Radio Receiver BC-348-E Operations, Maintenance, and Repair Manual
August 21, 2022 | Author: Anonymous | Category: N/A
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A R M Y AIR FORCES TECHNICAL O R D m NO
INSTRUCTION BOOK FOR
OPERATION and MAINTENANCE OF
RADIO RECEIVER BC 348 E RADIO RECEIVER BC 348 M RADIO RECEIVER BC 348 P
RESTRICTED PUBLISHED
Y AUTHORITY
OF THE
FOR
HIEF SIGNAL OEFICER
IRPL
F SERIAL
NE TYPE
No.
December
15
942
08-10-119
ARMY AIR FORCES T E C H N I C A L O R D E R NO. 08 10 119
INSTRUCTION BOOK FOR
OPERATION
nd MAINTENANCE OF
RADIO RECEIVER BC 348 E RADIO RECEIVER BC 348 M RADIO RECEIVER BC 348 P
RESTRI TED NOTICE NOTI CE::-Th This is docume nt contains inform ation aff affecting ecting the national defense of of t he United States within t he me aning of th e Espionage Ac Act, t, 5 0 U. S. S. C., 31 and 32, as amende amended. d. Its transmission transmission or the re revelation velation of its contents in any man ner to a n unauthoriz unauthorized ed person is prohibi prohibited ted by law. AR 380-5 The information containe contained d i n restricted documents and the essential characteristics of restricted material will not be communicated to the public or to the press, but may be given to any person known to be in the service of of t he Unite United d States and t o persons of undoub undoubted ted loyalty and discretion who are cooperating in Government work.
PUBLISH ED BY AUTH O RITY OF
THE CHIEF SIGNAL OFFICER
December 15,
942
RE PO RT OF M JO JOR R F ILUR ILURE E In the event of major failure of any of the component units of this equipment a repo rt shall be submitted in the f or m indicate indicated d be belo low. w. Copies Copi es o off thi s repo rt shall be forwa rded t o th e Chie Chieff of Signal Sec Section tion Air Service Command Patte rson Field Ohio an d to the Director Signal Corps Aircraft Signal Serv Service ice Wr ig ht Fie Field ld Ohio Ohio.. 1
Contract or Order Number.
2
Organization and station.
3. Nomenclature of Equipment. 4. Nomenclature of component unit.
5. Date and nature of failure. 6. Type of of ai rpl ane in which installed. 7
Recommendations.
Digitally signed by Andy (James A.) Moorer DN: CN = Andy (James A.) Moorer, O = Adobe Systems Incorporated, OU = Enterprise Services Reason: I am the author of this document Location: Panacea, Florida, USA Date: 2004.07.28 00:14:01 -04'00'
Destruction of bandoned Materiel in the Combat Zone In case it should become necessary necessary to prevent th e captu re o off t his equipment and when ordered ordered to do so DESTRO DES TROY Y IT SO THAT N NO O PART O F IT C A N BE SALVAGED RECOGNIZE RECOGNIZED D OR USED BY THE ENEMY.
BURN ALL PAPER PAP ER S AND BOO BOOKS KS..
Means 1
Explosives Explosiv es when pr provided. ovided.
2
Hamme rs axes sled sledges ges or whatever heavy heavy object is readily avai availabl lable. e.
3
Burni ng by means of incendiaries such as gasoline oil oil paper or woo wood. d.
4
Grenades and shots from available arms.
5
Whe re po possib ssible le an d when time permits bury all debris or disp dispose ose of of it in str eam s or oth er bodies o off water.
Procedure 1
Obliterate Obliterat e all identifying marks.
Destroy nameplates and circuit labe labels. ls.
2
Demolish all p panel anelss
3.
Destroy all con controls trols switches relays
4
Rip out all wiring in elec electrical trical equipment. systems in gas-engin gas-engine e generators etc.
5.
Sma sh every electric electrical al or mechanica mechanicall pa rt whet her rotating
6
Break up all operating i nst rum ent s such as keys pho phones nes microphones etc.
7
Destroy all classes of car ryi ng cases strap s conta iners etc.
castings switch- and instrument-boards. connect connections ions and meters. Smash gas oil and water coolin cooling g moving or fi fixed xed..
T AB L E OF C ONT E NT S SECTIO N I-GENE I-GENERAL RAL
DES CRIPTIO N
Paragraph 1
2
6 7 9 10 1
Page
GENERAL COMPONENT UNITS CABINET MOU NTING FT.15 FT.154. 4.E. E. FT -15 4-P or FT.154.W P L U G P L - Q 1 0 3 and P L - P I 0 3 CHASSIS PANEL DIAL AN D MASK ASSEMBLY ASSEMBLY LLUMINATION R-FANDOSCILLATORUNITS IL L A T O R A N D CR CR Y S T A L F I L T E R F T R A N S F O R M E R C - W O S C IL
1 1
3 3
3 5 5 5
6 6
8
SECTION 11-EMPLOYMENT 2
NSTALLATION Unpacking Mounting c P o w e r C o n n e c ti ti o n s d T r a n s m i t t e r C o n n e c ti ti o n s e O u t p u t C o n n e c ttii o n s Bonding and Shielding g Mounting of Receiver S a fe f e ty ty W i r e Ground Antenna 13 PREPARATION FOR USE 4 O P E R A TI TI O N Power Switch
12 12 12 12 12 12 12 12 13 13 13
Operating Test Operating Routine
13 14
SECT ION 11 1111-DE DETA TAIILE LED D 5 6 7 8 19 20 1
11 11
11
FUN CTIO NING O F PA RT S
C I R C U I TS TS F R E Q U E N C Y R A N G E A N D F R E Q U E N C Y B A N DS DS NPUTCOUPLING NPUT PROTECTION RADIO FREQUENCY AMPLIFIER FIRST DETECTO R H E T E R O D Y N E O S C IL IL L A T O R
23 IC N Tw E ER ROM EIDLL TTO FREQUENCY AMPLIFIER S CI C LILAATE TEO R
17 17 17 17 17 17 17 l1g8
TABLE OF CONTENT S
Continued)
Paragraph
Page
BA N D - P PA ASS FILT ER 2 4 C R Y S T A L BA
21
25
SECOND DETECTOR AND AUTOMA AT T IC IC V O L U M E C O N T R O L
23
26
OUTPUT
23 23
a Description NoiseCompensator
24 24
7 DYNAMOTOR
BE ES. LAMPS S.. V O L T A G E R E G U L A T O R A N D F U S E 28 CHARACTERISTICS O F TUB
25
SECTION IV-MAINTENANCE 9 INSPECTION NA M O T O OR R 0 C A R E A N D S E R V I C I N G O F D Y NA
27 27
E M O VA VA L O F F R O N T P A N E L 1 R EM
29
2 DIAL AND MASK ASSEMBLY VA AL AND REP LACEM ENT O F DIAL MECHA AN N IS IS M 33 R E M O V LL LATOR UNITS 4 REMOVAL O F ANTENNA R-F DETECTO R AND OSCIL
5 TROUBLE LOCATION AND REMEDY
General EquipmentRequired c W e a k o r N o S i g n al a l s o n A l l B a n d s , M o d u la la t ed ed R e c e p t i o n d W e a k o r N o S i gn g n a ls l s o n A n y B a n d , M o d u la l a t ed e d R e c e pt p t iioo n e W e a k o r N o S ig i g n a ls ls o n A l l B a n d s , C - W R e c e p ti t i o n M o d u l a te t e d R e c e p ttii o n N o r m a l ) M e a s u r e m e n ts ts w i t h T e s t S e t 1 56 C FailureofDialLights h Performance Characteristics
30 31 32 33 33 34 35 39 40 40 44 45
SECTION V-APPENDIX 6 TABLE O F REPLACEABLE PARTS 37 L I S T O F M A N U F A C T U R RE ERS
47 69
LIST O F ILLUSTRATIONS
Page
ig~cre
3
0 12
13
14
15
6 17
r
Radio Receiver Bottoin a nd Back View of Cabinet Mounting Base Plug PL-Ql03 With Terminal Receptacle Disassembled Plug PGP103 With Terminal Receptacle Assembled Chassis. Panel Removed Re Rear ar View. View. Detail of of Precision Dial Mechanism Top View of of Chassis Bottom Bot tom View of Chass Chassis is Plu g and Cab Cable le Connec Connections tions Antennaunit R-F Unit Detectorunit Oscillator Unit Detail of Bleeder Circuit. C-W Oscillator Switching and A-V-C Time Constant Crystal Filter Circuit Load Compensator. Bleeder Circuit and Noise Compensator
2 3 4 4 5 6 7 9 18 19 20 21 22 22 23
18 Dynamot or 9 Bottom View View of of Dynamotor Showing Filte r Open 0 Dynamotor Filter Wiring Diagram
24 28 29
21 Dyn amot or Disassembled 22 Detail of of Tu be Shel Shelff A rrangem ent Looking Th roug h Pane l Opening. Opening. Cover Removed 23 Trouble Locati Location on and Co Corre rrectio ction n Chart Numerals Refer to Pertinent Paragraphs) 4 Cha Chart rt o off Socket an d Dyn amot or Voltages Voltages 25 Interme diate Frequ ency C-W Oscillator Oscillator Coi Coill and Crystal of of Filter Assembly Assembly 6 Rea r View of Chassis 27 Resistor Boards. Fr on t View 8 Resistor Boards. Boards. Rear V View iew 9 Schema tic Diagra m Wiring Diagram 31 Tube Shelf Shelf Wiri ng Diagra m Fo r Exte rna l Connect Connections ions See Fig 30) 32 Antenna Uni Unitt Wiri ng Diagra m See Fig 30) 3 R-F Unit Unit Wiri ng Diagra m See Fig 30) 4 Detecto Detectorr Uni Unitt Wiri ng Diagra m See Fig 30) 5 Oscilla Oscillator tor Unit Unit Wiri ng Diagra m 6 Crysta Crystall Filter Wiring Diagram 7 Wir in g Diagram C-W Oscillator Oscillator Ass Assemb embly ly 8 Drilling Pla n fo r Mountin Mounting g Bas Base e 39 Wiri ng Diagram, Diagram, Intermedi Intermediate ate Freq Frequency uency Transformers 0 Wiri ng D Diagram. iagram. Resistor Boards 41 Detail View Views. s. Top. Pan el an d Botto m 2 Details of Precision Precisi on Dial Mechanism and Mas Mask k Assemb Assembly ly 43 Dimensional View Viewss and Cable Pl ug Detai Details ls
30 33
vii
34
35 6
39 41 41 70 71 72 72 73 73 74 74 75 75 76 77 78 79 80
.
INSTRUCTION BOOK
Pars 1 2
FOR
OPERATION AND MAINTENANCE OF RADIO RECEIVER BC 348 E RADIO RECEIVER BC 348 M RADIO RECEIVER BC 348 P SECTION I GENERAL DESCRIPTION
FIGURE R ADIO RECEIVER RADIO 1. GENERAL
Radio Receiver BC-348-E BC-348-E Radi Radio o Receiver B BCC348-M and Radio Receiver BC-348-P are identical both electrically and mechanically. Each radio receiver is a locally controlled 8 tube 6 band superheterodyne receiver intended for use in U S Army Aircraft and covers the frequency ranges 200 to 500 kilocycles and 1.5 to 18 megacycl mega cycles. es. These receiver receiverss are not intended fo r remote control and no features or units have been provided provi ded for remote opera operation. tion. They are c capabl apable e of voice tone or c-w c-w reception with ma nu nual al or automatic auto matic volume control. When equipped with
tubes dial lights and fuses and with the antenna tubes ground and primary power source connections properly made mad e these receivers become c complete omplete and operative equipments by t he addition o off head head-sets as all coi coils ls and t he high-voltage power supply units are contained contained wi within thin the re receiv ceivers. ers. The total power consumed by these receivers is 56 watts from a 28 volt d-c source.
.
2
OMPONENTUNITS
The following is is a list of the component units of these receivers:
GENER
Par.
Quantity
L DESCRIPTION Dimensions (Inches)
Component
Weight (Lbs.)
11 /4 x 1/4 dia. dia.
Fuse FU-35
Ys x 3/8 dia.
Lamp LM-27, each
x
Mounting (not including plugs PL-PI03 or PL-Q103)
x
Plug PL-PI03 (straight) Plug PL-QlO3 (angle) Radio Receiver Receiver (includi ng Dynamot or and Mounting and equipped with all accessory components except headphones) Tube VT-48
4
x I & dia.
0.08
Tub e VT-65 VT-65
2
x
Tube VT-70
:
li
Eia.
0.06
x IT
ia.
0.09
I & dia.
0.07
1
dia.
0.07
I
dia.
0.07
Tube VT-86, each
3
Tube VT-91
3
Tube VT-93
3Ys x
Voltage Reg., RCA 991
1gCx
x
g
dia.
0.014 Total weight 44.917
FIGURE-BOTTOM FIGURE -BOTTOM
AND
BACKVI W O F CABINET
GENERAL DESCRIPTION
Pars. 3 5
4. MOUNTING FT-154-E FT-154-P or FT-154-W
3. CABINET
The receiver cabin et is of of spot-welded alum-
The moun ting is const ructed of of stainless steel steel
inum construction with black wrinkle finish,
exceptt for the a luminum base which carries the excep
and is embossed on top and back to add rigidity
mounting holes and to which are attached the
and strength. The panel fron t) end allo allows ws the removal of the receiver chassis which runs on
bases of fo ur shock shock absorbers. To the top of the shock absorbers is fasltened the stainless steel
the stainless steel strips mounted in the end
support, which provides for the attachment of
corners of the cabinet.
Two tapped inserts are
the receiver cabinet by by mean s of of st uds an d snap-
placed in the rear to receive the thumb screw
slides. slid es.
rods which secure the chassis in the cabinet.
steel support to facil itat e the engagement of of the
A cutout in the rea r botto bottom m permits the entra nce
studs of of t he cabi net with the mounting.
of Plug PL- PI0 3 or PL-Ql03.
Grooves Grooves are provided in the stainless stainless
An alum inum
casting is mounted over this cutout and acts as a seal between the cabinet and the chass chassis. is. The
5
PLUG PL UG PL -PI 03 AND PL-Q103
bottom of of th e cabinet is reinforced by a stainless
The plug, attached to the mounting by screws,
steel plate to w which hich are attached the fo ur mount-
is provided with eight terminals which are ac-
ing studs for securing the cabinet to mounting.
cessible upon rem oval ova l of of the th e rear rea r cover cove r of the th e
Two snap slides are mounted on the downward
plug housing. housing.
projection projecti on of the fron t of of the stainless stain less steel plate.
straight outlet, becomes Plug PL-Pl03.
The plug, when provided with a A right
GENER
L DESCRIPTION
Pars. 5 8
GENERAL DESCRIPTION angle outlet which may be mo unted so as to joi join n the cable in any of three horizontal posit positions ions to the right left or back of the receive receiverr
may be
used use d wit with h the p plug lug making it Plug PL Q103.
rods secure the chassis in the cabinet and pass through a cutout covered b by y a plate which is Provided to give access to the wiring under the r-f tube shelf for servicing and maintenance. The followi fol lowing ng panel items are mounted on the front
6
of the panel:
CHASSIS
Th e chassis consis consists ts of an alum inum ca sting mounted between two end plates of of sheet aluminum which serve as runners and guides when placing placi ng the dlassis in the cab cabinetinet- The end plat plates es are provided w ith cutouts to facilitate servicing. 7
alignmenit control; dial light rheostat control; tuning control; band switch control; dial wind window ow housing which covers the dial lights; beat frequency control;
filter control; volume
control; AVC-OFF-MVC control; C-W OSC. control; and two telephon telephone e jacks.
PANEL
The front panel is attached to the chassis and to .the fron t end plates by scr screws. ews. Two handles are mounted on the panel.
Antenna and ground binding posts; antenna
Two thumb-screw
8
DIAL A N D M A S SK K ASSEMBLY
The dial and mask assembly is mounted on an aluminum casting which carries the gearing of
Pars
GENERAL DESCRIPTION
8 10
the tuning tuning condenser drive and the detent. detent. This unit is attached to the front panel and connects to the band switch drive shaft throug h a coupling of the Oldham type. The dial is divided into six frequency bands and the dial and tuning condenser are so geared to the tuning control shaft that the tuning condenser covers the frequency range indicated on the dial for each band in approximately
9
revolutions of of the tuning knob.
Splist gearing is used extensively to minimize backlash. A positive stop is provided to prevent undue pressure on the gears and to limit the travel of of the dia l and tun ing condenser. A mask, with suitably located and marked windows, is mounted before the dial. The mask is controlled by the band change switch and is positioned by the sta r detent.
ILLUMIN TION
9
The receiver tuning dial is illuminated by mea ns o off two dial lights
Lam p LM LM-2 -27) 7) whose
brilliancy is controlled by the DIAL LIGHTS rheostat.
Th,i Th,iss rheostat has a n o offf position for
use when the illumination is not desi desired. red.
The
dial lights are located beneath a readily removable housing which which pe rmits the easy replacement of a d ial lamp d urin g fligh flight. t. 10
R F
ND OSCILL OSCILL TOR UNITS
The Th e a anlt nltenna enna,, r-f, 1st detector an d oscillator subassemblie assem bliess ar e moun ted on the right rea r portion of the c chassis. hassis.
Eac h sub-as sembly consists of
the r-f coils, trimmers and band switch wafers
-
Pars 10 11
GENER
L DESCRIPTION
with the necessary fixed fixed capac itors a nd resistors. Passing throug h a l l of these sub-assemblies is the
11. I-F TRANSFORMER TRANS FORMER C-W OSCILLA OSCILLATOR TOR
AND CRYSTAL FILTER
band switch switch drive shaft whic which h is pulled out fro m
These units are mounted on the left front por-
the right en d o off the receiver chassis before a sub-
tion of of the chassis. chassis. Th e variable capacitor of the
assembly assem bly is removed.
c-w oscillator is controlled through a flexible
Three grounding straps are provided for the purpose of of bonding the ante nna unit r-f unit and the oscillator unit cans to the tuning condenser.
shaft terminating in a knob on the front panel.
/
EMPLOYMENT
Par.
2
I1
SECTION
EMPLOYMENT NOTE NO TE-N -No o
a
att emp t a t either mechanical or elec elec--
trical servicing of these receivers should be made except at Signal Co Corps rps Repair Shops and Signal Corps Radio Sec Sections tions or Signal Sections) at Air Depots, unless suitable shop and testing facil facilitie itiess a re availab available le and a uthorit y to repair h as been granted by the Corps Area Signal Offic Officer. er. A stand ard signal generator, a phantom antenna, Test Set I-56-C, and other like equipment should should be used fo r alignment purposess and ins tructions in this boo purpose book k carefully followed. 12
INSTALLATION
Unpacking
Carefully open the packing box a nd remove Carefully the cardboard cartons which it contains. Open each of these cardboard containers; one contains the receiver in its cabinet; the other holds the mounting base assembly. Take the receiver chassis from the metal cabinet and remove the cardboard reinforcing material which is packed around the dynamotor. Clean the receiver of any surplus packing material or dust, replace it within the metal cabinet, and put the cabinet upon the mounting base assembly. b Mounting
important considerations necessary forThe themost successful installation and operation of this receiver are as follows:
The receiver should be mounted on a plane surface with sufficient clearance being alOUTPUT
TRANSMITTER
INTERPHONE IF REQUIRED
T O
R ELA Y
C LO SED FOR R
ECElVlNG
eo MA. MAX.)
ZO D V. F O P
GROUND
I
THESE
AUXILIARY
E Q U I P M E N T WHEN NEEDED BETWEEN Z ~ ~ D i f 5
LEADS NOT TO
F TRAPJSMITTER 15
BE
TO
RECEIVER
OT
T H C PLUG
CONNECT
THESE
TH E S E L E A D S MAY REPLACED BY A
O R e
MAIN
LE ADS J O IIN NED AT B TTERY BUS A N D N O T A T PLUG
T H E S E L E A D S MAY BE R E P L A C E D BY A
SINGLE
CONDUCTOR
CONDUCTOR
POWER. SOURCE
FIGURE0-PLUG FIGURE 0-PLUG
AND
CABLE ONNECTIONS
Par.
2
lowed on all sides to per mit f ree action of the shock absorber mounting. The mounting should be permanently attached to the rigid members memb ers o off th e plane. Th e drilling plan o off the mounting is shown in Section V Figure 38. c Pow Power er Connections The leads to the primary power source are connecte conn ected d as shown in Figure 10. The parallel connected lead from plug terminals 3 and 4 may be replaced by a single conductor of cross section equivalent to the two separate leads. Similar Similarly, ly, the parallel connected leads from plug terminals and 8 may be replaced by a single conducto r of eq uival ent cross sectional area. The power source to which these leads are connected should be 28 volts d-c for this equipment. d
Transmitter Connecti Connections ons Provisions have been made for the protection of of the these se receivers when the associated transmitter is being use used. d. Leads from plug terminals 2 and 6 should be wired to contacts on the transmitter relay. If the transmitter is removed from the installation, or if these recei receivers vers ar e bein being g installed without an associated associated transmitter, the wires wires fr om plug terminals 2 and 6 must be connected together to have the receivers operate. Output Connections
f
Bonding and Shielding At the time of installation of this equipment, care should be taken to insure that t he engine ignition system, generator, and other possible causes o off distu rbanc e are properly shielded and that bonding of of meta l parts is or has been carefully carried out.
g Mounting of Recei Receiver ver When proper wiring connections have been made, place the receiver on its mounting with the st uds on the bottom o off th e cabinet entering the slots of the mounting. See that the cabinet is well down on the mounting and that all four studs are fully seated, then push the cabinet towards the re ar an d secur secure e in place by the snapslides on the lower front corne rs o off the cab inet. h Safety Wire Safety wire should be passed through the holes of of the s napslide assemblies, care being taken that the wires are not twisted too tightly. Ground The ground binding post G should be connected by a short, direct, low resistance lead to some groun ded metal porti on o off t he plane an d soldered at the point, iiff pract icable. The lead should have enough slack to prevent vibration being transmitted to the receiver.
The output of this receiver has been brought to plug terminals and 5 and to the two front-panel jack jacks. s. Leads from thes these e te terr-
The antenna circuit aligning capacitor is
minals should be wired to the interphone system o r as otherwise desired. If the output is desired only at the receiver, it should be taken directly from th e phone ja jacks cks and no connections made to plug terminals 1 and 5. The output transformer has two output impedances available at its terminals. These are terminal 5 for high 4000 ohm) impedance output, or terminal #6 for low 300 ohm) impedance connection. These terminals are marked both with numbers, and with the designation HI and L O on the transforme r terminal board, and a deta detailed iled co connec nnec-tion diagram on the top of of the tra nsfor mer
such that the ante nna circuit can be prop properly erly aligned when using antennas that range in effective capacitance from 50 to 200 micromicro farad s. H'owever, satisf aclt acltor ory y per forma nce wil willl be obtained on practically any type of of mast, fixed, or traili ng wire ante nna , although in extreme cases, that is, very short mast or very long trailing wire, the most favorable setting of the antenna alignment con~trolmay con~trol may no nod be obtained. In general, the most effective antenna is one whose length away from the grounded metal fuselage is the gre greatest. atest. The receiver should b be e located as near as possible to the lead-in in-
shows thatbetween t he green lead o off tthe he audio jack is shifted these terminals according to the output impedance desired.
sulator and connected from Atheby insulator to the antenna binding post a copper wire. The lead should have enough slack
Antenna
EMPLOYMENT to prevent vibration being transmitted to the receiver. r-
13. PREP R TION FOR USE
These receivers are self-contained units, having their high voltage power supply and all coil sets built f oirt eh itnhset arleli liqnugi rtehde tt uu bb ee sc ht heecyk esrh.o uBl de b e c h in. e c k eBd e w
s u re re t h a t t h e p r o p er er t u b e s w e l l p u sh sh e d d o w n a nd nd firmly seated n t h e i r s o c k e t s a r e i n s t a l l e d t h a t t h e t u b e s h i el el d i s p r o p e r l y s e a t e d a n d t h a t g ri ri d c a p s fit t i g h tl tl y o n t h e t u b e s .
Check Che ck d~ial ights an d fuse and see tha t they are properly an d securely placed. Mak Make e sure that the leads to the dynamotor unit ar e properly connected at the dynamotor terminal strip and that the screws holding them in place are tight. Place the receiver AVC-OFF-MVC switch in the MVC position, and the band switch on band 2. By mean s o off the tunin g control, tun e in a signal at approximately 3.4 megacycles, to maximu m signal strength. Reduce volume b by y means of volu me control knob until s ignal is just audible.. Read just the tunin g contr ol to secure any ble dditional increase possible possible.. Adjust the ant enn a alignment control to give maximum volume. 14. OPER TION
a Power Switch Power to the receiver is controlled by the receiver AVCAVC-OF OFFF-MVC MVC switch. Wi th this switch in the OFF position, no power is supplied to the recei receiver. ver. Wh en switched switched to either the MVC or AVC position, power from the primary source is supplied to the tube heaters and dynamotor placing the equipment in operat operation. ion. The screen grid voltage volt age supply leads ar e carried out of the receiver through the power plug to the keying relay o off the assoc associat iated ed transmitter w h e ~ e the circuit is opened when actually transmitting mit ting Refer Refer to Paragr aph 12d).
r
b Operating Test
When the receiver has been completely installed, an operating test should be made as follows 1) Plug a heads et into one o off the jacks
marked TEL. Set receiver switch to MVC. The dyna motor should sta rt and
Pars. 12-14
after the the tubes have warme d up approximately 30 seconds), the volume control knob should be advanced until a slight background noise is heard. Set band switch to the frequency band in which test signals are available. 2) Using the calibrated tuning knob andon with ence to the scale thereferdial, tune in the desired signal. NOTE:-AIZ
t u n i n g s h ou o u l d b e d o n e o n M VC VC w i t h t h e volume control advanced only enough to give the desired signal strength. I n t h e absence of a signal the setting of of th e volu m e c o nntt r ol o l c a n b e ju ju d ggee d b y t h e l o u d n e s s of t h e b a ck c k g r o u n d n o i se se . O n M V C w i t h t h e v o l u m e c o n ttrr o l s et e t aatt m a x i m u m v e r y strong carrier upaves upaves will block the receiver and intelligible signals cannot be received.
3) Set the receiver switch to AV AVC. C. desired signal should still be heard.
The
4) With the beat frequency adjustment at zero beat position arr ow on knob pointing up), turn the c-w oscillator switch to the position ON. An audible beatnote should be heard which should vary in pitch when the beat frequency adjustment is changed.
5) With the c-w oscillator still ON, throw
the crystal filter switch to IN. Noise should be greatly reduced and the signal can be tuned o ut by a much s malle r mo movevement of the tuning control knob than when the crystal filter switch is in the OUT position.
6 ) Tur n the dial light rheostat a nd obser observe ve if control of illumination is secured with both dial lights functioning.
7) A check should be made before flight and with the airplane engine running. An increase of background noise when the engine starts, indicates imperfect shielding, bonding, faulty generator regulator, faul ty generator, open filter capacitors, or a combi natio n o off these faul ts. Always turn when the receiver switch is to not the 8) OFF position the receiver to be used.
Par
c
EMPLOYMENT
4
Operating Routine
1 ) CONTROLS
a ) A and G Th e antenn a is connected tto o the binding post mar ked A, and the gro und lead to the binding post marked G
b ) ANT. ALIGN. This control varies a capacitor for aligning the inp ut circuit to a give given n anten na. This adjustment should be made with the receiver tuned to approximately 3 4 megacycles.
c ) TUNING This control varies the setting of of the 4-gang 4-g ang variable tuning capacitor.
d ) BAND SWITCH This control selects the desired frequency band as indicated on the dial mask.
e ) DIAL LIGHTS
adjustment on AVC operation. When switching from MVC to AVC or vice versa, it will generally be necessary to readjust this control to maintain a given volume level as only under certain conditions of of signal streng th wil willl th e volume level remain unchanged. j ) AVC-OFF-MVC This three-position switch in the OFF position removes all power from the receiver. In the MVC position the receiver is operative with manual volume control, while in the AVC position the automatic volume control is functioning. I c ) TEL.
These are open circuit jacks providing connections to the headset.
a ) Throw the AVC-OFF-MVC switch to
MVC an d set other switches and controls as follows :
This knob contro ls the intensity of of dial illumination and is provided with an OF F posit position. ion.
C-W OS OSC C OF F CRYSTAL OUT ANTENNA ALIGNMENT -Adjustt control to give -Adjus maximum volu volume. me.
f ) C- W OSC. ON- OFF This toggle toggle switch controls the op eration of the cc-w w oscillator a s well as the a vie time constant for c-w reception.
g ) CRYSTAL OUT-IN This control perm its the insertion o off an i-f crys tal filter whe n ext reme selectivity is desired.
h ) BEAT FREQ. This control permits vernier adjustment of the cc-w w oscillator frequency a nd in tuning it should be set near the zero beat posit position ion arr ow on knob pointing up).
b ) Set the band switch to the desired frequency band and adjust the tuning c quency conontrol to the desired frequency. frequency. It is of great importance that this tuning be accomplished with the receiver switch in the M V C position. NOTE
The AVC position should not be employed while tuning in a signal. Tunin g should always be done in the MVC position and with the volu me control advanced only as far far as required for a comf ortab le output level.
i ) INCREASE VOL. This control is fo r sens sensitiv itivity ity adju stment on MVC operation and output level
the volume control until the cdesired ) Increase signal is heard or the background noise attains a fair level.
\
EMPLOYMENT d ) Adjus Adjustt the tuning control until maximum output from the desired signa signall is obtained. This insures correct alignment or pro per t uning o off the rece receiver. iver.
e ) If automatic volume contro l is de-
sired, switch to the AVC position and readjust the volume control for the desired ou tput level.
3 ) C-W RECEPTION a ) The procedur e is the sam e as outline outlined d above with the exception that the c-w oscillator switch is ON and tuning accomplished with the beat frequency control set nea r the zero beat po position sition arrow on knob poin pointing ting up).
b ) After tuning in the desired signal the beat frequency control may be varied
Par
4
and the frequency of the beat note adjusted as desired.
c ) Automatic volume control may be employed for c-w reception by switching to the AVC position and readjusting the volume control.
d ) When extreme selectivity is desired
to minimize interference, the crystal filter is switched IN A slight readju stme nt of of th e tuning, beat frequency and volume controls may be required to secure the desired beatn ote frequency an d vo lume leve level. l. NOTE: T h e c r y s t a l b a n d p a s s f il il ttee r i s in
t e n d e d p r i m a r i l y f or or u s e i n c w rec e p t i o n . H o w e v e r , t h e a d d e d s e le le cct i v i ty t y m a y a t t i m e s pr p r o ve ve h e l p f u l i n r e c e i v i n g m o d u l a t e d s i g n a ls ls t h r o u g h heav y interference.
Pars. 15 21
SEC TIO N II11 11 DETAILED FUNCTIONING OF PARTS 15. CIRCUITS Electrically the receiver comprises two stages of tuned rad io frequen cy amplification amplification preceding the first first dete detector ctor a temper ature compensated heterodyne oscillato oscillatorr three interm ediat e frequency amplifier stages a secon second d detector an d one stage of of audio-frequency amplification amplification with a transformer output circuit. A crystal bandpass filter filter a nd beat-frequen beat-frequency cy oscillator oscillator ar e also The former is for increasing selecincluded. tivity and the latter for receiving c-w signals. The schematic and wiring diagrams are shown in Figures 29 29 and 30 in Section V.
16 FREQUENCYRANGEANDFREQUENCY BANDS Th e freque fre que ncy r an ge s of of 20 200 0 to 50 500 0 kilocycles and 1.5 to 18.0 megacycles are covered in six bands which ar e und er the control o off a band change swit switch. ch. The frequency range for each of the six bands is given in the following table:
Band 1 2 3
5 6
Frequency Range 200 1.5 3.5 6.0 9.5 13.5
to 500 kc to 3.5 mc to 6.0 mc to 9.5 mc to 13.5 m c to 18.0 mc
17. INPUT COUPLING The antenna input circuit is capacitively coupled to the first tuned grid circuit by means of the antenna alignment capacitor. Sufficient range is available in this capa.citor to permit alignment for ante nna capacities within th e limits of 50 to 200 micromicrofarads. Th e ant enn a input circuit is designed for antennas with resistances between an d 75 ohms. \
18. INPU T PROTECTI PROTECTION ON The resistor 50-1 provides a leakage path for static charges may bewill collected on the antenna. The which input circuit withstand the application of 250 volts direct current without damage. Fo r protection against the application
of r adio frequenc y voltages up to 30 volts rms the inp ut circuit provides fo r the building u p o off a protective negative grid bias across the grid filter resistor 48 48-1 -1 whenever the in put sign al is sufficient to drive the grid into the positive region causing grid curre nt tto o flo flow. w. The voltage drop which occurs across the grid filter resistor 48-1 48-1 as a resul t of of t his grid cu rre nt flow is additive in effect to the other bias supplied the tube serving to accommodate extremes of of r adio frequency input. 19. RADIO FREQUENCY AMPLIFIER Two stages of of t uned rad io frequency amplific amplificaation and a third tuned circuit before the first detector comprise the radio frequency preselection system handling the signal inpu t before deliver delivery y to the grid of the first detector. The two r-f amplifiers utilize super-control pentode tubes Tube VT VT-8 -86. 6. Separ ate induc tance s ar e employed for each frequency band. Th e r-f r-f gain of each of the six band s is ke pt unifo rm by selection o off the tur n ratio betw between een the grid and p late circuit fo r each o off the respect respective ive bands. A relatively low signal level is maintain ed a t the grid o off the first first detector ttube ube thus insuring freedom from cross modulation interference. 20. FIRST DETECTOR DETECTOR The first detector employs Tube VT-91 which has a sh arp cuto cutoff ff characteristic. The low signal level at the grid of of the first detector together with the r-f r-f preselectio n insur es a minim um of of undesired responses. responses. The oscillator outpu t is coupled into the cathode circuit circuit o off this tube and se parate cathode coupling coils provide optimum oscillator output for each frequency band. 21. HETERODYNE OSCILLATOR The heterodyne oscillator employs a tuned grid pla te feed-back circuit utilizi utilizing ng a triode tube Tub e VTVT-65 65.. Th e effects of wide var iat ion s in ambie nt temperature under serv service ice conditi conditions ons on the oscillat oscillator or frequency have been reduced to a mini mum by th e use o off a highly stabilized tuning capacitor and temperature compensation
Pars. 21 22
DET ILED FUNCTIONING OF P
RTS
with ceramic fixed capacitors 33, 34, 35, 36). Individual inductances and trimmers are employed for each frequency band, and the low impedance coupling circuit to the cathode of the first detectolr insures a freedom from frequency instab instability ility with l oad variation or detecto detectorr circuit tuning. tuning. On the four lower frequency tuning bands, the oscillator oscillator frequency is higher than the desired signal by the intermediate fre-
22. INTERMEDIATE FREQUENCY AMPLIFIER
quency.. On the two higher frequenc y ranges, quency Bands and 6, the oscillator is on the low frequency side of of the desired signal.
ing from t he use o off the ir on cores contributes largely to the highly selective transformer characteristics while the lowered tuned circuit im-
The intermediate frequency amplifier comprises three low gain amplifying stages coupled by four highly selective, double tuned circuit transformers. The interme diate frequency employed is 915 kc. The i-f transformers ar e tuned by means of adju stable ir on cores and fixed fixed capacitors. capacit ors. The increased permeability resultresult-
DET ILED FUNCTIONING OF P
pedance, secured by the relatively large fixed tuning capacitors, provides an inherently stable amplifier. Tub e VT-86 VT-86 functio ns as the first ii-ff amplifier while the pentode section of Tube VT-7 VT -70 0 is employ ed as th e second ii-ff amplifier. Tube VT-93 VT-93 as the th ird i-f amp lifier supplies a relatively high level signal to the diodes of this same tube. 23. C W OSCILL a
TOR
e ube c-w c-w oscillator employs e triod e sect section ion oTh f T VTVT-70 70 (second i-f i-fthamplifier tu be) in a tuned grid plate fe feed-bac ed-back k circuit. The adjustable iron core in the grid inductance
RTS
Pars. 22 23
98 is employed for rough frequency alignment while a panel-operated panel-operated control permits fine adju stme nt o off the beat frequency within a rang e a ppr oxi mate ly 4, 4,00 000 0 cyc cycles les each side of zero. Th e effec effects ts of amb ient temp erat ure variations are minimized by the use of temperature-compensated tuned circuit. The c-w oscillator operates at an extremely low level, minimizing harmonics and stray oscillator pickup. The output is capac capaciti itively vely coupled to the plat e circuit of the second amplifier tube by the coupling lead connected to to the oscillator grid. Amplif Amplificat ication ion by the th ird i-f a mplifier stage, the gain o off which
Par. 23
b
D ET
ILED FU N C TIO N IN G O F P
R TS
is not controlled either by manual or a-v-c provid es sufficie sufficient nt output f ro m the cc-w w oscillator to the diode detector. This valu e of oscillator output is somewhat below the levell at which the a-v-c leve a-v-c operates thus permitting the use of automatic volume control even for c-w reception.
necting the additional capacitor 101-C. Switch 106 supplies the oscillator plate voltage by connection to th e screen gr ids o off the first an d second i-f i-f a nd first r-f r-f tubes. The same switching connects the load ing resistor 43 4 which drops the screen voltage to the first and second i-f i-f and first rr-ff tubes to a value that reduces the sensitivity by an
The c-w oscillator switch 106 in the O N position supplies the oscillator plate voltage position and increases the a-v-c time constant by con-
amo unt sufficient to keep th e overall set noise essential essen tially ly c constant. onstant. This arrangem ent for supplying the c-w oscillator has added ad2
DETAILED FUNCTIONING OF PARTS
Pars. 23-24
vantages which which a re n not ot o obvi bvious ous.. In order to have sufficient oscillator excitation available to handle high detector levels encountered with a-v-c operation and strong signal inputs, while still keeping the no signal c-w excitation below the-a-v-c delay level, it is desirable to have the c-w oscillator output increase as a strong signal input raises the a-v-c a-vc bias. This circuit arrangeme nt, as shown i n Figure 15, accomplishes accomplishes this result, since with switch 107 in the a-v-c position, resistors 42-6, 56, 62, and 59-A form a fixed
24
bleeder supplying gridAvoltage to r-f, 1st detector the and screen ii-f -f tubes. stron g inp ut signal building up the a-v a-v-c -c bias causes a considerable decrease in screen current
to 3,000 cycles at 20 decibels down from reson96 ance. ance . The tappe d tuned circuit 19 and matches th e impedan ce o off t he crystal bridge to the 1st ii-f grid. The crysta l filter may be switched
and hence an increase in the screen supply voltage. This increases the voltage supplied to the c-w oscillator and hence the excitation increases in proportion to signal level at the detector. CRYSTAL BAND PASS FILTER
Additional selectivity is available by the use of the i-f crystal filter preceding the first i-f amplifier tube. This cryst al filter comprises a balanced capacity bridge circuit which may be adjusted internally to provide a ba nd wi dth of 80 800 0
Y
DETAILED
PLATE PLAT E SUPPLY
SG I RF SG
I
IF
SO
2
IF
FUN
TIONI TIONING NG OF
PARTS
DyN MoTOR
SUPPLY SG
g
CW. O SG
101 C TIME CONSTANT
FIGUREDE FIGURE DE DETAIL
9 6 2 3
OF
BLEEDERCIRCUIT C -W OSCILLATORWITCHING N D A- V- C TI MECONSTANT ME CONSTANT
-
9 7
VC CON TRO L BUS
PL TE SU SUPPL PPLY Y FIGURE 6-CRYSTAL FILTERIRCUIT
DET
ILED FUNCTIONING OF P
TO TRANSMITTER/ RELAY
I RF
2 RF
IIF
PLAT E
RTS
Pars 24 26
SUPPLY
2 IF
56 RFEllF SG SUPPLY
40 2
40 1 62
58 I HF
END AVC
MVC
TUNING CAPACITOR
FIGUREL O
D
COMPENSATOR, LEEDERIRCUIT LEEDER IRCUITN D NOISECOMPENSATOR
in o r out of t he c ircuit by CRY CRYSTA STAL L OUT-I OUT-IN N switch swit ch 105 105 actuated from the front pane panel. l. The filter ban d width is adj usta ble by means o off balancing capacitor 7. As delivered by the manufacturer, the band width is set at approximately
without addit ional audio amplific amplification. ation. The design choice of three i-f amplifier stages and high level detection results in a number of opera ting advantages. The high level detection is relatively free from distortion due
2,000 cycles. For adjustment see Paragraph 35c 10)
to avoiding the characteristic curvature at the lower end of the diode curve. The direct drive of of the outpu t tube from the diode detector simplifies the dynamotor ripple filtering and eliminates possible microphonics resulting from high audio amplification. The high diode level further provides relatively high bias voltage insuring an unusually flat automatic volume control characteristic with the desired time delay. The dual volume control comprises potentiometers 59-A 59-A an d 5 599-B. B. Th e lat ter , 5959-B, B, funct ions only with switch 107 in the a-v-c position and in this condition it permits the desired
25. SECOND DETECTOR AND AUTOMATIC VOLUME CONTROL
Tube VT-93 also functions as the second detector tect or and automatic volume volume control. control. A relatively high level signal is supplied by the third ii-ff am plifie r to the diod es of this tube. One diode functions as the signal detector while the other diode is capacity coupled an d provides high level, delayed a-v-c control bias. 26. OUTPUT a
escription The high level signal diode supplies audio output for driving output tube, VT-148,
adjus and tmenload. t of of the io lev level el tto o the control output tube Foraud manual volume with switch 107 in the m-v-c position, the potentiometer 59-A becomes the active con-
Pars 2 6 2 7
DETAILED FUNCTIONING OF PARTS
trol oper ating on the cathode bias of t he r-f r-f and 1st and 2nd i-f amplifier tub tubes. es. These potentiometers have two linear resistance taper s providing a smooth varia tion of sensitivity.. Automatic load compensation is obsitivity tained by the method of biasing the output tube.. Here, the grid bias is obtained from tube the resistance drop across the dynamotor filter reactor, thus, any tendency towards a decreasing load on the dynamotor results in a slight decrease in the bias of of t he output tube with a compensating increase in the load curren t. See Figure 17 Tube VT-48 provides a considerable margin of power capability above that necessary to operate a numbe r of of headsets in parallel.
b. Noise Compensator
ence to Figur e 1 17. 7. Here noi noise se compensator 58 is mechanically connected to the shaft of the ganged tuning capacitor with the electrical connections such as to give minimum resistance a t the llow ow frequency end o off the band. The cathode re tu rn lea d of the second r-f r-f ampl ifier tube connects to noise co commpensator 58 and hence th e gain o off this stage is decre,ased propo rtiona lly as the r-f r-f tuned circuit impedance increases when tuning towar d the higher frequency end o off the frequency band. This arr arrangement angement tends tto o maintain the noise level and receiver sensitivity essentially constant over the tuning ranges. 27. D Y N A M O T O R
The dyna motor a nd associated rr-f -f filter circuits are assembled in one unit. The r-f filters a re of
The characteristic increase of of intern al receiver noise when tuning from the low to the high frequency end of of a band h as been
N O T E : D o w e l p i n o n c h a s s i s of f h e s e r a d i o receivers which fits n h o l e n d y n a -
corrected in this design by mean s o off vari able resistor 58 58. The function o off this potentiometer can be more clearly understood by refer-
m o f o r m o u n f i n g b a s e p r e vvee n ts t s a cc c c iid e n t a l i n s t a l l a t i o n of o t h e r s i m i l a r d y n a motors with different ratinas.
I
DET
ILED FUNCTIONING OF P
the unbalanced unbalanced type for use with a prima ry supply in which the negative side is grounded. This dynamotor su ppl ies all of of the high voltage direct curren t required for the operation of the receive receiverr and in addition a maxim um o off 20 milliamperes for use in operating accessory equipment.
RTS
Pars. 27 28
CHARACTERISTICS OF TUBES, LAMPS, VOLTAGE REGULATOR AND FUSE 28.
In the following tables are shown the characteristics of the tubes lamps voltage regulator and fuse as used in these equipments.
TUBE CHARACTERISTICS
Tube
Heater Volts Amps
Screen Plate Volts Volts
Grid Grid Volts
Plate Screen Ma Ma Ma Mu
Plate TransconResistance ductance Ohms Micromhos Microm hos
VT-86 VT-8 6
6.3
0.3
100
250
-3
7. 0
1 .7
1 160
800 000
1 450
VT-91
6.3
0.3
100
250
-3
2.0
0 .5
1 150
1 500 000
1 225
VT-70
6.3
0.3
100
250
-3
6.5
1. 5
900
850 000
1.100
100
-3
3.5
8
16 000
500 500
Tri
VT-93 VT-9 3
6.3
0.3
125
250
-3
10
2.3
800
600 000
1 325
VT-65 VT-48 VT-4 8
6.3 6.3
0.3 0.4
.
250 250
-8 -18 -18
8 32
5.5
20 150
10 000 68 000
2 000 2 200
250
Dial Lamps Lamp
LM-27
6.3 volts
Voltage Regulator RCA-991) RCA-991) 0.25 amp
Fuse Fuse
FU-35
5 amp
Starting Supply Voltage
87 volts min.
Operating Voltage
60 volts
Operating Current
0.5 to 2 milliamperes
Pars. 29 30
SECTION IV MAINTENANCE NOT OTE E-No -No at atte tempt mpt a t eithe eitherr mechan ical or electrical tri cal servicing servic ing of of these receivers should be made except at Signal Corps Re Repair pair Shops and Signal Corps Radio Sections (or Signal Sections) a t Ai Airr Depo Depots, ts, unles unlesss suitable shop and testing facili facilities ties are availab available le and authority t o repair has been granted by the Corps Area Signal Offic Officer er.. A stan dar d signal gener ator, a phantom antenna, Test Set I-56-C, and other like equipment should be used for alignment purposes and the instructions in this book carefully followed. 29.
Loosen the two thumb screws on the receiver panel, and draw the chassis from the cabinet. Lay the chassis with top upwards on a smooth, flat surface with the rear toward the operator. Loosen the five connector screws on the. dynamotor terminal strip and withdraw the spade terminals from beneath them. Loosen Loose n the f our captive screws 211 211, Figure 18, which hold the dynamotor unit to the chassis. Remove the d ynam oto r and filter assembly Remove assembly from the receiver by gralsping the dyna-
INSPECTION
a. DailyDaily-Turn Turn on receiver. Check dial lamp s. Check for operation on all bands with c-w oscillator O N This test can best be. made by observing noise level level with vo lume control at maximum. b
After 20 ho urs operation-Repeat above with additi onal check of ant enna, ground and cable connections fo r effec effects ts o off vibration.
c
After 40 hour s operati operation-Rep on-Repeat eat above with a dditio nal check of of all vacuum tubes, regulator tube and dial lamps lamps.. Inspec Inspectt receiver for loose grid clips, tube shield, etc. Inspect all tubes with combination Tester
motor and lifting vertically. The filter portion of of the d ynamotor unit is made accessible accessible by by th e removal of the cover at the bottom. See Figu re 19. 19. This dynamotor requires lubricating after 1000 hours or approximately 6 months of ordinary service and should be lubricated with none other than Air Corps Grade 375 grease.. grease Directions Directions for lubrication are stamped on the inside of the end-bell dust covers.. Access covers Access to th e bea rin gs of th e dynamotor is obtained by fir first st removing the dust covers cov ers after cutting the safety wires and removing the retaining screws, then unscrewing the bear ing end plates. Do not PAC PACK K the lubricant in these bearings.
of T est Set I-56-C. d
Each 6 month months-R s-Repea epeatt above with additional cleaning and lubrication of dynamotor a s described described in p ara grap h 30 30..
a. The dynamotor and filter assembly is re-
Whe n necessary to replace the ball bearings bearings or t urn down the commutators, first first remove remove the brushes from their cartridges cartridges.. Remove Remove the nuts from the tie rods which hold the bearing end-bells and pull the end-bells away from the field coil coil assembly assembly.. The arma ture can now be taken out. Examine the brushes to see that they have worn properly and are free from har d spots spots.. Should Should such spots spots be app arent (they generally generally cause grooves in the commutator surface), the
movable from the receiver chassis without disturbing other parts, provid,ed the procedure outlined below is followed:
brush should be replaced and the commutator smoothed smoothed down. down. The ball bearing reretainers and the shaft a re machined machined fo r very very
e.
Year-Re Year-Repeat peat above wi th inspec tion an d rep lac emen t o off d yn amotor brushes, if necessary. Lubricate dial and tuning condenser drive mechanism. Che Check ck dynamot or an d tube socket voltages as described in paragraphs 35c (1) and 35c 3).
30. CARE AND SERVICING O F DYNAMOTOR
b
Par 3
c
MAINTENANCE
snug fits, but a slight tapping will loosen them.. To remove the bearing retainer them retainerss fro m the end-bells use two small screwdrivers as wedges between the oulter ball race and the end-bell.. If the grease slinge r becomes ben t end-bell during removal, it should b be e straigh straightened tened and replaced on the shaft before replacing the bearing.
brushes, check to see that the and markings on the brushes correspond with those on the brush holder supports, and that the ma rked side of of the brush is towards the top of the dynamo tor. The commut ator must be given a final inspection inspection for free ru nning, cleanliness and absence of grease or oil. oil. The end end-bells -bells should be wiped clean and dr y before replacing them on the dyna-
Toa smooth down atlhe in llathe holding llathe fin fine ecommutator grade o off sanrotate dpa peitr not coarser than size 00, lightly against the commutator surface. Do not use emery cloth. All residue o off dust, sa nd an d dir t should be wiped away to leave a clean, smooth polish polished ed commutator su surface. rface. A commutator having a smooth or polished surface should never be sanded or turned down simply because it is discolored. If the commutator is turned down in a lathe, the mica segment separators must be undercut.
motor.
e . The nominal rating of the dynamotor is:
input, 1 23 amperes at 27 9 volts; output, 7 milliamperes at 220 volts; regulation 12 p e r cent.. Aver cent Average age perform ance data on dynamotor is as follow follows: s: Dynamotor an d filter filter disconnected from receiver and negative high voltage connection made to case of unit). NOTE: Dowel pin on chassis of these radio
Re-assembly embly o off the dyn amo tor is accomd . Re-ass
receivers w hi ch fits fits in h o l e in d y n a m o t o r m o u n t i n g b a s e p r e v e n t s a c c i d e n t a l in
plished in substan tiall y the o off the the disassembly disass embly procedure. In reverse replacing
swtiatll lhl adti tiiof fne rof oefn t ortahteirn gssi.m i l a r d y n a m o t o r s
.
M
INTEN
NCE
Par
3
DYNAMOTOR Input Volts
Output Volts Milliamperes
Amperes
24
0 7
21 215 5
0
24
1 1
210
30
24
1 3
202
60
28 28
0 8 1 1
25 258 8 246
0 40
28
1 5
236
75
REMOVAL OF FRONT PANEL
31 a
For adju stment o off dial or mask or for se serrvicing of ce rtain parts it ma y bec become ome nec necesessary to remove the panel. The ch chassi assiss with pane l attached should be taken comple completely tely out of of the cabinet an d plac placed ed f or inspection with the panel facing upwards. Unsold Unsolder er the lead to the antenna binding post and the lead from the chassis to the dial lights. Remove the dial light housing cover the two thum b screw rods the handles an d all knobs an d retaining nuts o off all controls except the DIAL LIGHTS control. Th e retaining nuts of the TEL. jacks should also be removed. removed. Th e pane l may be lifted o offf after the rem oval o off the end-plate holding
screws the chassis holding scre screws ws the dial casting holding screws and a screw which supports the crystal filter assembly to the panel. b
In replacing the BEAT FREQ. control knob turn the flexible shaft until the set screw in the coupling at the internal end points away from the panel. Now mount the knob so that the arrow points vertically tow ards the top of the receiver. This kno b has two set scre screws. ws. In replacing the other ltnobss on the shafts it will be noted that ltnob flatss on the s hafts provide fo r prop er locaflat tion. All set screws mus t be securely ttightightened an d the se sett sc screw rew on the band switc switch h knob in particular should be given a second
Pars
31 32
MAINTENANCE
tightening after the shaft has been rotated a few times.
plate is purposely given a larger clearance than bearing requirements would dictate, since its use is to support the shaft against forces which might spring it or damage the inte rnal bearing. The shaft extends through through a long bushing pressed in the dial housing. At the inside en d of of the shaft, the dete nt sta r wheel) an d the driving portion of the coupling member are pinned in place by mean s of taper pins. pins. The dial assembl assembly y run s on the ou tside surfa ce of of the long bushing referred to above above.. Just inside the panel the shaft ha s attache d to it by taper pin, the hub of the mask.
DIAL AND AN D MASK MASK ASSEMBLY
32 a
Attached to the front panel, and to the main Attached frame or chassis casting, is an aluminum casting which is the frame for the switch drive shaft, dial mask and detent, and also for the tuning dial, tuning shaft, reduction gears and stop. All of these par ts ar e assembled, and ca n be moved, as a unit, which simplifies any service operations which might be required.
b. The switch drive sha ft p passes asses through a hole hole
in an housing adjustable located in the hole dial lamp and plate through a clearance in the panel. The hole in the adjustable
c
On the back of of the di al fram e casting is is a stop which engagesto a 6pin in the detent so as arm, to limit to its rotation positions which are spaced 6 degre degrees es apart. There is at-
M
INTEN
NCE
plished by a cam on th e oute r edge of the tuning dial which operates an arm pivoted on a pin on the fra me casting. One end o off thi thiss a rm has a roller which runs on the outer edge of the dial. The roller is held in contact with the dial by a spring. The edge of the dial is cut away in such a manner that when
tached th e assembly o off pivot pins, a rm s with rollers, and spring which positions the detent.. This asse tent assembly mbly is locked with two dowell pins after the correct locat dowe location ion is made.
/
d. On the front (pa nel end) o off th e bushing through which the switch shaft passes, there is a narrow shoulder which supports the lower end of the dial index plate. This index plate is attached to the casting at its upper end with means for removing any slack and keeping keeping it straight straight and tau taut. t. The inne innerr end of the mask h ub a nd th e outer end of the dial hub turn a nd ar e held against oppoopposite sides of of the inde x plate.
the point corre sponding to eithe r end of of the tuning capacitor travel is reached, the roller roller,, and therefore the end o off the arm, ca n mov move e toward the cente r of of the dial, being forced in that direction direction by the sp spring. ring. Thus the opposite end of the stop arm is moved so that the hook at the end o off the ar m enga engages ges the rotating stop on the tuning shaft and the shaft is thereby thereby prev prevented ented fro m further turning. Wh en the direction o off rotation o off the tuning tun ing shaft is reversed, reversed, the roller an d a rm are pushed outward against the spring by the cam edge of of the dial, an d the stop disengages.
e. The dial is attached to a flange on a hub
which run s on the outside surface o off the bushing through which the switch switch drive s haft passes pas ses.. This hub al also so carries a large gear which is driven by a pinion combined with a split idler gea gear. r. This split idler gear and pinion has adjus tment in the clearan ce ho holes les for the mounting screws to to enable the backlash in the mesh of the pinion with the large dial gear to be reduced to the smallest practicable amount when assembling. f
r
The tuning shaft has, in addition to the pinion referred to above, a stop, and a worm which meshes with a split worm gear on a cross shaft at the back o off the fram e. Both this cross shaft and the tuning shaft run in bearings which are integral in the casting. Both shafts have spring thrust washers to remove end play. The c cross ross shaft carrie s a pinion which is meshed with a split gear on the tuning capacitor shaft at assembly. The degree of of mes h o off th is pinion a nd gear is adjus table by moving moving the tuning capacitor toward or away from the panel after it is placed in position and before the holding screws a re finally tightened.
g. The overall gear ratio between the tuning shaft and the capacitor shaft is 200 to 1 Since the design o off th e tunin g capacitor permits but a small amount of of rota tion a t either end of its tr avel beyond the 180 degrees required to give give it complete range in electric electrical al capacity, means are provided to stop the tunin g shaft at either end o off a tota l o off ap proximately 100 revolutions. revolutions. Thi s is accom-
Pars. 32 33
h
Since a definite relation must be set and maintained between the dial position and the an gul ar position o off t he rotor o off tunin g capacitor, adjustment is provided at the pinion on the cross shaft a t the rear of the frame. (This is the shaft whic which h also carries the worm gear). This pinion is held in plac place e by two set screws which bear in a groove on the shaft . By loosening these ttwo wo set screws, scre ws, either the dial or the tuning capacitor can be rotated while the other part remains fixed. fix ed. The correct relat ion bet between ween the these se is such that the tuning capacitor rotor plates are fully meshed with the stator plates (maximum capacity) when the dial is set with the isolated index mar k at the low frefrequen cy en d of the 13. 13.5 5 18.0 18.0 M C band in line with the index.
33. REMOVAL AND REPLACEMENT O F DIAL
MECHANISM a
In the event that the dial mechanism is to be removed from the chassis for any servicing operations, it is necessary first to remove the front panel in accordance with instructions given given earli er in this book ( Par agr aph 31 . The fram e o off the mechanism is attached to the chassis by the bracket holding the fuse, and by two slotted hexagonal head screws through the flange on the under side
M
Pars. 33 34
INTEN
NCE
of the cha chassis. ssis. Note tha t one of these screws is beneath the removable sh ield which covers the termin als o off the first i f transformer. When these screws are removed, the complete unit can be rremov emoved. ed. The center disc of the flexibl flexible e coupling is loose an d will dro p out of engagement. b.
c
To remove the index a nd dial, the tap er pin holding the mask hub to the switch drive shaft must be be removed. It is necess necessary ary to support the shaft when driving out this pin so that excess stress will not be placed on the cent er bushing. After the removal o off the mask an d the index, the dial and its g gear ear are fre e to slide off the bu bushing. shing. In replacin g these parts, the thrust washer behind the dial hub must be turned in the position to give maximum thrust, which is with the convex side outward.
f
If the dial is removed an d replaced, it is possible meshing the dial gear the idler that gear,inthe stop relationship maywith not be correct, in which case it ma y be necessary to change the meshing a tooth at a time in order to correct correct th the e error. The stop relatio relationnship must be such that the roller arm hook and the tuning shaft stop arm engage fully at the end of the last revolution. On the previous revolution, the arm must not start to move until after the rotating arm has passed passe d under the roller roller arm h hook. ook. This adjustment can only be made by trial and inspection, but it can be secured in one or two trials. Substitution of a different stop ar m may also require re-adjustment but in this case the adjustment should be made by lengthening or shortening the roller end of the arm. This iiss done by lloosening oosening the two nuts on the arm , after which the ar m can be adjusted by the slotted holes provided.
d. When the dial mechanism is replaced, the flexible coupling must be properly positioned so that the position of of t he mask corresponds to the switch position. Otherwise the-band switches will not operate properly. The correct positions are obtained when the mask set to band 200-500 kc and the set screw locking the flat switch shaft to the large
back e
gears have been unmeshed in disassembly, the split gears must be reset to put tension on the loose section when they are again meshed. Normally a displaceme displacement nt of one tooth between the two sections is sufficient. Trial will show whether this will remove the backlash.
gear hub is l degrees away fro m panel ) from vertical. vertical.
If any of the gear trains including split
When the dial mechanism is re-assembled to the chassis, the relation between the dial and the tuning capacitor must be carefully adjusted in orde r to maintain the calibra calibration tion and prevent over-ru over-running nning the capacitor Refer to Paragr aph 32h). This is done by loosening the two set screws in the pinion on the cross shaft on the back of of the dia l assembly. assem bly. Before putti ng the mechanism in place, this pinion can be moved along the shaft toward the worm gear so as to clear the capa citor split gear. This facilitates assembly, sembl y, sin since ce the gears can be meshed a fter the d ial mechani mechanism sm is bolted in place, making it easier to get the tension on the split gear in the capacitor assembly.
REMOVAL OF ANTENNA REMOVAL ANTENN A R-F DETECT DETECTOR OR AND OSCILLATOR UNITS
34
In ma ny cases servicing of these unit s will require o nly the removal o off t he top or bottom cover of a par tic ula r uni t; however however,, any unit may be removed and replaced independently a s fol follows: lows: a
b
Unsolder the lead to the main tuning capaciUnsolder tor at the capacitor by first removing the capacitor shield. shield. Unsolder all oth er leads at the unit. Disconne Disc onnect ct the ban d switch drive shaft an d
withdraw withdra w it from the antenna unit end. c. In case of of a nte nna unit, disconnect the antenna alignment control shaft.
d. Remove screws holding unit to the tie strips at the bott bottom. om. e
f
Remove screws holding the unit to the chassis. Lift the unit from the receiver, taking care tha t it comes out freelv.
Whe n replacing a unit, reverse the above pr prooced ure ; howev however, er, do no t tighten the chassis chassis-hol -holdding screws tightly until the drive shaft has been replaced and the band change switch knob has been rotate d a num ber othe f times. This the will proper insure the self-alignment of of unit and action of of t he detent.
MAINTENANCE TROUBLE LOCATION AND REMEDY
35 a
General
The normal sensiti sensitivity vity num ber of microvolts inpu t to produc e 10 milliwatts output into a 4,00 4,000 0 ohm resistance lo ad) of the receiver is better than 3 microvolts when measured under the following conditions AVC-OFF-MVC switch at MVC; 28 volts input; c-w oscillator ON; crystal filter OUT; output load 4,000 ohms non-inductiv tive e resistance; resistance; p ur e c-w c-w inpu t fr om signal generator applied between between ante nna ground terminals through a 100 mmf dummy antenna; volume control set to produce 0.3 milliwatts noise output.
Par.
5
This sensitivity will, of of course, be sub ject to variation with time due to tube aging, etc.
T h e r e f o r e i t is i s r e c o m m e n d e d t h a t n o a ttt e m p t - b em e m a d e t o r e t r i m o r r eeaa l ig ig n t h e e q u i p m e n t u n l e s s t h e s e n s i t iv iv i t y i s f o u n d t o b e w o r s e t h a n 20 m i c r o v o l t s w i t h n e w a v er e r a ge ge tubes.
This receiving equipment has been carefully adjusted and aligned by the manufacturer before shipment and should maintain these adjustments over reasonably long periods of of time. time. Major adju stme nts an d repair should be made only in an authorized repair shop equipped with the necessary servicing tools and equipment. All others
m u s t r e f r a i n f r o m c h a n g in in g a n y of of t h e a dd-
Input sig nal at terminals of antenna required to obtain 10 milliwatt output over internal noise.
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Par. 35
INTEN
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SIGNALS ALL 8 a NDS
CHECK FUSES 8 VOLTAGE AT
WEAN OR NO SIGNALS
CHEW VOLTAGES
1W ONE BAND
35 C 131
_
35 TEST AF AMPI ER
DEFECTIVE TUBES
I
35 C 151 CHEU
YaRTS
8
TEST H E T E M E OSULUTW
TE S T I F W P Ll Ll F lE lE R
u m m ETC. 5 C HI
35 C Ill)
35 C 161
TEST R F AMPLIFIER
WE CK CIRWIT Y PAND O NE NTS
35 C 121 CHE C CK K Uf f iUlT
WECK ClRWlTS
m
COMP
T O c Y I T s
3s
c
ISIANDII~I
CH CHE EC CK K URW lT AND WMPMENTS
IF ALI ALIG G NME NMENT NT 5 C I81 WEAK R NO RECEPTIW
AUWlUEWT RF BOSCILLATW
NT
CRVSTU. FILTER
W
35 C 10) C
OSCILLATOR
N D CORRECTION FIGURETROUBLE LOCATION HART
Numerals refer to pertinent paragraphs)
j u s t m e n t s of t h e radio frequency circuits
The difficulties usually experienced are the resul t of of exte rnal deter iorat ing influence influences, s, such as worn-out vacuum tubes, improper opera ting voltage, blown fuse, external noises, nois es, etc. However, in orde r tto o permit the
EQUIPMENT EQUIPME NT RE REQU QUZR ZRED ED-s -see ee
servicing of of this equip ment , the testing procedure shown should be followed in determinin g the source of trouble. This has been divided into the following major divisions, with respect to the nat ure of the troubles being experienced
Pa ra gr ap h 35 b
Wea k or No signals on all bands
Modu Modulate lated d receptio reception n
Weak or No sign signals als on any one band Wea k or No signals on all bands
Modul Modulated ated reception See Par agr aph 35 d CC-W W recepti reception on (modulated reception normal) See Paragraph 35 e
Figure 23 graphically outlines the prolcedure for trouble loca location tion,, the numbers in each block blo ck referring to the paragraph numbering in the following discussion: b
E q ui p m e nt R e q uir uir e d Few instruments other than those found in a standard set analyzer (Test Set I-56-C) are required in locating the most probable troubles in this receiver receiver.. The indiv idual instru me nh required a re as fol follows lows::
See Par agr aph 35 c
modulated test oscillator (standard signal gener ator) with a frequency range fro m 200 to 18 18,0 ,000 00 kc with provision for calibration accuracy better than 0.1% at aligning frequencies.
1)
2)
Voltmeter-100 Voltmeter -1000 0 ohms per volt, rang ranges: es: 0-10; 0-100; 0-250 volts.
3)
Continuity tester.
Output met er rectifier type, 00-15 15 volt, 4,0 4,000 ohms.
4)
*Part of Test Set I 56 C.
>
M INTEN NCE
(5) Microameter, 0-200.
Par
at the dynamotor terminal board should closely approximate the values shown in Figure 24 fo r this equipment. equipment. Condi Condition tionss of measure ments ar e as follows: Input voltage 28 v for these receivers; Crystal OUT; MVC; Volume Max.; C-W Osc. OFF;
(6) Audio frequency oscillator.
(7) Pa ir of telephone receivers. (8) Adapter Adap ter FT-211 which consists o off a n 8-prong octal plug and an prong octa octall socket connected together by a short length of 8-conductor cable, to permit use of Test Tes t Set II-5656-C C ana lyz lyzer er on the r-f tubes on the tube shelf.
Load resistanc resistance e 4 ohms. If these volta voltage ge reading s do not approximate the values shown, check the fuse, dynamotor and filter circuits, wiring and components.
c. Weak or N No o Sign Signals als on Al Alll Bands Moduluted Reception
(2) Tube Check
1) Check of of D ynam otor Voltages
If the voltages at the dynamo tor term inal board approximate the values give given, n, proceed to chec check k all tubes fo r emission an d character characteristics istics or replace all tubes with those of known average characteristics.
When all signals signals on all bands are weak, or no signals ar e hea rd even when known to be pr es en t, the procedure fol follows lows that shown in the chart . The voltages checked
~
~
-
+
4
t
Z
D
4
VT-93
8
t
BOTTOM VlEW
I
t
C
N
CW OSG ZND IF
VT-70 6
28 VOLT
INPUT
cw osc O F F +
M M . VOL.ON.MVC
BOTTOM
VlEW
FROM FRONT PANEL
FIGURE CH
RT
OF
5
OLTAGES OLTAGES SOCKETN D D Y N A M O T O R
P51
Par.
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5
I NT E N
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FIGURE 5-INTE 5-I NTERME RMEDIA DIATE TER EQU ENC Y -W OSCILLATOR OIL A N D CRYSTAL OF
FILTERSSEMBLY
3) Check of of Soc ket Voltages
If tubes check satisfactorily, or if after replacing wth tubes known to be good, the sensitivity sensit ivity is still low, proceed to check al l tube socket voltages as outlined under Par ag ra ph 35f 35f with T Test est Set Set II-56 56-C. -C. The average socket voltages are given in Figure 24
4) Chec Check k o off ponents
Circuit
Wiri ng
an d
Com-
If t he tube socket vo voltagqs ltagqs do not approxi mate the values shown in Figure 24 the associated assoc iated circuits circuits a nd components should
be checked checked for grounds, shorts an d similar defects. 5) Test of Audio-Frequency Amplifier Having checked all socket voltages and found the values to be correct, proceed to the test of of the a udio frequency amplifier. amplifier. This can be checked by capacitively coupling a 400-cyc 400-cycle le volta ge of of a ppro xima tel y 2 volts rms. Between the detector diode socket pron g No. No. an d ground, through a 0.5 mfd capacitor. capacitor. As an alternative a modulated 915 kc signal of 2 volts may be coupled couple d to to this this point an d ground. Proper functi oning of of the au dio amplifier will be
M
INTEN
indicated by an output well over 10 milliwatts fo r the 2-v 2-vol oltt audio input or approximately milliw milliwatt att output fo r 915 kc input. Circuits, wiring and components should be checked if this order of response is not obtained.
NCE
Par
5
the resultant double response peaks symmetrically located approximately 5 kilocycles each si de of of the 915 kc i-f i-f alignme nt frequency. In general, it will not be necnecessary to realign this transfor mer because because of its broad characteristic. However, i f
AmAm-
realignment becomes necessary, the following procedure should be followed.
Following a satisfactory test of of t he audi o amplifier, check the intermediate frequency amplifier by capacitively coupling the modulated test oscillator oscillator from the grid cap of the first detector tube to grou nd, through a 0.1 mfd capacitor, the frequency being adj uste d to 915 915 kc. A roug h check of the prop er funct ioning o off the ii-f -f amplifier is indicated by a comfortable headphone output level with low input from the test
Connect the modulated test oscillator through a 0.1 0.1 mfd ca pacito r to the grid of Tube VT-9 VT-93 3 thi rd ii-ff amplifier tube) an d to ground. ground. Set the input frequency at 91 910 kc an d adjust alternately first the primary tuning core, then the secondary tuning core of of t he fourth i-f i-f transfor mer until maximum output is obtained when both cores are turned i n a right-hand right-hand screw direction. The modulat ed test test oscillator oscillator should then be tu rned slowly slowly through the
6) Test of plifier
Interme diate- Frequen cy
oscill oscillator. Approxi mately input ator. f or 1 0 milliw milliwatts atts outpu25 t). microvolts
7 ) I-F Amplifier Circuit Check If t he ii-ff a mplifie r does not respo nd as above or lacks senstivity, a progressive check, stage by stage, should be made. The test oscillator 915 915 kc modulat ed input, is connected through a 0.1 mfd capacitor to the second detector diode socket prong and to ground. ground. A signal respon response se indicates prop er functioning. Coupling the test oscillator to the grid of the third i-f should indicate a decided gain in sensitivity. tivi ty. Proceeding similarly towards the first detector, each stage should show a decided gain, and a faulty stage can be circuit checked checked fo r grounds, grounds, shorts, or defective components.
915 kc asetting and to approximately 920 920 kc where second response peak of approximately equal amplitude as that at 910 kc should be obtained. This indicates correct alignment. Slight supple mentary adjust ments of of the prima ry an d secondary secondary tuning cores may be necessary to secure a symmetrical double peak response with the slight hollow between response peaks located at the 915 915 kc a lignment frequency. If a sweep frequency modulated test oscillat or is available, this fourt h ii-f -f transfor mer can be conveniently aligned by visual observation on a cat hode ra y oscillos oscilloscop cope. e. In this case, the tuning core adjustments ar e made to obtain a double peak response pattern centered a t 915 kc. 9) Check and Alignment of of C-W Oscillator
When all stages have been tested, the i-f amplifier alignment is checked by capacitively coupling a low level input signal of 915 915 kc to th e first first detect or grid a nd a djusting t he ii-f tun ing cores of both primar y an d secondary windings o off t he first, first,
The c-w c-w oscillator is checked an d adjuste d by coupling coupling the 915 915 kc input modulation off)) to the grid of the first detector tube off and then switching the c-w oscillator ON. With the beat frequency contro controll set at midposition, oscillator inductance tuning core 98 is adjusted f or zero beat. If no c-w c-w beat can be heard, the c-w oscillator circuit should be checked fo r grounds, grounds, shorts, or
second and th ird ii-f transformers a nd the tuned circuit of the crystal filter assembly for maximum output. The fourth i-f transformer is slightly over-coupled with
defective components. Wi th the c-w oscillator ON the screen voltage at the first and second i-f sockets drops to approximately 45 volts measure d to grou nd).
8) Alignment of I-F Amplifier
ar
5
MAINTENANCE
(10) Test an d Adjustment of Crystal BandPass Filter Normally the crystal band-pass filter is adjusted at th e factory for a bandw idth of 1500 to 2000 cycles at 20 db down from resonance. This filter can be tested by applying an unmod ulate d signal of appro ximately 915 kc, connected through a 0.1 mfd capac itor to the grid of the first detector tect or tube tube and g ground. round. Wit h th the e cr crystal ystal filter switch in, and a 200-microampere meter connected connected i n the lead from the vol vol-ume c ontro l 5 599-B B to the cat hod e of of the thi rd ii-ff amplifies Tu Tube be VT-93 (available at the bottom bottom ter minal o off the rea r volum volume e contro l), the frequency of th e test osciloscillator should be slowly slowly varied until the response pea k of the, cryst al filter is located. The signal input voltage or the volume control (MVC) should then be adjusted to give give a readi ng of appro ximat ely 7 70 0 microamperes on the response peak. Switching the crystal filter OUT should not produce a rea din g o off mor e tha n 11 110 0 microamperes. This test indicates the correct functioning of this filter. The cc-w w oscillator should be off off dur ing this test. To adj ust the band width of the crystal filter, a signal generator or microvolter having an expanded iuning scale in the vicinity of of 915 915 kc a nd hav ing also an attenua tor with a mu ltipli er o off 1 0 times (20 db) is required. The foll following owing procedure is recommended: recommended: Wit h the sign signal al input tuned to the crystal filter response peakof (CRYST YSTAL AL IN) and athe n outpu t uat read reading of(CR 100 microamperes, at ten oris set to multiply the input voltage by 10 times and the signal generator detuned on each side of of reso nance, noting the frequencies of the points where a reading of 100microamperes is again obtained. From the difference of of these freque ncy readings, the crystal filter filter band width can be determined. mine d. The ban d width can be adjusted by changing the capacity setting of balancing condenser 7. For each setting of this condenser, the band width at 10 ti times mes input should be checked as described abo above. ve. In general the minimum bandwidth is obtained with the balancing condenser condenser a t approximately mid-cap mid-capacit acity y (adjustment slot perpendicu perpendicular lar to fro nt panel panel)) with the
band width increasing for condenser settingss near maximum or minimum capa ting capacit city y (adjustment slot parallel to front panel). After conclu ding the above describe d tests, tests, remove the microammeter and restore the circuit to normal.
\
(11) Check of Heterodyne Oscillator Having checked the function ing of the i f and audio amplifiers, iiff signals are not heard on any band, the heterodyne oscillator should be checked for oscillation. This can be done by observing the cathode voltages a t the socket o off the first detector, Tube VT-91, when grounding the stator of th e osci llato r section (1-D) o off the tuning capacitor. If no change in v voltage oltage is noted with this test, the oscillator circuit should be checked for grounds, shorts or defective components.
12)
Testt of Tes of th the e R-F Amplifier Having completed the test and alignment of the audi o amplifier, ii-f -f ampl ifier and heterodyne ascillator, the r-f amplifier is tested as follows: With the band switch set on the band lacking sensitivity, a modulated signal from the test oscillator is capacitively coupled through a 100 mmf dummy antenna to the antenna post and to gr ground. ound. This input signal signal frequen frequency cy should be set quite accurately to the alignment frequency shown in the Tabl Table e of Alignment Data fo r the band under ttest. est. With the tuning control set for the approximate tune slowly aroundalignment this point frequency, until the maximum response with the least signal input is obtained. Capacitive coupling of the test oscillator to the grid of of t he fir first st rr-f -f an d second r-f r-f tubes should show a progressive decrease in output indicating the proper functioning of of the particu lar r-f stage or circuits preceding preceding.. If a decrease in response is noted when the signal input is capacitively coupled progressively from the gr id o off the first detector to the second an d ffirst irst rr-f -f gri d caps a nd finally tto o the anten na post (with the 100 mmf dummy antenna capacitor), the stage which indicates a decrease in response should be checked for circuit, ground, shorts or def ective components.
-,
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INTEN
(13) Alignment of R-F Amplifier
n e r a l a l i g n m e n t s t a rt rt w i t h NOTE:F o r a g e ne t h e 2080-500 l cc Band No 1. In the r-f alignment for any particular band, the tuning control is adjusted for the alignment frequency (Table of Alignment Data) and the modulated test signal at this alignment frequency is coupled from t he test oscillator oscillator to the antenna post through the 100 mmf d ummy a ntenna . The three r-f trimmers (ANT., R-F, and DET.) DET .) fo r this band, a re then adjust ed for maximum output. similar procedure is followed in t he alignment of of each band. (14) Alignment of Heterodyne Oscillator
r a l a l i g n m e n t s ta ta r t w i t h NOTE:F o r a g e n e ra t h e 200-5 00 kc B a n d N o 1 Th e alignment of th e Heterodyne Oscil Oscil-lator is necessary only when the tuning dial frequency calibration is in error by more tha n 0. 0.5 5 pe r ce cent. nt. To align th the e
NCE
Par
5
oscillator follow the same general procedure as was followed followed for the alignment of the rr-ff amplifier. amplifier. Wi th the b a n d s w i t c h on ban d No. No. (2 (200 00-5 -500 00 kc) a nd th e t u n i n g c o n t r o l set to the alignment frequency, couple the outpu t of of t he modulated test test oscillator (set at the alignment frequency) to the antenna post through the 100 mmf dumm y antenna. The oscillator oscillator trimmer for this band is adjusted for maximum audio output. output. A similar procedure procedure is followed in the alignment of of e ach band.
d . Weak or No No Signals On Modulated Reception
n y One Band
The condition of of satisfactory reception on several sever al bands and weak or no signals on one or more bands, indicates the correct functioning of of the i-f i-f an d a-f a-f amplifiers and requires checking only the r-f amplifier amplifier and heterodyne oscillator oscillator for the defective defective band or bands. The procedure outlined outlined in Para gr ap hs 35c 35c (11) (11) to 35c (14) shou ld be followed for the defective band or bands.
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5
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.
Table Tabl e of of Alignment Alignme nt Data Band No
1
2 3 4 5 6
Freq. Range M
Trimmers
Alignment Frequency M
200-500kc 1.5-3.5 3.5-6.0 6.0-9.5 9.5-13.5 13.5-18.0
480 kc 3.3 mc 5.8 9.3 13.3 17.8
Ant.
R. F.
65 2* 3-1 5-1 5-2 4-1
37-1 5-3 3-2 5-4 3-3 4-2
1
Det.
Osc.
37-2 5-5 3-4 5-6 3-5 4-3
6-1 6-2 3-6 5-7 5-8 3-7
*Refer to schematic schematic diagram, diagram, wiring diagra m and marked photographs for location. The alignment controls for the various bands ar e numbered on the ch chassi assiss adjacent to the cont control rol.. Controls Cont rols for band 1 are marke d 1, those for band 2 are marked 2, etc. etc. **Antennaalignment **Antenna alignment control control knob on fron t panel. e . Weak or N No o Signals On All All Bands, C-W Reception Modu lated Reception Normal) Weak or no signals on all bands for c-w reception with satisfactory modulated signal reception requires testing and alignment of the c-w c-w oscillato oscillator. r. Proceed as outlined in paragraphs 35c (8) and 35c (9). f
Measurements with Test Set I 5 6 C The following readings are typical values obtai ned with Test Set II-5656-C. C. If a ll plug s seem to be securely in position with the dynamotor running and faulty or poor operation is obtained from the receiver, a carefu l check should first be mad e o off the cables and plugs using the 666 SC volt-ohmmeter as outlined und er Detailed Tests on Radio Sets , page 16 of the Instruc Instruction tion Book fo r Test Set I-56I-56-C. C. If all plug-in cab le connections seem to be functioning properly, a test should be made of the tubes in the receiver using the tube tester as outlined in the same paragraphs as mentioned in above. Should neither of these tests locate the difficulty, voltage and current or resistance measurements should be made as outlined in the following parag raphs : (1) Voltage and Current Measurements Set up th e rece receiver iver and analyzer of Test Set I-56-C for operation as outlined under general voltage and current measurements. To obtain the various readings readings,, connect the jumper leads from the socket selector block to the analyzer pin jacks in accordance with the instructions given below.
Procedure 1. Release the thumb screws and pull
the complete ch assis out of the case. 2. Power connections should be made to the plug socket socket at the re ar o off the receiver chassis. 3. Be sure the plug and tube top grid connections are secure when taking readings. 4. Keep the on DC.
analyzer
AC-DC
switch
5. Place the analyzer left-hand toggle switch in the VOLTS-MA position. 6. Connect the short jumper cables for the various tests as indicated in the table below. 7. Connect jump er
cable fr om block
terminal GND to receiver chassis. 8. Set the receiver control switch on the MVC position unless otherwise specified. 9. Set the receiver with t he volume control at the maxim um positio position n (extreme clockwise). 10. Set the tuning control to 201 kc (I-f end of band 1 ; eadings should deviate but slightly when switching to other bands with the tuning control remaining at the low frequency end of each band. 11. The c-w oscillator should be OFF for
the readings in Table and ON for the readings readings in Table B.
M
INTEN
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Par
MAINTENANCE
5
NOTE: Th e readings give NOTE: given n below ar e average values tak en on receivers o off this type using a 28-vol 28voltt power supply. Mete Meterr indications within *lo of these thes e values will in most cases indicate correct operation. In using the analyzer on the oscillator stage, precautions must be observed in order to as-
insure that oscillations are sustained during measurement. measuremen t. Wit h the analyzer analyzer arranged tto o measure oscillator plate current and with the band switch and dial set as described, an oscillating condition should be obtained, which may be demonstrated by placing a finger tip upon th e sta tor sect section ion o off th e oscil oscillator lator tunin g
sure that voltage and current measurements are made under actual operating conditions. The analyzer plug and adapter are plugged into the oscillat oscillator or tube sock socket et contained within the box box and the tube placed in the approp riate analyzer socket. Before measurements may be made, it should be ascertained t hat voltage voltage regulator tube 991 is functioning, as indicated by a glow within the tube. The switch should be set so as to select the I lowe lowest st frequenc y) .ba nd and the dial adjusted to 200 200 kc. It is necessary that these steps be taken in order to
cond ense r, 1-D 1-D.. If placi ng the finger tip upon this stator insulated) sect section ion causes an increase in plate current, this shows that the oscillator oscillat or was functioni functioning ng until disturbed manually. uall y. Th e higher value of plate curre nt represents the non-oscillating condition, which will probably be duplicated by switching to any other band, because the inter-electrode capacities contained within the analyzer connecting cable are of of s uch magn itude a s to mak e it impossible for the oscillator to function on the higher frequency.
TABLE A
Stage Stag e R-F 2 R-F 1 Det. osc. 1 I-F 2 I-F 3 I-F Output 2 Det. 1
Tube
1
R-F R-F Det.
0
.
2
I-F I-F I-F
1
2
3
Output C-W osc.
OFF
Plate Volts
Screen Volts
Cathode Cathode Volts
Heater Volts
Plate Current
Screen Curre nt
MA
MA
Plate C urrent
Screen Curre nt
MA
MA
VT-86 184 VT-86 186 VT-91 215 215 VT-65 58 VT-86 202 VT-70 225 VT-93 207 VT-48 197 VT-93 Diode 8.0
TABLE B
Stage Stag e
C-W OSC.
C-W OSC.
ON
Tube
Plate Volts
VT-86 VT-86 VT-91 VT-65 VT-86 VT-70 VT-93
197 232 204 58 195 210 210
VT-48 198 VT-70 Triode 18.0
Screen Volts
Cathode Volts
Heater Volts
MAINTENANCE (2) Resistance and Continuity Measurements
switches without running the dynamotor and causing voltages to be built up across the various resistors and condensers. Any voltages set up by the dynamotor in the receiver would cause serious errors in reading on the ohmmeter rang es or might possibly damage the test instruments. Procedure Set the receiver control switch to MVC unless otherwise specified.
2. Set the receiver with the volume control at the maximum posi positio tion n (extreme clockwise). 3. Set the tuning control to 200-500 kc (1(1-f en end do off ba nd 1 ) ; eadings should not deviate when switching switching to other bands with the tuning control remaining at the low frequency end of each band. 4
2/3 of the scale and wherev er possi possible, ble, the range should be chosen that will give indications in this area.
g. Failure of
ial L i g h t s
The two dial lamp s ar e conne connected cted in series. Hence, the fai lure o off either lam p does no nott necessarily indicate failure of both lamps. Removal of of the dial light housing gives ready access to the lamps.
The c-w oscillator should be OFF for the readings in Table C and ON for the readings in Table D
5. Shift the analyzer left-hand toggle switch to the ohms position.
5
Tests in the test set instru ction book book.. BeBefore taking a resistance reading on any range, short the two jumper leads plugged into the ohmmeter pin jacks and rotate the batter battery y adjustment knob until the instrument pointer reads exactly full scale. Should it be fou nd iimpossibie mpossibie to bring the pointer up to the top mark refer to the paragraphs on battery replacement under the heading Main Maintena tenance nce in the test set instru ction book. Plug the pin tip end of the 3 foot clip lead int o the block hole marked G N D and clip the other end to th e chassis. Connect one of the jum per leads between the remaining ground jack and one of of the o hmme ter jacks jacks on the require d range. Connect the other jumper lead from the remaining ohmmeter range jack to the tube element under test. In general, ohmmeter readings will be most accurate when taken on the upper
Remove the chassis from the cabinet and do not make any connections to the plug socket at the re ar o off the chassis. chassis. This procedur e permit s the operati on o off a ll
1
Par.
Set up the Analyzer for resistance and continuity measurements as outlined un-
T h e r e a d i n g s t a b u l a t e d b e l o w a r e a v e rraa g e v a l u e s t a k e n o n r e c eeii v eerr s of of t h i s t y p e w i t h t h e storage battery disco nnec ted. M eter indicat i o n s w i t h i n p l us u s o r m i n u s 10% of f he se value s
der
will
NOT
General Resistance an d Continuity
n
most cases indicate correct operation.
Resistance to Grou Ground nd Ohms) TABLE C. Stage
R-F 2 R-F 1 Det. osc. 1 I-F 2 I-F 3 IF Output 1
C W OSC.
Tube
OFF
Cathode
Plate
Screen
MVC Gri Grid d
AVC Grid Grid
100,000 100,000 0 100,000 500,000 500,000
1.8 meg. 1.8 meg. 0 100,000 1.8 meg. 2.25 meg.
5,000 700,000
5,000
M
5
Par
TABLE D. Stage
C-W OS OSC. C.
Tube
I NTEN
NCE
OF F
Cathode
Plate
Screen
MVC Grid
AVC Grid
R-F
1.8 meg.
R-F Det. osc. 1 I-F 2 I-F 3 I-F Output C-W 0 . Det. Diode AVC Diode
1.8 meg. 0 100,000 1.8 meg. 2.25 meg. 5,000
1
2
1
h Note
1
2
3 4 5
Performance Performance Characteristics
Test
Specification
Average
Performance
Performance
Sensitivity Sensitivity less than 7. microvolts 1.2 microvolts Receiver sensitivity should be better than 20. microvolts at 20 volts d-c primary input to the receiver. Audio Powe r Output MVC MV C 400 milliwatt milli wattss 590 milliwatt milli wattss AVC AV C 200 milli milliwatts watts 830 milliwatt milli wattss Receiver Noise Noise less than 15 milliwatts 0.8 0.8 milliw atts Audio Hum : less than 50 microwatts Selectivity: Input Ratio Inpu Inputt off Resonance) Input at Resonance) Bandwidth Bandwidth KC) 2 :1 1O:l OO:l OOO:l
10,OOO:l
j20 j200-5 0-500 00 kc 11.5-1 11. 5-18.0 8.0 mc
2.1 min. min.,,, 10 10 max. max. 5 min. min., 18 max. 30 max. 40 max . 52 max.
KC) 3.0 3. 0 7.6 13.8 19.1 26. 26.2 2 32.4
M
INTEN
NCE
Par.
5
CONNECTIO CONN ECTION N CH CHART ART FOR USE OF TE TEST ST SET I 5 56 6 C USIN USING G ADAPT ADAPTER ER FT 211 211.. Test
Tube
Plate Voltage
VT-86 VT-91 VT-93 VT-65
R-F I-F Ampl. 1st Det. 3rd I-F R-F OSC.
VT-48 VT-70
Audio 2nd I-F
VT-86 VT-91
R-F I-F Ampl. 1st Det Det..
VT-48 VT-70
Output 2nd I-F C-W Osc.
VT-93
3rd I-F
VT-86 VT-91 VT-65
R-F I-F Ampl. 1st Det. R-F Osc.
VT-70
2nd I-F C-W Osc. Osc.
VT-93
3rd I-F 2nd Det.
VT-48
Output
VT-65 VT-86 VT-91 VT-93
R-F Osc. 1st R-F 2nd R-F 1st Det Det.. 3rd I-F
VT-86
1st I-F
VT-70
2nd I-F
Screen Voltage
Cathode Voltage
Function
Block Terminal Number
to
Analyzer Jacks
3 grid
2 grid
4 grid 3 grid
6 grid
8 grid
6 grid
Heater Voltage
8 gnd 5 grid
7 2 2 7 7
VT-48
Output
Triode Voltage
VT-70
C-W Osc.
4 grid
Diode Voltage
VT-93
2nd Det.
5
Plate Current
VT-86 VT-91 VT-65 VT-93
R-F I-F Ampl. 1st Det. R-F Osc. Osc. 3rd I-F 2nd Det.
VT-48
Screen Current
6
grid
3 outside 3 inside
10 ma. ma.
Output
2 outside 2 inside
25 ma. - ma.
VT-70
2nd I-F C-W Osc. Osc.
2 outside 2 inside
10 ma. - ma.
VT-86 VT-91
R-F I-F Ampl. 1st Det.
outside 4 inside
10 ma. ma.
VT-48 VT-70
Output 2nd I-F C-W Osc.
3 outside 3 inside
10 ma. ma.
VT-93
3rd I-F 2nd Det.
6 outside 6 inside
1 ma.
Par.
5
MAINTENANCE
REFERENCE NOTES for Perfor mance Character Characteristics) istics) NOTE1 Sensitivity shall be measured as follows: The radio receiver is to be be operated at 28 volts with a 4000 4000 ohm non-in non-inductive ductive outpu t load. The calibrated signal generator output is to be fed to the receiver through a 100 mmf mic a capa citor. Antenna trimm er alignment is to be made at 3.4 mc. only, and before sensitivity measurements are taken. A. For MCW measurements turn C-W OSC. switch OFF and CRYSTAL switch OUT. Adjust the standard signal generator to give approximately 110 milliwatts receiver output at the resonant fr frequency. equency. Alternat Alternately ely adjust the receiver INCREASE VOL. control and the signal generator attenuator to obtain 10 milliwatts receiver output with a 400 cycle 30 modulated signal and 2.5 milliwatts nois noise e output with the unmodulated carrier applied to the receiver. Read microvolts sensitivity on the signal gene rator attenuato r. If n noise oise adjustment is not necessary set receiver INCREASE VOL. control at maximum. B. For C-W Measurements turn C-W OSC. switch ON and CRYSTAL switch OUT. Adjust the receiver volume control to give 0 3 milliwatt noise ou tput, if possible, with no signal sign al input. With an unmodulated carrier
input and the receiver BEAT FREQ. control adjusted for approximately 800 cycles the signal generator attenuator shall be adjusted to obtain a receiver o utput of 10 milliwatts. milliwatts. Read microvolts sensitivity on the signal generator attenuator. NOTE . Audio power output shall be measured into a 4000 ohm non-inductive load and with a 4 cycle 30 modulated signal signal input. Receiver ceiv er input voltage voltage shall be held a t 28 volts. NOTE3. Receiver noise shall be measured with a 4000 4000 ohm load, w ith a 28 volt primary powe powerr input, and with the INCREASE VOL. control at maximum . A 100 mr mrnf nf mica capacitor shall be connected between antenna and ground termi nals o off the receive receiver. r. NOTE4. Audio hum is to be measured using a 4000 ohm load, with a 28 volt primary power input and with the INCREASE VOL. control at minimum. NOTE5. Th e selectivity of t he rece iver on M MV VC with the CRYSTAL switch OUT shall comply with the values given in the table when measured at normal sensitivity by the single standard signal generator method.
36
Reference No 1-A
Signal Corps Stock No 3D9016 3D9016V-2 V-2
TABLEOFREPLACEABLEPARTS
Name of Part Capacito r
Description A Section, 16 to 331
Function
Mfg Symbol
Dwg No
Main Tuni ng
RC
D-5 D-5024 024
D-3 D-3450 450
mmfd +0.5 Special Special Section, Sectio n, 1 6 to 331 mmfd t 0 .5 Spe Speci cial al C Section, Section, 1 6 to 331 mmf d *0.5 Special Special D Section, 16 to 331 mmf d +0.5 Speci Special al
1-B 1-C D
Capacitor
Air Tr imm er 50 mmf d max; Type APC Special
Antenna Coupling
RC, AW, OM
Capacitor Capac itor
Air Trim mer 50 mmf d max; Type A P C
Antenna Antenna Unit Tri mmer
OM OM,, RC, AW
R-F Unit Trimmer R-F Unit Unit Tr immer 1st Det. Det. Un Unit it Trim mer 1st Det. Det. Unit Trimme r Osc. Unit Trimmer Osc. Unit Trimmer 4-1
3DF101
Capacitor
Air Tr im mer 50 mmfd max; Type APC
Antenna Unit Tr imm er
44-2 2
R-F Unit Tri mmer
44-3 3
1st Det. Det. Unit Tri mmer Capacitor
Air Tr im mer 25 ininfd max; Type APC
Antenna Unit Tri mme r
OM, OM, RC, AW
D-3 D-3448 448
RC, AW, OM
D-3 D-3455 455
Antenna Unit Trimmer R-F Unit Trimmer R-F Unit Trimmer 1st Det. Unit Trimmer 1st Det. Unit Trimmer Osc. Unit Trimmer Osc. Unit Trimmer
Reference No. 6-1
Signal Corps. Stock No No.. 3DF105
Nam e of Pa rt Capacitor
Description Air Tri mme r 25 mmfd max; Type APC
6-2 6-2
Function Osc. Osc. Unit Tr im mer
Mfg Symbol
Dwg. No No..
RC, AW, OM
D-3 D-3535 535
Osc.. Unit Tr im mer Osc
7
3DF103 3DF1 03
Capac Capacitor itor
Air Tri mmer 10 mmfd max; Type APC
Crystal Crystal Filter Adjustment
FWS
D-38 D-3823 23
8
3DF102
Capacitor
Air Tr imm er 10 mmf d max; Type APC Special
C-W Os Osc. c. Freq. Adjustment
FW S
D-3 D-3809 809
Capacitor
Paper , 400 V D-C, 0.01 mfd 4207 with Leads MR Type Ty pe 340 SMC Type MPW
1st 1s t R-F Cath ode By-pa ss
SMC, MR
D-3682
1st R-F Screen By-pass
2nd R-F Cathode By-pass 2nd R-F Screen By-pass 1st Det. Screen By-pass 1st I-F Transformer By-pass Crystal Filter Transformer
1st I-F Cathode By-pass 1st I-F Plate By-pass 2nd I-F Transformer By-pass 2nd I-F Cathode By-pass C-W Osc. Plate By-pass Plug Terminal By-pass AVC By-pass 3rd I-F Transformer By-pass 3rd I-F Cathode By-pass Heater By-pass Battery By-pass
Reference No. 10-1
Signa l Corps. Stock Stoc k No. 3DAlO-4 3DAlO-44 4
Na Name me of Part Capacitor
Description Pap er, 400 V D-C, 0.01 mfd t 2 0 % wit with h le lead adss MR Type 340 SMC Type MPW
Funct ion Anten na Coil By-pass
10-2
R-F Plate By-pass
10-3 10-4
R-F Coil By-pass 2nd R-F Plate By-pass
11-1
3DA10-44 3DA10 -44
Capacitor
Pape r, 400 V D-C, 0.01 mfd +20% with leads MR Type 340 SMC Type MPW
11-2
Hete rodyn e Osc. Pla te Heterodyn By-pass
Mfg. Symbol
Dwg. No No..
SMC SMC,, MR
D-3682
SMC, SMC, MR
D-3682
1st Det. Cathode By-pass
12
3DA 3DA55-18 18
Capacitor
Paper , 500 V D-C D-C,, .005 mfd 2 20 % wit with h leads leads MR Type 340 SMC Type MPW
Audio Tra nsf orm er Secondary By-pass
SM, MR
D-3932
13
3D93 3D9375 75
Capacitor
Mica, 500 V D-C D-C,, 375 mmfd 1.5% with leads, CD Type 5R, A Type 1464, MR Ty pe PO, ER Type K
Osc. Series Seri es
MR,, A, ER MR ER,, CD
D-4383
14
3DA2.24 3DA2.240 0
Capacitor
Mica, 500 V D-C, 2240 mmfd +5% with leads, CD Type 1R, or A Type 1464
Osc. Series Ser ies
MR, MR, A CD, ER
D-3564
Capacitor
Paper, 500 V D-C D-C,, 1500 mfd 22 0% with lead leadss MR Typ Type e 340 SMC Type MPW
Audio Coupling Coupl ing Conden Condenser ser
MR, SMC
D-3941
Audio Trans former Audio Primary By-pass
Reference No
Signal Corps Stock No
Name of Part
Description
Function
Mfg
Symbol
Dwg No
16
3D967 3D9670 0
Capacitor
Mica, 500 V D-C D-C,, 670 mmfd 21.5 with leads, CD Type lR, or Type 1464
Osc. Seri es
CD, MR, ER
D-4391
17
3D914 3D9147 7
Capacitor
Mica, 500 V D-C D-C,, 147 mmfd 21 with leads, CD Type 5R, ER Type K, MR
Osc. Seri Series es
CD, ER , MR
D-4379
Type 0 Capacitor
Mica, 500 V DD-C, C, 500 mmfd 2 5 with leads, CD Type 5R, ER Type K
1st I-F Tra nsf orm er Second Secondary ary Tuning
1
CD, CD, ER, MR, MR, FWS
DD-37 3778 78
t I-F Transformer Secondary Tuning
21-1
3D9250-18 3D9250-18
Capacitor
Mica, Mica, 500 D-C D-C,, 290 mmfd 2 1 with leads, CD Type 5R, ER Type K
Crystal Tra nsf orm er Tuning
CD CD,, MR, MR, ER FW S
D-382 D-3824 4
Capacitor
Mica, 5 V D-C, 260 mmfd 2 5 with leads, CD Type 5R, ER Type K
2nd I-F Tra nsf orm er Primary Tuning
CD, CD, MR, MR, ER FWS
DD-37 3775 75
CD CD,, MR, MR, ER FWS
D-37 D-3774 74
Capac itor
2nd I-F Transformer Secondary Tuning 3rd I-F Transformer Secondary Tuning
Mica, 500 V DD-C, C, 250 mmfd with leads, CD Type 5R,
1st I-F Tra nsf orm er Prima ry Tuning
ER Type K
21-2 21-2
3rd I-F Tran sfor mer Primary Tuning R-F Unit Padd er
2121-3 3
Reference No. No.
Signal Corps. Stock No. No.
22-1
3D9168
Name of Pa rt Capa Capacito citorr
22-2
24-1
3D9155
Description
Functi on
Mica, 500 V D-C, D-C, 240 mmfd 2 5 with leads, CD Type 5R, ER Type K
C-W Osc. Pa Paddi ddi ng
3D9 3D9025 025-30 -30
Dwg. No.
CD, MR, ER FW S
D-38 D-3813 13
2nd Det. By-pass
Capacitor
Mica
Osc. Seri Series es
CD, MR, ER
D-4372
Capa Capacito citorr
Mica, 500 V D-C, 155 mmfd 21.8 with leads, CD Type 5R, ER Type K
Ante Antenna nna Seri Series es
CD, ER, MR
D-4043
Antenna Unit Pa dde r
CD CD,, MR MR,, ER
D-4 D-4398 398
G W Osc. Grid
CD CD,, MR MR,, ER
D-37 D-3776 76
CD, MR, ER
D-4357
500 V D-C D-C,, 168 mmfd k1.276 with leads, CD Type 5R, ER Type K, MR Type
2nd R-F Series 1st Det. Series
24-2 24-3 25
Mfg. Symbol
Capacitor
Mica, 25 mm fd a 5
,
CD Type 5R, CD Type 0 , ER Type K Capacitor
27
3D9134
Capa Capacito citorr
Mica, Mica, 500 V D-C, D-C, 150 mmfd 2 5 wit with h leads, CD Type 5R, ER Type K
Mica, 500 V D-C, 134 mmfd with leads, CD Type 5R, ER Type K MR Type
4th I-F Transformer Secondary Tuning Hetero Het erodyne dyne Osc. Seri Series es
Reference No. 28-1
Signal Corps.
St Stock ock No.
3D9135
ame
Capa cit citor or
2828-2 2 2828-3 3 2929-1 1
3D9460
Description
of Part
Cap Capaci acitor tor
Mica, 500 V D-C, 135 mmfd *2 with leads, CD Type 5R, ER Type K, MR Type PO
Mica, 500 V D-C, 460 mmfd -t2 with leads, CD Type 5R, ER Type K, MR Type
2929-2 2 29-3
Function Antenn Antennaa Unit Serie Seriess
Mfg. Symbo l
Dwg
No. No.
CD, MR, ER,
D-404 D-4042 2
CD, MR, ER
D-4371
R-F Unit Series 1st Det. Unit Series Ante nna Unit Pad din g
R-F Unit Padd ing 1st Det. Unit
30
3D9100-19 3D9100-19
Capa cit citor or
Mica, 500 V D-C, 100 mmfd 2 5 wit with h leads, CD Type 5R, ER Type K
Heterodyne Heter odyne Osc. Grid
CD, MR, ER
D-40 D-4044 44
31-1
3D9075-2 3D907 5-2
Cap Capaci acitor tor
Mica, 500 V D-C, 75 mmfd +5 with leads, CD Type 5R, ER Type
R-F Pad din g
CD, MR, ER
D-404 D-4040 0
Capacitor Capaci tor
Mica, Mica, 500 V D-C, D-C, 47 mmfd 2 5 with leads, CD Type 5R, ER Type K
4th I-F Tra nsf orm er Primary Tuning
CD CD,, MR MR,, ER
D-3 D-3777 777
Capa cit citor or
Mica, 500 V 50 mmfd 2 5 with lead leads, s, CD Type 5R, MR Ty Type pe 0 , ER Type
Antenna Unit Padder
CD CD,, MR ER
D-4370
t
31-2 31-3
33-1
3D9050-7
3333-2 2 333
1st Det. Padd ing Diode Coupling
2nd R-F Unit Padd er 1st Det. Unit Padder
Reference No.
Signal Corps. Stock No
Name of Par t
Descrip Description tion
Function
Mfg. Symbol
Dwg. No No..
34
3D908 3D9085 5
Capacitor
Ceramic 500 V 85 mmf d *2. *2.5 5 with leads , ER Type NPOM
Osc Osc.. Temp eratu re Compensat ing
ER
D-405 D-4053 3
35
3D904 3D9047-1 7-1
Capacitor
Ceramic 500 V 47 mm fd -+5 with leads, CRL Type 813 ZTC
Os Osc. c. Temp eratu re Compensating
CRL
D-4052
36
3D9027 3D9027-1 -1
Capacito r
Ceramic, 500 V 27 mmf d t2 .5 with leads, ER Type N680K
Osc. Osc. Temp eratu re Compensati Compensating ng
ER
D-4 D-4055 055
37-1 37-1
3DF98
Capacitor
Air Tr imm er 25 mmf d Max. APC
Band
R-F Tr im mer
RC, AW, OM
D-502 D-5023 3
Band
1st Det. Det. Trimm er SS, MR
D-3933
SS, MR
D-2 D-233 334 4
3737-2 2 38-1A 38-1A
3DA500 3DA500-60 -60
Capacito r
215
38-1B 38-1B 38-2A 38-2 A 3838-2B 2B 38-3A 38-3 A 38-3B 38-3B 39-1A 39-1A
Oil, 250 V D-C, 0.5 mfd
3DA500-61
Capacito r
Oil, 250 V D-C, 0.5 mf d
4th I-F Tr an sf or me r Filter Volume Control Filter Screen Voltage Fil ter Output Plate Filter Noise Comp ensat or 1st I-F Screen Filter 4th I-F Tra nsf orm er
+15
Filter 4th I-F Transf ormer Filter Output Grid Filter Screen Voltage Filter 1st I-F Screen Filter 3rd I-F Screen Filte r
39-1B 39-1B 39-2A 39-2A 39-2B 39-2B 39-3A 39-3A 3939-3B 3B 40-1 40-1
32604 326047-5 7-5
Resistor
Insul. 470 ohms 2 1 0
1st R-F Cathode
W, Type EB
40-2 40-3 40-3 40-4
AB
P-281 P-28154 54
2nd R-F Cathode 1st I-F Cathode 2nd I-F Cathod e
Reference No. 4141-1 1
Sign al Corps. Stock No. 326100-58 326100-58
Name of Pa rt Resistor
4141-2 2 41 41-3 -3 42-1
326470326470-8 8
Resistor
42 42-2 -2 4242-3 3 4242-4 4 42-5 42-6 42 7 4242-8 8 43-1 w
324529
Resistor
Description Insul. 1,000 ohm s + l o W, Type EB
Osc. Plat e
Insul. 4,70 4,700 0 ohm s W, Type EB
1st R-F Plat e
+lo
Insul. 10,000 ohm s W, Type EB
43 2
Function
4343-3 3 43-4
Mfg. Symbol
Dwg. No. No.
AB
P-28158 P-28158
AB
P-28166 P-28166
AB
P-28170
3rd I-F Cathode Is R-F Primar y
2nd R-F Plat e 1st Det. Plat e 1st I-F Screen 1st I-F Plate Bleeder 3rd I-F Cathode Cathode Voltage Regulat or Series 1st R-F Screen 2nd R-F Screen 1st Det. Screen C-W Osc. Bleeder
45
324614
Resistor
Insul. 15,000 ohm s +lo W, Type EB
1st Det. Cathode
AB
P-28172 P-28172
46
326656 326656-1 -1
Resistor
Insul. 56,000 ohm s t l O l/zW, Type EB
Output Loadi ng
AB
P-28178
47
326668
Resistor
Insul. 68,0 68,000 00 ohms 210 W,T y p e E B
C-W Osc. Plate
AB
P-28179
4848-1 1
326700-61 326700-61
Resistor
Insul. 100,000 ohm s t l O l/zW,, Type EB l/zW
1s t R-F Grid
AB
P-28006 P-28006
48-2 48-3 4848-4 4 48 48-5 -5
2nd R-F Grid Osc. Grid Outpu t Grid Filt er Bias Control
Reference No.
Signal Corps. Stock No.
Name of Pa rt
Description
Functio n
Mfg Symbol
Dwg. No. No.
49
326718
Resistor
Insul. 180,00 180,000 0 ohms *lo /ow, Type Type EB
3rd I-F Screen
AB
P-2818 P-28182 2
50-1
326747-9
Resistor
Insu l. 470,000 oh ms 21 0 W, Type Type E
Antenn a Prot ective
AB
P-28187
AB
P-28188 P-28188
50-2 50-3 50-4 51
1st I-F Grid 2nd I-F Grid C-W Osc. Grid 326756-6 326756-6
Resistor
Insul. 560,000 560,000 ohms
Outpu t Grid
21 0
W, Type EB
52
32680lA5 -6
Resistor
Insul. 1.5 megoh ms 21 0 W, Type EB
AVC AVC Diode
AB
P-28193
53
326722-5
Resistor
Insul. 220,000 oh ms 21 0 W, Type EB
AVC Fil ter
AB
P-28183
56
326610-59 326610-59
Resistor
Insul. 10,000 ohm s +lo W, Type G
Bleeder
AB
P-30417 P-3041 7
57
326627-8
Resistor
Insul. 27,000 ohm s 21 0 W, Type G
Voltage Regul ator Series Resist Resistor or
AB
P-34578
58
326 32635O 35OV-4 V-4
Resistor
Vari able 3,500 * l o 10 ohms 0.1 0.1 W, Special
Noise Compensator
CTS, IRC
D-3673
59-A
2C4348M/Rl
Resistor
Vol. Contr ol Fr on t Unit, 20,000 20,000 21 0 to 10 ohms, 2.0 W Special Vol. Contr ol Back Unit 350,00 350 ,000 0 21 0 to 50 ohms, 0.2 W
MVC MVC
AB, CTS
D-3717
Insulated, 2,400 2,400 ohms *5 , W, Type EB, or W Type G.
Outpu t Plate
AB
P-34650 P-34650 D-5783 D-57 83
59-B
61
326240
Resistor
to
AVC AVC
Reference No.
Signal Corps. Stoc k No.
Na me of Part
Description
Dwg. No No..
326647-1
Resistor
Insulated, 47, 47,000 000 ohms *lo , l/z l/zW, W, Type EB
Bleeder Bleeder
63
3Z6006H4
Resisto r
Insula ted, 68 ohm s 210 S W , Ty yp pe EB
AVC Compen sating
AB
P-28144
64
3D9035-3
Capacito r
Ceramic , 500 V, 35 mmfd-2.5 with leads, ER Type NPOM
Osc. Unit Pad der
ER
D-43 D-4380 80
65
3DF97
Capacitor Capacitor
Air Tri mmer 10 mmfd, Special Special
Ant. Unit Tri mmer
RC, OM, AW
D-3562
Capac itor
Mica, 500 Volts, 20 mm fd *20 MR, Typ e
Part of 82 Part of 88
Inductan ce
Ant. Ant. Ant. Ant. Ant. Ant.
1st 1st 1st 1st 1st 1st
66-2* 71 72
73 74 75 76 Transformer
Band Band Band Band Band Band
6
R-F Band
1
1
2 3 4
5
R-F Band 2 R-F Band 3 R-F Band 4 R-F Band 5 R-F Band 6
U se d on Radio Receiver BC-348-P
Mfg. Symbol
62
66-1 66-1
\
Function
R-F R-F R-F R-F R-F R-F
Tuned Tuned Tuned Tuned Tuned Tuned
1st R-F to Coupling 1st R-F to Coupling 1st R-F to Coupling 1st R-F to Coupling 1st R-F to Coupling 1st R-F to Coupling File 2542-WF-42)
only.
Circuit Circuit Circuit Circuit Circuit Circuit
2nd R-F 2nd R-F 2nd R-F 2nd R-F 2nd R-F 2nd R F
Reference No. No.
Signal Corps. Stock No. No.
Name of Pa rt Trans former
Description 1st Det. Band 1st Det. Band 2 1st Det. Band
3
1st Det. Band 4 1st Det. Det. B a n d 5 1st Det. Band 6 Osc. Osc. Osc. Osc. Osc. Osc. Trans former
Band Band Band Band Band Band
1st I-F
C-W Osc. 3rd I-F
101-B 101 -B
to to to to to to
Mfg. Symbol
Dwg
No. No.
1st Det. 1st Det. 1st Det. 1st Det. 1st Det. Det. 1st Det.
1st Det. Coupling 1st Det. Coupling 1st Det. Coupling 1st Det. Coupling 1st Det. Coupling 1st Det. Coupling
1st Det. to Clrys Clrysta tall Coupling Crystal to 1st I-F Coupling 1st I-F to 2nd I-F Coupling Grid and Plat e Couplin Coupling g 2nd I-F to 3rd I-F
2nd I-F
2C4348M 2C4348M/T2 /T2
2nd R-F to Coupling 2nd R-F to Coupling 2nd R-F to Coupling 2nd R-F to Coupling 2n 2nd d R-F to Coupling 2nd R-F to Coupling Osc. Osc. Osc. Osc. Osc. Osc.
2 3 4 5 6
Crystal Filter
101-A 101A
Function
FW S
D-3 D-3753 753
FW S
D-38 D-3817 17
FW S
D-37 D-3754 54
FW S FW S
D-37 D-3795 95 D-37 D-3755 55
4th I-F
Coupling 3rd I-F to 2nd Det Det.. Coupling
FW S
D-3756
Tra nsf orme r
Audio
Output
CT AEM ST
D-356 D-3560 0
Choke
Audio Frequency
Filter
Capacitor
Pap er 0.05 mfd 400 V D C
C-W Osc. Time Constant
&lo
Reference No
Signal Corps Stock No
Name of Part
Description
Function
Mfg Symbol
Dwg No
102-1 102-2
2C4348M/Jl
Jac k
Single Circuit Single Circuit
Headphone Headphone
PRM
10 3
2V991
Regul ator
Xeon Bulb RCA 991
Osc. Plat e Volt Regulat or
RCA
104
225927 225927
Dial Lamp LM-27
6 to 8 V. GE-44 Mazda
Illum inates Dial
WE-GE
D-3866 D-3866
105
329692-1561.1 329692-1561.1
Switch
SPST Type 1561-KC
Cryst al Fil ter
AHH
D-3819
106
329858-1
Switch
DPST Type 81009
C-W Osc. Osc.
AHH
D-3734
107
329825-1
Switc h
3 Positions, 2 Waf ers ,
AVC-OFF-MVC AVC-OFF-MVC
OM
D-3719
PRM, OM
D-3489 D-3489
PRM, OM
D-3519 D-3519
ARH
D-3961
OUT-IN)
ON-O FF)
D-3726
Type 15824-H2 108
329693-2 329693-2
109
329693-1 329693-1
6 Position,
Waf er
6 Position,
Waf er
110
6 Position,
Waf er
Band Switch Antenna Unit Band Switch Antenna Unit Band Switch R-F Unit
112 113
6 Position, 6 Position, 6 Position,
W afe r Waf er Waf er
Band Switch R F Unit Band Switch Det. Unit Band Switch Det. Unit
6 Position,
Waf er
Band Swit ch Osc Osc.. Unit
6 Position, 6 Position, 6 Position,
Waf er Waf er Waf er
Band Switch Osc. Osc. Unit Band Switch Osc Osc.. Unit Band Switch Osc Osc.. Unit
114
329693-1
Switch
Switch Assembly
115 116 117 119
32635
Binding Post
Panel
Antenna
120
32635-1
201
2C4348M/HL
Binding Post
Panel
Ground
ARH
D-3718
Crystal Assembly
915 KC Crystal in Moulded Case
I-F Filter
FWS
D-3828
Handl e
Panel, modified, Type 0130.
Carr ying
Symbol
Dwg No
Reference No
Signal Cor Corps ps Stock No
Name of Part
Descripti Description on
Function
202
226190
Leve r
Contro l
AVC-OF AVC-OFF-MVC F-MVC
D-3735
203
2257 225748.1 48.1
Knob
Control
Antenna Alignment Crystal OUT-IN Switch Dial Lam p Control and Volume Control
Knob
Control
Beat Freq. Control
Thu mb Screws Screws
Dia Diall Window
Holds Dial Window
Knob
Control
Band Change
Knob
Control
Main Tuning Cond.
Cover
Panel
Permit s Access Access to Tube Shelf
Special Speci al Screw
Shouldered
Main Tuning Capacitor
Speciall Screw Specia
Shouldered Flathead
Dynamotor Assembly to Mounting Plate
Special Screw
Captive
Dynamotor Assembly
Speciall Screw Specia
Slotted Hex Head
Dial Assembly to Chassis
Special Speci al Screw
Shouldered
Secures Plug to Mounting Mounti ng P late
Cover
Plate with Captive Screw
Covers tube in Osc. Unit
SG
Shield
Tube Shield Special
Shield fo r Tub e VT-70
AG
Socket
Tube Octal Type 6744Wl
Fo r Tub es VT-91 VT-86 VT-93 VT-65
CM
Socket
Bayonet Type Specia Speciall
Fo r Voltage Regulator
CH
Socket
Tube 6 Prong Type 2-13Wl
Fo r Tu be VT-48
CM
Socket
Tube 7 Pron g Type U-13W1
Fo r Tub e VT-70
CM
ECE
Reference
Signal Corps.
No No..
Stock No.
Nam e of Pa rt
Description
Function
Mfg.
Dwg.
Symbol
No. No.
221
3C43 3C4348M/S 48M/S2 2
Socket
Lam p
Fo r Dial Lam p
PRM
D-3870
222
223084
Socket SO-104
8 Pole Male
Pow er Connect ions
AP
D-3849 D-3849
251
2C4348M/ 2C4348M/T3 T3
1st I-F Transformer Assembly
Complete with Shield Can Includes 18-1 18-2 21-1 95
1st Det. to 1st I-F Coupling
FWS
252
2C4348M/T4 2C4348M/T4
2nd I-F Transformer Assembly
Complete with Shield Can Includes 20-1 20-2 97
1st I-F to 2nd I-F Coupling
FWS
253
2C434 2C4348M/T 8M/T5 5
3rd I-F Transformer Assembly
Complete with Shield Can Includes 20-3 21-2 99
2nd I-F to 3rd I-F Coupling
FWS
254
2C4348M/T6
4th I-F Transformer
Complete with Shield Can Includes 26-2
3rd I-F to 2nd Det.
FWS
Coupling Assembly
32 100
255
2C4348M/F 2C4348M/F1 1
Crystal Filter Assembly
Complete with Shield Can Ihclud es 7 19 96 105 121
Controls I-F Selectivity Selectivity
FW S
256
2C4348M/P5
C-W OSC. Assembly
Complete with Shield Can Includes 8 9-12 22-1 26-1 47 98
C-W Recept Reception ion
FW S
257
2C4348M/All
Antenna Unit Assembly
Complete with Shield Can Incl udes 2 3-1 3-2 4-1 5-1 5-2 10-1 24-1 28-1 29-1 31-1 48-1 71 72 73 74 75 76 108 109
Antenna to 1st R-F Tube Coupli ng
258
2C4348M/F13 2C4348M/F13
R-F Unit Assembly
Complete with Shield Can Includ es 3-3 3-4 42 43 5-3 5-4 10-2 10-3 242 28-2 29-2 31-2 42-1 48-2 77 78 79 80 81 82 110
1st R-F to 2nd R F Tub e Couplin g
Reference No No..
Signa l Corps. Stock No.
Nam e of Pa rt
Descriptio n
Funct ion
Mfg.. Mfg Symbo l
Dwg. No.
259
2C4348M/D l2
Det. Unit Assembly
Complete wit h Shield Can Includes 3-5 3-6 4-4 4-5 5-5 5-6 10-4 24-3 28-3 29-3 31-3 42-2 83 84 85 86 87 88 112 113
2nd R-F to 1st Det. Tube Coupling
D-341 D-3412 2
260
2C4348M/P6
Osc. Unit Assembly
Complete with Shield Can Inclu des 3-7 3-8 6-1 6-2 6-3 6-4 11-1 11-2 13 14 16 17 23 27 30 33 34 35 36 37 41-1 45 48-3 89 90 91 92 93 94 114 115 116 117 214 217
Heterodyne Osc. to 1st Det. Coupling
D-3414 D-3414
Resistor Board
17 Termin als
Suppor ts Par ts 12 4242-6 6 44 48-4 56 57
CM
Resistor Board
32 Termin als
Suppor ts Par ts 9-1 9-13 3 9-14 9-15 9-16 9-18
CM
271
D-3 D-3927 927
15-1 15-2 41-2 42-7 46 49 51 54 61 Resistor Board
14 Termin als
Suppor ts Par ts 9-9 9-1 9-10 0 9-11 40-4 42-4 42-5 50-3
CM
Resistor Board
14 Termin als
Suppo rts Par ts 9 6 4343-4 4 50-2 55 62
CM
D-39 D-3928 28
Dial Mechanism Complete with Mask Index Gear Drive Stop and Detent Mechanism
Freque ncy Indicator Tun ing Condenser Drive
RM RMC C
D-5029
301
2C43 2C4348M/ 48M/C2 C2
Choke
R-F
Filter fo r Dynamo tor
D-39 D-3909 09
302
2C4348M/C1 2C4348M/C1
Choke
R F
Filter for Dynamotor
DD-39 3908 08
Reference No No..
Signal Corps. Stock No No..
Name of Pa rt
Description
Function
Mfg. Symbol
Dwg. No No..
303-A 303A
3DA500-62
Capacito r
Oil, 250 V D-C, 0.5 mfd
303-B
305
Filter fo r Dyn amot or
SS, MR
D-4033
Filt er fo r Dyna moto r
SMC, SMC, MR
D-36 D-3682 82
220
3DH1.8129 3DH1.8129
Capacito r
Pap er, 400 mfd k2 0
D-C, 0.01 with leads leads
Capacito r
MR Type 340, SMC Type MPW
Filter for Dynamotor
Capacitor
Oil
Filte r fo r Dynamoto r
SS
D-3 D-3915 915
Capacitor
O1
Dyn amot or Filt er
MR MR,, SMC
D-3682
mfd t 2 0
400 V
mfd *20 400 V Paper, MR Type 340, SMC SMC Type MP W
Bearing (Set of 2)
Pa rt of Ref. 510
Dynamo tor
WC
D-3 D-3472 472
3Hl628M/B4 3Hl628 M/B4
Brush and Spring
Part of Ref. 510
Pos. H-V
WC
D-4348
3H1628M/B 3H162 8M/B4.1 4.1
Brus h and Spring
Part of Ref. 510
Neg. H-V
WC
D-4349
End Bell
Pa rt of Ref. 510
Low Volt Voltage age End Bearing
WC
End Bell
Pa rt of Ref. 510
High Voltage End Bearing
WC
Tie Bars
Pa rt of Ref. 510
Hold Items 315, 316 to Frame
WC
Brush Caps
Part of Ref. 510
Holdss Brushes Hold
WC
Grommet
Part of Ref. 510
Protects Terminal Wires
WC
Gasket
Part of Ref. 510
Preve nts Leakage of Lubdcant
WC
Plate
Part of Ref. 510
Bearing Retainer
WC
Reference No
Signal Corps Stock No
Name of Part
Function
Description
324
Cover
Pa rt of Ref. 510
Dust Cover
350
Brack et and Gear Assembly
Pai r of Beveled Gears and Coupling
Drives Band Change Switch
Coupling
Flanged Collar with Rectangular Slot
Coupling Band Change Knob Shaft to Item 350
Disk with Two Rectangular Keys
Slide Between 2 of Item
Window Frame Window Assembly
Removable Cast Housing which Holds Dial Glass
Covers Dial Lamps
Friction Spreader
Phosphorus Bronze Spring
Prevents Controls from Turning Under
Jack Cover Assembly
Sprin g Actua Actuated ted Cover
Vibration Seals Jack Openings
Bushing
Threaded Bushing
Holds Handle to Panel and Provides Bearing for Thum b Screw
Special Locking Nut
Holds Item 357
Thumb Screw Assembly
No. 10-24 x 10 inches Long Special)
Holds Chassis in Cabinet
Nut
Special Lock ing Nut
Holds Upper En d of Handles
Coupling Slide
ut
351
Mfg Symbol
Dwg No
D-3685
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