5 fa ' . cm Q C << rl i » CM OT fa « +o^'o1?'A uses c?ils made in accordance with RCA dwg. KX-289494. J§C-312-C uses coils made in accordance with RCA dwg. KX380082 or TX-262208 1 with RCA dwg.'TXa2d6e2208aCCOrdaM'i ”ith KCA dWg' T-620350 n“pt that oscillator coils are made in accordant. 3 JE.or n2'olo'T an'i ®C-342-F and N use Farnsworth dwg. 2556. 0 — JFor BC-312-J, L, M and BC-342-J, L. Al use RCA dwg. TX-262208 and T-620350. A A A A A A +» © -2_2_goo° JS 4 asi £ . co S ® E Cl " be « 2 - 6o _> ? 5 « J ■£ ci g -E ci S -2 3 ~ - 2 <1 5 x? co w <1 >o.l C >, oo © » _ k E > .E x E a X 5 4 v E ci1 £ a “g E ©> x ® S2°+» ? 2 ” °0 CM ™ ©CM >. 4 « N 7S e fa “ 1 CM © £□ >7 w 1 . O E - «S _>-^-^cS©3 -t-> fa ® • n, +U fa A 7 » >. ■£ -5 A © ■ c 2 50 £ 2 C 3 ui + o -a 3 W ■£ L ° co S 0s «£N-O.£m«£ ■” x fa ~ ° § £ kA S O 4? © S + y + O 58 3^ u
________________________________Roe-) __________________ ■
118
TM 11-850
RADIO RECEIVERS BC-312-(*>, BC-312-(*)X, 40
BC-342-(*), BC-314-C*) AND BC-344-(*)
Signal Corps Drawing No. O o O 2 2 §11111 d d d CO CO CO
) (Cont’d) — n, and receiver model. Function a y ii CO 2 a o d -s g S S £ > ° .'E 5 > m | s *»? t '7 i i 1 < i Li 4J d A m W «C -g TS'QnS’XJ c 2-1 j~L co co co co co co
-312-(*), BC-312-(*)X and BC-342-(* nt parts by stock number, name and descriptioi Name and Description of Part 3 2 3 to £ g< odd ci -Ed •£ 2 o « £ o « y 2 ■’8 » - V t- K -q •E ~ . .E ~ X - fl o> „ o> ® S' $ -8 .2 w Q 0 , ~ _ —4 ;*S +> co .-g r w 2 >.7 M m -e CS » £ rt _> g to >5 & S «2 w ?’ ~ « > o. > y u p 0 0 — W PS PS m PS S E - 0 * ” 2-co !2 g C O , N tf- g i ~ 2 CS « cs 05 ” CM CS 'Z O co 0 > K a 3 " £ « M H d T5 LZ 'T5 - «8 M 'fl S 8 S S 8 ” P CO $ 3 S^'C^r<+7rt5j'C?C§ fl{ScS fl‘^U cc' •- . ® +1 22 -j t E d « E - - K - co g io s to t- ss a a co 10 £ E - Ec.fl»c!iE^wwTKi«2®®^228 does -< n co t± CO -fl tt >—- CO co „ . 0 .COCOCOCOCO^ CO co g .g tffl.to gg K | . Pig . w W 2 S « « - 5 PS Pi PS PS PS > « » g s s 2 2 ^f,N'O +r d O 8 O O O O O -s O- H w H PS H apqH-fl.'KHHHE-iE-'V H 2 "7 £2 V “ s ® .wotfwaicowcog^wm co L 5 co ® . ?!ocoEto<2wfltoMcocococo~2jcod a cs ps a s >■ ps w a 0 & co w £'Q £ .2 O M ' W s "2 2 -2 -Q 3 «H q_| q_, 2 m 'S 3 3 T5 ’"O "O '"O W IZT ,-o 72 ’"O N N cq N rH < Q £ H (N
Ascription of Part 4* 1 5 r J 1 a W «> C • s ™ ' t •S 5 •£ x,.E $ .£ « b •” -E $ •£ $ x?o » tr, > i-1 ns CO 75 ” s if s' -8 '3 'p, S w 75 * O C O' s x 2 3 03 2 t? s £ —. 3 s s pq o * 5 . £ > « ’43 g 3 - £ 3 . 3 D -3? ““““•sf -I--Sg 8 B » « .« s - o 3 " £ „■ SPSS’S - ^Ti « ^2 J 73 g < g E 8 k s-. a> a) t w Q, •—1 a; ® D Z, ry oj - S a, 11 a> « « d 3 k x - * +1 - x 7! ~ k * 2 § * +l ~ (72 02 Oj H a> . "a. h H ^ ,• H h q " >—<>—II—II—II—( cS^-i—( CS bi.'T-H rt to I—i CST5 ® M It—( cs^tji—(1—( C? &£' O2O2O2O2O2'-g'O2'q S 02 "3 C Cfi 3 aS 2 „ o M 3 " 02 0273 S a a W O w g w g o w S « s £ pq w w x K W 04 PS « P3 c4 03 04 03 03 03 04
Signal Corps Stock Number 3Z4571 3Z4562 3Z4561 3Z4623 3Z4565 3Z4531
Quan.in Equip. 1 1 1 1 ~ ” 1 ~
Ref. No. ?i ?i ?! Vi ?i ?i « x x 04 04 04 04 04 04 04 04 0404
121
TM 11-850
40
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-3 1 2-(*), BC-3 1 2-(*) X and BC-342-(*) (Cont’d) —
Order replacement parts by stock number, name and description, and receiver model.
Neb Name and Description of Part Function Signal Corps
No. Equip. Stock Number r Drawing No.
1 2Z7289 POTENTIOMETER RS-174; dual-section, 1
watt.
R3( — — Section D of RS-174; 0-500,000 ohm, ±10%, -Volume Control SC-D-1982
taper “L”, right-hand.
R3- — — Section E of RS-174; 0-50,000 ohm, ±10%,
taper “L”, left-hand.
(3Z4511 RESISTOR RS-111; fixed, composition, in-
sulated, 100,000 ohm, ±10%, 1 watt, 7/8"
long, 9/32" dia., pigtail leads. (Used in all
R3(i 1 j receivers except BC-312, BC-312-A, C, BC- -Cathode bias voltage SC-D-970
' 342, BC-342-C.) divider
— RESISTOR RS-150; (Same as R.,3.) (Used
in BC-312, BC-312-A, C, BC-342, BC-342-C.)
R37 — — RESISTOR RS-150; (Same as R.,3.) C-w oscillator plate —
R3(S — f RESISTOR RS-169; (Same as R2.) (Used in 2d i-f transformer —
all receivers except BC-312, BC-312-A, BC- primary shunt
342.)
R3S 3Z4578 RESISTOR RS-178; fixed, metal-enclosed, 12 Heater
ohm, 15 watt, 14 volt. (Used only in BC-312,
BC-312-A, BC-342.)
R3!i — RESISTOR RS-178; (Same as R3S.) (Used Heater
only in BC-312, BC-312-A, BC-342.)
R4o — RESISTOR RS-178; (Same as R3S.) (Used Heater
______________________________only in BC-312, BC-312-A, BC-342.)___
fPart of an assembly, not a replaceable part.
122
123
TM 11-850
RADIO RECEIVERS t$C-312-(-), BC-312-(*)X, 40
BC-342-(*), BC-314-C*) AND BC-344-f*)
Par. 40 a. Radio Receivers BC-3 1 2-(* ). BC-3 1 2- (*)X and BC-342- ( * ) (Cont’d )._
Order replacement parts by stock number, name ant! description, and receiver model. Ref. I Quan, in | Signal Corps I . I e;„ir
No. I Et-uip. Stock Number Name and Description ot Part I Function Signa) (orps
I. — . - ... —__________|_______________________________________|_____________________ Drawing No.
R|<> 3Z4620 । RESISTOR RS-220; fixed, com position, in- I Bleeder SC-D-970
sulated. 65,000 ohm, 2 watts. (Used in BC-
342-C, D, F, J, L, M, N only.)
1 3Z4539 RESISTOR RS-139; fixed, composition, in- R-f oscillator plate SC-D-970
sulated, 30,000 ohm,,±10% , 1 watt, 7/8" long, dropping’
9/32" dia., pigtail leads. (Not used in BC-
312-C.)
RESISTOR RS-140; (Same as R|5.) R-f oscillator grid leak —
1 3Z4548 RESISTOR RS-148; fixed, composition, in- C-w oscillator grid leak SC-D-970
sulated, 200,000 ohm, ±10%, 36 watt, %" long, 34" dia., pigtail leads. 3Z4635 RESISTOR RS-235; fixed, composition, in- j
sulated, 3000 ohm, ±10%, 1 watt, 7/8" long, | 9/32" dia., pigtail leads. (Used in all re- |
R44 1 5 ceivers except BC-312, BC-312-A, BC-342.) }>R-f oscillator cathode SC-D-970
3Z4527 RESISTOR RS-127; insulated, 3000 ohm, bias, band C
±10%, 36 watt, %" long, 34" dia. (Used in
BC-312, BC-312-A, BC-342.)
3Z4637 RESISTOR RS-237; fixed, composition, in-
sulated, 5000 ohm, ±10%, 1 watt, pigtail
leads. (Used in al) receivers except BC-312, ^45 1 I BC-312-A, BC-342.) >R-f oscillator cathode SC-D-970
3Z4528 | RESISTOR RS-128; insulated, .5000 ohm, bias, band B
±10%, 36 watt, %" long, 34" dia. (Used in
_______________________________I BC-312, BC-312-A, BC-342.)______
TM 11-850
40
SIGNAL CORPS
Signal Corps Drawing No. o o o o Ci O । Oi । CTi । Q Q 1 Q 1 Q II II U O Q O xn co xn xn
(Cont’d).— , and receiver model. Function ■* ►R-f oscillator cathode bias, band A Filament voltage equalizer 1st detector screen bleeder 2d detector diode output 1st detector screen divider C-w oscillator output 1st i-f grid input
312-(*), BC-312-(*)X and BC-342-(*) nt parts by stock number, name and description Name and Description of Part RESISTOR RS-238; fixed, composition, insulated, 7500 ohm, ±10%, 1 watt, pigtail leads. (Used in all receivers except BC-312, BC- 312-A, BC-342.) RESISTOR RS-177; insulated, 7500 ohm, ± 10%, % watt, %" long, 34" dia. (Used in BC-312, BC-312-A, BC-342.) RESISTOR RS-176; fixed, composition, insulated, 60 ohm, ±10%, % watt, %" long, 34" dia., pigtail leads. (Not used in BC-312- NX or HX.) RESISTOR RS-169; (Same as R2.) RESISTOR RS-133; fixed, composition, insulated, 500,000 ohm, ±10%, 34 watt, %" long, 34" dia. RESISTOR RS-140; (Same as R15.) RESISTOR RS-129; fixed, composition, insulated, 10,000 ohm, ±10%, 34 watt, %" long, 34" dia. RESISTOR RS-175; fixed, composition, insulated, 10,000 ohm, ±10%, 34 watt, %" long, 34" dia., pigtail leads.
dio Receivers BC-Order replaceme; Signal Corps Stock Number 3Z4638 3Z4577 3Z4576 3Z4533 3Z4529 t
Q Quan.in Equip. tH r-l | t-H [ rH —'
Par. 40 Ref. No. ftT pf cL pT p? 124
fPart of an assembly, not a replaceable part.
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342- (*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. ,1 § 82 < n i §
Function 1st r-f grid input 2d audio cathode bias Heater dropping VT-134 Dial light control Dial light control Power supply
Name and Description of Part RESISTOR RS-173; (Same as R(i.) RESISTOR RS-223; (Same as R31.) (Not used in BC-312, BC-312-A, BC-342.) RESISTOR RS-267; molded, insulated, 75 ohm, 15 watt. (Used only in BC-312-HX, NX.) RHEOSTAT RS-256; wire-wound, 75 ohm, 2 watt, grounded contact arm, off position in extreme counterclockwise position; 46" long shank threaded %"-32 threads, complete with holding nut, 44" dia., %" long shaft, 7wo terminals. (Used in BC-312-L, M.) RHEOSTAT RS^256. (Same as R.-,-(.) (Used in BC-312-N, NX.) RECTIFIER RA-20; complete a-c power supply, 110-120 v. 60-cycle input, 250 v. d.c., 95 milliamperes output, two 12 v. a.c. filament supplies; contains power transformer, filter choke, electrolytic capacitor, ON-OFF switch, fuse and holder, input plug, bleeder resistor, terminal board, and tube socket. (Used in BC-342, BC-342-C, D, F, J, L, M, N.)
Signal Corps Stock Number | | 3Z4667 CM LQ r-f CM 1 N N CO CM
Quan, in Equip. II W I w
Ref. No. £
125
TM 11-850
40
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont'd).—
Order replacement parts by stock number, name and description, and receiver model.
%,f- tei"' Name and Description of Part Function
RL, 1 2Z7613 RELAY BK-13; closes at 8.5 v. when mounted Antenna grounding SC-D-1942
in a vertical position, 60 ohms d-c resistance, coil consists of 2100 turns AWG #32 silk enamelled wire, 25 layers wound on- iron
core. (Not used in BC-312-HX, NX.)
RL. 2Z7641A RELAY BK-41-A; double-pole, single-throw, Antenna grounding
24 volt coil. (Used in BC-312-HX, NX.)
SO, 1 2Z8794.1 SOCKET SO-94; aluminum alloy shell, 14 Power supply and SC-D-2592
contacts, four mounting holes 0.1285" in dia., control connector 1-1/16" between centers, 18 threads per in.,
V threads, pitch dia. 1.393".
SO. 6Z7589 CONNECTOR; two-contact. (Used only in. A-c input SC-D-1610
BC-342-C, D, F, J, N.) SW, 1 3Z8131 SWITCH SW-131; toggle, SPST, 3 ampere, Send-receive SC-A-1042
250 volt, 15/32" threaded shank, complete with two hex nuts.
SW. 8 3Z8310-2 SWITCH; gang section, ceramic stator plates, Band change, 1st r-f SC-D-4046
single rotor contact, “X” type spring tern- grid pered brass, silver plated. (Same as SW.{,
_______________________________SW4, SW-,, SW,.„ SW? SWs, SW,,.)_"
126
TM 11-830
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-C) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Nm QEquipn StockaNumber Name and Description of Part Function Dwwin^No.
— — SWITCH; (Same as SW2.) (Except BC-312, )
BC-312-A, C, BC-342, BC-342-C.) ]
SW3 . 1 — SWITCH; made in accordance with RCA dwg. (Band change, 1st r-f _
KX289313, part l.(BC-312, BC-312-A, C, antenna
BC-342, BC-342-C only.) J
SW4 SWITCH; (Same as SW2.) Band change, 2d r-f grid _
SW5 — SWITCH; (Same as SW2.) Band change, 1st r-f __
plate
SW(. SWITCH; (Same as SW2.) Band change, 1st __
detector grid
SW7 — — SWITCH; (Same as SW2.) Band change, 2d r-f —
plate
— SWITCH; (Same as SW2.) Band change, r-f _
oscillator grid
SW., — SWITCH; (Same as SW2.) Band change, r-f __
oscillatox1 plate
SW10 — SWITCH; ganged to C51. (Not used in BC- Crystal switch SC-D-2564
312-L, M, N, or NX.)
(3Z8139 SWITCH SW-139; toggle, SPST, 13/32" '
threaded shank, complete with two hex nuts.
(Used in all receivers except BC-312, BC-1 / 312-A, BC-342.) (C-w oscillator control SC-A-1042
3Z8105 SWITCH SW-105; toggle, SPST, 3-ampere,
250 volts. (Used only in BC-312, BC-312-A,
_____________________________BC-342.)___
504330 0—44-----9
127
TM 11-850
40 •
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-/*), BC-312-(*)X and BC-342-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model.
Nt QZipn Name and Description of Part___________Function
SWjo 1 3Z8119 SWITCH SW-119; three-position, rotary, off OFF-MVC-AVC SC-D-2574
position in extreme counterclockwise direction, brass bushing, %"-32 threads, %" long, 34'" dia., 34" long nickel silver shaft, all terminals hot tin dipped.
SW13 — — SWITCH SW-131; (Same as SWr) (Used Heater switch —
only in BC-312, BC-312-A, BC-342.) SW]3 — SWITCH SW-105; (Same as SW1P) (Used A-c line switch in RA-20 —
only in BC-342-(*).) Tj 1 2Z9805 TRANSFORMER C-205; made from C-124 by Audio interstage SC-D-2567
soldering brackets in place. (2Z9760 .^TRANSFORMER C-160; primary 5000 turns, 1
secondary 1885 turns, 2%" between centers | T., • 1 of mounting bracket. Audio output SC-D-2569
2Z9760A TRANSFORMER C-160-A; Secondary tapped
at 250 ohms, otherwise same as above.
T3 1 2Z9828 TRANSFORMER C-228; power transformer, Rectifier transformer SC-D-1598
110-120 volt, 60 cycle primary; 700 volt, in RA-20 ±5%, center tapped, 100 milliampere secondary; rectifier heater 5 volt ±234%, 3 ampere; heater supply 12.5 volt, 2 ampere; auxiliary heater supply 12.5 volt ±5%, 3 ampere. (Used only in BC-342-(*).)
♦When stock is depleted use TRANSFORMER C-160-A.
128
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-C*), BC-314-C*) AND BC-344-C)
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan, in Signal Corps ,T . . . „ „
No. Equip. Stock Number Name and Description of Part Function Signal ^°TPS
------------- --------------------------------- Drawing INo. THS, 1------2Z9182 THERMOSTAT BK-12; 2.3 amperes, 14 volts, 1
normally closed, opens at 111° F. (Used in (Oscillator BC-312, BC-312-A, BC-342 only.) compartment SC-A-2590
2 1 2Z9181 THERMOSTAT BK-11; 1.15 amperes, 14 temperature
volts, normally closed, opens at 109° F. control (Used in BC-312, BC-312-A, BC-342 only.) 3H1621A/3 BRUSH; input (dynamotor), carbon, with %- Lew voltage SC-D-2723
inch pigtail and spring soldered to end cap, 1/4" x 11/64" x 9/16", 1-5/8" overall length.
(Not used in BC-342-(*).) 3H1621A/4 BRUSH; output (dynamotor), carbon, with High voltage SC-D-2723
%" pigtail and spring soldered to end cap
34" x 36". (Not used in BC-342-(*).)
1 2Z1650/16.1 DIAL AND GEAR ASSEMBLY, (split gear For tuning SC-D-5431
tuning dial.) . RCA, MX-
244065-501 Farn., 98-133S
1 2Z8550 SHUTTER ASSEMBLY To blank out portion SC-D-5431
of tuning dial not Farn., 98-124C
being used RCA, MX-
243063-502
1 2Z7560/2 PANE; dial, clear glass, 2-39/64" long, 1/16" Dial pane SC-D-2535-13
thick, 2" wide at one end and %" wide at
______________________ the other end.
129
TM 11-850
40
SIGNAL CORPS
Par. 40 a. Radio Receivers BC-312-(*), BC-312-(*)X and BC-342-(*) (Cont'd).— Order replacement parts by stock number, name and description, and receiver model.
QVan."’n Name and Description of Part Function Signal Corps
No. Equip. Stock Number Drawing No.
— 2Z5986 LAMP MOUNTING ASSEMBLY; consisting For dial lamps
of:
1 2Z5986/1 (A) MOUNTING; right hand for lamp, min- SC-D-2573-1
iature bayonet base.
1 2Z5986/2 (B) MOUNTING; left hand. (Same as above SC-D-2573-2
except for bracket, which is of opposite
hand.)
3 3Z3275 FUSE MOUNTING; 2-13/32" long, complete Fuse holder SC-D-2532-76
with bright zinc plated nut and neoprene Farn., 98-1021-
washer. RCA, K-
99088-2
1 2Z6702 MOUNTING FT-162; consisting of: 4 alumi- Receiver mounting SC-D-2577
num alloy bases, 4 aluminum alloy mounting supports, 4 steel studs and 4 felt pads, mounted on steel plate %" thick, 18" long,
6.906" wide.
1 2C4314G/B2 BRACKET ASSEMBLY; (Not used in BC- Dynamotor mounting SC-D-2532
342-(*).) Farn., 98-1346
RCA, K-881940-501
1 2Z5650-K JACK COVER ASSEMBLY; consisting of: Key Jack SC-D-2532-36
cover, 0.843" x 0.750" x 0.21875", brass cover support, spring and pad, word “KEY”
engraved on cover.
130
TM 11-850
40
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, BC-342-(*), BC-314-(*) AND BC-344-(*)
a ® o W w xn O m 2? 2 h qo as F? s S s iS 888 sgs 8 “ => § 4J 03 cs O Js o O o xn a «h a ■g £ .2 -2 * ri *> > ri = 1 5 ri .2 .2 r ri ri C c 3 Sh 5 ri a; £ 2 2 o > £ o S x W S w Ph £ U < o Q ” fo
adio Receivers BC-3 12-(*), BC-312-(*)X and BC-342-(* Order replacement parts by stock number, name and descriptim Name and Description of Part JACK COVER ASSEMBLY; (Same as 2Z5650-K except for word “MICRO” engraved on cover.) JACK COVER ASSEMBLY; (Same as 2Z5650-K except for words “SPEAKER 2ND AUDIO” engraved on cover.) JACK COVER ASSEMBLY; (Same as 2Z5650-K except for words “PHONES 2ND AUDIO” engraved on cover.) JACK COVER ASSEMBLY; (Same as 2Z5650-K except for words “PHONES 1ST AUDIO” engraved on cover.) (Except BC-312-L, M, N, NX, BC-342-L, M, N.) COVER; aluminum die casting, 2-5/8" high, 2-5/32" wide, 1-43/64" deep. BINDING POST ASSEMBLY. BINDING POST ASSEMBLY. NUT AND FERRULE ASSEMBLY. KNOB, SHAFT, AND PINION ASSEMBLY; consists of: compression nut, pinion, spring washer, knob, shaft, setscrew and standard #6 split-spring washer. FAST TUNING KNOB AND DRIVE ASSEMBLY, (Same as above except includes eccentric bushing in assembly.)
Signal Corps Stock Number s S S 7 5 s a 2 ~ 5 - « g g f | 8 28S I- g । » । । । iiii
C I Q Q Q Q Q QQQQ
b£ L. I I I । । Illi
Sq O U O O OOOO
02 w O! 02 02 02 02 02 02 02
O> -3 X
C t 3 bZ) -©
§ Q _ b£ g 3 g
•2 > n © .E .§ s ° ©
D Q -4-J -4-2) O CG
Ci-^hSC bC 3 3 +3 £
3 O 3 -2 £ § C X 3 3
* > « : I §
C s I E ° A ~ A I
£ .1 1 £ ~-3
X —< I S3 © 3 81 3S m o Ph > x
A' A A q A 7-1 — S' + + A
© 0)^0)© O— 2 te ~ o
“ » 5 w c + £ r1 x > -
m -c xi E A A l t •
-O - X> © X A O u S bC >
*4 £ E o E cj ©5 © A ~ A •— F
U w GS CJ £ rrj > —< r-H T J 4->
3 'S S ® 3 ” ” «
* +-> 4J w A r< _,5^ A< • . JX ex CG
J ai « U ° .. « A G £
© CC o CC W q_( 5 CM O 5
° c s C bt C : O© ^HL 03 TH ° rt
c m •£ 3 fc?
• 2 i-* C /-m C/i AC •’“l -s OS $■"• r O
"S S ~ CG Q 1—1 ro C ix
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•> _ •£ H > g « <=> 3 g A
£ §q w w- - C § CP
% - C + < ° tri £ q © 5 ■” » A
q >h£>h^;>h • - H J ~ eg •- ;» «nW
X be X >-« x O ■ t > c T> w
3 S . g 0 S I S co © 73 > ± + — .2 7c
O K I M - a > s - “ 2 ± :£© -C;Spi
g m £ W A W P- U .£ t y ijC ~ © CO S o
rt W 81 02 < OT S-1 5 sg 3 3 2 s A >s2
q < - <■' “w"N©©t--©^-' 3
r 0 •£<+.-> O ...........,E 3
MgragCPg^CP^^PPgi m pq ± pq g £ O 8 0 £o 2 oOTsooO ? s? « o O x O Z £Z £ £ Z ^5 += Z KrH^ZIziIziZrt^ k>K>K> k> k> k> K> K> <-<
U
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2 00 O O CO co t- t-' CM rf
& Q t- t- 00 t- 00 r- t> Ti< CM
A © t- r- t- t- t- c- i~ oo ©?
rr, hj us us us u: us minus’-;
^02 SJ N N N iSJ NN N O
CM CM CM CM CM CMCMCMCO
T2
CSrHTH^ m - -
3 a o’"
‘S ®
ajZ
132
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 a. Radio Receivers BC-3 12- (♦) , BC-312-(*)X and BC-342-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model. Ref. I Quan.in I Signal Corps ~ TT 7~ ~ ~----
No. Equip. Stock Number Name and Description of Part Function Signal Corps
_____________ _____________ _________________________________ _____________ Drawing No. 1___________3G1921________TERMINAL ASSEMBLY; (insulators.)_For leads through SC-D-2538
mounting shelf
o 2Z6931/21 LOCKSCREW AND NUT ASSEMBLY; Secures panel to box SC-D-2532
panel lock, medium straight knurled head 11/16" long, 5/8" dia., for 3/16" panel. 1 2Z1650/42 SHAFT; switch, steel, 10 ¥2" long. Removable band switch SC-D-5431-42
shaft
1 2Z1650/17.2 SPRING; music wire. For switch detent SC-D-5431-6
plunger
I SzJXt! raUSic Wire- For anti-backlash gears SC-D-5431-14
1650/7.4 SPRING, music wire. For tuning capacitor SC-D-5431-36
worm gear
BALL; steel, 0.21875" dia. For switch detent SC-D-5431-94
1 6L6632-9.10 SCREW; brass, tapered, slotted flat fillister Secure dial & shutter SC-D-5431-4
head. shaft
1 6L7949-4.89S SCREW; steel, headless pilot point setscrew. Secure band switch SC-D-5431-85
wafer shaft
2Z8762.2 SOCKET; octal, 8 “cinch” type contacts, Vacuum tubes sockets SC-D-2538-63
phosphor bronze silver plated, complete with #4 nickel plated beryllium copper retaining ring.
1 2C8795.il SOCKET; 8 prong octal with mounting plate. VT-97 tube socket SC-D-1612-24
1 6L50514-1 ____WASHER; fiber, gray vulcan ¥2" OP._ Spacer SC-D-2550-61
133
40
SIGNAL CORPS
TM 11-850
b. Radio Receivers BC-314-(*) and BC-344-(*).—
NOTE: Unless otherwise indicated, parts as listed apply to all equipments covered by this manual.
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan.in Signal Corps Name and Description of Part Function Signal Corps
No. Equip. Stock Number H Drawing No.
Ct 1 3D293 CAPACITOR CA-293; variable, air, 10-210 Antenna alignment SC-A-2580
ppi, isolantite base, overall length 3-9/16" x -1-9/32" high, plates, studs, and shaft silver plated.
C<> 16 3D290 CAPACITOR CA-290; variable, air, 4-50 ppi, Band D trimmer, 1st r-f SC-A-1728
14 plates, 0.008" minimum spacing between rotor and stator plates, isolantite base, overall length 136", screwdriver adjustment, special contact spider, plates and wiper contacts silver or nickel plated, all other parts nickel plated. (Same as C3, C4, C5, Cu, C12, C]3, Co9, Co], Co2, C23, C24, Co-,, C2G,
and C27.)
C3 — — CAPACITOR CA-290; (Same as C2.) Band C trimmer, 1st r-f —
C4 — — CAPACITOR CA-290; (Same as C._>.) Band B trimmer, 1st r-f —
C- — — CAPACITOR CA-290; (Same as C2.) Band A trimmer, 1st r-f —
CG 9 3D277 CAPACITOR CA-277; fixed, 0.1 pi ±10%, R-F oscillator plate SC-D-1995
400 v. d.c. working, paper, pigtail leads. bypass (Same as C13, C37, C3f), C63, C72,
C73, C7G, and C81.)
— 1 3D340 CAPACITOR CA-340; variable, air, 13-256 Tuning gang SC-D-2568
* ppi, 4 sections. (C7, ClB, C4S, and C67.)
134
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-C*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-3 14-(*) and BC-344-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan, in Signal Corps ,T , _
No. Equip. Stock Number Name and Description of Part Function ”lgna* ^PS
-----------______________ _______________________________ Drawing No. —________________________One section of CA-340; (See preceding item.) 1st r-f tuning
3 3D255 CAPACITOR CA-255; fixed, 3 section, each SC-D-512
0.1 /xf -f-14% —6%, 400 v. d.c. working, paper, oil impregnated, 3 terminals, metal case. (C8, C9, and C10; C17, C18, and C19;
C18> C49, and C50.)
One section of CA-255; ( See preceding item.) 1st r-f cathode bypass —
One section of CA-255; (Same as C8.) 1st r-f screen bypass —
Cio ~ — °ne section of CA-255; (Same as C8.) 1st r-f “B” supply —
_ bypass
11 CAPACITOR CA-290; (Same as C2.) Band C trimmer, 2d r-f —
12 CAPACITOR CA-290; (Same as C2.) Band B trimmer, 2d r-f —
13 CAPACITOR CA-290; (Same as C.>.) Band A trimmer, 2d r-f _
CAPACITOR CA-290; (Same as C.,.) Band D trimmer, 2d r-f _
£15 ~ ~ CAPACITOR CA-277; (Same as C(i.) 2d r-f A VC bypass —
~ — One section of CA-340; (Same as C7.) 2d r-f tuning _
One section of CA-255; (Same as C8.) 2d r-f cathode bypass ____
~ ~ One section of CA-255; (Same as Cs.) 2d r-f screen bypass —
One section of CA-255; (Same as C8.) 2d r-f “B” supply bypass _
CAPACITOR CA-290; (Same as C2.) Band C trimmer, 1st ____
detector
21 CAPACITOR CA-290; (Same as C2.) Band B trimmer, 1st __
_______________________________________________ • detector
135
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d) —
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan, in Signal Corps Name and Description of Part Function n™ vLS°T
No. Equip. Stock Number Drawing No.
Co., — — CAPACITOR CA-290; (Same as C2.) Band A trimmer, 1st
detector
C23 — — CAPACITOR CA-290; (Same as C2.) Band D trimmer, r-f —
oscillator
C24 — — CAPACITOR CA-290; (Same as C2.) Band C trimmer, r-f —
oscillator
CgB — — CAPACITOR CA-290;- (Same as C2.) Band B trimmer, r-f —
oscillator
Co« •— — CAPACITOR CA-290; (Same as C2.) Band A trimmer, r-f —
oscillator
Co7 — — CAPACITOR CA-290; (Same as C2.) Band D trimmer, 1st —
detector
C28 1 3D348 CAPACITOR CA-348; fixed, 2500 yyf ±2%, Band D padder, r-f SC-D-1993
400 v. d.c. working, silver mica, pigtail leads. oscillator C29 1 3D347 CAPACITOR CA-347; fixed, 2000 yyf ±2%, Band C padder, r-f SC-D-1993
400 v. d.c. working, silver mica, pigtail leads. oscillator C30 2 3D346 CAPACITOR CA-346; fixed, 900 ±2%, Band B padder, r-f SC-D-1993
400 v. d.c. working, silver mica, pigtail leads. oscillator
(Same as C82.)
C3i 1 3D345 CAPACITOR CA-345; fixed, 800 yuf ±2%, Band A padder, r-f SC-D-1993
400 v. d.c. working, silver mica, pigtail leads. oscillator
136
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d) — Order replacement parts by stock number, name and description, and receiver model. Ref. Quan.in Signal Corps Q. .
No. Equip. Stock Number Name and description of Part Function signal Corps
___________________________ ___________________ _____________ Drawing No.
f t_________________CAPACITOR CA-344; fixed, 400 nA ±2%, '
400 v. d.c. working, silver mica, pigtail leads.
I (Same as C34, C3G, C40, and C41.) (Except
BC-314 and BC-344.) (1st detector i-f tuning SC-D-1993
f CAPACITOR CA-343; fixed, 125 nA, 400
v. d.c. working, mica. (Used in BC-314 and BC-344 only.) f t CAPACITOR CA-371; fixed, 0.01 A ±10%, D RL-D-6222
450 v. d.c. working, mica, 1 between centers of mounting holes, rigid pigtail leads. (Same as C35, C42, and C43.) (Except BC-
C33 ) ol4, BC-314-G, BC-344, and BC-344-D.) (1st detector bypass
t CAPACITOR CA-281; fixed, 0.01 A ±10%, SC-D-1995
400 v. d.c. working, paper, pigtail leads. (Used in BC-314, BC-314-G, BC-344, and
BC-344-D.)
f t CAPACITOR CA-344; (Same as C3.>.) (Ex- )
cept BC-314 and BC-344.) ^.34 4 1 CA.PACITOR CA-342; fixed, 100 nA ±2%, .1st detector i-f primary _
. 400 v. d.c. working, silver mica, pigtail tuning
_______I______[____________ leads. (U^ed in EC-314 and BC-344 only.) tp_____z ■
137
'art of an assembly, not a replaceable pan
™ H-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d) —
Order replacement parts by stock number, name and description, and receiver mi
odel.
Nt Nam. and Description of Part pFFF
f t * CAPACITOR CA-371; (Same as C33.) 1
C35 ( f CAPACITOR CA-281; (Same as C33.) (Used (1st detector plate bypass —
( in BC-314, BC-314-G, BC-344 and BC-344D.) J
C36 — t CAPACITOR CA-344; (Same as C32.) 1st i-f tuning —
C37 — t CAPACITOR CA-277; (Same as C(i.) 1st i-f “B” supply —
bypass
f f CAPACITOR CA-372; fixed, 1000 wrf ±2%, 1
250 v. d.c. working, silver mica, pigtail
C38 — ■ leads. (Except BC-314 and BC-344.) >lst i-f coupling SC-D-1993
t CAPACITOR CA-352; fixed, 1000 wf ±2%,
400 v. d.c. working, mica. (Used in BC-314
and BC-344 only.)
C39 — t CAPACITOR CA-277; (Same as C(i.) 2d i-f AVC bypass —
C40 — t CAPACITOR CA-344; (Same as C32.) 2d i-f secondary tuning —
C41 — t CAPACITOR CA-344; (Same as C3.,.) 2d i-f primary tuning —
C42 — t CAPACITOR CA-371 or CAPACITOR CA- 2d i-f plate bypass —
281; (Same as C33.)
C43 — — CAPACITOR CA-371 or CAPACITOR CA- 2d a-f grid coupling —
281; (Same as C33.) C44 1 3D?79 CAPACITOR CA-279; fixed, 10 wzf +14% C-w oscillator coupling SC-D-1993
—6%, 300 v. d.c. working, mica, pigtail leads.
(Use to replace Erie type NPO-K, 10 wzf + 14% —6%, 300 v. d.c. working, in BC-314-E and BC-314-F.) ______________________________________________
part.
fPart of an assembly* not a replaceable
138
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(♦) (Cont’d) ._
_____________Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan, in Signal Corps ~ ~ ---------------
No. Equip. Stock Number Name and Description of Part Function Signal Corps
--------- -----------------— —-------------------------- • Drawing No. C45------1 3D350-------CA«tG™nR CA’350; fixed’ 25---+ 14% AVC diode coupling SC-D-1993
—b%, 300 v. d.c. working, mica, pigtail leads.
(Use to replace Erie type N400K, 20 MMf,
+ 14% —6%, 300 v. d.c. working, in BC-314-
E and BC-314-F.)
p46 ~ ~Q One section of CA-340; (Same as C7.) 1st detector tuning
47 CA-349; fixed, 150 +14% 1st detector coupling to SC-D-1993
—6%, 250 v. d.c. working, mica, pigtail leads. r-f oscillator
48 ~ One section of CA-255; (Same as C8.) 1st detector cathode —
r . bypass
49 ~ One sectlon of CA-255; (Same as C8.) 1st detector screen —
P bypass
50 “ One section of CA-255; (Same as C8.) 1st detector “B” supply _
1 ononn bypass
~ 1 3D339 CAPACITOR CA-339; fixed, 3 section, each - SC-D-2567
0.1 nf +14% —6%, 400 v. d.c. working, paper, oil impregnated, 3 terminals, metal case, 1.738" long, 1-9/16" high, 9/16" wide, one mounting bracket at side and other at
front. (C51, C52, and C53.)
r51 One sectl0n of CA-339; (See preceding item.) 1st i-f cathode bypass _
p52 ~ “ °ne section of CA-339; (Same as C51.) 1st i-f screen bypass -
53 “ One sectlon of CA-339; (Same as C51.) 1st i-f “B” supply _
bypass
139
140
TM 11-850
40 SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. No.' Quan.in sToc^Number Name and Description of Part Function Drgawing°No!
— 2 3D338 CAPACITOR CA-338; fixed, 3 section, each SC-D-2567
0.1 pi +14% —6%, 400 v. d.c. working, paper, oil impregnated, 3 terminals, metal case 1.738" long, 1-9/16" high, 9/16" wide, mounting brackets at right angles. (C34,
C,)5, and C36; C37, C38, and 39.)
C34 — — One section of CA-338; (See preceding item.) 2d i-f cathode bypass —
C33 — — One section of CA-338; (Same as C34.) 2d i-f screen bypass —
C3(i — — One section of CA-338; (Same as C34.) 2d i-f “B” supply bypass —
C37 — — One section of CA-338; (Same as C54.) 1st audio “B” supply —
bypass
C.-,8 — — One section of CA-338; (Same as C54.) 1st audio cathode bypass —
C59 — — One section of CA-338; (Same as C54.) AVC bypass —
C60 1 3D275 CAPACITOR CA-275; fixed, 4 pi +14% 2d audio cathode bypass SC-D-512
—6%, 50 v. d.c. working, paper, 2 terminals, sealed in metal case 2" long, 2" high, 1" wide, 2%" between centers of mounting brackets. — 1 3D276 CAPACITOR CA-276; fixed, 3 section, each SC-D-512
0.1 pi +14% —6%, 400 v. d.c. working, paper, 3 terminals, metal case 1-27/32" long, 1" wide, 13/16" high, 2%" between centers of mounting brackets. (C64, C62 and C63.)
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BO344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Ref. Equip. Signal Corps XT TT ’ ~———————— _ -----
No. Quan.in Stock Number Name and Description of Part Function Signal CoLps
----------- --------- ----------------------- ------------------------------------ Drawing No. C4 CAPACITOR CA-281; (Same as C33.) 1st audio grid coupling —
D351 CAPACITOR CA-351; variable, air, 30 Selectivity control SC-A-2634
max., silver plated. (Used in BC-314 and
BC-344 only.)
^80 1 3D297 CAPACITOR CA-297; fixed, 1600 /z/zf ±2%, 2d det. a-f bypass SC-D-1993
250 v. d.c. working, silver mica, pigtail leads. ^81 CAPACITOR CA-277; (Same as C6.) 2d r-f “B” supply bypass _
82 CAPACITOR CA-346; (Same as C30.) C-w oscillator tuning __
88 CAPACITOR CA-341; (Same as C77.) 2d r-f band A tuning ____
^84 CAPACITOR CA-341; (Same as C77.) 1st detector band A __
tuning
^85 CAPACITOR CA-341; (Same as C77.) Except 2d r-f band D tuning _
BC-344.)
C8« CAPACITOR CA-341; (Same as C77.) Except 1st detector band D __
BC-344.) tuning
1 3D329 CAPACITOR CA-329; fixed, 2 section, each SC-A-1490
8 /zf, 450 v. d.c. working, electrolytic.
C85 ~ “ One section of CA-329. (Used in BC-344 only.) “B” supply filter, RA-20 —
(See preceding item.)
c86 — — One section of CA-329. (Same as C85.) (Used “B” supply filter, RA-20 —
in BC-344 only.)
C89 — — One section of CA-329; (Same as C85.) (BC- “B” supply filter, RA-20 —
344-D only.)
C9O ~ ~ One section of CA-329; (Same as C85.) (Used “B” supply filter, RA-20 —
in BC-344-D only.)
594330 0—44-----10
143
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).—
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. co co o> CM CO CO t- oo co 7 l|77 I Q 1 1 Q Q 1 d do C/2 C/2 (72
Function C © £ o © rt -*? o 2 .+ £ - g 3 | | o> c« .b >» 8 8 s 73 fa £ 43 o & a O . O .2 + § c2 O O ,-C Q. O 5 2- be o g.g % O fa 03 13 fa © fa1 W fa L • — -rs fa + Q Q , BC-314-(*) AND BC-344-(*) ®? § % CO co o § g o S U" CM * r—4 t'— I-'"” 1 - 1 <7 1 1 eq H to £ H 5 9 1 1 Q C ± 2 Q c: T G 0 6 s O S ' 6 k □ S « w £ « **Used in BC-314-G and BC-344-D. " ' • M *Used in BG-314-C, D, E, F. ® y* 00 o
Function ! Q m C I Q C TJ'2'O'QbC _ OJ c c c c c § S S OS J2 42 J2 E CO # O l *7 ^7 *7 T q-, qg CP CJ >> ,, L L r>, •-< qj y> .(j +j 4J 4J w S M 5 .2 J2 “ 1,3 S T! r-f r-f r-f r-f CM CM
Name and Description of Part JACK JK-33-A; phone, 3 circuit type for %" maximum panel, brass sleeve threaded %"-32 threads, complete with brass nut, pin, washer, ring, locating plate and 2 beryllium copper contacts, cadmium plated. (Same as J4.) JACK JK-33-A; (Same as J3.) JACK JK-34-A; (Same as Jv) First r-f unit assembly consisting of: 5 terminal board assemblies; 2 gang switch sections, 4 CAPACITORS CA-290 (C..-C-), C7, Lp-Lp COIL C-310 COIL C-309 COIL C-308 COIL C-307 Second r-f unit assembly, consisting of: 7 terminal board assemblies, 2 gang switch sections, 4 CAPACITORS CA-290 (C11-C14), ^ir>» c37, c76, c85, l5-l12, r7. TRANSFORMER C-306.
Signal Corps Stock Number r cm 22 C73, C78, C81, C84, Csf(, L13-L2(; r". 621251-501
7 I 1 3C1083A-11 TRANSFORMER C-302 1st detector, band D
1J14 )
L15 i t < 1 3C1083A-10 TRANSFORMER C-301 1st detector, band C
nic> )
L17 t ( 1 3C1083A-9 TRANSFORMER C-300 1st detector, band B
^18 ) .
Lt <> )
t ( 1 3C1083A-8 TRANSFORMER C-299 1st detector, band A
__ । (*¥2C4314G/A1 | R-f oscillator unit assembly consisting of: R-f oscillator tuning SC-D-2710 ( *2C4314F.1/A4 J 3 terminal strips, 2 gang switch sections, unit Farn., 2700-39
4 CAPACITORS CA-290 (C.,3-C.M5), C.,8-C31, RCA, P-
L21-L28. " “ ’ 722223-501
**Used
*Used
in BC-314-G and BC-344-D. in BC-314-C, D, E, F.
146
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*)» BC-314-(*) AND BC-344-(*)
147
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model. Ref. Quan.in Signal Corps KT . _ ’ ~7~ ~ ~ ~ ----
No. Equip. Stock Number Name and Description of Part Function Signal Corps
--------------------------------------------- ------- Drawing No. U. I 1 3C1083A-15 TRANSFORMER C-298.--------R.f oscillator, band D
L.„, | <
l" ' 1 3C1083A.14 TRANSFORMER C-297. R.f oscillator, band C •
L.;’ { 1 3C1083A-13 TRANSFORMER C-296. R-f oscillator, band B '
L... )
L-s | 1 3C1083A-12 TRANSFORMER C-295. R.f oscillator, band A '
L „ ) c
L3ft ( 1 2Z9892 TRANSFORMER C-292; assembly consisting 1st detector transformer SC-D-4171 J
of: coil assembly and 2 core and stud assem- Farn., C-292
blies, C32-C35, R17, R1S. (Use to replace RCA TX- >
TRANSFORMER C-232 in BC-314 and BC- 261945 506 5
344.) ’ ' C
Lai 1 2Z9893 TRANSFORMER C-293; assembly consisting 1st i-f transformer SC-D-4171 ?
of: coil assembly, core and stud assembly, Farn C-293
and mounting strip assembly, C3(!-C3!„ Rp RCA’TX- t
R51. (Use to replace TRANSFORMER C-
L > 233 in BC-314 and BC-344.)-
L^“ ( 1 2Z9894 TRANSFORMER C-294; assembly consisting 2d i-f transformer SC-D-4171
of: coil assembly, core and stud assembly, Farn. C-294
and mounting strip assembly, C40-C4„. (Use RCA TX-
to replace TRANSFORMER C-234 in BC- 261945-505
______ | 314 and BC-344.)
TM 11-850
40
SIGNAL CORPS
Signal Corps Drawing No. LO lO , i oc o S o o o o 2 2 , £ o S £ SC Y o Q < Q 1 Q Q Q Q O O Q O fc, P4 t/2 <72 W <72 m <72 m
i, and receiver model. Function C-w oscillator Rectifier filter choke Antenna circuit overvoltage protection Dial illumination Dial illumination 2d i-f grid input 1st r-f cathode bias 1st r-f screen bleeder 1st r-f screen divider
idio Receivers BC-3I4-(*) and BC-344-(*) (Cont’d) — Order replacement parts by stock number, name and description Name and Description of Part COIL assembly. COIL C-227; filter choke, 14.5 henry choke coil. (Used in BC-344 and BC-344-D only.) LAMP; neon, assembly. LAMP LM-27; miniature bayonet base, 6.3 V. 0.25 amp. G. E. type #44. LAMP LM-27; (Same as LM2.) RESISTOR RS-161; fixed, composition, insulated, 1 megohm, ±10%, 36 watt, %" long, 36" dia., pigtail leads. RESISTOR RS-166; fixed, wire-wound, insulated, 350, ohm, ±10%, 1 watt, 1" x %" x 36", pigtail leads. (Same as R8.) RESISTOR RS-141; fixed, composition, insulted, 75,000 ohm, ±10%, 36 watt, %" long, 34" dia., pigtail leads. (Same as R9, R45.) RESISTOR RS-149; fixed, composition, insulated, 40,000 ohm, ±10%, 36 watt, %" long, 34" dia., pigtail leads. (Same as R10, R21, )
Signal Corps Stock Number IO CO t— CO Cl t- Cl CM CO -r 'T t- cm oo ci. i io io io CM CM U5 IO | ■M’ Tf O O N N N N N CM CO CM CM CO CO co
ci Quan.in Equip. t-H 1—1 rd CM | [ CM CO
Par. 40 Ref. No. n co S § § w ci co ■* ►4 kl « Pi «
fPart of an assembly, not a replaceable
148
TM 11-850
RADIO RECEIVERS BC-312-C), BC-312-(*)X, 40
BC-342-(*>, BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).—
Order replacement parts by stock number, name and description, and receiver model.
y M O O
l! 4 I I I l i i
E " ±
02 CP O C£-
S- •> RS 'O 70
d 47 . -cc • o> •r*
C+J a 5c 47
•2 « a I ,) 5 S g
= B . r 5 2 s § «
U ffl
72 72 ~
,. A A a
M 02 t t: ’r: ~ ~
CM CM CM CM CM
'3 L" E * S d ~S «
gOW » § « « 2 & M 73 72
•S ~ - -E „ O - ~ O CD
E + pi _r * - ® c~ 3 c Ld ±
U § Ph .2 X5 «S B # B
« 75 - 05 ■J7 p, „ 7t<
a, •-. £ cC .■*!“» o> 7 ' ■'* _ co
2 m £ a »
2 £+1* —(r-lr-l’-HXr-f-'J'
E * g 2- PiP4PiPitt^«u
5 o' r 2 - tD ” 2 -a P4P4PSPiPi>Pim
z 22.2 g 2 d T o o oooooeo-
a cs >- pi g ci > pi cay o^MWMMaHsam
«Pi Pi Pi Pi Pi cs
u 72 0) a xj S E
rt _
c o U5 t?-
bC V 7 CM (£>
“O 3 a I I II I I
co CO CO
.E • "” —— _
0" n । । ।
cr
&£ >-. •-- .- -Z C-. 2 =
Pi Pi Pi Pi Pi Pi
149
TM 11-850
40
SIGNAL CORPS
150
Par, 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. Ref. Quan, in Signal Corps Name d Descri tion of Part Function Signal Corps
No. Equip. Stock Number H Drawing No.
R12 — — RESISTOR RS-150; (Same as R-.) 1st detector AVC filter
R13 1 3Z4539 RESISTOR RS-139; fixed, composition, insul- R-f oscillator plate SC-D-970
ated, 30,000 ohm, ±10%, 1 watt, %" long, d.opping 9/32" dia., pigtail leads.
R14 1 3Z4568 RESISTOR RS-168; fixed, composition, insul- 1st detector injector SC-D-970
ated, 50,000 ohm, ±10%, 34 watt, %" long, grid input 34" dia., pigtail leads.
Rl5 3 3Z4564 RESISTOR RS-164; fixed, wire-wound, in- 1st detector cathode bias SC-D-970
sulated, 500 ohm, ±10%, 1 watt, 1" x %"
x 34", pigtail leads. (Same as R]0, R24-)
R1(i 2 3Z4540 RESISTOR RS-140; fixed, composition, insul- 1st detector screen SC-D-970
ated, 30,000 ohm, ±10%, 34 watt, %" long, divider 34" dia., pigtail leads. (Same as R53.) R17 — f RESISTOR RS-125; (Same as Ro.) 1st detector “B” supply —
filter
R18 — t RESISTOR RS-150; (Same as R5.) 1st i-f AVC filter ’ —
Rl9 — — RESISTOR RS-164; (Same as R15.) 1st i-f cathode bias —
R20 2 3Z4563 RESISTOR RS-163; fixed, composition, insul- 1st i-f screen bleeder SC-D-970
ated, 60,000 ohm, ±10%, l’watt, %" long,
9/32" dia., pigtail leads. (Same as R25.)
R21 — —- RESISTOR RS-149; (Same as R4.) 1st i-f screen divider —
R22 — — RESISTOR RS-125; (Same as R6.) 1st i-f “B” supply filter —
fPart of an assembly, not a replaceable part.
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d)._
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan.in Signal Corps M _ q.„naj
No. Equip. Stock Number Name and Description of Part Function ??gna? „
R23 — — RESISTOR RS-150; (Same as R5.) 2d i-f AVC filter _
R->4 RESISTOR RS-164; (Same as R4.-,.) 2d i-f cathode bias —
R-’"’ RESISTOR RS-163; (Same as R20.) 2d i-f screen bleeder —
26 RESISTOR RS-149; (Same as R4.) 2d i-f screen divider —
R27 — — RESISTOR RS-125; (Same as RG.) 2d i-f “B” supply filter —
R2k 2 3Z4531 RESISTOR RS-131; fixed, composition, insul- 2d detector diode output SC-D-970
ated, 50,000 ohm, ±10%, 3a watt, %" long,
34" dia., pigtail leads. (Same as R3S.)
— 1 2Z7289 POTENTIOMETER RS-174; dual-section, 1 '
watt.
R-‘‘)
R32 1 3Z4561 RESISTOR RS-161; fixed, composition, insul- Diode AVC input SC-D-970
ated, 1 megohm, ±10%, % watt, %" long,
____________________________3s" diaM pigtail leads.
151
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344- (*) (Cont'd) .■—
Order replacement parts by stock number, name and description, and receiver model.
No.' ^quip" sToTNumber____________Name and Description of Part Function Dr^win^Nm
R33 2 3Z4623 RESISTOR RS-223; fixed, wire-wound, insul- 2d audio cathode bias SC-D-970
ated, 2000 ohm, ±10%, 1 watt, 1" x %" x
Vs", pigtail leads. (Same as R52.)
R34 — — RESISTOR RS-162; (Same as R31.) 1st audio grid —
R35 — — RESISTOR RS-162; (Same as R31.) (Except 2d audio grid —
BC-314-G and BC-344-D.)
R35 — —- RESISTOR RS-131; (Same as R.,8.) (Used in 2d audio grid —
BC-314-G and BC-344-D.)
R33 — — RESISTOR RS-162; (Sarpe as R31.) C-w oscillator plate
R37 1 3Z4571 RESISTOR RS-171; fixed, wire-wound, insul- 1st audio cathode bias SC-D-970
ated, 750 ohm, ±10%, 1 watt, 1" x %" x
pigtail leads.
R38 — — RESISTOR RS-131; (Same as R28.) R-f oscillator grid —
R39 1 3Z4548 RESISTOR RS-148; fixed, composition, insul- C-w oscillator grid leak SC-D-970
ated, 200,000 ohm, ±10%, % watt, %" long,
14’" dia., pigtail leads.
R40 3Z4620 RESISTOR RS-220; fixed, composition, insul- Bleeder, RA-20 SC-D-970
ated, 65,000 ohm, 2 watts. (Used only in
BC-344-D.)
Rjo 3Z4578 RESISTOR RS-178; metal encased, 12 ohm, Heater
15 watt, 14 volt. (Used only in BC-344.)
R4i — RESISTOR RS-178; (Same as R40.) (Used Heater
only in BC-344.)
152
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*>, BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(♦) (Cont’d).—
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. SC-D-970 s i r । । 6 d W2 c/2
Function Heater Filament voltage equilizer 4 (Cathode bias voltage divider (1st detector screen 1 bleeder J L1() shunt L12 shunt Lls shunt
Name and Description of Part RESISTOR RS-178; (Same as R40.) (Used only in BC-344.) RESISTOR RS-176; fixed, composition, insulated, 60 ohm, ±10%, 36 watt, %" long, 34" dia., pigtail leads. RESISTOR RS-111: fixed. cnmnnRition insiil- ated, 100,000 ohm, ±10%, 1 watt, %" long, 9/32" dia., pigtail leads. (Used in all receivers except BC-314, BC-344.) RESISTOR RS-150; (Same as R5.) (Used only in BC-314, BC-344.) RESISTOR RS-141; (Same as R3.) (Used in all receivers except BC-314, BC-344.) RESISTOR RS-150; (Same as R-.) (Used in BC-314, BC-344.) RESISTOR RS-221; fixed, composition, insulated, 75,000 ohm, ±10%, 36 watt, %" long, 11/64" dia., (Used in BC-314, BC-344 only.) RESISTOR RS-221; Same as R4(!.) (Used in BC-314, BC-344 only.) RESISTOR RS-168; (Same as R14.) (Used in BC-314, BC-344 only.)
Signal Corps Stock Number CC> rH I io m 1 T* Tj< N N co co , — 3Z4621
Quan, in Equip. TH tH |
Ref. No. of pT pT pT pT
153
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).
Order replacement parts by stock number, name and description, and receiver model.
Ref. Quan.inl Signal Corps NT , . .. _ _ x Qi«nalCnms
No. Equip. Stock Number Name and Description of Part Function Drawing No
R49 — RESISTOR RS-168; (Same as R14.) (Used in L.,o shunt _
BC-314, BC-344 only.)
R50 — RESISTOR RS-168; (Same as R14.) (Used in L3() shunt _
BC-314, BC-344 only.) R51 t RESISTOR RS-131; (Same as R28.) 1st i-f transformer —
shunt
^52 RESISTOR RS-223; (Same as R33.) 2d audio cathode bias —
^53 RESISTOR RS-140; (Same as R](i.) 1st detector screen —
divider
R54 — — RESISTOR RS-220; (Same as R40.) (Used in Bleeder, RA-20 _
BC-344 only.) RA 2Z7512 RECTIFIER RA-20; complete a-c power sup- Power supply SC-D-1609
ply, 110-120 v. 60-cycle input, 250 v. d.c. at 95 milliamperes output, two 12 v. a.c. filament supplies, contains power transformer filter choke, electrolytic condenser, ON-OFF switch, fuse and holder, input plug, bleeder resistor, terminal board, and tube socket.
(Used only in BC-344-(*).) 1 2Z7613 RELAY BK-13; closes at 8.5 v. when mount- Send-receive relay SC-D-1942
ed in a vertical position, 60 ohms d-c resistance, coil consists of 2100 turns AWG #32 silk enamelled wire, 25 layers wound on iron core.
fPart of an assembly, not a replaceable part.
154
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-C*), BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344- (*) (Cont’d).—.
Order replacement parts by stock number, name and description, and receiver model.
Signal Corps Drawing No. SC-D-2592 SC-D-1610 SC-A-1042 SC-D-4046-2
r-f r-f 1 r-f r-f r-f
fl o *> *2 । . 4J 75
on fl Q “ w tn » H w 03 ^H w q cT s2 £ —< 75 to P , ceramic “X” type olate. (Sa 7, SW8, S w2.) W.,.) Wo.) W2.) Wo.)
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g -f? A ° o 5 05 03 °s 03
and 94; C x £ £ 8 X M O , *> IO © l> 33 02 C - C/2 ctS « A fl A 03 E g 02 02 02 02 02 to 4J cs . ‘O’—'
H w © > H; ro br; SW H; H; H; H; H;
a 03 ►—x O o > O « 75 - o o O o o
OCX cont dia., per ONb (*) & o 5 £ 8 > & a kJ kJ kJ k; £ 'S fl (Z2 £
02 o C/2 02 02 C/2 02 02 C/2
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fa o fa fa fa
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c © ° s E > © E C © 3 ® + 0 3 a fa t> © - ° X 3 >; fa 3 Q o ;> cj । o bJC
cription of Part 18; power transfo :le primary; 700 100 milliampere, s 5 volt ±2%%, 3 12.5 volt, 2 am ply 12.5 volt ±5 >344-(*)). ; 2.3 amperes, 14 is at 111° F. (Us ) 1; 1.15 amperes 3d, opens at 109 C-344 only.) otor), carbon, wit _ . - fa fa c + O § 7 ® ® 3 B m O © Q . fa fa — M © fa 7 g -fa 77 © °? £ q B 2 g 7 fa £ s tn t co 3 bjr; — "a tn A fa fa S fa fa fa
a> © Q C-2S ) eye ped, eater fa 3 pq fa ® 2? i r .s w ° § 7 © pq e fa fa 3 w u 2 oo q F .E fa x fa fa b w S 1 Mh r- •£ rH CG < fa
Name anc SFORMER 20 volt, 6( center tap ; rectifier h 3 © — W ’fa fa m fa 7 a © fa 3 © fa tn co ^ © © O 1 © x h © ° © L • O X? - r? £ 0) X r-fa .2 b S 3 S >> CO 7 6 x < g pp g H F a w © c s O c — S . fa tc fa ® 3 | fa 5® O 7 o’SF "t3 X .S + .&? fal o Q Z < 7 bO’
7 •-6 a fa £ 7 « 42 £ w 3 i fa fa a * C
< ® © s fa r-l +1 fa S 3 S g o O © c« 3 qq c pq ffi > — fa an 3 fa > c 3
H H H pq pq Q
ax
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s 00 CM T—< 1—' tH Ci
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157
TM 11-850
40
SIGNAL CORPS
Par. 40 b. Radios Receivers BC-314-(*) and BC-344- (*) (Cont’d) — Order replacement parts by stock number, name and description, and receiver model. Nof- QSp"| StXku'XT Name and Description of Part Function
1 2Z8550.1 SHUTTER ASSEMBLY; consists of shutter, To blank out portion of Farn., 98-1573
spur gear and 4 brass rivets. tuning dial not being RCA, MX-
used 243063-501
1 2Z7560/2 PANE; dial, clear glass, 2-39/64" long, 1/16" Dial pane SC-D-2535-13
thick, 2" wide at one end and %" wide at the other end. — 2Z5986 LAMP MOUNTING ASSEMBLY; consisting For dial lamps
of:
1 2Z5986/1 (A) MOUNTING; right hand, for lamp, min- SC-D-2573-1
iature bayonet base.
1 2Z5986/2 (B) MOUNTING; left hand. (Same as above, SC-D-2573-2
except for bracket, which is of opposite
hand.)
3 3Z3275 FUSE MOUNTING; 2-13/32" long, complete Fuse holder SC-D-2532-76
with bright zinc plated nut and. neoprene washer.
1 2Z6702 MOUNTING FT-162; consisting of: 4 alumi- Receiver mounting SC-D-2577
num alloy bases, 4 aluminum alloy mounting supports, 4 steel studs and 4 felt pads; mounted on steel plate, 36" thick, 18" long, 6.906" wide.
1 2C4314G/B2 BRACKET ASSEMBLY; (Except BC-344- Dynamotor mounting SC-D-2532
_________________________(*)•)_________________________________________________________________
158
594330 0—44-----11
159
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. Quan, in 0xig?aLTCorLS Name and Description of Part Function Signal Corps
No. Equip. Stock Number K Drawing No.
1 2Z5650-K JACK COVER ASSEMBLY; consisting of: Key jack SC-D-2532-36
cover, 0.843" x 0.750" x 0.21875", brass cover support, spring and pad; word “KEY” engraved on cover.
1 2Z5650-M JACK COVER ASSEMBLY; (Same as Microphone jack SC-D-2532-37,
2Z5650-K except for word “MICRO” engraved on cover.) 1 2Z5650-S2A JACK COVER ASSEMBLY; (Same as Speaker, 2d audio jack SC-D-2532-38
2Z5650-K except for words “SPEAKER
2ND AUDIO” engraved on cover.)
2 2Z5650-P2A JACK COVER ASSEMBLY; (Same as Phones, 2d audio jack SC-D-2532-39
2Z5650-K except for words “PHONES 2ND
AUDIO” engraved on cover.) 2Z5650-P1A JACK COVER ASSEMBLY; (Same as Phones, 1st audio jack SC-D-2532-40 2Z5650-K except for words “PHONES 1ST
AUDIO” engraved on cover. (Used in BC-
314, BC-314-C, D and BC-344 only.)
1 2Z8794.1/C1 COVER; aluminum die casting, 2-5/8" high, Cover for Socket SO-94 SC-D-2534-6
2-5/32" wide, 1-43/64" deep.
1 3Z510 BINDING POST ASSEMBLY Alternate signal antenna SC-D-2532-71
1 3Z763 BINDING POST ASSEMBLY Ground SC-D-2532-78
1 2C4312/N1 NUT AND FERRULE ASSEMBLY Cable connection for SC-D-2532-13
shielded binding post
TM 11-850
RADIO RECEIVERS BC-312-C*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
TM 11-850
40 SIGNAL CORPS
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).— Order replacement parts by stock number, name and description, and receiver model. M MX Name and Description of Part Function
(2Z5782.1 KNOB, SHAFT, AND PINION ASSEMBLY; ) SC-D-5431
consists of: compression nut, pinion, spring RCA, KX-
washer, knob, shaft, setscrew and standard 381510-501
1 j #6 split-spring washer. (Fast tuning drive
2Z5782.2 FAST TUNING KNOB AND DRIVE AS- Farn., 98-1469
SEMBLY; Same as above except includes eccentric bushing in assembly.
1 2Z5778 KNOB ASSEMBLY; with insert and set- ' OFF-MVC-AVC SC-D-2532-43
screw, arrow engraved on face.
1 2Z5779 KNOB ASSEMBLY; with insert and set- Align input SC-D-2532-44
screw, “ALIGN INPUT” engraved on face.
1 2Z5780 KNOB ASSEMBLY; with insert and set- C-w oscillator SC-D-2561-17
screw, “CW-OSC ADJUST” engraved on adjustment face.
1 2Z5773 KNOB ASSEMBLY; consists of: 1 each knob, Volume control SC-D-2532-45
dial, insert, 3 F. H. machine screws, and 1 #8-32 %" setscrew.
1 2Z5783 KNOB; zinc alloy, die casting, knurled, with Band change SC-D-5431-56
arrow engraved on face, O. D. 1-11/16", 136" overall thickness, 0.1927" wide slot, hub dia. %".
1 2Z5842-5 KNOB; Vernier, assembly. Consisting of: Vernier tuning SC-D-5431-58
aluminum dial, clutch, knob and screw.
1 3G1921-1 INSULATOR ASSEMBLY For leads through r-f SC-D-2553
coil box assembly
160
TM 11-850
RADIO RECEIVERS BC-312-(*), BC-312-(*)X, 40
BC-342-(*), BC-314-(*) AND BC-344-(*)
Par. 40 b. Radio Receivers BC-314-(*) and BC-344-(*) (Cont’d).—
Order replacement parts by stock number, name and description, and receiver model.
No? feZ SMZ Name and Description ~f Part
1 3G1921 TERMINAL ASSEMBLY (insulators) For leads through SC-D-2538 ,
mounting shelf '
5 2Z6931/21 LOCKSCREW AND NUT ASSEMBLY; Secures panel to box SC-D-2532
panel, medium straight knurled head 11/16" long, 5/8" diameter, for 3/16" panel.
1 2Z1650/42 SHAFT; switch, steel, 1036" long. Removable band switch SC-D-5431-42 ।
shaft '
1 2Z1650/17.2 SPRING; music wire. For switch detent SC-D-5431-6
plunger
1 2Z1650/7.3 SPRING; music wire. For anti-backlash gears SC-D-5431-14 >
1 2Z1650/7.4 SPRING; music wire. For tuning capacitor SC-D-5431-46 :
worm gear ,
1 2Z1650/2 BALL; steel, 0.21875" dia. For switch detent SC-D-5431-94
1 6L6632-9.10 SCREW; brass, tapered, slotted flat fillister Secure dial and shutter SC-D-5431-4 ।
head. shaft ;
1 6L7949-4.89S SCREW; steel, headless pilot point setscrew. Secure band switch SC-D-5431-85
wafer shaft.
9 2Z8762.2 SOCKET; octal, 8 “cinch” type contacts, Vacuum tubes sockets SC-D-2538-63
phosphor bronze silver plated, complete with #4 nickel plated beryllium copper retaining ring.
1 2C8795.il SOCKET; 8 prong octal with mounting plate. VT-97 Tube Socket SC-D-1612-24
1 6L50514-1 WASHER; fiber, gray vulcan, 36" OD. Spacer SC-D-2550-61
☆ U. S. GOVERNMENT PRINTING OFFICE 0—1944
161
UNT LIBRARIES DENTON TX 78203 lllllllllllllll 1001899252
jnSo library