Weed Eater | 177019 | tm 11-235 radio sets scr-536-a, scr-536-b,i . a scr-536-c

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RESTRICTED
TM 11-235
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WAR DEPARTMENT
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TECHNICAL MANUAL
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RADIO SETS SCR-536-A, SCR-536-B,I
A
SCR-536-C
May 14, 1943"
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*TM
11-235
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RESTRICTED
'l'ECHNICAL MANUAL
No. 11-235
WAR DEPARTMENT,
WASHINGTON, May 14, 1943.
RADIO SETS SCR-536":'A, SCR-536-B, AND SCR-536-C
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DESTRUCTION NOTICE
Depending upon.the time and materials available, when the
capture of this equipment by the enemy is certain, completely
destroy it by one or more of the following means:
1. Explosives such as grenades or TNT.
2 . Incendiaries such as wood, oil, and gasoline.
3. Axes, hammers, large rocks, or other hard, heavy objects
such as hand generators, dynamotors, etc.
Removal of the chassis from the case will simplify the above
means of destruction. When this is done be sure to smash
crystals and holders, tubes, coils, microphone, earphone, and
batteries.
Destroy all instruction books, Technical Manuals, circuit
diagrams, or other literature for this radio set at the same
time.
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SAFETY NOTICE
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The voltages used in this radio set are not high enough to
be injurious. A slight shock, of negligible magnitude,. may
result by touching the antenna and case at the same time, when
the set is transmitting.
Paragraphs
I.
II.
III.
IV.
V.
SECTION
Description
EmploymenL
Functioning of parts
Maintenance
Supplementary data
_________________________ _ �___________
________________________
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_________________________ .___________
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1-9
10-23
24-38
39-78
79-80
Page
INDEx
___________________________________________________ _
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*This manual supersedes TM 11-235, March, 1942.
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82
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SIGNAL
CORPS
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SECTION J
DESCRIPTION
Paragraph
lJse______________ ___________________________________________________ __
_
1
Components, weights, and rlinlf'm;ions______________ ____ ________ __________
2
weights________________________ _______________________ ---________
3
Source of power and power requirernents_________ _____________________ ___
4
Total
I>istance range_________________________________________________ ---- ---covera ge ____________________.. ___.______________________ ______
6
Modes of tram:mi!'ision and rpception_ _____ _______________________________
7
L�ntrols _____ _____________ _________________________ _______________ _____
8
9
Frequency
])escription of cornponents_______________________________________________
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1. Use.
Radio set SGR-536 -(*) is designed for short-range two­
way voice conversation. Descriptively, it is a press-to-talk portable
radio telephone, receiving and transmitting on the same frequency.
.
No skill is required to operate it.
a. The set is self-contained ; all equipment necessary for reception
and transmission is contained in one aluminum case.
b. The set may be held in either hand when operating, although it
is designed and balanced for left-hand operation. The microphone
and earphone are attached to the case in such manner that the set
resembles a hand telephone. An adjustable carrying strap is attached
to the case. ( See figs. 1 and 2.)
"Radio sets SCR-G36-A, SCR-536-B, and SCR-536-C are alike, for all practical
purposes.
The different suffix letters indicate d ifferent procurements.
For con­
venience, they are referred to throughout this manual as radio set SCR-536�(*)
except where some difference exists between types.
Similarly thl" component
parts, radio recei.vers and transmitterS BC-611-A, BC-611-B, and BC-611-C are
referred to as radio receiver and
transmitter B�611- ( "' )
IE-17-A, IE-17-B, and IE-17-C are referred to as IE-17-("').
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Test equipments
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RADIO SETS SCR 53 6-A, -B, AND -{j
2-4
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2. COlVl PONKNTS, WEIGHTS, AND DIMFrNSIONS.
Dimensions (inches)'
Quan­
tity
-L
L
2
1
1
1
--
Article
--,-
-
Heigllt
------
---
Widtll
Depth
I-�·--I---
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_
--;---
Length
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Diameter
---
_ _ _ ___ _ _ _ ___
L%6
FYs2 _ _ _ _ __ __ ____
_ _ _ ___ ___ ___ _ _ _ _
5% ___ ___ _ _ _ _
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Unit
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weight
(pounds)
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0. 55
1. 10
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3. 85
.
_ _ _ _ _ _ __ ____
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______ __ ____
_ _ _ _ _ _ ______
______
_ _ ___
___ _ _
______
_ _ _ _ __
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01
01
01
. 01
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·
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--.-
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Battery BA-37 (1.5 volts)____
61� -_____
Battery BA-38 (103.5 volts)__ 11%
P7�2
Preliminary instructions_____ _ 1 1
8%
Radio receiver and transmit15%
3%
ter BC-611-(*) (with coils,
crystals and tubes, but
without batteries).
Set of crystals (spare).2
Tube set GK-174 (spare):
Consisting of;
__
1 tube VT-17L _ _ _ _____ _ _ _ _ _ _
1 tube VT-172____ _ _ _ _ _ __ _ _ __ _ _ _ _
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1 tube VT-173___ _ _ _____ _ _ _ _ _ _ _
2 tube VT-174__ ________ _ _ _ ___ _____
Box BX-49 Containing;3
12 sets of crystals (transmitting and receiving)
12 sets of antenna coils.
12 sets of r-f tank coils.
(1 set of coils and crystal
for each of 12 operat­
ing frequencies).
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DimenSiOns, wbere unappreciable, are omitted.
, ('oml'oncnt of SCR-536-A only.
'-Component of SCR-53&-C only.
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Total weight of radio set SCR-536-( * ) , including batteries, is 5.5 pounds. Over-all dimensions and weights of
l"omponents are given in paragraph 2.
4. Source of power and power requirements. Radio receiver
and transmitter BC-611- ( * ) is battery powered. Space for both A
and B batter!es is provided in the housing. ( See fig. 1.)
a. The filament or A batt€ry BA-3'l, rated at 1.5 volts, is cylindrical
in shape and fits into the round compartment in the housing.
b. The B battery BA-38, rated at 103.5 volts, is oblong in shape
and fits into the oblong compartment in the housing. (The bottom
.
of the case has a hinged cover which permits access to the batteries
and radio chassis.)
c. PO'l1!er requ.irements.
Batteries should last 15 hours, under
almost continuous operation.
3. Total weights.
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Drain transmitting
Drain receiving
Battery
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A battery BA-37 1.5 volts ________ 0.25 amperes ___ _ _ ___ 0.30 amperes.
B battery BA-38 103.5 volts _ _ _____ 11 milliamperes___ _ _ 35 milliamperes.
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3
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SIGXAL CORPS
5-6
-��.-�-. ,
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COVER
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PRESS.,. TO-TALK SWITCH'
.PlUG
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MI(:�ION[ I'l\!G
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A
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EARPHONE'
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LAfCtiING
BATTERY CONTACT
SOARD
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801..T ""'
,.,..,·
.....-'
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·B" BATTI;:RY BA-38 ---""'-'-<
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- -� BATTERY BA·37
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FIG eRE 1.
Radio set ::;CR-;;:�(j-(*)
?-
7'L55J)
showing battery compartment.
5. Distance range. The set is desi gned to operate over distances
from IOU feet to 1 mile The dependauility of opera ti on at the
.
greater distance will depend on the terrain and the freedom from
signal absol'bil1g objects such as steel buildings, trees, hi lls, and tele­
phone and power lines between the two sets. This is particularly
true for sets operating at the higher frequencies in the band. The
maximum range may be consi derably greater when operating over
water or in the air.
6. Frequency coverage. Radio set SCR-536- (*) is crystal con­
trolled on both reception and transmi::;sion , and will operate over the
frequency range of 3500 to 6000 kil ocycles. However, each unit is
adjusted to operate at only one frequency in this band. The set
can be made to operate at any frequency in the band by proper
choice of crystals and coils. For correct performance, each set
must be adjusted to the crystals used. The coils and crystal changes
and their adjustments cannot be made by the operator, but are
preset by the manufacturer or by maintenance men at authorized
repair points. ( See sec. IV.)
4
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RADIO SETS SGB
5 3 6-A, -B, AND -C
7. Modes of transmission and reception.
5:W-(*)
7-9
Radio set SCR-
transmits and receives amplitude modulated voice signals
only.
S. Controls.
a.
Send-receive.
A
press-to-talk switch, conven­
iently located under the finger ti ps when the radio set is held in
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nOl'11ml operating position, is the only control required for operation
of this equipment.
b. On-off.
(See fig.
1.)
By fully extendi ng the telescopic antenna rod, the set
is automatically turned on,
'Vhen the telescopic antenna rod is
fully retracted the set is automatically turned off.
(The bottom
section of the antenna operates the on-off power switch.)
c.
Volume.
No volume cont.rol is used with this set.
The volume
in the earphone is set to a normal level by the design of the
equipment.
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d. T'Il.ning.
The operator is not required to make tuning
justments of any kind.
(See par.
6.)
9. Description of components.
radio receiver and transmitter
ad­
a.
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The housing which incloses
B0-611-(*)
is an aluminum casting.
Its interior is divided i nto three compartments, one for the radio
ehassis, one for the
RA-38.
A
battery
BA 37 ,
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and one for th_�
B
battery
Two projecti ons from the housing contain the earphone
and microphone units,
These projections are so spaced and of such
length that when the unit is held with the earphone against the
Pour or the operator, the microphone or mouthpiece is in the proper
position for talking.
b. The press-to-talk switch, mounted
on the side of the case,
operates the change-over switch on the radio chassis.
the set from a receiver to
a
transmitter.
This converts
This switch is so l ocat€d
that it may be operated easil y with the fingertips when the set i s
held in the left hand.
c.
,
The bottom cover hinges to the housing and is provided with a
sl ot into which a l atching bolt fits.
It is through this end of the
housing that the chassis and batteries are inserted or removed.
A
contact terminal board inside the bottom cover provides the con­
nections between
d. A
tIll:' batteries and the radio chassis.
small card holder below the press-to-talk switch contains
a plastic card on which the operating frequency and date of bat­
tery replacement are marked.
by a tra.nsparent cover.
This card is protected from weal'
To remove the card from its container the
bottom cover must be opened.
(See fig. 1.)
e.
The top cover of the set contains an opening for the antenna
rod.
This cover is hel d in place by a mounting screw which holds
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SIGNAL CORPS
9-11
the chassis securely in the housing. Spring battery contacts and
a spacer for the A battery BA.-37, fastened to the top "OVCl', make
electrical connections to the batteries.
f. A.n antenna cap, attached to the top cover on the outside by a
chain, protects the telescopic rod antenna against weather conditions
when the set is not in use.
Early issues of radio set SCR -536-A were furnished with a crystal
NOTE.
microphone and crYRtal earplJOne.
All later issues of SCR-536-A and radio sets
SCR-536-R and SCR-536-C are furnished with an inductor microphone and an
inductor earphone.
These components are electrically and mechanically inter­
changeable with the crystal Ilnits they repIacf' .
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SECTION Il
EMPLOYMENT
Paragraph
Initial procedure________________________________________________________.
10
Installation____________________________________ ._________________________
11
Preparation for use____ ..:__________________________________ :..____________
12
Starting the seL________________________________________________________
13
Receiving__________________________ _____________________________________
14
Transmitting____________________ ________________________ _______________
15
Turning off set__________________________________________________________
16
Opera tioD over long periods__________ _________ __________ ________________
17
NettiDg___________ ____________ __ ________________________________________
18
Change of frequeucy_____________________________ ____________ __ ________
19
Power outpnt______________________________________ _____________________
20
Replacing batteries____________________ ._________________________________
21
Operation in the raiu___________________________________________________
22
Poor reception and transmission_______ __ ______ ________ __________________
23
Unpack the equipment carefully to pre­
vent. damage or loss of components. Check against list of com­
ponents in paragraph 2. Also note the channel on which the radio
receiver and transmitter are alined.
11. Installation. a. General. The set is furnished by the manu­
facturer with everything contained in the housing except the bat­
teries. To put the set into operation, the batteries must be inserted
in their proper place.
.
b. Installation of batteries BA-37 a'l1d BA-38. Open the radio
set bottom cover by turning the latching bolt knurled nut in a
counterclockwise direction, until the nut begins to turn with diffi­
culty. Then press the cover against the case and push the bolt away
from the housing. Release the cover and it will open. ( See fig. 1. )
( 1 ) Battery BA-37 (filament or A battery) is cylindrical in
shape and fits into the round compartment of the radio set housing.
Insert the battery into the housing with its positive end out. The
10.
Initial procedure.
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RADIO SETS SCR 536-A, -B,
AND
-C
11-13
Jlositive terminal is marked with a large positive ( + ) sign. It can
he idt'lltifieJ also by a small raised metal buttoll. The raised buttull
permits positive identification when installing battery in darkness.
(2) Battery BA-38 (B battery) is oblong in shape and fits into
the oblong compartment of the radio set housing. It also must be
placed into the battery compartment with the positive ( + ) end out.
The positive terminal is marked with a large plus ( + ) sign and also
can he identified by the small raised metal button.
NlJ'o:,--Uefore closing t.he raflio set bottom cover. mark tile date of battery
installation on the dabl card located in tbe pocket just below the press-to-talk
"witch, 'I'he card is remoVl'd by sliding it out of the bottom of the pocket, The
transparent protective cover will come out with the card,
Erase the old date
that is marked on the card. and put on the new one, When replacing the card.
l'cnwmlif'r to put the transpal'ent protective cover OVi'r the canl.
(3) After the batteries are installed close the bottom covC'r of the
raJio set by pressing the cover against the housing with one hand,
while the other hand moves the latching bolt into the cover slot and
tightens the knurled nut by turning it clockwise. The cover then
:-;hould be pressed against a solid object and the knurled nut tightened
by hand until it turns with great difficulty. This will assure positive
contact between batteries and battery contacts.
12. Preparation for use. Before radio receiver and transmit tel'
BCr-fill-(*) can be placed in operation, the following must be done:
fl. Unscrew the antenna cap which covers the telescopic a,ntenna.
(See fig. 1.) To prevent losing it, this cap is attached to the hous­
ing by a small chain. Screw the cap on the threaded metal stud on
top of the housing. This will prevent the cap from rattling against
the housing when operating the set. See that the chain is not
. wrapped around the antenna rod and that there is no chance of it
touching the rod.
h. Pull the antenna out gently until all four sections of the rod
are fully extended. The alltcnna then will be about 39 inches long.
c. The unit is now held in the left hand, in the same malIller as a
telephone handset, and is l'eady for use as a radiotelephone set.
(See fig. 2.)
13. Starting the set. In succeeding paragraphs radio set SCR536-(*) will be referred to as "the set." The set is turned on when
the antenna is fully extended. This is 'accomplished by a small lever
attached to the antemut rud which operates the power switch on the
radio chassis. A rushing nuise in the earphone will indicate that
the receiver is on. Also a click will be heard when the switch
tumbler snaps over.
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SIGNAL
13-1 5
CORPS
Caution. A stop at the lower end of the antenna rod prevents it
from being pulled out of the ca8e, but the bottom Hcction of the
antenna mU8t be fully exte?lded since it operates the power switch on
the (]n.aBsis BY WHIOH THE SET IS TURNED ON .
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FIGURE 2.
14.
Radio set SCR-5<lti-(.)
in operating position.
Receiving. The set is normally in the receive position so that
the operator can hear signals from another set if it is transmitting
on the same frequency. The set should be held in the hand as
shown in figure 2. The antenna will then extend above the head in
an approximately vertical position. This is important for best re­
ception and transmission.
15. Transmitting. a. In order to transmit, the press-to-talk
switch on the side of the housing must be depressed. This is done
with the fingers of the hand holding the unit. The operator then
can speak to the operator of the other set. The press-to-talk switch
makes the necessary circuit changes to convert the receiver into a
transmitter.
8
RAaIO SETS
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SCR
5 3 6-A, -B, AND -C
15-18
b. In order to receive, the press-to-talk switch must be released
when transmission is completed.
c. When the operator is speaking into the microphone, the speech
level should. be varied according to distance of transmission. It
should be very soft for short distances. The operator should speak
clearly, and should take care that the press-to-talk switch is de­
pressed befol'e starting to speak, and is released immediately upon
compl!:'tion of conversation. In the beginnin�, the operator may ex­
perience some difficulty in synchronizing the operation of the press­
to-talk switch with tJH� beginning and end of his speech. Ther!:' is
a natural tendency to hold the switch down when through speaking,
and to forget to press the switch before starting to speak. A litt1..,
pradice will eliminate this difficulty. It is good practice to pause
for a mOmellt after pressing the press-to-talk switch.
16. Turning off set. Telescope the anteuua into the case. The
bottom section of the antenna rod must be pushed into the case a.�
far as it �vill go. This will turn off the set. The operator can hear
the toggle switch snap over. Put the antenna cap in place, covering
the alltellla when the set is not in use.
17. Operation over long periods. When operating the set for
long periods, it will be found less tiring to carry the set slung over
the shoulder rather than to carry it in the hand. To carry it in this
manner, lengthen the strap by pulling the strap slide toward the
antenna end of the case . The reverse action will tighten it. Place
the left arm between the strap and the set housing so that the set
rests on the left shoulder. The set is slung to the front of the
operator. The set then can be held there with a slight pressure
from the arm, or by permitting it to rest in the crook of the arm.
The sound caused by one station calling another will be loud enough
to be hellrd, even though the earphone is several inches from the
ear. The unit then can be brought into position for use.
18. Netting. For two-way conversation, two sets adjusted to op­
erate on the same frequency are required. Two sets operating at
different frequencies will be unable to converse with each other.
More than two operators can engage in conversation by the use of
mOl'e sets operating on the Silme frequency. Because of the receiver
arrangement used, it is possible to opernte Heveral receivers without
interference at the same frequency and in close proximity.
However, more than one radio set transmitting at the same time
on the same frequency is likely to cause confusion in orders. Uadio
Eet SCR-536-(*) also can be used for voice communication with other
types of radio sets adjusted to exactly the same frequency.
5203Gl°
43:
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19-23
SIGNAL
CORPS
Changing the operating frequency
of the unit requires a change of the two crystals and of two coils. Coil
and crystal equipment is available to cover the frequency range of
3.5 megacycles to 6 megacycles if required. Special equipment is re­
quired for retuning of the sets, and a trained technician must do the
job. The frequency presetting and realinement procedure will be
found in section IV of this book.
20. Power output. Maximum power output is obtained in the
transmitting position with the antenna fully extended. If the units
are not at a great distance from each other and a reduction of the
power radiated is desired, telescope one or two of the top sections of
the antenna. The bottom section mu.st remain fully ewtended.
2 1 . Replacing batteries. See procedure given in paragraph lla.
Replace both batteries even though one is in better condition than the
other. This 'will reduce the chances of battery trouble.
19. Change of frequency.
NOTE. When sets are to be placed in storage for long periods of time, remove
the batteries from the case. This will prevent the batteries from becoming
wedged in the battery cumpartment, should they swell when aging.
The set is designed to exclude water,
but, if operated in the rain, it may be found that the water film cover­
ing the antmma insulator at the base of the antenna acts as a short
circuit between the antenna and case, making the set weak or
inoperative. Wipe the insulator frequently with a dry cloth to improve
operation.
23. Poor reception and transnlission. a. If the distance be­
tween sets in communication with each other is between 100 feet and
1 mile, and the transmission is poor, it may be that the batteries are
weak. The batteries are designed to give about 15 hours of use, assum­
ing that the unit is on for long periods of time and that the operator
is transmitting much of the time. They will last much longer if not
used constantly. A sign of weak batteries is a low noise level in the
earphone when the set is in the receive position and no other station
is being received. Another cause of poor reception may be signal
absorbing objects, such as steel buildings. trees, hills, power and tele­
phone lines, and large metal objects between the two units. The
straight-line distance between units shuuld be as clear of such objects
as possible. Operation often will be imprJJved by moving one or both
sets to new locations. Placing the set as high as possible, as on top of
a hill or building, will help to increase the range of operation. Be
sure that the antenna is fully extended, held, as nearly as possible, in
a vertical position, and clear of obstructions for several feet around
it. When operating the unit in the underbrush. keep the antenna.
from coming in contact with branches or green foliage of any kind.
2 2 . Operation in the rain.
,
10
RADIO SETS SCR 536-A, -B, AND -C
23-25
llrecautions should be taken particularly in the early morning when
dew is on the ground, or after a rainfall. Conditions of this kind
may render the unit inoperative.
b. 1£ the set does not work when the antenna is extended, that is,
no sound is heard in the earphone, check to see that the bottom section
of the antenna is extended out of the case to its full length. This is
necessary to operat.e the power switch on the chassis.
c. If the set still does not work, refer to sect.ion IV for further cor­
l'ective measures.
SECTION III
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FUNCTIONING OF PARTS
Receiver functioning_____________________________________________
Paragraph
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24
Basic receiver circuiL___________________________________________________ 25
R-f alnplifier _____________________________.______________________________ 26
Converter-oscillator ______________ _______________________________________ 27
I-f amplifier_____________________________ ______________________ _________ 28
�ecol1d detector first a-f aml1lifieL______________________________________
29
Second a-f ampJifieL____________________________________________________ 30
'rmnsll1itter functioning______________________ ___________________________ 31
Basic transmitter cit'cuiL_______________ ________________________________ 32
Oscillator____________________________________ ____________________ _______ 33
R-f power amplifier_____________________________________________ _____ ____ 34
:\[ierophone ampJifier ___________________________________________________ _ 35
J\Iodulator ______________________________________________________________ 36
ClIange--over switch _____________________________________________________ 37
Description of parts_________________________________________________ ____ 38
NOTE.
This description is based on radio set
SCR-536-C.
SCR-rl36-A and
B are similar e:::cc ept for minor differences.
In the receive position, the set acts .
as a five-tube superheterodyne receiver consisting of one r-f amplifier
stage� using a t.ube VT-174, one oscillator-mixer st.age using a tube
VT-l71, one i-f amplifier stage using a tube VT-173, one diode detector and first audio amplifier stage using a tube VT-172 , and one audio
power output stage using a tube VT-174. The functional diagram
of receiver is shown in figure 3.
25. Basic receiver circuit. a. TilP antenna is series tuned by the
mica trimmer C7• The signal voltage developed across C7 is amplified
by t.ube V1 and applied to the grid of tube' V2• In V2, the mix!'l'­
oscillator tube, the incoming signal is mixed with the oscillator signal
generated in the tube and produces a beat frequency signal of 4!)5 kc.
The oscillator uses a crystal in a Piel:.ce circuit, and functions �lt 455
kc above the carrier or incoming signal frequency. The receiver
24.
,
Receiver functioning.
11
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25-27
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SIGNAL CORPS
crystal MI, therefore is 455 kc higher in frequency than the transmitter
crystal M2•
b. The beat frequency or i-f signal produced in the mixer is am­
plified by tube Va and is applied to the diude section of tube V.. Due
to the detection process, the modulated i-f signal is demodulab�d, and
an audio voltage is impressed across R20, the grid resistor of the pen­
totle section of tube V4• The signal is thell applied to the grid of tube
V�, the power amplifier, where it is further amplifil'(l and then applied
to the earphone.
26. R-f amplifier. a. Capacitor C1 is not IWC{!SSary for the re­
('Piving function, but serves to block the d-c component of the plate
voltage from thl' antenna rod in the transmit position. The induc­
tance Ll is a loading coil which aids in resonating the antenna. Re­
sistor R2, the grid resistor of V" provides a d-c path for the bias ap­
plied to the grid of tube VI and a high impedance to the r-f CUlTl'nt,
preventing it getting into the avc circuits. Capacitor C7 is the· an­
tenna tuning capacitor. Capacitor Cs is an r-£ bypass fur the fila­
mf'nt circuit to reduce regeneration. Capacitor C2 bypasses the r-f
current from the screen. Resistor Rl8 helps make the bypassing of
C2 more effective as it. increases the impedance of the path through the
n battery BA-38. This arrangement is commonly cal1ed a decou­
pIing filter. Resistor Rl8 also reduces the screen current.
b. The permeability-tuned inductance L2 provides the r-f plate load
for tube VI and is resonated by a capacitance made up of the dis­
tributed capacitance of the coil. the output capacitance of tube V"
the input capacitance of the tube Ve, and the capacitance of circuit
wiring. L2 is adjusted to its operating frequency by a movable pow­
dered iron slug.
c. Capacitor Ca and resistor RIO makl' up a decoupling filter for the
plate circuit of tube VI' The resistor RIO also serves to lower the plate
voltage of tube VI which reduces its plate current and gives more
ecunomical operation of the B battery BA-38.
27. Converter-oscillator. a. Capacitor CIO is the coupling ca­
pacitor which provides passage for the r-f current to the grid of
tube V2, but prevents the d-c at the plate of tube VI from reaching
the grid. Resistor RI is the grid resistor of tube V�. Resistors Ra and
R4 make up the grid leak which provides the bias voltage for the
oscillator grid as well as the bias voltage for the audio output tube
YT-174. A vultage suitable for biasing purposes is produced across
these resistors because of the d-c component of the grid current which
exists as a result of driving the oscillator grid positive. The three
resistors R2o, R7, and Rr. make up a voltage divider to provide the
pl·oper values of bias for tubes VI, V2, and Va when necessary to
reduce regeneration.
12
•
V2
VT-171
VI
VT·174
CONVERTER a
R-F AMP
V3
YT-173
osc.
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VT-IT2
2ND. DET. - A.V. C.- A-F AMP.
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M7
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FIGURE
,
3.
!ATT
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M5
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a
YOI.T"N BATT.
1111h--._­
Me
Functional diagram of receiver.
•
"
27-29
I
I
•
•
,
SIGNAL
CORPS
b. Capacitors CIa and C14• and resistors Ro and ReB make up a filter
for the automatic volume control (avc) voltage applied to the grids
of tubes V,-, V2, and Va. This avc voltage is obtained from the de­
tector load resistance made up of resistors R1S and R14• The filter
removes the audio component of the detector voltage from the d-c
component which is used for tIl{' avc function. Capacitors Co and C2a
are r-f bypasses to prevent a voltage of the oscillator frequency
getting into the grids of the other tubes through the bias system.
It reduces the voltage
c. Capacitor C4 is a neutralizing capacitor.
of the oscillator frequenc y on the signal grid due to coupling within
the tube, by feeding back a voltage of the oscillator frequency out
of phase with the internally coupled voltage.
d. The r-f choke La is a shunt feed arrangement, for the screen grid
of tube V2 . It provides a low-resistance d-c path and a high-im­
pedance 1'-f path to the screen grid.
e. The crystal Ml connected between the No.1 grid (oscillator grid)
and the screen grid provides the coupling necessary for oscillation.
This arrangement is known as the Pierce oscillator circuit.
f. Capacitor Cll and resistor R17 make up a decoupling filter for
the screen circuit of tube V2.
28. I-f amplifier. The first i-f transformer Tl (two windings)
is wound on iron cores and is surrounded by an iron sleeve to increase
the inductance of the primary and secondary coils and to reduce their
size. The coils are tuned by the trimmers CI5 and C16• Resistor Rs,
which is contained within ·the shield, serves to broaden the response
of the transformer. Capacitor C17 and resistor RI2 make up a de­
coupling filter for the screen grid of tube Va. Capacitor CIS and
resistor RI5 comprise a decoupling fli ter for the plate circuit of
tube Va.
29. Second detector first a-f amplifier. a. The second i-f
transformer T2 is also wound on an iron core and is surrounded by an
iron sleeve. The trimmer CI9 tunes the secondary.
b. Resistor R14 is the detector load across which the audio voltage
is obtained. Resister RIa and capacitors C20 and C2l make up a filter
to remove the i-f component. from the audio component of the detector
voltage.
c. Capacitor C22 couples the detector to the grid of the 1st audio
amplifier, and prevents the d-c component of the detector output from
biasing this grid.
d. Resistor R20 is the grid resistor of the pentode section of tube V 4.
As it has 10 million ohms of resistance. the small amount of grid
current which exists in the tube and flows through the resistor pro-
14
•
•
RADIO SETS SCR
•
5 3 6-A, -B, AND -C
29-32
\'illes additional bias for this tube 011 large signal inputs. Capacitor
( '25 is an i-f bypa:-.;s to eliminate allY i-f current which exists in the
plate circuit from getting into the audio plate load resistor R22• Ca­
plwitor C26 and l'esistor R21 make up a decoupling filter for the screen.
Rl':rister R22 is the plate load of tube V4, and C21 is the coupling
ea pacitor.
Resistor R2:l is the grid re­
:-:istor of tube V5 ' Capacitor C29 and resistors R2< and R16 make up
u decoupling filter for the screen of tube Vs.
RiG
also
helps
Resistor
,
reduce battery drain by lowering the screen CUl'l'ent.
b. The audio choke L4 provides a low resistance doc path for the
plate current, and offers a high impedance path to the audio plate
current. Capacitor Cso and resistor RIl make up a plate decoupling
filter. Resistor Rll also serves as a llroppiug l'esistor to lower the
plate voltage. Capacitor C24 prevents the doc at the plate from reach­
ing the earphone.
c. Notice that only one filament section of each of the tubes VT-174
is used in the receive position. This arrangemeut reduces the A
battery BA-37 drain.
31. Transmitter functioning.--Tn the transmit position only
four tubes are used. The circuit consists of a crystal controlled oscil­
lator in a Pierce circuit, which driyes a tube VT-174 as an r-t power
amplified. The r-f power alllplifier is plate modulated by a modu­
lating amplifier made up of a voltage amplifier stage and a modulator
stage. The functiona I dia gram of the transmitter is shown in fig­
ure 4.
32. Basic transmitter circuit. u. The r-f carrier is generated in
the oscillator section of tube Ve. The crystal used for the transmitter
is 455 kc lower in frequency than that used for the recpiver. The
�renerated r-f voltage is applied to the grid of tube V1 where it is
amplified and fed into the ante.nna. The antenna is coupled to the
amplifier tank or tuned circuit by an impedance matching network
of the 7r type in which the capacity between the antenna rod and
housing makes up one shunt branch.
b. The microphone output. is amplified by the pentode section of
tube V4 and then applied to the grid of tube V5 where it is fnrther
amplified. The output of tube V5 is then fed into the plate circnit of
tube Vi' the r-f power amplifier. Notice that since the screen of tube
VI is tied to the lower end of coil L�, the modulating voltage is intro­
duced into the screen circuit as well as the plate circuit..
c. The earphone is a Iso connected across the a L1dio output so that
the operator can hear what he is s<lyil1g. This is known as sidetone.
30. Second a-f amplifier.
•
a.
•
•
15
•
•
I
------- ---•
VI
VT-17.
VT-171
R-F POWER AMP.
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VT-17.
VT-172
MlCROPHONE AMP.
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FIGURE 4,
Functional diagram of transmitter,
--,
RADIO
33. Oscillator.
a.
SETS
SC'R
5 3 6-A, -B,
AN� -C
33-36
In the transmit posit.ion only the oscillator sec­
tion of the tube VT-171 is ut.ilized. Resistors Ra and R4 make up the
grid leak which provides the bias voltage for the oscillator grid.
The doc component of the voltage developed across R4 is used also for
the grid bias for the mudulator tube V5.
b. The ref choke La provides a shunt feed arrangement for the
screen grid. Capacitor Ce determines the amount of feedback to the
grid. Capacitor Cu is the screen cil·cuit bypass. Capacitors C�,
CIB, C14, and C2 3 are not necessary to the transmitter circuit ; they
are hold-overs from the receiver function. The sallle is true of reSistOl·S R." RIB, Rg, �4' R25, R7, and R5• These resistors, however, do
tie the No. 3 grid of tube V2 to ground.
34. R-f power amplifier. a. Capacitor Cg is the t:(mpling ca­
pacitor and provides a path for the ref current t.o the grid of tube Vu
but prevents the doc at the screen of tube Vz from being applied to the
grid. Resistor Rs is the grid leak and provides the bias voltage for
the grid uf tube VI. Capacitor Cz is the ref bypass for the screen grid.
b. Coil L2 is the ref amplifier tank coil and CI2 is the ref amplifier
tank turning capacitor. Capacitor C1 2 also acts as oile branch of the
7r network connecting the antenna to the amplifier tank.
The capacity
between the antenna rod and the housing acts as the other shunt
hranch of the 7r network. In the receive position this antenna capaci­
t.ance becomes a part of the tuning capacitance of the antenna. The
antenna coil L� is t.he series branch of the 7r network, and also acts
as the antenna loading inductance.
c. Capacitor Cs is the plate circuit ref hypass.
The current j ack in
the plat.e of tube VI provides for the plate Cllrrent measurement nec­
es.<;ary for tuning up the power amplifier stage properly.
35. Microphone amplifier. Resistor Rzo is the grid resistor of
tube V4, the first audio amplifier. Resistor R-27 acts as a load
resistor for the microphone. Resistor R21 and capacitor C26 act as a
decoupling filter for the screen grid of tube V4. Resistor R21 also
serves to obtain the proper operating voltage on, the screen. Resistor
RZ2 is the plate load. Capacitor C25 is a hold-over fI·OlIl the receiver
.
function.
36. Modulator. a. Capacitor C21 is the coupling capacitor, and
R23 is the grid resistor of tube V5• Capacitor C29 and resistor R24
llmke up a decoupling filter for the screen grid of tube Vu. Capacitor
C2 8 provides a low impedance path around the modulation choke L4
for the current of the carrier ll'equency. This is necessary as the ref
amplifier tank nnd modulator choke m·e in series. The mooulator
choke L4 provides a low resistance doc path to the plate of the 1llodu•
-
•
520361 0. 43!--,3
17
I
SIGNAL CORPS
86-87
I
lator and r-f amplifier tubes, and offers a high impedance load to the
audio frequency plate current of the modulator.
b.
Resistor R'l9 prevents overloading the monitoring earphone, as
the audio output for modulating the r-f amplifier is quite high.
Capacitor C24 removes the d-c at the plate of tube
phones.
Capacitor
Cao
as well as capacitor Cl1 are
V5 from the ear­
B battery BA-38
bypasses.
37. Change-over switch.
The press-to-talk switch operates the
change-over switch which makes the necessary circuit changes to
convert the set from a receiver to a transwitter.
switch is made up of H sec1;ions.
The change-over
Each section has a name which is
marked on the celluloid insulating strip covering the change-over
switch.
For simplicity, however, each section has been designateg by
a letter of the alphabet on the schematic and fUllctional drawings.
3, 4, 16, and 17.)
a. Section A connects the proper crystal into thf' circuit.
b. Section B connects the voltage divider made up of R251 R7,
( See figs.
.
and
R5 across resistor R4 in the receive position, and disconnects the
voltage di'vider in the transmit position.
vides the grid bias voltage, for tubes
c.
0 COlmects the control
Section
This voltage divider pro­
V1, V., and V3•
grid of tube V1
I
to the ave voltage
line in the receive position, and connects the control grid to the gIid
leak risistor R6 in thf' transmit position.
connects the antenna to the tuning capacitor C7 in the
receive position, and to the plate of the r-f amplifier tube VT-174,
d.
Section
D
in the transmit position.
E connects the plate of the r-f amplifier tube V1 to the
coupling capacitor C10 of the signal grid of the mixer tube V2 in the
)
e.
Section
receive position, and connects the plate to the r-f amplifier tank capaci­
tor C12, in the transmit position.
f.
Section
F connects
the oscillator feedback control capacitor C6 to
ground in the receive position, and com1ects capacitor C (I to the oscil­
lator grid of tube V2 in the transmit position.
g. Section
G puts the voltage dropping resistor
RlO in seri!,)s with
the plate of tube V1 in the receive position, and shorts out the resistor
in the transmit position.
h. Section H connects the B battery BA-38 to the plate and
of Va in the receive p osition, and disconnects the battery in the
mit position.
Section
H
screen
trans­
also puts the voltage dropping resistor
in series with the plate of tube
Rl1
V5 in the receive pOsition, and shorts
out the resistor in the transmit position.
i. Section ,' groill1ds the microphone in the receive position, thereby
eliminating the }Jussibility of pick-up on the microphone being intro-
18
•
I
•
RADIO SETS SOR 5 3 6-A, -B, AND -C
37-38
duced into the audio amplifier. In the transmit position se ction J
connects the m icrophone to the grid o f the first audio amplifei r tube
V4•
j. Se ct ion K in the receive position connects the filament of tube
Va to the A battery BA-37 and disconnects one filament sect ion of
e ach tube VT-174 from the A battery BA-37. El iminating one
fil ament section of each tubo VT-174 reduces the total A battery BA37 drain by 100 m illiamperes in the receive posit ion.
k. In the transmit position , the filament of tube V a is d isconnected
from the A battery BA-37 and the second se ction of the filament in
each tube VT-174 is connected to the A bat tery BA-37. Since one
filament is cut out fmd two are cut in , the d rain is only 50 milli­
amperes higher in the transmit position as comp ared w ith the drain
.
in the re ceive posit ion.
1. Se ctions L and .11 are tied together ele ctrically through the mov­
ing elemen t of the switch. In the receive position the dropp ing re­
sistor RI6 is placed in ser ies with the screen grid of tube V 5 by sec­
tions L and 111. These swit ch sections also place the dropp ing resistor
R17 in series with the screen cir cuits of tubes VI and V2, and connect
the B battery BA-38 to the plate of tube V I' In the transmit posi­
tion resistors R17 and R16 are shorted out by sw itch se ct ions L and
M.
m. Sections N and 0 are t ied together electrically through the mov­
ing element of the swit ch. In the receive posit ion they place the
earphone across the audio choke in the plate of tube V 5 , and in the
transmit position they connect the screen and plate circuits of the r-f
amplifie r, tube VI , to the plate of the modul ator tube V 5• This switch
section also places the dropping resistor RI 9 in series with the ear­
phone to reduce the intens ity of the signal in the earphone in the
tr ansmit position .
38. Description of parts. a. RpsistoT-capacitoT cont(tineTs. On
the chassis there are four resistor-capacitor conta iners which are called
cups. These cups fit around the tube sockets and are att ached to them
with cem ent . The purpose of the cups is to provide tie terminals and
a place for some of the resistor s and cap acitors used in the set . Each
cup cons ist s of a th in bakel ite shell of cir cular shape , with an inner
and outer wall. The res istors and capacitors are placed in the sp ace
between these walls . Impregnating compound seals these parts into
the cup. The top piece joining the two w alls is drilled so that the
leads from the capacitors and res istors can be brought out . Some of
the parts are suldered to termin als riveted to the top piece of the cup.
I
•
•
i
19
•
I
f
I
•
38
SIGNAL
CORPS
Each cup has a part number marked on it, as wel1 as a schematic
drawing of the parts in it. (See fig. 23. )
b. Antenna coil. The antenna coil is of the solenoid type and is
wound on a polystyrene form. This is a plug-in coil and has three
pins on its base. Two of these pins are connected to the coil. The
top of each coil is marked with the name, the frequency, and the part
number. The antenna coil socket is also of polystyrene1 and is fastened
to the chassis by a long rivet through its center. This rivet also
fastens the antenna clamp and the antenna polystyrene support to the
chassis.
c. Plate circuit tank coil. The tuned r-f amplifier plate coil has
been marked TANK and is wound on a small mica filled bakelite form.
The coil is permeability tuned and has a powdered iron core in the
form of a hexagon nut. The winding and core are not visible as they
are surrounded by a bakelite shell which completely incloses them.
This shell is riveted to the coil form. A threaded bakelite sci:ew
fits into the threaded iron core, and motion of the screw moves the
core relative to the winding thereby determining the inductance
value.
(1) In addition �o the word TANK the coil is marked with the
frequency and the part number. The Signal Corps part number
carries the letter C as a prefix to the part muuber. This identifies
it and eliminates confusing it with the frequency numbers. Coils
issued with radio set SCR-536-A are marked ·with the frequency range
and the part munber.
(2) The coil form has a female type base. The coil socket contains
two pin connections which fit into holes in the coil form and make
electrical contact to the coil. The pins are gripped by spring clip c on­
nections in the base of the coil form. A hole is provided in the socket
for the inductance adjusting screw which extends through the form.
A spring clip in the socket grips the tuning scrcw and provides a more
rigid support for the coil. A spring clip on top of the form prevents
the coil from working loose from the socket.
d. First i-I transformer. The i-f transformer windings are on a
powdered iron core and are surrounded by a powdered iron sleeve to
further incr:e ase their inductance. This typc of construction gives a
high inductance with a small winding which results in a !Small size
transformer. The primary and secondary of the first i-f transformer
I
I
•
20
•
RADIO
•
SETS
seR
5 3 6-A, -B, AND
38
--c
are tuned by small adjustable mica trimmers contained in the shield
ean. The adjustment of the trimmers is reached through two holes in
the top of the can. A one megohm resistor is shunted across the
secondary winding and serves to broaden the response of the tran,.;­
former. This resistor is contained in the shield can. The transformer
is held in the can by a metal bottom plate which is secured by rolling
the side walls of the shield over the edges of the plate. Two U-shaped
clamps riveted to the back side of the chassis hold the transformer in
place.
e. Second i-f transformer. ( 1 ) The second i-f transformer con­
struction is similar to that of the first. i-f transformer. Only one
trimmer is used, however, and it is connected across the secondary
winding. This trimmer is accessible through a hole in the top of the
shield can.
(2) A 220,OOO-ohm resistor and two 70-",f-mica capacitors are also
mounted in the shield can. The transformer fastens to the chassis
in the same manner as the first i-f transformer. They make up an
i-f filter for the detector circuit.
f. Orystals. ( 1) There are two crystals used in the radio receiver
and transmitter BC-611- (*) . The receiver crystal is 455 kc higher
in frequency than the transmitter cl'ysta 1. The crystals are con­
tained in plug-in type hulders with two pin connections. They are
completely sealed against moisture. The receiver crystal holder is
plainly marked REC. and the transmitter crystal is marked TRAN.
F�ach crystal holder has an arl'OW indicating the direction in which
it should be placed in the socket. As the sockets carl'y a similar
marking, the possibility of getting the crystal s into the wrong socket
.
or seated improperly is minimized.
(2) The crystal holder has a metal cover plate on which are marked
the frequency, crystal manufacturer's name, and the model number.
This plate does not make contact with the crystal blank in the holder,
but it does have a capacitive effect on the crystal. If it comes in con­
tact with the chassis or metal clamp which holds the crystal in the
socket, the operation of the crystal will be affected. A piece of insula­
tion material covers the chassi::; where the transmitter crystal might
touch when the set is jarred. 'When the crystal activity is low, it
should be replaced with another. Do not attempt to take the holder
apart.
,
•
21
,
I
SIGNAL CORPS
39
SECTION
IV
MAINTENANCE
•
Gl'neraL
_ _ _ _ _ _ _____ _______
_______ _ _ _ _. _ _ _ ___
Replacement of b att er i es
Replacement of tub es
Replacement of antenna coiL
Replacement of r-f tank coiL
______ __ _ _ ____ _ _ ___ _
__
_
_ __ ___ _ _
_
_
Paragrapli
_
__
__
_ __
_ _ _ _ __
__ ___ _ _ _ _ _
__ _ __ _
____ _ _____ _ _
__ _ _ _ _ _ _ __
_____ _ _ _ _ _ _
____
_ _
__ _ _ _____ _
_ _ _ _ _ _ _ ________ _ _ _ _ _ _ _ _ _ _ _ _ _
___
__
____
____ _ _ _ _ _ _
_____ _ __ _ _ __ __
_____ _ _ _ _ _ _ _ _ _
_
_
__ ____ _ _ _ _ _ _
____
I{eplaeement of microphone
Replacement of earphone _
_
Removal and replacement of crystals
'Veak si�nals------------- ------------------- ---------------No signals
Test equ ipmen ts
_ _ ___ _ __
___
Test equipment 1E-17- ( * ) ____ _
Test case C8-81-( * } __
_ _
_ _
Test stand FT-252- ( * ) and Antenna A-82- ( * } _
_ _ ___ _ _ _ _ _ _ _
_
_ __ _ ___ _ _
_
__ _ _ _ _ _ __ _ __ _
__ _
__ __ _ ___ _ _ _ _ __ __
__
_
___
__ _ _
_
__
__ _ _ _ _
__
___ __
__
_
__ _ _ _ _ _
_ __ _ _
_ ____
_ __
__ _ _
_ __
_
__ _ _ _
__ _ _ _ ___ _
__
__ _ _ _ _ _ _ _ _ _____ _ _ _
______________ _
_____ _
_
_
_
_
_ _ _ _ _ _. _____ __ _
_____ _ _ _ _ _ _ _ _ _ _
_
________
_______
_ __ _ __ _ _
__ _ _ _ _ __
_
___
___________ _ _ _ _ _ _ _ __
_
_
Presetting frequen cy with IE-17- ( * )
Removal and replacement of coils and crystals
Setting up test equipment 1E-17- ( * )
_
___ _ __
Crystal activity tesL
Presetting receiver
____
_
Presetting transmitter
Procedure if badly out of alinemenL
_ -"
__ __
____
Lsing signal generator
I-f alinement using test equipment 1E-17-( * )
_
Testing batteries BA-37 and BA-38
Test equipment IE-15-A
__
__ _
Use of test case C8-81- ( * }
_ _
Use of test stand FT-252- ( * )
_
__
_
Test harness and rneters_ _
Use of test set 1-56- ( * )
_
Presetting frequency with IE-15-A
Changin g coils and crystals _ _
Setting up test equipment IE-15-A
Presetting receiver willi IE- 15-A_
Presetting transmitter with 1E- 15-A
I-f alinement
Checking for image frequency
BG-611- ( * } as signal generator _
_
Replacpment of parts
_
Trouble location and remed y
_ _ _ _ __
_ _ _ _ _ _ _ _ _ _
_______
__
_ _ ______
____
_ __ _ ____ _ _ _ _ _ _
_
_
_ ___
_ __
___ _ _ _
__ ___ __ _ ___ _
_ _ __ __ ___
_
_
__
__
Test unit 1-135- ( * }
_
__
__
_
_
__
_ _ __ _ _ _
- - - _____ _ _ _ __
_ __
__ _ _ ___ _ _ _ _ _ _ _ _ _ _
-:-
_ _ _ _ _ _ _ _ _ _ __
_
______
________
_ _ _ _ __________ _ _ _ __
_ __ _ _ _
___
___
__
_ _
_ __________
___________
_____
_
__
_
____
_
____________
-_
_
_
_
_
______ _
_
__
____
__
__ __
__
__ _ _____ _ ___ __
__
__ _ __ __
_ ___ _ ___ _
_
_
_
____
_
_
_
_
_
_
_
_
_
__
_
_
_ __
___
_ _ _ ____
_ _ _ _ _ _ _ __ _ _ _ _ __ _
___ ____
___
__
_
_
_
_
__
_
__
_
___ _ _________
____ _ _ _
___ _ _ _ _
_ __ _ _ _
_ _ __
_
__
_ _ _
_
_
_
_______
_ _ __ _ _ _
_ _____ _
_ _ _ _ __
_
_
_______
_______ ______ ________ _ _ _ _ _ _
__
__ _ _ _ _ _ _ ___ _ __ _ _ ___
___
_ _
__
___
__________
_ _ _ _ __ _ _ _ _ _ _
__
_
__ ____ __ ___ _
_
_ __ _ __
_____________ _ _ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _
_
_
_ ______ ___ _ _ _ _ _ ___ __
_
_
_ __ _ _ _________ __ _
____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_
__ _ _ __ _ _ _ _ _ ______ _ _ _ _ _
__ _ _ _ _ _ _ _ _ _ _ _ _
_
_
_
_
_
_ _
_
__ ___ _ _ _ _ _ __ __ _ _ _
_____
_______________ _ _ _ _
_
_
_____
_
_
_ _ _ _ ____ _ _
____ _
_
_______
_ _ _________ _ _ _ _
,
__
_
_
____
_
_
_
____
__
_
_
_
_
_____ __ _______ _
_ _ _ _ _ _ _ _______ _________ _ _ _ _ __ _ _ _ _ _
_
__
_ __
_
__ _ _ _ _ ___ __
_
_ ___ _ _ __ _ _ _ _ _
___ _ _ _ _ _
_______ _ _ _ _ _ ___
_____
__
_ _ _ _ ___ _ _ _
_
_
_
_ ___
_ _ _____ __ _ _ _ _
_
_
_ ____ _ _ _ _ _______ _
_ _ _ _ _ __ _ _ __ _______ _ _ _ _ _ _
_
_
_
_ _ _ _ ____ _ _ _ _ _ _ _ _ _____
_
_
_
_
_
_
________
_
__ _
·
�
_ __ _
_ _ _ _ __
__ __ _ __ _ _
_ __
_
_ __ _ _ ____ _ ___ _ _ _ ___ _ _ _ __
39
40
41
42
43
44
45
46
47
48
49
50
5] /
1 52
53
54
55
51l
57
58
5!)
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
Maintenance work on this equiPlllent should be
done by qualified radio repainnen only. A logical process of check­
ing accessories such as tubes and batteries, when the radio set operates
poorly, will oftell locate the trouble.
39. General.
22
•
•
•
RADIO
SET'S SCR
5 3 6-A, -B, AND -C
40-48
40. Replacement of batteries. See paragraph lla.
4 1 . Replacement of tubes. Remove the cha::;::;is from the hom;·
ing. To do this, unfasten the bottom cover of the housing and remove
the batteries. Disconnect the microphone and earphone plugs from
the terminal board on the end of the chassis by gently pulling out.
Plugs and jacks are color coded with small spots of color : green for
microphone and red for earphone. Remove the mounting screw in
the top cover of the housing, and the chassis can be slid out of the
bottum of the housing. Lift the tube retainer bracket at the top of
the tube and remove the shield, if there is one. Insert a narrow rod
th . on gh the bottom center of the tube socket and gently force the
tube out. �\.. small Ilu rrov:-bladed SCl'('W driver will be found useful
for this purpose. ,\Vhen replacing the tube, be sure it is the right
type, that the base of the tube is so turned that the pins fit into the
socket properly und are straight. The wide space behveen pins 1 and 'I
of the tube can be used as a guide to line the tube \vith the socket.
( See fig. 10. )
42. Replacement of antenna coil. See paragraphs !)5 and 70.
43. Replacement of r-f tank coil. See paragraphs 55 and 70.
44. Replacement of microphone. Remove the batteries, card­
board separator, and chassis from the housing. Then unscrew the
bakelite microphone cover on the housing and the unit can be lifted
out of the housing. To detach the microphone unit from the housing,
it will be necessary to remove the screw which grounds one of the two
leads to the housing. The lead with the connecting plug (green dot ) ,
which fits into the jack on the tenninal board, is withdrawn through
the ho 11' in the housing.
45. Replacement of earphone. The earphone is replaced in the
same manner as the microphone.
48. Removal and replacement of crystals.
t")ee paragraphs
55 llnd 70.
47. Weak signals. ·If the distul1ce between units in operation is
between 100 feet and 1 mile, and tIlt' transmission is poor, the batteries
may be weak. The batteries are designed to give about 15 hours of
operation, assuming that the unit is operated for long periods of
time and that the operator is transmitting much of the time. They
will last longer if not used constantly. A sign of weak bat­
teries is a low noise level in the earphone when the set is in the receive
pu::;ition with no incoming signal.
48. No signals. a. If the batteries are placed in the battery com­
partment, positive end first, the set will not operate. If the batteries
are inserted correctly and the set does not operate, the batteries may
be dead. Replace them with a new set of batteries.
I
-
I
/
•
23
I
•
48-52
SIGNAl.
CORPS
b. A tube may be bUTIled out or shorted. Remove thf' chassis from
the housing. ( See pal'. 41.) Locate the defective tube and replace
it. Reinstall the chassis in the housing. Take care that the chassis
fits between the guides provided for it in the case.
c. Make certain that the plate current jumper (fig. 1 ) is inserted
in its proper place. The set will not operate if this jumper is mi ssing.
49. Test equiPlllents. The test equipments are designed to sim­
plify testing, frequency presetting and general alinement of radio
receiver and transmitter chassis B C-61 l ( * ) whicli is the heart of
radio set SCR-536- ( * ) . IE-17-(*) is an improved version of IE15-A. The components and method of using both of these equip­
ments is described in the following paragraphs. Either equipment
may be used with all models of radio set SCU-536-( * ) .
50. Test equipment IE:-17-(*). This equipment consist." of the
following components :
-
•
Antenna A 82 ( * ) , artificial.
Test stand FT-252- ( * ) .
Test case CS-81- ( * ) .
Test unit 1-135-(*) containing multi-range meter, harness,
r-f and a-f oscillators, insulated screw driver, and battery
connectors. (This unit combines in one case all the meters
and additional equipment required with test equipment
IE-15-A.)
-
I
-
A.c:. the tuning adjustments are inac­
cessible because of their location on the chassis, which is covered by
the case or housing, a special housing is required to make these, ad­
justments. (See fig. 5.) Test Case CS-81- ( * ) is similar to the
radio set housing except for the holes that have been provided to
permit access to the chassis adjustments. This apparatus permits
tuning the set under conditions identical to those of normal opera­
tion. The presetting adjustments should not be made on the set
without the test case being around the chassis, because the set would
become detuned when inserted into the regular housing. This de­
tuning or misalinement would result from the additional capacitance
introduced into the circuit by the housing.
52. Test stand FT-252-(*) and antenna A-82-(*). a. The
test stand c.ontains clamps to hold the test case and the dummy an­
tenna.
b. Antenna A-82-(*) comprises a 50-milliampere r-£ milliarmneter
to measure antenna current and a receiver and transmitter dummy
antenna consisting of a receive-transmit switch, a 56-ohm resistor,
and a variable capacitor of 8 �f maximum capacitance.
51. Test case CS 81-(*) .
I
24
!
..
•
•
RADIO SETS SCR
•
5 3 6-A, -B, AND -C
53
53. Test unit 1-135- (* ) . This unit is a multirange voltmeter
and milliammeter. it crystal tester, and an r-f and a-f signal source
(fig. 6) . Test unit 1-135-(*) is u�ed for the measurement of battery
, voltage and current, r-f amplifier plate current, audio output voltage,
and crystal activity. It is used as a modulated r-f signal source for
the alinement of tIlE' receiver and as an a-f signal source for determin­
ing the modulatioll capability of the transmitter. It combines in
one case all the meters and additional apparatus required for test
equipment IE-15-A.
ANTENNA
ANTENNA CURRENT METER
I
CONNECTION
f
CHANG E - OVER
SWITCH
,
ANTENNA
MY
CAPACITOR
CHAS SIS _
_:_­
MOUNTING
CONTROL
SCREW
.
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TEST UNIT
•
.
1- 135-(*'
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SECONDARY
tt.Ulf'R SWITCH
....
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TRIMMER
TEST STAND FT-252-(
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-
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•
HARNESS TERMINAL BOARD
FIGURE 5.
CltY'3TAl
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....
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2 N D I-F SECONDARY
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TRIMMER
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TRIMMER
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Test equlplllPnt lE-1 7- ( * )
TL.- 5559A
set up.
The r-f signal source is a Pierce crystal oscillator and makes use
of the radio set transmitter crystal such as is contained in radio
receiver and transmitter BC-6l1-(*) or one of the same frequency.
It generates a signal of the carrier frequency. 'I11is r-f oscillator also
serves to check both the receiver crystal and the transmitter crystal for
activity.
b. The a-f signal source is a Colpitts oscillator generating a signal
of 1,000 cycles pel' second. . This tone is used to modulatf' the 1'- f
osrillator and can be applied also to the microphone input terminals of
the transmitter to test for modulation capability.
a.
.
-
520361°
4:l
4
25
•
�ri
,
,
SIGNAL
53
CORPS
A test harness attached to the test unit provides the means for
connecting to the chassis. (See d below.) An insulated screw driver
attached to the cover of the test unit is for alining purposes.
d. Compartments are provided in the test unit for A battery BA-37
and B battery BA-38 to permit these batteries to be tested under load.
( SeE} fig. 7.) Also connections are provided for the use of external
batteries. A heavy-duty 1.5-volt battery (battery BA-23 or battery
BA-35) and a heavy-duty 90-volt battery (two batteries BA-26 or
two batteries BA-36) will be satisfactory for all alinement and testing
purposes. Battery BA-37 and battery BA-38, part of radio receiver
and transmitter BC-61l- ( * ) , also can be used for this purpose, but
are not recOlmnended because of their short life under these conditions.
e. The positions of the MASTER SWITCH of the test unit are as
follows :
(1) OFF, which disconnects external and internal batteries of test
unit 1-135- (*) from both the test unit and the radio set chassis. The
radio set and oscillator are ON in all other positions of the MASTER
SWITCH.
(2) BA-37, 0-3V. D.C., which indicates on the meter the voltage of
external A battery or battery BA-37 when the radio set is in either
the receiver or transmit position.
(3) BA-37, 0-600 MA. D.C.. ·which indicates on the meter the cur­
rent drain of external A battery or battery BA-37 when the radio
set is in either the receive or transmit position.
(4) BA-38, 0-150 V. D.C., which indicates on the meter the voltage
of external B battery or battery BA-38 when the radio set is in either
the receive or transmit position.
(5) BA-38, 0-60 MA. D.C., which indicates on the meter the cur­
rent drain of external B battery or battery EA.-38 when the radio set
is in either the receive or transmit position.
(6) PWR. AlVIP., 0-15 MA. D.C., which indicates on the meter
the r-f power amplifier plate current when the radio set is in transmit
position.
(7) OUTPUT 0-60 V. A.C., which indicates on the meter the audio
output voltage of the radio receiver ; the meter is connected across the
earphone in the test unit.
(8) CRYSTAL ACTIVITY, 0-1.5, MA. D.C., which indicates on
the meter the grid current of the crystal oscillator to show condition of
crystal. The MODULATE TESTER switch must be OFF when
crystal activity is being checked.
(9) The switch marked MODULATE TESTER is used to modu­
late the r-f oscillator with a 1,OOO-cycles-per-second tone when the test
ID1it is to be used for receiver alinement purposes.
c.
-
.
26
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FIGURE B.-Test unit
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I-135- ( * ) ,
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SIGNAL
53-54
r
CORPS
f. The switch marked .MODULATE TRANSMITTER applies a
1,000-cycles-per-second audio voltage across the microphone iliput cir­
cuit of the transmitter as a test of the modulation capability of the
transmitter.
The MODULATE TESTER switch must be ON and a crystal must be in
place in the compartment socket when this test is made.
NOTE.
g. Test unit 1-135-(*) also contains an earphone and a microphone
which are mounted in the front panel of the case. These can be used
to listen to the audio output of the receiver or to modulate the trans­
mitter by speaking into the microphone.
54. Presetting frequency with IE-1 7-(*). To cover the au­
thorized range of frequencies from 3.5 to 6.0 megacycles. individual
matched sets of antenna coils, r-f tank coils, and crystals are avail­
able. Each coil is marked with its frequency and part number so that
errors of coil selection will be minimized.
•
.
•
-- .
•
BATTERY
CONTACT
BOARD
-_
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•
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-
,
.
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KNURI.FD
SOLT
NUT
5A - 37
FIGURE 7.
Test unit 1-135- ( ' )
COVER
....... B" BATTERY
BA - 38
,
"
d
a
i
L
!...
showing battery compll.rtment.
The coils supplied with radio set :s<.�R-r.36-A are not preset to one fre·
quency. Instead each is adjustable over the small frequency range marked on
the coil. The frequency range of each is indicated in chart I ( par. 70 ) . The
coils manufactured for radio sets SCR-536-B and 536-C are identical but have
been preset to the frequency indicated on each.
NOTE.
•
•
To preset the operating frequency of the radio recei vel' and trans­
mitter BC-611- (*) , obtain a coil and crystal equipment of the de­
sired frequency. 'The coil and crystal equipment comes in an india.
28
•
•
RADIO
SETS SCR
5 3 6-A, -B, AND
-C
54-55
vidual carton marked with the frequency and ('ontain s the transmitter
and receiver crystals, the antenna coil and the r-f tank coil
Radio sets SCR-536-A are issued with one set of spare crystals. The
coils for these radio sets are available in the frequency ranges indicated in chart I
(par. 70 ) . Radio spt SCR--536-B is issued with only one set of coils-and crystals.
Radio set SCR-336-D is issued with box BX-49 containing 12 sets of antenna
coils, 12 sets of r-f tank coils alHI 12 sets of crystals ( to cover operation on 12
(lifferent frequencies ) .
NOTE.
b. The antenna coil is larger and of different shape than the r-f tank
coil. Its base connections also differ, so it is impossible to put the
coib in the wrong sockets. Both coils are of the plug-ill type_ (See
figs. 8 and 10.)
c. Remove the chassis of radio receiver and transmitter BC-611-(*)
from its housjng. To do this, unlatch the bottom cover of the housing
and remove the batteries. Place them aside for tost. Disconnect the
microphone and earphone plugs from the terminal board on the end of
the chassis by gently lifting them up. Next remove the screw in the
top cover of the housing ; the chassis then will slide out of the bottom
end of the housing.
55. Removal and replacement of coils and crystals. a. An­
tenna coil. Remove the plug-in antenna coil by carefully lifting it
out of its socket. See figure 10 for its location. In its place insert
another coil of the desired frequency
b. R-f tank coil. To remove, loosen the screw holding down the
coil retainer spring on top of the coil. ( See fig. 9. ) Swing the
spring free of the coil.
The coil then can be lifted out of the socket.
When replacing with another coil of the desired frequency, carefully
fit the coil over the two pins projecting up from the socket so that the
pins fit into the holes in the coil form and the coil adj ustment shaft
fits into the hole in the socket. Gently press the coil into the socket,
replace the coil retainer spring on top of the coil, and tighten the
screw holding the �pring_
c. Orystals.
The crystals are mounted in plug-in type holders.
( See fig. 10.) To l'emove a crystal, lift up the clamp located on top
of the crystal holder. This clamp pivots on a stud fastened to the
("h assis. Place a small screw driver between the crystal holder and
the socket and gently pry it up. To remove the other crystal holder,
the s'ame procedure is followed. Select a transmitter and a receiver
crystal holder of the desired frequency (the frequency of the trans­
mitter crystal will be the same as that of the coils, while the receiver
crystal will be 455 kc higher in frequency) . Insert the receiver
crystal holder in the crystal socket marked REe. It should be in­
sorted so that the frequency printed ou the -metal side faces out and the
.
29
1
SIGNAL
55
CORPS
arrow on the holder points in the same direction as the arroW' on the
socket. When the transmitter crystal is inserted, place it in the
socket marked TRAN. in exactly the same way. The printed metal
I
side of the holder should show through the opening in the chassis.
Hmoever, do not insert the transndtter crystal in the radio set at this
time. Instead, replace the metal clamp on the receiver crystal holder
on the chassis and leave the transmitter crystal socket empty.
•
30
•
RADIO
SETS
SGR
-B, AND
5 3 6-A,
55
•
•
.
•
,
. £:WOKE·
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•
•
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·VR. AN-, AtiJVS:rME�T
.
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Ei\lr-A V.OM;,.
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--
FIGURE 9.
.
.
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.
.
-
-
.
.
Radio receiver and transmitter BC-611- ( * )
31
bottom view of cha�sis.
•
SIGNAL CORPS
55-56
•
----
.
-
----
,
•
•
-
-
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TRANS. �F
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ANT ADJUST,
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.
.
AN"'�NNA
,
_ .
I!'IGURE 10.
Radio receiver antl tr311sButter
HC-till- (*}
-front view of chassis.
Place the
chassis into test case CS-81- (*) housing. The chassis mpst be in­
serted into the test case through the bottom as is done when inserting
the chassis into its own housing. Take care that the chassis fits
between the guides provided for it in the case. It should not be
necessary to force the chassis. If force is necessary, withdraw the
chassis and check to see that no parts are catching on the test case or
that the chassis has not jumped the guides. Slip the top cover over
the antenna rod and fasten the chassis to it with the knurled mounting
screw. The chassis now will be held securely in the test case. Now
56. Setting up test equipment
32
I F:-17-(*).
a.
I
T
I
RADIO SETS SC'R 5 3 6-A, -B,
AlloT)) -C
56-58
remove the plate current meter jumper from the terminal board at the
bottom end of the cha8sis.
Caution : Do . not misplace this jumper since it must be replaced
after alinement tests.
b. Attach the terminal board of the 1-135- ( * ) harness to the
terminal board of the chassis so that the two sma}] pins on the halTIeSS
terminal board fit into the plate current meter jacks, and that the two
large locking pins, one on each end of the terminal board, fit into the
holes provided for them. Lock the two terminal boards together by
a sideward movement of the levers attached to the locking pins.
c. Next, clamp test case CS-81-( * ) into test stand FT-252-( * )
with the antenna end up, and the housing in such position that the
change-over switch is opposite the left side of the operator as he
faces the stand. (See fig. 5. ) The upper clamp should grip the
housing on the edges of the top cover. The lower clamp should not be
made too tight, as the pressure may crack the housing.
d. Make certain that the MASTER SWITCH of test unit
1-135-(*) is in the OFF position. Place the transmitter crystal
holder of the desired frequency in the crystal socket in the front
panel compartment of test unit 1- 135- ( * ) . (See fig. 6. ) Be sure
the crystal is of the smne frequeney as the coils in the radio set
and that its frequency is 455 kc less than the receiver crystal. Con­
nect external 1.5'-volt and 90-volt heavy duty batteries (of the type
described in paragraph 53d) to the battery terminals marked EX­
TERNAL 1.5 VOLTS and EXTERNAL 105 VOLTS on the front
of 1-135- ( * ) .
57. Crystal activity test. Be sure that the transmitter crystal
has been properly placed in the crystal socket of the test unit.
Place the MODULATE TESTER switch in the OFF position.
Then turn the 1Ii.A.STER SWITCH to the CRYSTAl, ACTIVITY
position. The meter should read between .3 and .8 milliamperes.
If it reads less than .3 milliamperes the crystal is defective and must
he replaced. Before replacing a crystal for poor activity, be sure
that the external battery voltages applied to the test unit 1-13;1-( * )
are 1.5 and 90 volts. The foregoing tests apply equally well to re­
ceiver crystals. Tunl in defective crystals for salvage. Leave a
good transmitter crystal of the proper frequency in place in test unit
1-135-( * ) for receiver frequency presetting adjustments.
58. Presetting receiver. Use the following procedure :
a. Extend the radio set antenna rod to its full length, 39 inches
above the top cover of test case CS-81- (* ) . This will turn 011 the
radio set. Do not press the press-to-talk switch of the test Ca8e during the receiver presetting adjustments.
.
520361°
43
5
33
,
I
I
I
SIGN AL OORPS
58
b. Before proceeding with the necessary set adjustments, check
operating voltages and currents, using the multirange meter of test
unit 1-135- ( * ) . The following voltage and current readings are
normal :
•
-
B A-37
0-3 V. D. C.
MaRter Rwitch set at_
-
Meter should read . . _
1
\
Ir
B A-37
0-600
MA. D. C.
B A-38
0- (;0
M A. D. C.
BA-38
0-150
V. D . C.
-
1.35 (min) 1 to 1.5 v _
250 ma
_ _ _
85 v (min)
1_
5-1 1 rna.
Replace battertes If voltage is less than minimum figure.
The receiver is now ready for alinement. Be sure that a good
transmitter crystal of the proper frequency is in place in the test
unit. The preceding activity check of the transmitter crystal will
assure that a radio-frequency signal is being generated.
d. Turn the MASTER SWITCH to OUTPUT, 60 V. A. C., posi­
tion. A reading should now be indicated on the meter and a 1,000cycles-per-second tone shOll Id be heard in the earphone of the test unit.
e. Set the MODULATE TESTER switch to ON. The 1,000cycles-per-second tone will now modulate the carrier signal.
c.
NOTE.
The rof signal for alinement is fed into the receiver by radiation from
the compartment of the test unit in which the crystal is located. The slid!' cover
of the crystal compartment acts as a radiation control pt·eventing the signal from
radiating when closed and allowing maximum radiation when open. If the
set is badly out of alinement, the r-f si�mal pi cked up by the receiver may not
be sufficient to give a reliable audio voltage reading on the meter ( OUTPUT
0-60 V. A. C. position ) . For snch a condition, connect a short piece of wire to
the Fahnestock clip mat"ked R-F. OUTPOT. This clip is located in the crystn)
compartment of the test unit. The wire will act as an antenna and increase the
radiation of the r-f signal. Vat'ying the pol"ition of this wire with l'espect to
the antenna of the radio set or varying the length of the wire will control the
strength of the signal radiated, In extreme cases of misalinement the wit"p
connected to tl1e R-F OUTPUT terminal may have to be wrapped a couple of
turns around the radio set antenna.
.
,
f. Grasp the test case with onp hand during the following alinement
adjustments on the receiver.
g. The location of the receiver tuning adjustments on the radio
chas::;is arc shown in figures 5 and 11. With tl�e insulated 8crew
driz'e7', turn the receiver ante'f/!n(l adjustment screw clockwise. Notice
the eff(>ct o f this adjustment on the output meter reading. If the
meter rea/ling increases, continue to tighten the screw until a maxi­
mum reading is ohtained. If the reading decreases, turn the screw
counterclockwise uJllil u nmx imum reading is obtained. Be careful
34
-------
...
...
..
-
RADIO
SETS SCR 5 3 6-A, -B, AN'D -C
58
not to tighten the screw after it begins to turn hard as the threaded
base of the trilmner will be stripped. The setting of the trimmer screw
for maximum output should fall somewhere between the point of hard
tuning and that of minimmn preSSUI'e. If the maximmn is not
reached in these limits of the screw adjustment, try another antenna
coil. If the set appears to be badly out of alinernent, proceed as indi­
cated in paragraph 60.
Antenna
ful ly
extended
\
./" Don't connect Clip
I
Adjust for maximum
reading on output
meter.
Don 't touch ! -------T-
(Keep' under
by reaucing cou­
Q) Grosp housing ,
( Don ' t touch PRESS­
TO-TALK switch ) ,
20 rna
pling to 1-135 test un it)
Adju st for maxim u·m
rea d i ng on output
met e r.
'
Don t touch !
(Keep under 20 mo)
FIGUIm
11.
ReceiYer presetting adjustments.
Be sure that the r-f signal is 110t stl'ong enough to cause overloading
the receivel'. If this condition e.�ists, n<ljul"truent of tlw receiver alltenna trim­
mer will have little or no effect on the output reading.
Best results will
NO'rE.
be obtained if the r-f input is adjusted so that the meter reading on the 60-volt
scale <loes not exceed 10 volts, although satisfactory l'esults may be obtained with
readings up to 20 volts,
h. Using the i·nsulated screll' dlil'er, turn the receiver tank adjust­
mf'llt screw for maximum output using the same method employed in
step g above.
This screw, which is made of bakelite, fits into a powdel'ed iron core
which is threaded. The movement of the screw changes the position of the
core in the coil. If the screw is turned too far clockwise, the core will rille
up against the screw head, and the threads in the core will be stripped. If the
screw is turned too far counterclockwise. the core will come in contact with the
coil socket, and further turning will again strip the core threads. TIll' �crew
NOTE.
setting for maximum output should fall somewhere between these two limits of
adjustment. If it does not. a wrong tank coil may be in the set.
35
•
•
I
SIGN" AL CORPS
58-59
,
i. 1\u'n tIll' MASTER SWITCH to OFF. Remove the transmitter
crystal from test unit 1-135- ( * ) . Telescope the rod antenna and
remove the test harness and the knurled fastening screw from the
cha.ssis in the test case. Then slide the chassis out of the test case
and remove the receiver crystal and install it in 1-135- (*) test unit.
Insert. the t ransmitter crystal -in its proper socket in the radio set.,
making" snre it is properly installed, and put the chassis back in the
test case. (See par. 55. ) Attach top cover and the harness terminal
board. Put test. ca.se in place on the test stand. Then test. the receiver
crystal for activity in the same manner as for the transmitter crystal
(par. 57) . Leave a good Tecei-llcr crystal in place in the test wnit
while presetting the tran smitter portion of the radio set.
59. Presetting transmitter. a. Grasp the test case and depress
the press-to-talk switch with one hand during all following preset­
ting adjustments of the transmitter. The MODULATE TESTER
switch shonld be OFF unless otherwise specified.
b . Extpnd the antenna of the radio set to its full length. This will
operate the power switch in the radio set. chassis.
c. Before proceeding with the necessary set adjustments, check op­
erating voltages and currents, using the multirange meter of test
unit 1-135-(*). The following voltage and current readings should
be obtained with press-t.o-t.alk switch on the radio set depressed :
I
Master switch !'let.
aL
_ _
_
_
_
_
_
_
_
_
_
_
_
BA-37
0-3 V. D. C.
-
Meter should read_
1
1.35 (min.)
v.
1
to 1 . 5
BA-37
0-600 MA.
D. C.
BA-38
0-150 V.
D. C.
275-300 ma_; 75 v. (min.)
BA-38
0-60 MA.
D. C.
1
26-30
rna.
Replflc{l hau;(�ries if voltage is l�ss than the minimum figure.
d. The transmitter is now ready for alinement.
Turn the MAS­
TER SWITCH on test unit to PWR. AMP. position. Adjust the
fymmmdtter tank adjustment screw for minimUrm current reading on
the meter in the test unit.. The normal reading in t.his position is
approximately 7 milliamperes. See figures 5 and 12 for location of
transmitter tank adjustment. Be sure to depress the press-to-talk
switch �oith one hand dUJ'ing this operation.
e. Telescope the upper three sections of the antenna rod, leaving
only the bottom or fourth section fully extended from the housing.
Clip the dummy antenna connection to the upper part of t.he antenna
rod. ( See fig. 12. ) Set the antenna change-over switch on the
panel of test staml :FT-252-(*) to TRANS. position, and then, still
36
•
I
RADIO SETS SC'R
5 3 6-A, -B,
AND --c
59
grasping the test case and press-to-talk switch, use the insulated
shaft extension to adjust the dummy antenna capacitor control for
minimum current reading on the meter in test unit 1-135-( * ) (ap­
proximately 7lh rna in PWR. AMP. position) . This adjustment of
the dUlmny antenna capacitance for minimum power amplifier plate
current is necessary to compensate for the change in antenna capaci­
tance due to telescoping the upper three sections of the antenna rod.
Observe the reading of the antenna current meter on test stand
FT-252- ( * ) . This should be from 15 to 24 milliamperes and repre­
sents the ullmodulated antenna current.
@ Release PRESS -TO-TALK
switch and telescope
three upper sections
of rod antenna (Ieave
:.fourth section fully
extended ).
Clip dummy a ntenna con ­
nection to top of section
4 of antenna rod.
-­
_
_
Don"t touch !
Set change-over switch
at TRAN S .
PRESS-TO-TALK
and adjust this
control for minimum R-F
Am p pla te cur ren t ( 7 rna )
.....
_
_
_
®Adju st for minimum R-F Amp plate cur­
reni ( 7 mo )
<D Extend antenna rod
fu l ly; don't conne c:..;..t_
antenna cl ip.
---
--
Don ' t touch !
PRESS - TO
.
TA LK
switch
housing and operate
PRESS -TO-TALK switch.
FIGURE 12.
Transmitter presetting adjustments.
.
f. ( 1 ) Place the MODULATE TESTER switch to ON position and
press the MODULATE TRAKSMITTER button on the test unit.
This modulates the transmitter by applying a .2-volt, 1,000-cycles-per­
second audio signal across the microphone terminals. Note the rise
in the antenna current meter reading when the modulated signal is
applied. This rise should be at least 6 percent over the Ul1modulated
current reading. A 6 percent increase in antenna current indicates
50 percent modulation. For example, aSSUlne that the Ul1modulated
•
37
•
(
SIGNAL OORPS
59-61
antenna current is 20 milliamperes and that the modulated current
is 22 milliamperes :
The increase in current is then
22 /20=2 milliamperes ;
The percentage increase will be
2/20 X l 00
10 percent.
=
(2) Another method is to divide the antenna current obtained
with modulation by the antenna current without modulation ; the
answer should be greater than 1.06. For example, take the values
of current previously given. Dividing the modulated"current by the
unmodulated current gives 22/20= 1.10.
NOTE.
Further checks on modulation may be made by whistling into the
microphone or holding a sustained note. The modulation rise should be sub­
stantially greater. l\IODlJLA'l':m TRAXSMIT'l'ER button must not be pressed
when using the microphone method.
g. This completes normal frequency presetting adj ustments.
Re­
move the chassis from the test case, replace in the radio set. housing
and reconnect microphone and earphone. Be sure to replace the plate
current meter jumper. Reinst.all the A and B batteries, making cer­
tain that the positive ( + ) ends face outward. Close the cover, move
the latching bolt into place. and tighten the knurled nut. The set
is now ready for operation.
60. Procedure if badly out of alinenlent. If the i-f transform­
ers are badly out of alinement, it may be impossible to get. a carrier­
frequency signal through the receiver as outlined in paragraph 58.
For such a condition, the i-f transformers must be realined. There
are two ways of doing this, one way being to use a 455-kc signal
generator connected to the signal grid of the mixer tube, while the
second method makes use of test equipment IE-17- ( * ) .
61. Using signal generator. a. Remove t.he chassis from the
test case and with the mounting screw fasten it to the t.op cover of the
housing. Place the chassis in the test stand in the same relative posi­
tion as when in the test housing, and hold it there by gripping t.he
housing cover with the upper clamp of the test stand. ( See fig. 13.)
Leave test unit 1-135- ( * ) cOllnf'eted to the chassis by means of the
harness.
b. Connect. the ground lead of the signal generator to test stand
FT-252- ( * ) . Connect a .05-fLf capacitor in series with the output
lead of the signal generator and connect the other end of the capacitor
to the No. 6 pin of tube VT-l71, used as a converter-oscillator. Set
•
38
•
RADIO SETS SC'R
5 3 6-A,
-B, AND -c
61
•
I
I
·
,
,
·
,
•
•
•
,
•
I
II
I
I
•
•
•
r
,
•
•
,
•
,
,
•
•
>
I
·
,
•
•
•
,
,
,
,
,
•
•
,
•
•
•
,
•
•
•
,
I<' W(;IlE
13.,-lSerncing set-up with test stand
39
FT-252- ( * ) .
I
6 1 -62
SIGNAL CORPS
the signal generator frequency accurately to 455 kc by means of fre­
quency meter set SCR-211-(*) . Set the MASTER SWITCH of the
test unit to OUTPUT 0-60 V. A. C. position. Do not depress the
press-to-talk switch. Adjust the generator output until a 10-volt
reading is obtained on the output meter. Considerable generator out­
put will be required when the set is badly out of alinement.
c. Adjust the trimmer on the second i-f transformer for maximum
audio output. Do not grasp the test stand during i-f alinement.
Reduce the generator output as the audio output increases above 10
volts. Next, peak the secondary on the first i-f transformer, and then
peak the primary trimmer. After these adjustments have been made,
put the chassis back into test case CS-81-(*) and aline the set as de­
scribed in presetting receiver procedure, paragraph 58.
62. I-f alinelllent using test equiplllent IE 1 7 ( * ) . a. Be
sure that the frequency of the REC ( receiver) crystal is 455 kc higher
than that of the TRANS (transmitter) crystal. The chassis may be
left in the test case when using this method. The receiver crystal
must be installed in the chassis and the transmitter crystal in the test
unit 1-135- (*) .
b. If the presetting receiver procedure described in paragraph 58
has been followed, and no readable audio voltage has been obtained
on the OUTPUT 0-60 V. A. C. position of the test unit meter, first
make sure that a maximum r-f signal is being radiated. This can
be assured by connecting a short length of wire to the R. F. OUTPUT
terminal of the test unit and placing this wire close to the receiver
antenna.
-
-
•
NOTE.
Test
in s truction s
unif'
I-135-A does
furniShed
with
not
the unit
have an R. F.
expl ain
how
OUTPUT terminal. The
to mnke this connection.
With the MASTER SWITCH of the test unit on OUTPUT 60
V. A. C. (modulate tester switch ON) . adjust the second i-f secondary
trimmer for maximum output, next the first i-f �econdary trimmer,
and the first i-f primary trimmer last. (See fig. 5.) All i-f trim­
mers are adjusted for peak output meter reading. As the i-f trim­
mers are alined, loosen the signal coupling to the receiver antenna so
the maximum audio output reading of the meter is not over 10 volts.
This is necessary to prevent overloading the receiver and consequent
poor alinement of the i-f circuits. The above alinement adjustments
must be performed very carefully for good results. Go over the aline­
ment a second time.
d. After the i-f alinement adjustments have been made, complete
the procedure by adjusting the receiver antenna adjustment screw
and the receiver tank adjustment as described in paragraph 58g and h.
c.
40
l'
RADIO
SETS SCR 5 3 6-A, -B, AXD -C
63
•
a. Use test equip­
ment iE-17-(*) for tIllS test, but be sure that the external heavy-duty
batteries are disconnected. The radio set chassis with both crystals
in place is mounted in the test case, connected to the test unit, and then·
placed in the test stand with antenna rod extended. The press-to-talk
switch must be in transmit position. The MASTER SWITCH of the
test unit should be OFF. Place radio set batteries BA-37 and BA-38
in the compartment of the test unit. Close and secure the compart­
ment cover. (See fig. 7.) MODULATE TESTER switch must be
OFF.
63. Testing batteries BA-37 and BA-38.
.•.
-
�� � -
,
..
.
.
...-..,..��r--
-
-
_�----,
-
,
ANTENNA
•
•
SWITctI
,
•
•
,
•
•
I
I
.
'7L-556tf
-
HEADSET
,
FIGnttl 1!.- Te.�t efluipment IE-I5-A
-
set up.
b. Place the MASTER SWITCH on test unit in B�\.-37, 0-3 V. D.
C. position and observe the meter reading. Normal readings will be
between 1.35 and 1.5 volts. If the voltage is less than 1.25 volts, the
battery should be discarded and replaced with a new one.
c. Place the MASTER SWITCH on test unit in BA-38, 0-150
V. D. C. position and observe the meter reading. Be swre the set is in
transmit position. The normal meter readings will be between 75' and
103.5 volts. If the voltage .is below 70 volts the battery should be dis­
carded and replaced with a new one.
520361°
43
6
41
I
63-66
,
SIGNAL CORPS
d. When it beoomes neoessary to disoard battery BA--37 or battery
BA-38 beoame of low voltage, both batteries in the radio set slUYflld be
'replaoed at the same time. B:ltteries which are near the lower voltage
-limit may be used, but they will reduce the overall performance of the
radio set.
64. Test equiplllent IE-1 5-A. a. The purpose of this test
equipment is identical to that of test equipment IE-17- ( * ) . Test
.
equipment IE-15-A consists of the folluwing cumponents :
Test stand FT-252-A, including dummy 'antenna and 1'-£
galvanometer
Test case CS-81-( * )
Milliammeter, 0-50, d-c
Milliammeter, 0-15, d-c
Harness
Feedback capacitor
b. The following additional equipment is requirf'o when using test
.
Equipment IE-I5--A :
R-£ signal generator
Test set 1-56- (*)
Frequency meter SCR-211-- (*)
Battery supply (BA-40)
Microphone
Headset.
In sulated hilling screw driver
Small screw driver
65. Use of test case CS-81-( *). Since the tuning adjustment
points o£ the radio set are inaccessible because o£ their locations on
the chassis being covered by the case or housing, a special housing is
required to contain the chassis while making these adjustments. ( See
fig. 14.) Test case CS-81- (*) used for this purpose, is similar to a
chassis housing except for the holes that have been provided to permit
access to the chassis adjustments. This permits tuning the set under
conditions identical to those o£ normal operation. The tuning adjnst­
ments should not be made on the set without the test case housing
around the chassis, because the set would become detuned when in­
serted into its regular housing. This detuning would result from the
additional capacitance introduced into the circuit by the housing.
66. Use of test stand FT-252-(*). This test stand contains
clamps to hold the test case CS-81-(*) or the radio set chassis,
a 50-milliampere r-f meter to measure transmitter antenna current,
and a receiver and transmitter dummy antenna consisting of a re­
ceive-transmit switch, a 56-ohm resistor, and a v'uriable capacitor o£
8 p.p.£ maximum cnpacitance.
_
42
•
•
•
RADIO SETS
8CR
5 3 6-A, -B, AND -C
67-69
A special test harness cord sup­
plied with the stand provides connections for the batteries, r-f am­
plifier plate current meter, total B current meter, audio output meter,
earphone, and microphone. The schematic drawing of this harness
is shown in figure 15. The 15-milliampere meter is used to measure
the r-f amplifier plate current while the 50-milliampere meter is
used to measure the total B battery BA-38 current. The terminal
board attached to the harness provides a simple method of making
the connections to the chassis.
68. Use of test set 1-56-(* ) . Since radio receiver and trans- .
mittel' BC-611- ( * ) output is designed to operate into a high-imped­
ance earphone, the output meter provided in test set 1-56-( * ) is IDl67. Test harness and meters.
,
MICROPHONE
EARPHONE
OUTPU T
METER OR
V. T. V.
A::L_
TERMIN
BOARD
PLATE
METER
0-15 MA
D-C
/
o-+r--I
I
RED
+
-
--'
CAB LE- '
@
I
-11--
•
_
_
_
,I - t-­
I
0:
0---1
F"'URE 1;:;.
-
R
ED
-:
?
�
--':;.:
RE:=..
D
_
_
_
_
_
_
+
_ -
TOT AL B
M A MET ER
0 -50 MA
O-C
RED
8+
YEL '----+
M
8L�
__ 8-
CABLE
_
®
I
BATT E R IE S
-_ A-
Tc,;t etjuiprnent IE-H'i-A
barness connc<'tions.
satisfactory for alinement purposes because of its low internal re­
sistance. This output meter has a resistance of only 4,000 ohms. A
vacuum tube voltmeter with a minimum input impedance of 10
megohms would be preferable ; however, the a-c voltmeter of the
selective analyzer test set 1-56- ( * ) , makes a satisfactory output meter
if the 50-volt a-c range is used. Since the meter sensitivity is 1,000
ohms per volt, 50,000 ohms is placed across the receiver output when
the 50-volt range is ul:ied. No external blocking capacitor in series
with the A-C output meter is necessary to prevent the B battery
BA-38, voltage ftom reaching the meter, as one is contained in the
receiver circuit. The output meter leads of the test harness are fitted
with pin jack tips, so they can be plugged into the voltmeter.
69. Presetting frequency with IE-1 5-A. To cover the au­
thorized range of frequencies from 3.5 to 6.0 megacycles, individual
matched sets of antenna coils, 1'-£ tank coils, and crystals are 'avail-
43
�I
SIGNAL CORPS
69-70
able. Each coil is marked with its frequency and part number so
that errors of coil selection will be minimized.
NOTE.
The coilS supplied
frequency. Instead, each is
on the coil. The frequency
manufactured for radio sets
been preset to the frequency
with radio set SCR-536-A are not preset in one
adjustable over the small frequency range marlwd
range of each is indicated in chart I. The coils
SCR-536-B and SCR-536--C are identical but have
indicated on eaclt.
•
a. To preset the operating frequency of radio receiver and trans­
mitter BC-611- ( >I;) , obtain a coil and crystal equipment of the desired
frequency. The coil and crystal equipment comes in an individual
carton marked with the frequency and contains the transmitter and
receiver crystals, the antenna coil, and the r-f tank coil. The antenna
coil is larger and of different shape than the r-f tank coil. Its base
connections also differ, so it is impossiblp to put the coils in the
wrong sockets. Both coils are of the plug-in type. ( See figs. 8
and 10.)
b. Remove the chassis of radio receiver and transmitter BC-6l1-(*)
from its housing. To do this, unlatch the bottom cover of the hous­
ing and remove the batteries. Place them aside for test. Disconnect
the microphone and earphone plug» from the termin al board on dIP
end of the chassis by gently lifting them. Remove the screw in the
top cover of the housing ; the chassis then will slide out of the bottom
end of the housing.
70. Changing coils and crystals. a. Antenna coil. Remove
the plug-in antenna coil by carefully lifting it out of its socket. See
figure 10 for its location. In its place insert another coil of the desired
frequency.
b. R-I tank coil. To remove, loosen the screw holding down the
coil-retainer spring on top of the coil. (See fig. 9.) Swing the spring
free of the coil. The coil then can be lifted out of the socket. When
replacing with another coil of the desired frequency, carefully fit the
coil over the two pins projecting up from the socket so that the pins
fit into the holes in the coil form, and the coil adjustment shaft fits into
the hole in the socket. Gently press the coil into the socket, replace
the coil-retainer spring on top of the coil, and tighten the screw holding
the spring.
.
c. Orystals. The crystals are mounted in plug-in type holders.
(See fig. 10.) To remove a crystal, lift up the clamp located on top
of the crystal holder. This clamp pivots on a stud fastened to thE'
chassis. Place a small screw driver between the crystal holder and
the socket and gently pry it up. To remove the other crystal hulder,
the same prucedure is fullowed. Select a transmitter and a receiver
crystal holitcr of the desircd frequency. (The frequency of the trans•
44
•
RADIO SETS seR 5 3 6 -A,
B , AND -()
70-7 1
-
•
mitter crystal will be the same as that of the coils, while the receiver
crystal will be 455 kc higher in frequency.) Insert the receiver crystal
holder in the crystal socket marked REC. It should be inserted so
that the frequency printed on the metal side faces out and the arrow
on the holder points in the same direction as the arrow on the socket.
Place the transmitter crystal in the socket IllHrked TRAN. in exactly
the same way. The printed metal side of the holder should show
through the opening in the chassis.
Frequency range of coils for radio set SCR-.586-A
CHART I.
------
-
I
R-F Tank
Frequency
(in kc)
----------- I -!-
C-370
_
C-37L
C-372
C-373
C-374
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
__
_
_
_
_
_
_
_
_
�
_
,
-
------
-------
3825-4225
4225-4625
4625-5075
.
------�
- ---- --------
{C-358
_
C-359
C-360
C-361
C-362
C-363
C-364
C-365
C-366
C-367
C-36.8
C-369
{
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
5500-6000
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_ _ _ _ _
_ _ _ _ _
_
5075-5500
_
_
_
_
C-357
Frequency
. (in kc)
Antenna
3500--3825
_
_
_
I
-------
,
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
•
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
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_
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_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
._
_
_
_
3500-3675
3675-3825
3825-4025
4025--4225
4225--4425
4425-4625
4625 4825
4825-5075
5075-5300
5300-5500
5500-5775
5775-6000
Connect the four
wires of the harness marked A + , A , B + , B - , to their proper
terminals on the batteries. Connect the two wires marked VT-174
PLATE M.A to the 15-milliampere meter ; connect the two wires
marked TOTAL B MA to the 50-milliampere meter ; and connect the
two unmarked wires to the 50-volt a-c range of the selective analyzer
unit of test set 1-56- ( * ) . Connect the earphone to the terminals
marked G and P on the junction box attached to the harness. The
earphone lead connected to the braided shield should connect to the
G (ground) terminal.
b. Place the chassis into the test housing. The chassis must be in­
berted into the test housing through the bottom, as is done when
�nserting the chassis into its own housing. Take care that the chassis
fits between the guides provided for it in the housing. It should not
be necessary to force the chassis. If it is, withdraw the chassis and
check to see that no parts are catching on the housing or that the
chassis has not jumped the guides. Slip the top COver over the
antenna rod and fasten the chassis to it with the 8/32 mounting screw.
The chassis then will be held securely in the test housing. NoV!
1'pmo'oe the plate current meter jumpeT from the terrni'lwl board at
- the end of the chasl:fis.
71. Setting up test equipment IE-1 5-A.
45
a.
j,
,
•
SIGNAL C()RPS
71
-
ANT
ASSEM
M12
-
V2
VT-171
VI
VT-174
RECEIVER. CONVERTER a esc
�
R-F AMP
RECEIVE
TRANS, R-� PW'R AMP
'"
TANK
COIL
I
ANT COIL
SOCKET
L2
m
){NO
(BOlT VIEfIII)
L\.IGS IN 2 B
N
co
ANT
COIL
LI
-
,
•
A
8
"
M3
•
-
SEND· RECEIVE SWITCH
ISWITCH SHOWN IN RECEIVE POSITION}
V1·171
v1-114
V1-173
VT·'72
,
,
,
V1-174
"
,
KEY TO SYMBOLS
.1.
,
,
,
HOOK-UP
FILj.MENT
K
+---<>�
A.
.
RECEIVER
M4
M1CROPt-10N[
PAPER
CAPACITOR
AOR
CAPACITOR
(VARIABLE)
FIGURE 16_--Hauio receiver and transmitter BC-611-A.-schematic Uiagram.
-
46
- - ..
•
RADIO SETS
�F AMP
USEE)
I
4!)5 t<C.
I-F
5 3 6-A, -B, AND -C
RECEIVER. 2ND VET. A V.C., A� AMP
TRANS. MICROPHONE AMP.
-
71
V5
VT-174
' V4
VT-172
V�
VT-I73
SC�
RECEIVER,. OUTPUT AMP
TRANS, MODULATOR
'"
'"
0:
C
I:
m
,�
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N
o
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-- - -"
"
"
---- - --- - -- -
CllRR£NT
,Moo<
.
] '
•
103i- VOlT "8' SATT.
.t
•
.. 5
PHONE
,
!ail!
FIGl:mJ 16.
c--< \.\.\.\.\ .
'I
I'i
VOlT
I
ON OFF
SWlT,,"
MEG . MEGOtiM U,OOO,OOO-OHM5)
TO FIL. e. SW. )( 1I
NOTE:' SW1TCH OPERATED
y.. 1,000
NUt,uRS AROUNO T\R SYMeOl,S
AR PIN tiUM5£AS
E
nadio receiver and
J
0
,. BATT.
'
PVLL
PUSH
TO TURN 'Off�
transmitter BC-611-A
.. e
'
1111�
ANT.
OUT ANT, TO TURN 'Ot('.
ANT. ALL THE WAY IN
Br
..
7
�
schematic diagram
Continued.
47
.
..
71
SIGNAL CORPS
V2
VT-I Tt
VI
VT-t74
V3
V1'I73
.
RECEIVER, CONVERTER a O!;C
TRANS. OS:;C�TU
RECEIVER. R-F AMP
TRANS. R'F PWR
R-F
"""
COoL
, L2
•
•
,
�
•
A
8
ly
SENO· M:CEIV(
SWITCH
tSWITCH SH6wN IN R(C(I\I[
"1.174
....
•
•
\lY·nt
.
.
\11.112
,.
,
,
,
- - .... • - - -
NOTE ·
•
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f"lLAM£NT
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K
"
J,tl1.
NEG
pf
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.
•
•
•
•
....,
I,,{JOO -o....s
.
MEGOHMS t'.ooo.ooo
MlCl10rAFl4DS
NIc.ROMI�florAIlADS
�!I[R$ AJlOUNO TUllE
ARE
FIGURE 17.
..
lf.RS,
.... NJ
0tW5J
$1"'9Ot.S·
Radio receiver and transmitter BC-611-B Rnd BC-611-C
schematic diagram.
I
,
I
I
,
48
•
RADIO
SETS SGR 5 3 6-A, -B, AND -C
71
VS
VT-174
RECEIVER, OUTPUT AMP
TRANS. MOOULAT�
V4
VT-172
RECEIVER. 2ND DET, AY. C . A-f AMP
TRANS, MJCROPHONE AMP
..
-
•
•
•
�-::-�=::::
....;:,
0-t
---..;
_
_
_
_
_
'.
CUFiRENT
JACK
�wtTCH
ON-Off
)(.
0
M6
-
•
•
FIGURE 17_
Radio receiver and transmitter BC-61l-B and BC-611-C
diagram Continued.
•
-
•
-
•
-
49
--
schematic
I
71-72
SIGNAL CORPS
Caution : Do not misplace the jumpe1'.
c. Attach the terminal board of the harness to the terminal board
of the chassis, so that the two small pins on the harness terminal
board fit into the plate current meter j acks, and so that the two large
locking pins, one on each end of the terminal board, fit into the holes
provided for them. Lock the two terminal boards together by a
sideward movement of the levers attached to the locking pins.
d. Next clamp the test housing into the test stand FT-252- (*) with
the antenna end up, and the housing in such position that the change­
over switch is opposite the left side of the operator, as he faces the
stand. (See fig. 11.) The upper clamp should grasp the housing on
the edges of the top cover. The lower clamp should not be made too
tight as the pressure may crack tIle housing.
e. The signal generator used should be modulated 30 percent by a
400 to 1,000 cycles per second tone and should be accurately set to the
carrier frequency of the radio receiver and transmitter BC-611- ( * ) .
The signal generator frequency mnst be checked with an accurate
frequency meter, such as SCR-211- ( * ) .
72 . Presetting receiver with I F:-1 5-A. a. Extend the radio
set antenna. rod to its full length, 39 inches above the top cover of test
case CS-81- (* ) . This will turn on the radio set. Do not press the
press-to-talk switch on the test ca::;e during the receiver presetting
adjustments.
b. Connect the ground lead of the r-f signal generator to the test
stand, but leave the output lead of the signal generator unconnected.
The 1'-£ input to the receiver will then be the pick-up on the antenna.
The generator output should be adjusted for a reading of approxi­
mately 10 volts on the 50-volt a-c range of the output meter. If the
receiver is badly out of alinement it may be impossible to get this
output reading or any at all ; in such a case fo]]ow procedure in para­
graph 74.
c. Grasp the test case with one hand during all of the following
adjustments.
d. The location of the receiver tuning adjustments is shown in fig­
ures 11 and 14. With the insulated screw driver, turn the 'J'eceive'l'
antenna adjustment screw clockwise. Notice the effect of this adjust­
ment on the output meter reading. If the meter reading increases,
continue to tighten the screw until a maximum reading is obtained.
If reading decreases, turn the screw counterclockwise until a maximum
reading is obtained. Be careful not to tighten the screw a.fter it begins
to turn hard as the threaded base of the trimmer will be stripped.
The setting of the screw for maximum output should fall somewhere
.
point
pressure.
between the
of hard turning and that of minimum
50
RADIO SETS SC'R 5 3 6-A, -B, AND -C
7 2-73
•
If a maximmn point is not reached in these limits of the screw adjust­
ment, try another antenna coil. If the set appears to be badly out
of alinement, follow procedure in paragraph 74.
NOTE.
Be sure that the r-f signal is not strong enough to cause overloacIing
of the receiver. If this conuition exists, adjustment of the receiver antenna ad­
justment SCl'ew will have little or no effect on the output reading. Best results
will be obtained if the r-f output from the Signal generator is adjusted, so that
the output meter reading on the 50-volt a-c scale does not exceed 10 volts,
although satisfactory results may be obtained with readings up to 20 volts.
e. Using the insulated screw driver, turn the receiver tank adjust­
ment screw for maximmn output, using the same method employed in
paragraph 72d.
•
NOTE.
This scre�, which is made of bakelite, fits into a powdered iron core
which is threaded. The movement of the screw changes the position of the
core in the coil. If the screw is turned too far clockwise, the core will riue
up against the screw head, and the threads in the core will be stripped. If the
screw is turned too fat· counterclockwise, the core will come in contact with the
coil socket and again further turning will strip the core threads. The screw
setting for maximum output should fall somewhere between these two limits of
adjustment If it does not, a wrong tank coil may be in the set. This com­
plptps the receiver adjustments.
73. Presetting transmitter with IE-1 5-A. a. Gral:fp test case
and operate press-to-talk switch with on.e hand during all the follow­
•
ing prnetting operation.'! to the transmitter:
(1) Using the small screw driver, adjust the transrn-itter tank ad­
justment screw for minimum current reading on the 15-milliampere
meter. The normal reading is approximately 7 milliamperes. See
figures 12 and 14 for location of the transmitter tank adjustment
screw. Release the press-to-talk switch.
(2) Telescope the upper three sections of the antenna rod, leaving
only the bottom or fourth section fully extended from the housing.
Next, clip the dummy antel1na connection to the upper part of the
antemla rod. ( See fig. 12. ) Set the antenna change-over switch
on the panel of test stand FT-252-( * ) to TRANS. position.
(3) Connect the microphone provided with the test set to the M
and G terminals of the test harness. The braided lead goes to the G
terminal.
(4) Grasp the test case and depress the press-to-talk switch again.
Using the insulated shaft extension, adjust the dummy an tenna capac­
itor control for minimum current reading on the 15-milliampere
meter. The reading should be approximately 7 milliamperes. This
adjustment of the dummy antenna capacitance for minimum power
amplifier plate current is necessary to compensate for the change in
antenna capacitance due to telescoping the upper three sections of the
51
•
•
•
-
COl
--
LI
0
1.6
.,
I
I
I
I
I
I
•
FIGURE 18.
Radio receiver and transmitter BC-61l-A
•
practical wiring diagram.
" ---9
•
VT-174
VT-17I
VT-I72
V4
VT-114
•
r------
•
--
I
I
I
"
o
"
(L4)
-,
I
I
I
I
I
....
I
•
N
U
0
LOC�,,,.e �IN
' 011 TESf
l(ft""A"
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e;,
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t:1
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HOT€,.
S£"'SlTWIfT AOJUSTM[HT 1.£10.
TMIS LUO ..., I( 'OUI'IO cerUtTI!) 10
IITICII
II!!,
"'I' 011 lin
/ref�rel1ces il7pQrel1tl7e.Jes ( ) -ref'er to sc;r·,s.36-C CI1/g
FIGURE 19.
Radio receiver and transmitter BC-61 l-B and BC-6ll-C
diagram.
practical wiring
n·s.5?)
•
SIGNAL CORPS
73-74
antenna rod. Observe the reading on the antemla current meter on
tesj' stand FT-252-( *) . It should be from 15 to 24 milliamperes,
representing the unmodnlated anten na current.
( 5 ) (a) Modulate the transmitter by whistling a steady note into
the microphone, and watch the antenna current meter on the stamI.
It will be found that the meter reading increases. Keep whistling
until the pointer on the meter reaches its highest position, then note
the reading. Be sure to whistle loud enough to cause the meter read­
ing to rise. The meter reading should increase 15 to 20 percent over
the reading obtained when not whistling into the microphone. For
example, assume that the current when not whistling is 20 milli­
amperes and when whistling is 24 milliamperes. The increase in current is then :
.
24 - 20 = 4 milli amperes
the percenta$e increase will be :
4/20 x 100 =20 Pl'l'l'l'ut
( b) Another method which can he
ns('d is to (livlfh' t hI' enrrent.
"'hen whistling by the current when not whistling. The answer
should be greater than 1.15. For example, take the valut,s of r-f cur­
rent, previously given. Dividing the modulated current by the un­
modulated current gives 24/20= 1.2.
b. If less than 15 percent increase is obtained, check the crystal for
acti vity ; and also check the modulator, r-f amplifier, and oscillator
tubes for output. Be sure that the battery voltage under operating
conditions is at least 75 volts.
c. This completes normal frequency presetting adjustments. Re­
moye the chassis from the test case, replacl' it in the radio set housing,
and reconnect the microphone and earphone. Be sure to replace the
plate current meter jumper. Reinstall the A and B batteries, mak­
ing certain that the positive ( + ) ends face out. Close the cover,
move the latching bolt into place, and tightell the knurled nut. The
set is now ready for operation.
74. I-f alineIllent. If the i-f transformers are badly out of alinement, it may be impossible to get a carrier frequency signal through
the receiver as outlined in the presetting receiver procedure. For
such a condition, the i-f transformers should be realined. Use the
following procedure :
a. Remove the chassis from the test case and fasten it to the top
cover of the housing with the mounting screw. Then place the chassis
in the test stand ill the same relative position as when in the test hous•
•
54
•
•
5 3 6-A, -B, AND --<:
RADIO S.E TS SeR
74
ing, and hold it there by gripping the housing coyer with the upper
clamp of the test stand. (See fig. 13. )
b. Connect the ground lead of the signal generator to the test stand
FT-252- ( * ) . Connect an .05-p.f capacitor in series with the output
Ir
W
-
p,tfJ'·u'
8
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•
-
leau of the signal generator, and connect the other end of the capacitor
to the No. 6 pin of the tube VT-171. Set the signal generator fre­
quency to 455 kc and then adjust the generator output until a lO-volt .
reading is obtained on the 50-volt a-c range of the output meter. Con­
siderable generator output will be required when the set is badly cut
of alillemellt.
55
I
SIGNAL CORPS
74-76
•
I
•
c. Adjust the trimmer on the second i-f transformer for maximum
output. Reduce the generator output as the output increases above
10 volts. Next peak the secondary trimmer on the nrst i-f trans­
fonner, and then peak the primary trimmer. After these adjust­
ments have been. made, put the chassis back into the housing and aline
the set as given in the presetting receiver procedure. (See fig. 5.)
75. Checking for image frequency.--a. GeneraZ. When setting the generator frequency, care must be taken that the frequency
is that of the signal to be received and not the image frequency, which
is exactly 910 1m higher than the carrier frequency. For example, a
unit alined for proper operation at 4,000 ke' wil1 have an image re­
sponse at 4,910 kc, while one which operates OIl 5,000 kc wilJ have an
image response at 5,910 kc.
b. Image frequency check. In checking for proper operation (in
regard to image reception) take the following steps :
( 1 ) Completely aline receiver to the carrier frequency. Note the
signal generator dial reading.
(2) Refer to the calibration charts of the signal generator (or to its
dial if it is directly calibrated) and estimate the dial reading for a
frequency of 910 kc above that in the step ( 1 ) above.
(3) Increase signal generator output to 1.000 times its output nec­
essary to produce 10 volts across the earphone and the output meter.
( 4) Rotate the signal generator dial to the dial reading UHCel'ta.i lied
in step (2) above. A signal should now be heard. Rotate the dial
for a maximum signal as indicated on the output meter. Adjust the
.generator output by means of tile attenuator so that the output meter
across the earphone indicates exactly 10 volts. Note the reading nec­
essary to produce 10 volts. If this image frequency sensitivity is
divided by the carrier frequency sensitivity, the resulting number
should never be less than 200. If no !-lIgna] is heard at 910 kc above
the carrier frequency, it is a certainty that the receiver is not correctly
ali ned, and the unit should be realined as outlined in paragr�lph 72.
76. BC-6 1 1-(*) as signal generator. a. General. ( 1 ) If a
situat ion should arise in which it is necessary to change the frequency
of radio receiver and transmitter BC-61l- (*) , and no signal generator
is available, it is possible to preset the frequency provided another
radio receiver and transmitter BG-61l- ( * ) operating at the same
carrier frequency is available.
(2 ) If another such set is available, but is not of the correct carrier
frequency, it can be made to operate at the correct frequency by in­
serting the correct crystal and proper antenna and tank coils.
.
.
•
.
56
.
f
•
RADIO SETS seR 5 3 6-A, -B, AND -C
(3) In order to preset one set, it
•
67
will be necessary to convert the
other set into a modulated signal generator. This may be done by
simply putting the set in the transmit position and placing a buzzer
near the microphone ; if a buzzer is not available, the carrier can be
self-modulated by converting the audio amplifier in the set into an
audio oscillator. This circuit change can be made easly by placing
a capacitor of lOOp.p.f between the microphone plug and the plate cur­
rent meter jack on the terminal board of the chassis. This capacitor
will provide enough feedback between the input and output to cause
the audio amplifier to go into oscillation. 'When the radio set is put
into the transmit position, an audio note will be heard in the earphone
of the unit and a signal will be radiated, modulated by this audio tone.
A special capacitor designed for this purpose is supplied with test
equipment IE-15-A. (See figs. 21 and 22.) To simplify connections,
one lead of the capacitor is tipped with a spade lug and the other lead
is tipped with a plate current meter jumper. The spade lug has a
small hole in it for the microphone plug and is designed to fit between
the microphone plug and the microphone jack on the terminal board.
The spade lug is painted green to identify it with the microphone
plug, which is marked with a green spot.
(4) The plate current meter jumper connected to the capacitor
replaces the plate current jumper in the set.
b. Setting up the signal generator. Procedure for converting radio
receiver and transmitter BC-6ll-(*) into a modulated signal gen­
erator is as follows :
(1) First remove the chassis from the housing of the set.
(2) Select a crystal of the exact frequency to which the other set
is to be preset, and place it in the transmitter crystal socket. Select
another crystal which is 455 kc higher in frequency and place it in
the receiver crystal socket. Select the proper antenna and tank coils
and insert them into their respective sockets.
(3) Place the set into the test housing and connect the test harness
as described in paragraph 71.
(4) With the antenna rod fully extended, grasp the test case and
put the set in the transmit position and with a small screw driver ad­
just the transmitter tank adjustment screw for minimum reading of
the plate current meter.
(5) Disconnect the harness from the chassis and remove the chassis
from the test housing. Do 'Iwt forget to 'J'epZace the plate cu/rrent
mete'J' jumpe'J'. Put the set into its own housing and connect in the
audio feedback capacitor. (See figs. 21 and 22.) Place the spade
lug of the capacitor lead between the microphone jack and the micro.
•
57
i'l
I
SIGNAL CORPS
76
•
!
,
•
•
•
•
.
••
.- '"
.
•
•
FIGURE 21.,-'Collllectiolls for SClf-Illodulation.
•
58
RADIO
SETS
SCR
5 3 6-A, -B, AND -C
7ti
!
,
I
,
•
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•
•
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.
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•
•
1<'IUUHE :t2.-- ·l'Jacement of auuio feeuiJack capacitor.
59
•
76-77
•
SIGNAL CORPS
phone plug. Remove the plate current meter jumper and replace it
with the jumper attaehed to the other capaeitor lead. Replace the
batteries and place the capaeitor irito the space between the housing
wall and the B battery spaeer and then close the bottom cover. Check
the set to see that it is oscillating by operating the press-to-talk switch
and listening for an audio tone. The set is then ready for use as a
modulated signal generator.
(1) Remove the chassis from the housing of
c. Prese tting the s.l' t.
the set to be preset and insert the eorrect erystals and mils.
(2) Put the chassis into the test housing and attaeh the test harness ;
then extend the antenna to its full length. Do not connect the dum/my
antenna.
(3) Tie down the press-to-talk switch of radio receiver and trans­
. mitter BC-611- ( * ) being used as the signal generator, with a pieee
of twine or wire, plaee it about 20 feet away from the receiver to
be preset and extend its antenna.
(4) 'Vith the set in the test case in the receive position, adjust the
antenna trimmer for maximlUn audio output. If the signal picked
up is too strong, (whieh will show up in a noncritical adjustment of
the receiver antenna adjustment screw) the signal radiated from the
set used as the signal generator can be reduced by telescoping sections
of the antenna rod. (Because the bottom section of the antenna rod
operates the power switch be careful not to turn off the set. ) If this
does not reduce the signal sufficiently, place the set used as the signal
generator on the ground with its antenna in a horizontal position
and pointing away from the set being adjusted.
(5) Next adjust the reeeiver tank adjustment screw for maximum
audio output. The receiver is now properly alined and the radio
l·eceiver and transmitter BC-611- ( * ) , used as a signal generator, can
bf' turned off.
(6) To preset the transmitter, place the set in the transmit position
and adjust the transmitter tank adjustment screw for minimum plate
current.
(7) Collapse the upper three sections of the antenna rod and con­
nect the dummy antenna to the top of the rod. Connect the micro­
phone to the M and G terminals of the junction box. Then adjust
the dummy antenna capacitor control for minimum plate current.
Whistle into the mierophone and check the antenna current increase
due to modulation as given in paragraph 73.
77. Replacement of parts. a. Antenna rod. (1) To replace the
antenna rod, first the chassis must be removed from the case. The
antenna rod fits into an insulated guide which is fastened to the
chassis at the terminal board by a machine screw. The antem1a rod
60
•
,
RADlO SETS SCR 5 3 6-A, -B, AND
77
in the extended position is supported by a meta] clamp attached to
a polystyrene base. At the side of the clamp, where it is fastened
to the polystyrene base, are three wiper contacts which grip the rod
tightly. It is through these wiper contacts that the electrical contact
to the antenna rod is made. An insulated plug in the bottom end of
the antenna rod oper.ates the toggle switch on the chassis.
(2) To remove the antenna rod, remove the screw which holds the
antenna guide to the terminal board. Then gently bend the terminal
board away from the antenna guide so that the plug at the end of the
guide disengages from the hole in the terminal board. Ewercise the
greatest care in this operation as it is possible to tear the terminal
board loose from its fastenings. Then with the guide unfastened, the
antenna rod is withdrawn from the metal clamp.
(3) To replace the antenna rod, slip the antenna guide over the
bottom section of the rod. Pass the antenna rod through the antenna
guide ferrule and seat the ferrule at the top of the guide. Insert
the tip of the antenna rod into the antenna clamp and push the rod
through the clamp gently, until the top of the antenna guide comes
in contact with the clamp. The antenna guide is then oriented so that
the insulated end plug on the antenna rod will engage the lever on
the power switch. Then very carefully bend the terminal board back
slightly ; just enough to permit the plug at the end of the guide to
seat in the hole in the terminal board. Replace the fastening screw.
( 1 ) There are four
b. Replacement of resistor-capacitor OlipS.
resistor-capacitor containers which are called cups on the bottom of
the chassis. These cups fit around the tube sockets and it will be
necessary to unsolder the wires from the tube socket as well as the
cup before removing. The cups are fastened to the tube sockets by
cement and must be pried loose from the socket by a screw driver
or a knife. The cup will be broken in the process.
(2) Each cup has a part number marked on it as well as a schematic
drawing of the condenser and resistor connections. When replacing
a cup, be sure that the new cup has the same part number as the
old one. As a great number of wires will have to be unsoldered, it
will be found helpful to put on paper a simple description of each
wire removed and the point to which it connects. Reference to
the cup diagrams shown in figure 23 also will be found helpful. The
old cement should be scraped off the socket base before cementing
the new cup in place. The new cups should be placed on the chassis
so that the part number on the cup faces the back of the chassis,
considering the press-to-talk switch side to be the front.
-
•
61
•
_
__
_
_
_
_
_
, _
•
c·
•
,
•
•
8 8 2 8 530
88 28529
-
1
6
' IIEGo_
R,
I
VT-171
o
SOC�ET
7
2
3
.01Jlf
•
TI.-5577A
FIGUnE 23.
L....
(
-J
/
_
C'7
�­
:1
0 ,
. ....26 I
0=>.,C
I
VT·'73
o
6.U'
R'5
,-,18 M
R' 2
'- - -�
�
M
C25
_
_
MEG.
1,000 OHMS
__
Reslstor·capacitor cups
-
!\1?"':=�
•
,,"-
•
00025)1'
schematic dlagmm .
•
•
I
•
�
� __
-'
'-'
I
I
I
- "';:':'- , I
I
I J
LJ
RADIO SETS SCR 5 3 6-A, -B, AND -C
Caution : 1-Vhen soldering connections to
77
new cup be careful not
to apply too much heat. The cup may liJe damaged beyond repair
if this precaution is not observed.
Disconnect the transformer
c. To replace an i-I transformer.
wires, and remove the clamps holding the transformer shield can to
the chassis. Make a note of the transformer position so that the
transformer wires can be put back in the same position as they
originally were ; otherwise, oscillation may result. The position of
the transformer with respect to the trimmers in the top of the can
5hould also be consideI'ed, so that the trimmers can be reached
through the openings in the test housing when alining the set. Make
sure the i-f unit clamps are not bent so that they come. in contact
with the swit�h, a condition which will result in a short circuit.
a
•
�_
•
5
--"--1
- - -
l10M VIEW
VT·171 DO
Ptn
Element
I-Filament
2-Plate
3-Screen Grid
4-Osc, Grid
5-Suppressor
&--Grid
7-Filament+
VT·173 BOTJ'OM VIEW
VT·171 BOTTOM VIEW
Pin
Pin
£Jeu.ent
I-Filament-Int. shield
2-Plate
3-Screen Grid
4-None
I-Filament
2-None
3-Diode Plate
4-Screen Grid
5-Plate
/>--{;rid
7-Filament +
FlGl'KE 24.
Element
S-SUWressor
6-Grid'
7-Fllament+
VT.174 BOTTOM VIEW
Pin
Element
I-Filament+
2-Plate
3-Grid
4-Screen Grid
5-Filament 6-P1ate
7-FiJament +
TL-
'I.'ube base cOllnectiolls.
•
d. To remove an eyelet. .As most of the parts are fastened to the
chassis with eyelets, removal of the eyelets is necessary for the re­
placement of these parts. A simple and effective way to remove an
eyelet is to place a drill point of a diameter larger than the eyelet
in a vise with the tip end up. Place another drill point of a similar
diameter in a brace. Put the eyelet to be removed over the drill point
in the vise, then apply the brace to the other side of the rivet and
drill it out. Take care to drill out only enough material to remove
t.he rolled over edge of the eyelet. Do not drill through t.he chassis.
This will enlarge the hole and make the replacement of a new eyelet
difficult.
e. To replace power switch. To replace the power switch it will
be necessary to first remove the a-f choke and the two tubular ca­
pacitors next to the switch. Next remove the nut holding the switch
to the chassis and then remove the wires to the switch. The switch
now can be remuved from the chassis by patient maneuvering.
'
63
SIGN AL
78
CORPS
The foJIowing are possible
78. Trouble location and remedy.
troubles and their remedies :
a. Exces8ive r-f mnpfifit31' l,[,rIte current in the tran.'I1nit positiou.­
( 1 ) If the r-f amplifier grid excitat.ion (the r-f voltage applied to the
amplifier grid) is low, illsnffi('ient bias voltage will be deVt'loped
across the grid resist.or Re" and the plate current wil1 be excessive.
Low grid excitation may be caused by a poor crystal or a weak or
bunled out oscillator tube. Also, no excitation would occur if the
coupling capacitor C9 were open 01' the oscillator were not functioning.
See chart II for transmitter charu(·teristics.
(2) High plate current might Le caused by an improper r-f am­
plifier tank coil. An incorrect coil will show up in the inahility to
get a dip ill the plate current reading of the r-f amplifier tube when
tuning this stage.
(3) High plate current could be caused also by short-cirruiteo
tUrns in the r-f amplifier coil. The pifect would be the same as when
nsing an incorrect coil. A leaky or short-circuited cOllpling capacitor
C9 would also cause excessive plate current.
•
CHART II.
011 U1·t of average tran8m.itte1· performal1<'e ('1t.((r(( ('f;eri8ti(;.�
•
•
Test
Minirnum
Avemge
R-f current :
Unmodulated _ _ _ _ _ _
rna (r-f
rnw) .
18
power :
power:
15
1 8. 1
rna (r-f power :
rnw) _
1 2.6
rna (r-f power: 17.0
mw) .
mw).
IV[odulation capability _ _ _ Over 50 pm'cent.. _ _ _ _ _ _ _ _ Over 50 percent.
A ba ttery BA-37:
Volfage _ _ _ _ _ _ _ _ _ _ _ 1 .4 volts _____ _ _ _ _ _ _ _ _ _ _
CurrenL _ _ _ . _ _ _ _ _ _ 280 rna __ .. _ _ _ _ _ _ _ _ _ _ _ _
1\1' odulated_ _ _ _ _ _._ _ _
20.5
rna
(r-f
17.5
25.53
_
R
batt.ery
_
BA-38 :
Voltage _ _ _ _ _ _ _ _ _ _ _ _
Current- _ _ _ _ _ _ _
..
_
_
95
30
volts _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
rna___ _ _ _ _ _ _ _ _ _ _ _ _ _ _
NOTE.-All values taken with chassis in Wst
C8S('
_
_
CS-81-(*).
b. Oscillator does not function (no reoeption and transmission) . To
check for operation of the oscillator, place a d-c voltmeter across R. ; a
reading should be obtained if it is functioning. ( See fig. 25 and chart
III.) Besides the cominon reasons for oscillator inoperation such as
part failure, a weak crystal, Jow battery voltages, etc., inoperation can
also be caused by defective switching. If in pressing the press-to­
talk switch, the moving blade of switch section A does not makp
contact with the switch lug connected to the transmitter crystal M2
at tll{' same time or bpfore the moving blade of switch section 111 Hhort­
circuits resistor R17l the energy pulse necessary to start crystal ltCtiv64
•
I
SETS SCR 5 3 o-A, -B, A.J.'>lD -<::
RADIO
78
ity will not reach the crystal and the oscil1ator will not function. As
a result of the high screen voltage and no bias, the tube VT-171 will
become paralyzed. To remedy this trouble, move the lug on switch
section A connected to the transmitter crystal 1\!2 so that it does make
...
.
..
......
•
•
on N
.. �
•
•
....
..
'"
--
or ...
•
-.
..
.
•
-
•
o
•
"'
...
>'
o
...
oor·
.
or ...
' I--�
..�
·
- -
or ...
or ...
�o
•
•
00
•
•
Q)
.D
'"
..,
I
or ...
or ...
,\0
•
•
or ...
-
•
•
on �
.. ..
or ...
-J
---j';'0
7�
or ..
00
•
•
•
or ...
.. ..
.: �
•
•
-
-
•
-
o
'0
-�
or ...
00
•
•
"
�
I
or ...
•
•
� ..,
-�
contact at the same time or before switch section M short-circuits
resistor R17• Also replace the tube.
(1) If the r-f amplifier
c. Audio osaiIlation in tram.8mit position.
tube VT-174 becomes inoperative, the load offered to the modulator
tube is removed. The plate load of the modulator tube then will be the
impedance of the modulation choke, which is high. Under this condi65
SIGX AL CORPS
78
tion, sufficient coupling exists between the input of the audio amplifier
and the output of the modulator to cau:se oscillation.
(�) Failure of the r-f amplifier tube VT-174 to operate can be
caused by an open filament, gas in the tube, or loss of vacuum due to
a crack in the glass. A cracked glass or gas in the tube will be indicated
.
by a milky color near the exhaust tip of the tube.
d. Noi8e due to regeneration. ( 1) A sUlall amount of regeneration
in the receiver is permissible, as it increases the selectivity and sensi­
tivity of the receiver ; however, because tubes of the same type vary .
somewhat in their gain characteristics, excessive regeneration may
occur when tubes are changed in the receiver. Excessive regeneration
results in a high circuit noise level, and in extreme cases causes oscil­
lation. Regeneration is caused by coupling between circuit elements
due to close spacing of parts on the chassis.
(3) The solution to this problem is to reduce the sensitivity of the
receiver to a value which permits an allowable noise level. Provision
for reducing the sellsitivity of rauio receiver and transmitter
BC-611- (*) for cases of excessive regeneration is provided for by an
adjustable bias arrlUlgement. The three resistors ReG, I{" and Ro,
connected across the osci1lator grid leak resistor R4, provide this
adjustable bias arrangement. The lead connecting the Iletector load
resistor R14 to the bias point should be moved one st!'}) up on the
voltage divider to decrease the :sensitivity. This adjustment will
increase the bias on tubes Vi' V2, and Va. Normally, this lead is
grounded, but for sets of abnormal sensitivity will be found con­
nected to one of the taps on the divider. The lead should be
connected to the lowest point on this divider which provides a
satisfactory noise level.
e. Sen.sitivity control ad;iuBtment. ( 1 ) If after the proper aline­
ment of a receiver it is found that the sensitivity is greater than 7
microvolts for a 15-volt. output reading 011 the 50-volt a-c scale of the
output meter, or 6 microvolts for a 20-volt reading on a vacuum-tube­
voltmeter type output meter, adjustment of the sensitivity control is
recommended. This adjustment, however, should be made only after
checking the receiver to see that the lack of sensitivity does not result
•
•
•
66
•
RADIO S.ETS SCR 5 3 6-A, -B, .A1o;D -C
78
from weak tubes, low battery voltage, or circuit failures. Charts IV
and V give receiver performance figures.
(2) The sensitivity of the receiver is controlled by an adjustment
of the grid bias on the r-f amplifier, mixer, and i-f amplifier tubes.
The adjustable bias is obtained by means of the voltage divider made
up of resistors R5, R., and R25• To increase the sensitivity of the
receiver. the bias should be reduced. The reduction in bias is accomplished by moving the wire connecting resistor R14 to the voltage
divider closer to the ground end of the divider. Minimum bias and
greatest sensitivity will be obtained when this lead is connected to
ground. Additional information on the sensitivity control is given
in 78d (2) .
f. Tube trcmble. (1) Tubes which have lost their vacuum because
of a crack in the glass will usually have a milky color near the exhaust
tip or base. The cracks are often plainly visible at the base of the
tube.
(2) To avoid breaking tubes when removing them for inspection,
remove the tube by inserting a rod through the metal tube in the center
of the tube socket on the bottom of the chassis and by gently forcing
the tube out. Be sure to remove the locking clip on top of the tube
before forcing the tube out of its socket.
g. Loose or tight adjustment of antenna trimmer. A very loose or
very tight adjustment of the receiver antenna adjustment trimmer in
the receive position indicates an incorrect antenna coiL
h. Loose corttrl.eCtions. ( 1 ) Some units may occasionally develop a
loose connection. This is the condition where a set becomes noisy
when rapped gently. Loose connections most commonly occur when
two metallic conductors momentarily break the contact they are ex­
pected to maintain. This may happen behveen the sections of the
antenna rod, between batt{'ries and their contacts, internally in tubes,
or in some cases, a poorly soldered connection.
(2) If a unit does develop a loose connection, the circuit elements at
fault may be located by gently tapping at various places on the unit
with the insulated handle of a screw driver. The noise becomes
louder as the loose connection is neared.
•
,
67
-
•
I
SIGNAL
78
OHART III.
Rece-iver
Component
-
R1
R2
_ _
R3
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
R4- - - - - - - - - - - - - -R5_
_
_
_
_ _ _ _
R6
R7
_
_ _
Rs
-
-
-
-
-
-
_
_
_
_
_
_
_ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
•
•
-
_
_
•
-
_
_
_
_
_
_
_
_
_
_
_
•
_
lig- - - - - - - - - - - - RIO - - - - - - - RII
- ----R,,
R'3
R'4
--- - ---- R15 R'6
-- - RI7
_
_
-
_
_
____
R1 8
-
-
_
_
-
_
_
_
_
_
_
_
-
_
-
_
-
-
-
-
_
_
_
_
_
_
-
-
_
-
-
_
_
_
_
_
_
_
_
_
_
_
_
_
_
-
-
-
_
_
_
_
_
-
_
-�--------_
_
_
-
R10- - - - - - - - - - - R,oR,,
R'L
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
R'3
R'4- - - - - - - - - - C;
_
_
_
0
0
2
2
1
15
2
0
0
18
18
28
0
0
10
65
45
15
18
0
65
5
0
•
0
-
_
_
_
_
_
_
_
_
_
_
_
_
_
--- -----�
C5
C6
�- - - - - - - - - - - - C�8
---- --Cg
_ _ _
_
-
-
-
_
_
_
_ _
-
_
_
-
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
-
_
-
_
NM
2
0
0
0
NM
•
OORPS
Point-to-point d-c voltage measurements
Voltmeter
range
Trans·
mitter
-
--
--
0
0
5
7
0
90
0
0
0
0
0
0
0
0
0
0
0
15
0
0
60
5
0
1
NM
2
2
0
1. 3
NM
•
•
Component
-
-
Receiver
---
--
---010_ - - - - Cn - - - - - - - - 012
C13- - - - - - - - - - 014 - - - - - - - - 015- - - - - - - - C1 6 - - - - - - - - - - C17 - - - - - - - - - - C18 - - - -- - - - - C'9- - - - - - - - - - - 0'0
0,,
3
3
3
3
3
300
3
3
3
30
30
30
3
3
30
300
300
30
30
3
300
30
3
3
-- - - - 3
3
3
3
-- ----
-
-
-
_
_
_
_
_
_
_
-
_
_
-
_
_
_
-
-
-
-
-
-
-
-
-
-
e"
-
_
_
_
_ _
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
C'3
0'4- - - - - - - - - - --- --- --0'5
C'6_ - - - - - - - - - - ---- - --C'7
R25- - - - - - - - - - - R26- - - - - - - - - - - R27- - - - - - - - - - - C1
(;2- - - - - - - - - - - - 03
_
_
_
_
_
_
_
_
_
_
_
_
-
_
-
-
-
_
_
_
-
_
-
_
_
_
_
_
_
_
_
_
_
�8- - - - - - - - - - - �9- - - - - - - - - - - _
_
_
_
_
_
_
_
_
_
_
_
_
C30_ - - - - - - - - - C31- - - - - - - - - 2
Lt; (14) - - - - - - - -
-
-
NM
50
0
0
0
0
0
27
80
0
0
0
NM
1 2
NM
2
•
•
•
1
NM
O. 1
0
0
0
5
24
85
40
80
95
0
Transmltter
-
-
NM
90
75
0
0
0
0
0
0
0
0
0
NM
0
NM
2
1
NM
0
0
•
•
0
0
80
80
80
85
90
0
10
Voltmeter
range
-
--
--
- --- 300
300
3
3
3
3
30
300
3
3
3
- -- 3
-----3
3
- -3
3
3
3
300
300
3.00
300
300
300
30
-
-
-
•
-
--
All readings taken across component UBing the volt-ohtDtDeter of test set 1-56-(*). Readings shown were
taken using a 1000 ohmjvolt meter. No doc voltmeter readings should be taken where the letters NM
appear in any column becaUBe of likely damage to the circuit. This is particularly true of doc voltages
reading across grid coupling capacitors.
.
I C.. voltage will depend on bias connection.,
I L. refers to SCR-536-A, and SC R-536-B . This component is marked L, in SC R-536-0 .
•
•
•
68
•
•
RADIO SETS SCR 5 3 6-A, -B, AND --c
78
•
CHART IV.
Average signal inputs for a fixed output (receiver)
NOTES
•
1.
2.
3.
4.
All values taken with chassis out of test case OS-81-(*).
A battery BA-37 voltage�1.45 volts.
B battery BA-38 voltage�100 volts.
Receiver earphone, or equivalent, connected across receiver output.
Signal generator connected
to-
Signal genera·
tor frequency
setting 1
Signal input to Signal input to
produce 20 volt produce 15 volt
output on
output on
V. T. V.'
S. O. V.'
Dummy
•
-
-
Antcnna_
.
_
_
_
_
_
_
_
_
_
Through test stand
FT-252-(*).
Through test stand
6115 kc
FT-252-(*) .
. 1 p.L
455 kc
. 1 p.L
5205 kc
. 1 p.L
455 kc
. 1 p.L
455 kc
. 1 p.L
455 kc
1000 cps _ . 1 p.L
�
5205 kc
_
Antenna (image frequency) .
Antenna
R-f grid
Converter grid
Converter grid
I-f grid
Microphone amplifier
grid.
A-f output amplifier
grid.
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
2.5 p'v
_
1850 p'v
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
1000 cps _ . 1 p.L
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _
_
20;000 p'v
27 p.v
190 p.v
180 p'v
2400 p'V
. 25 v
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
,
_
_
_
_
_
_
_
_
_ _ _ _ _
1.1 v___ _ _
3 p.v.
2250 p.v.
24,000 p.v.
28 p.v.
200 p.v.
180 p.v.
2400 p.v.
.275 v .
1.3 v.
Signal generator modulation 400 cps 30%.
' Values listed in this column are for 20·voit output reading on a general radio type 726-A vacuum tube
voltmeter:
, Values listed in this colnmn are for 15·voit output reading on 50·volt a·e range of selective analyzer of test
set I-li6-(*) .
1
CHART V.
Average receiver performance characteristics
NGTE.-All values taken with chassis in test case 0 S-81-(*)
Minimum
Average
Test
,
Using V. T. V.
_
_
_
_
_
_ _
_ _ _
_
_
_ _ _
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
50 volts
_
_
_
_
_
_
3 p.v ' 3
800
10,000
_
1.4 volts
235 ma
,
_ _
_ _ _
_ _ _ _
1 03 volts
1 1 ma
_ _ _
_
_
_
_
4 p.v 2 4
800
10,000
_
_
_
_
_
_
_
_
_
_
_
_
22 volts 2
1.4 volts
235 ma
_
p.v 1 3
200
4,000
6
_
_
_
-
---
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
,
40 volts
- 250 ma (max)
-
_ _
_ _ _ _ _
_
_
_
_ _ _ _
103 volts
1 1 ma
----
-
_
_ _ _
Using 1-56-(*)
Using V. T. V.
--
-
-
-
- -
Sensitivity
Image ratio
Direct transmission
ratio.
Maximum audio output.
A battery BA-37:
Voltage
Current
B battery BA-38:
Voltage
Current
Using 1-56-(*)
-
-
-
- - -
- - -
14 ma (max)
-
-
-
-
-
-
-
-
-
-
_
-
_
-
-
_
_
7 p'V 2 4.
200.
4,000.
18 volts.2
250 ma (max).
14 ma (max).
,
1
Readings made on a General Radio type 726-A vacuum tube voltmeter.
, Readings made on selective analyzer of test set 1-56-(*) .
Signal generator modulation 400 cps 30%.
• 20-volt output meter reading.
Signal generator modulation 400 cps 30%.
4 15·volt output meter reading.
SECTION V
SUPPLEMENTARY DATA
Paragraph
Table of replaceable parts Radio receiver and transmitter BC-6ll- ( * ) _____
Names and addresses of manufacturers__________________________________
69
79
80
79. Table of replaceable parts .
Signal Corps stock No.
Ref. No.
Radio receiver and tranl:im1�tter
BC-6J J-*.
Description
Name of part
•
CI
cs
C4
_
_
_
_
_
_ _ _ _ _ _
_
_
_
_
_
_ _ _ _ _
_
_
_ _ _ _
_
_
_
_
_
_
_
_
_ _ _ _ _
_
_
3D9007-2
_ _ _ _ _
C6_
_
_
_
_ _
_
_
_
_
_
_ _ _ _
_
_
_
3D9025-36
_ _ _ _
Cg
_
_
_
_
_
_
_
_
_
_
CIO
Cu
CI2
Cu
cl•
_ _ _ _
__
_ _
_
_
_
_ _ _
_ _ _ _
_ _ _
_
3D9015-18
_
_
_
I
_
_
_
_ _ _ _
_
_
_
_
..
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _
_ _ _
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
do
do
_
_ _ _ _ _
do
do
_
_
_ _ _ _
_
_
_
_
3D9007V-L
3 DA40-6
_
_
3 DA1 00-1 20
_
_
_
3DA10--102
3D9025-35
_
_
_
Cr- - - - - 3D9018V-4
Cs
Capacitor
-
c2
c&
3 D A6 4 L
_
_ _ _
do
do
do
do
do
do
do
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _ _ _
_
_
_
_
_
_
_ _
__
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_ _ _ _ _ _ _ _
_
_ _ _ _ _ _
_ _ _ _ _
_
_
_
_
_
_ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _ _ _ _ _
_
_
_
_
_
_
do . do
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _ _
_ _ _
_
_
_
_
_
_
_
_ _
Galvin
drwg. No .
Mfr.
Function
•
Fixed, paper, .006 p.f, ± 20 %, 100
v, part No. SB2S544.
Fixed, paper, .0005 p.f, ± 20 %,
100 v , part No. 8A28549. Part
of NI cup.
Fixed, paper, .006 p.f, ± 2 0 %,
100 v , part No. SB2S528. Part
of N2 cup . .
Fixed, ceramic, 7 p.p.f, ± 5 %,
Type D, part No . 21 A28815.
Fixed, paper, .006 p.f, ± 20 %,
100 v , part No. 8B2852S. Part
of NI cup.
Fixed, mica, 25 p.p.f, nominal, part
No. 20A27459.
Variable, mica, 18-160 p.p.f, part
No. 20A27459.
Fixed, paper, .01 p.f, ± 20%, 100
v , p art No. 8A28550.
Fixed, ceramic, 25 p.p.f, ± 1 0 %,
Type D, part No. 21 A28S1 6.
Fixed, ceramic, 15 p.p.f, ± 1 0 %,
Type D, part No. 21A28817.
Fixed, paper, . 1 p.f, ± 20 %, 100 v,
part No. 8A29S46.
Variable, air, 7-140 p.p.f, part No.
1 9A25H90.
Fixed, paper, .04 p'r, ± 20 %, 100 v ,
part No. SB2Sfi22.
Fixed, paper, .01 p.f, ± 20%, 100
v , part No. 8B28530.
Part of Na
cup.
Voltage blocking, VI
_
_
Screen grid bypass, VI
Plate bypass, VI
_
_
_
_
_
Grid ncutrali7.ing, Vi
_
_
_
_
_
_
_
_
_ _ _ _
_
_
_
_ _ _ _ _
_
Grid bias bypass, Vi
Oscillator feed-back
_
_
_
_
_
(*)
(*)
--
(*)
_
_
(*)
- -
--
Coupling, V2 to VI , trans-
1
Coupling, VI to V2 , recelVmg.
Screen grid bypass, V2
1
rlll ttmg.
•
•
•
•
_
Tuning, 12
Avc filter
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Grid bias bypass, Va
_
_
_
-
- -
(*)
_
-
( *)
Filament bypass,VI
_
- - -
---
(*)
_
-
(*)
Receiver antenna tuning _
_
-
-
-
- - -
- - - - - -
- -
-- -
-
- - - - - -
-
- --
-
-
- -
- -
- - -
-
- -
- -
- - -
--
- -
- - - -
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
- - - - - -
..
-
-
-
- -
-
-
- -
-
- -
- - -
-
- -
...
.
,
.... -
-
-
- - -
•
•
•
I
CI6
3D9058V
_ _ _ _ _
CI!
C17
3D9058V
_ _ _ _ _
_ _ _ _
CI8
__ _ _ _
CI9
_ _ _
C20
C21
C22
C23
C24
_
_
_
_
_
_
_ _ _
C21
__ _ _
_
_ _ _ _
_
C30
C31
__ _ _ _
__ _
_
_
-
-
-
_ _ _ _ _
_ _ _ _ _
_
_
_
_ _ _ _ _
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_ _
_ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _
3DA1 50-2
_
_
_
_
3DA75-L
_ _ _ _
_
_
_ _
_
_ _ _
3DAl-85
__
do
do
_
_ _ _ _ _ _
_
_
_
_ _ _ _ _
_ _ __ _ _ _ _ _
_ _ _ _ __
_
_ _ _ _ _
3DA20 43
_
do
•
_
3 DA6-42
_
- - -
3 D9007- L
3DA6-41
___ _
C28
_ _ _ _
-
_
_ _
_
-
_ _ _ _
___
_
-
_
C27
_
- - - - -
_ _ _ _
_ _ _ _
_
-
_
C26
_
_ _
__ _ _
C25
_ _ _ _
_
_
_ _ _ _ _
_
_
_ _ _ _
_
_
3D9070-6
_ _ _ _ _
_
_
_
3D9028V
_ _
_
_
_ _ _
- -
_
_ _ _ _ _
_
_
_
_
_
_
_
_
_ _
_
_ _
_
_
_
_
_
_
_ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_ _ _
_
_
_
_
_
_
_
_
do
_
_
_
_
do
do
do
do
do
do
do
do
do
do
_ _
_ _ _ _
_
-
_
_
_
_ _
_
_ _
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_ _
_ _
do_
do
_
_
_
_ _ _ _
_ _
_ _ _
_
_
_ _
__
_
_
_
_
_
_
_
_
_
__
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_ _ _ _ _
_
_
_
_
_ _
__
_
_
_
_
_
_
_
_ _ _
_ _ _ _
.
-
-
-
-
-
_
_
_ _ _
_
_
_
_
_
Tuning, L4 primary
_
_
_
·Denotes part made for or by Galvin Mfg. Oorp .• Ohicago, III.
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
Tuning, L4 secondary
Grid bias bypass, V3-
_
Plate bypass V3
g� �7°N;
_ _ _ _ _ _ _ _ _ _ _
do_
Variabl�� mica, 58 /J-/J-f, nominal,
'< o. 20A27340.
part 1
do
Fixed, paper, .01 /J-f, ± 20%, 100
Part of
v , part No. 8B28530.
Na cup.
2
Fi
r
t
���tPtf� 8�1G�3tf.
cup.
Variable, mica, 28 /J-/J-f, nominal,
part No . 20A 286 09 .
Fixed, mica, 70-100 /J-/J-f, nominal,
part No. 20A28609.
do
Fixed, paper, .006 /J-f, ± 20%. 100
v, part No. 8A28544.
Fixed, paper, .006 /J-f, ± 20 %, 100
v, part No. 8B28528.
Fixed, paper, .02 /J-f, ± 20%, 100
v, part No. 8A30263.
Fixed, paper, .00025 /J-f, ± 20%,
100 v, part No. 8B28531. Part
of N4 cup.
Fixed, paper, .01 /J-f, ± 20%, 100
Part of
v , part No. 8B28531.
N4 cup.
Fixed, paper, .006 /J-f, ± 20 %, 100
v, part No. 8B28531.
Part of
N4 cup.
Fixed, paper, .001 /J-f, � 2 0 %, 100
v, part No. 8A28545. .
Fixed, paper, .075 /J-r, ± 20 %, 100
v, part No. 8A28546.
Fixed, paper, . 1 3 I-'f, ± 20 %, 100
v, part No. 8A29848.
Fixed, paper, .01 /J-f, ± 20%, 100
v, part No. 8B28530.
Part of
Na cup.
_
_
_
_
_
_
_
_ _ _
_
_
Tuning, Ls secondary
Detector bypass
_
_
_ '_
_
do
A-f amplifier coupling
_
_
_
_
_ _ _ _
_
_
_
_
_
_
_
_
Grid bias bypass, V4
_
_
_
_
_ _
_
_
_ _
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Screen grid bypass, V4 Coupling, V. to VB
Plate bypass, VB
_ _ _ _ _
Plate bypass, V2
_
_
_
_
_ _ _
_
_
_ _ _ _ _ _ _ _
_ _ _ _
_
_
_
(*)
(*)
( *)
( *)
_
_
_
_ _
--
-
-
-
-
(*)
-
-
-
-
(*)
(*)
-
-
-
-
-
- - -
-
-
( *)
-
(*)
-
-
- -
--
-
-
-
- -
-
- - - - - - -
-
-
- -
- - - - - - -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- - - - - - - -
-
- - - - -
- - - - -
(*)
-
-
- - - - -
- -
-
-
- - - - - - -
- -
--
( *)
- - -
- -
(*)
(*)
-
-
-
-
(*)
-
- - -
( *)
(*)
_ _ _ _ _ _ _
Screen grid bypass, VI
Plate bypass, Vs
_
_ _
Voltage blocking a-f out­
put.
Plate bypass, V4
_
_
(*)
,- -
-
- -
-
-
-
-
-
-
-
- -
- - - - - - -
-
- - - - - -
o
•
•
Ref. No.
Signal Oorps stock No.
------
L1 _ _ _ _ _
Name of part
1-------------- 1-------
Lt - - _ _ _
L1 _ _ _ _ _
-------
1 -------
BO-61 1-(*)
Description
-----
-----
Continued
·---
3C299-358 _ _ _ _ _ _ Coil C-358 _ _ _ _ _ _ _ Antenna, range 3500-3675 kc (for
S CR-536-A) .
3C299-359 _ _ _ _ _ _ Coil C-359 _ _ _ _ _ _ _ Antenna, range 3675-3825 kc (for
S CR-536-A).
3C299-360 _ _ _ _ _ _ Coil C-360 _ _ _ _ _ _
Antenna, range 3S25-4025 kc (for
SCR-536-A) .
3C299-36L _ _ _ _ _ Coil C-36L _ _ _ _ _ _ Antenna, range 4025-4225 kc (for
S CR-536-A) .
3C299-362._ _ _ _ _ _ Coil C-362 _ _ _ _ _ _ _ Antenna, range 4225-4425 kc (for
S CR-536-A) .
3C299-363 _ _ _ _ _ _ Coil C-363 _ _ _ _ _ _ _ Antenna, range 4425-4625 kc (for
SCR-536-A) .
3C299-364_ _ _ _ _ _ Coil C-364 _ _ _ _ _ _ _ Antenna, range 4625-4825 kc (for
SCR-536-A) .
3C299-365 _ _ _ _ _ _ Coil C-365 _ _ _ _ _ _ Antenna, range 4825-5075 kc (for
SCR-536-A) .
3C299-366 _ _ _ _ _ _ Coil C-366 _ _ _ _ _ _ Antenna, range 5075-5300 kc (for
SCR-536-A) .
3C299-367 _ _ _ _ _ _ Coil C-367 _ _ _ _ _ _ _ Antenna, range 5300-5500 kc (for
S CR-536-A) .
3C299-368 _ _ _ _ _ _ Coil C-368_ . _ _ _ _ Antenna, range 5500-5775 kc (for
SCR-536-A) .
3C299-369 _ _ _ _ _ _ Coil C-369 _ _ _ _ _ _ _ Antenna, range 5775-flOOO kc (for
SCR-536-A) .
3C299-36L - - _ - _ Coil C-36L _ _ _ _ _ _ Antenna, frequency 4035 kc, part
No. 24K34970 (for SCR-536-B
and C) .
3C299-363 _ _ _ _ _ _ Coil C-363 _ _ _ _ _ _ _ Antenna, frequency 4495 kc, part
No. 24K34971 (for SCR-536-13
and C) .
3C299-365 _ _ _ _ _ _ Coil C-365 _ _ _ _ _ _ _ Antenna, frequency 4930 kc, part
No. 24K34972 (for SCR-536-B
and C).
1
_
L1 _ _ _ _ _
Lt - - - - Lt - - - - L1_ _ _ _ _
;;g
Radio receiver and transmitter
L1 _ _ _ _ _
L1 - - - - L1 _ _ _ _ _
Lt- _ _ _ _
L1 _ _ _ _ _
-----
------
-----
Galvin
drwg. No.
1--------
Antenna loading____ _ _ _ _ _
(*)
_ _ _ _ _ do__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
24B29012
- _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 'r
(*)
24B290 12
- - - - _ do _ _ _ _ - _ _ _ - - _ _ _ _ _ _ _ I
(*)
24B29012
I
_ _ _ _ _ do___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
( *)
_
L1 - - - - -
-
Mfr.
1
_
L1 - - - - -
---
Function
24B29012
24B29012
_ _ _ _ _ do__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
( *)
24B29012
_ _ _ _ _ do_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
( *)
24B29012
_ _ _ _ _ do_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
24B29012
_ _ _ _ _ do_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
24B290 1 2
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I
(*)
24B29012
(*)
241329012
(*)
24B29012
_ _ _ _ _ do___ _ _ _ _ _ _ __ _ _ _ _ _ _ _
( *)
24B29012
_ _ _ _ _ do_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
24B2901 2
_ _ _ _ _ do__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
24B29012
I
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1
I
_ _ _ _ _ do_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
•
L1 _ _ _ _ _
•
I
"
•
•
•
,
•
L1
L1
•
_ _
_
_
_
_
_
_
_
_
_
_
L1 - - L2_
L2
�
_
_
_
_
_
_
_
_
_
_ _ _ _ _
L2- L2
;!
�
L2
L2
L,
Lt
Lt
Lt
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
3 C299-366 _
3C299-367
3C299-368
_
_
3C299-370_
3C299-37 L
3C299-372_
3C299-373
3C299-374
3 C299-375
3C299-373
3C299-374
3 C299-374
3C299-357
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
3C299-37L
3C299-372
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Coil C-366
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Coil C-367
Coil C-368
Coil C-370
Coil C-37L
Coil C-372
Coil C-373
Coil C-374
Coil C-375
Coil C-371
Coil C-372
Coil C-373
Coil C-374
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_
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_
do
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_
Coil C-357
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_ _
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_
Antenna, frequency 5205 kc, part
No. 24K34973 (for S CR-536-B
and C) .
Antenna, frequency 5397.5 kc.
part No. 24K34974 (for S CR536-B and C) .
Antenna, frequency 5500 kc, part
No. 24K34975 (for S CR-536-B
and C) .
R-f tank, range 3500-3825 kc (for
SCR-536-A) .
R-f tank, range 3825-4225 kc (for
SCR-536-A) .
R-f tank, range 4225-4625 kc (for
S CR-538-A) .
R-f tank, range 4625-5075 kc (for
S CR-536-A) .
R-f tank, range 5075-5500 kc (for
SCR-536-A) .
R-f tank, range 5500-6000 kc (for
SCR-536-A) .
R-f tank, frequency 4035 kc, part
No. 24B35222 (for SCR-536-B
and C) .
R-f tank, frequency 4495 kc, part
No. 24K35223 (for SCR-536-B
and C) .
R-f tank, frequency 4930 kc,
part No. 24K35224 (for S CR536-B and C) .
R-f tank, frequency 5205 kc, part
No. 24K35225 (for S CR-536-B
and C) .
R-f tank, frequency 5397.5 kc,
part No. 24K35226 (for SCR536-B and C) .
R-f tank, frequency 5500 kc, part
No. 24K35227 (for SCR-536-B
and C) .
"Denotes part made for or by Galvin Mfg. Corp., Chicago, Ill.
_
_
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do
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do
do
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_ _ _ _
_
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_
R-f amplifier loading
do
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do
do
do
do
do
do
do
do
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- -
-
-
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•
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_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_
do
do
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_
(*)
24B29012
( *)
24B29012
( *)
24B29012
( *)
24A29061
(*)
24A29062
(*)
24A29063
( *)
24A29064
( *)
24A29061i
(*)
24A29052
(*)
(*)
24B35222
( *)
24B35222
( *)
24B35222
( *)
24B35222
( *)
24B35222
•
--_
.
------
---- -
-----------
•-­
---•
-
-
•
Radio reciever and transmitter BC-61 1 - ( *)
Rei. No.
Signal Corps stock No.
L3 _ _ - - -
3C362- 17 _ _ _ _ _ _ _
1Tl (L4)
2C535lA/ A4 __ _ _ _
IT,
(Ls)
2C535 l A/ A5 _ _ _ _ _
lL4 (La)
3C362-l6 _ _ _ _ _ _ _
•
M l _ __ _ _
2Z3543.50 _ _ _ _ _ _ _
M2 _ _ _ _ _
2Z3543.50 _ _ _ _ _ _ _
M3 _ _ _ _ _
3Z83l8 _ _ _ _ _ _ _ _ _
M4 _ __ _ _
2C535 1 A/A3 _ _ _ _ _
M4_ _ _ _ _
2C535lA/A3 _ _ _ _ _
Ms_ _ _ _ _ 2C535l A/A2_ __ _ _
�-- - - - 2C535lA/A2_ _ _ _ _
Mo- _ _ _ _ 3 Z 9 853 _ _ _ _ _ _ _ _ _
Name of part
Description
Coil _ _ _ _ _ _ _ _ _ _ _ _ _ R-f choke ; . 5 mh, part No.
24A28595.
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ I-f input transformer and shield,
part No. IB28670.
I-f output transformer and shield.
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _
part No. IB28668.
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ Audio output reactor; 590-850
ohms d-c resistance, part No .
25A28551.
CrystaL _ _ _ _ _ _ _ _ _ Receiver crystal (Specify fre­
quency) , part N o . 48K28681.
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ Transmitter crystal (Specify fre­
quency).
Switch _ _ _ _ _ _ _ _ _ _ _ Change-over switch, eight-pole,
double throw. part No. 40B25825.
Microphone _ _ _ _ _ _ Microphone and leads assembly,
dynamic, part No. lX3l 098.
� _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ Microphone and leads assembly,
crystal (Early issue of SCR536--A) .
Earphone _ _ ._ _ _ _ _ _ Earphone and leads assembly,
dynamic, part No. lX3l094.
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ Earphone and leads assembly,
crystal (Early issue of SCR53 6-- A) .
Switch _ _ _ _ _ _ _ _ _ _ _ Toggle, DPST, part No. 40A25820_
3A38 _ _ _ _ _ _ _ _ _ _ _ Battery _ _ _ _ _ _ _ _ _ _ 1 03.5 volts, Type BA-38, B, part
No. 48B25848.
M8 _ � _ _ _ 3A3L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ 1 >� volt, Type BA-37-A, part
No. 48B27576.
M9 _ _ _ _ _ 2Z1 1 1 00 . L _ _ _ _ _ _ Tube shield __ _ _ _ _ _ Metal shield, part No. 26A27204 _ _ _
2Z1 1 l00.L _ _ _ _ _ _ _ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ �_
1'11 1 0_ _
Mll _ _ _ _ 2 Z l 1 1 00. L _ _ _ _ _ _ _ . _ _ _ do __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
-
,
-
Galvin
drwg. No.
Mfr.
Function
_
M7- ___ _
-
Continued
Oscillator, V, _ _ _ _ _ _ _ _ _ _ _
(*)
Coupling V ,-V 3- _ _ _ _ _ _ _ _
( *)
Coupling. V3-V4- _ _ _ _ _ _ _ _
(* )
Output platp load _ _ _ _ _ _
(*)
••
_
Receiver stability con­
trol.
frequency
Transmitter
control.
Send-receive _ _ _ _ _ _ _ _ _ _ _ _
- ----
-
- -
-
.
-
-
--
--
-
-
-
-
-
-
- --
48B27212
( *)
-
- --- -
-
-----
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
---
Recei ving _ _ _ _ _ _ _ _ _ _ _ _ _ _
(*)
( *)
.
-
- -
(*)
( *)
_ _ _ _ _ do _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
-
-
48B27212
'1'rallsmlsslOn _ _ _ __ _ _ _ _ _ _ _
-
--
-
(*)
.
.
-
-
-
-
- -
- -
-
-
-
-
-
-
-
-
-
-
-
-
- -
-
--
- ---
Filament and plate power
( *)
supply.
Plate power supply _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
-
-
-
-
-
-
-
Filament power supply __ _ ._ _ _ _ _ _ _ _ _ _ _ _ _ _ _
VT-174 shield _ _ _ _ _ _ _ _ _ _
VT-l71 shield _ _ _ _ _ _ _ _ _ _
VT-l 73 shield _ _ _ _ _ _ _ _ _ _
(*)
(*)
( *)
--
.
.
-
-
-
-
-
-
-
-
-
-
-
-
-
- - - -
.
-
-
-
MI2
2 N1
2N2
•
_
_
�
�
R4
R5
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_
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_
_ _ _
R8
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_
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_
2C5351AjC5
2C5351A/C3
_
_
-
-
- -
-
-
-
-
-
-
-
_
_
_
- -
3Z6801-2L
_
_
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_
_
_
_ _ _
_
_ _
_ __ _
_ _
_
_
3 Z6330-4
3Z6747 6
_
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_
_
_
_
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_
_
_
2C5351A/C2
__
_
_
2C5351A/C4
_ _ _ _
R6- - R7
2A292-2
_
_ _ _ _
_
2N4_
_
_ _ _ _
_
2Na
R1
_
_
_ _
_
_ _ _
-
_
-
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-
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_
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_
_ _
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-
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_
3Z6470-9
3Z6801-23
_
_
_
_
_
_
_ _ _ _
_ _ _ _
-
_
_
_
_
_
_
Capacitor-resistor
cup (VT-174).
Capacitor-resistor
cup (VT-l71) .
Capacitor-resistor
cup (VT-l73) .
Capacitor-resistor
cup (VT-172) .
Resistor
_
_
_
Antenna
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _
do
do
do
do
do
do
do
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_ _
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_
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_
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_
_
_
_
_
_
_
_
_
_
_ _
4-section c ollapsible antenna
assembly part No. 1 C28682.
Contains O2, C6, C23, Ra and R"
part No. 8B28528.
Contains Ca, Cia, and R I, part No.
8B28529.
Contains CH, C17, C18 , Cal, R I2 and
RIG, part No. 8B28530.
Contains C25, C2t,1,. C27, Rg, R H, �2
and R21, p art 1'1 0. 8B2853 1 .
Fixed, carbon, 1 megohm, ± 1 0 %,
% watt, not insulated, part No.
8B28529.
Part of N2 cup.
Fixed, carbon, 1 megohm, ± 10%,
% watt, insulated , type MB %
INS. part No. 6B6337.
Fixed, carbon, 56,000 ohms, ±
1 0 %, % watt, not insulated,
part No. 8B28528.
Part of N I cup.
Fixed, carbon, 33,000 ohms, ±
1 0 %, % watt, not insulated,
part No. 8B28528.
Part of NI cup.
Fixed, carbon, 3,300 ohms, ±
10 %, Ya watt, insulated type
MB Ya INS. part No. 6B6379.
Fixed, carbon; 470,000 ohms, ±
1 0 %, Ya watt, insulated, typ e
Mif Ya INS, part No. 6B633 8 .
Fixed, carbon, 4,700 ohms, ±
1 0 % % watt, insulated, type
MB Ya INS, part No. 6B6351 .
Fixed, carbon, 1 megohm, ± 1 0 %
% -watt, not insulated, type
997-A, part No. 6B5564
,
_
_
_
_
_
_
_
_
_
_
_
_
Radiator for transmitter;
antenna for receiver.
Capacitor-resistor
container.
do
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
�
_
_
Capacitor-resistor
container.
Cap acitor-resistor Con­
tainer.
Converter grid, V2
_ _ _ _ _ _
Grid bias, V3
_ _ _
_
_
_
_
_
_
_
Oscillator grid bias, V2Oscillator grid bias, V2
Rensitivity controL
Grid bias, VI
_
_
_
_
_
Reference numbers in parentheses are for SCR-536-A and SCR-536-B.
These reference numbers do not appear on parts in illustrations nor in references to parts throughout this manual.
'Denotes part made for or by Galvin Mfg. Corp., C hicago, Ill.
_
.
_
_
_
_
_
_
_
_
_
_ _
_
_
_ _
_
_
_
.
_
(*)
-
(*)
4
_
_
_
-
(*)
_
_
-
(*)
(*)
_
Sensitivity controL
.
I
I
_ _
(*)
( *)
-
-
- -
-
-
4
4
4
3
-
-
-
- - - - -
- - -
-
-
- -
- - -
-
_
-
--
- -
- - -
- - -
-
-
- - -
•
- -
- - - -
-
_ _ _ _ _ _ _ _
- -
(*)
-
-
- -
-
- - -
- - - - - -
_
_
_ _
_ _
_
_
_
_
_
_
_
_
_
_
_ _ _
--
_
_ _
_
_
_ _
_
_
_ _
_ _ _ _ _
_
•
Radio reciever and transmitter
BO-61 1-(*)
,
Ref. No.
Signal Corps stock No.
Continued
Description
Name of part
Galvin
drwg. No.
Mfr.
Function
,
Ro-
_
_
_
3Z804A7- Z _ _ _
_
R 10- - - - 3Z6647-5
R ll R12
_
_
_
_
-
3Z6633-3
_
_
_
R16
_
_
_
_
_
. .. .. .
.. _ _ _
_
..
_
_
_
_ .. .. _
..
..
..
..
..
..
_
.. ..
RI8
_
_
_
_
_
_ _ _ _
_
_
_
R16- - - - - 3Z6733-2
R11
_
_
_
_
_
_
_ _ _ _
3Z6722-4
R13 - - - -
R14
_ _ _ _
_
3Z6627-7
3Z6722-9
_
_
.. ..
.. ..
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
-
-
_
_
_
_ _ _ _ _ _
_ _ _
_
_
_
_
_
_
_
_
_ _ _ _ _ _ _ _ _ _
_
..
..
_
_
_
..
..
..
..
..
_
_
..
_
-
.
_
..
_
_
_
-
..
_
_ _
_
_
..
_ _
_
_ _ _ _ _ _ _ _ _ _
_
..
_
_
_ _ _ _ _
_
_
Fixed, carbon, 4.7 megohm, ±
1 0 %, Ys watt, not insulated,
part No. 8B28531 .
do
Fixed, carbon, 47,000 ohms, ±
1 0 %, % watt, insulated, type
MB ,� INS, part No. 6B6323.
Fixed, carbon, 33,000 ohms, ±
do
1 0 %, � watt, insulated, type
MB � IN S, part No. 6B6448.
Fixed, carbon, 68,000 ohms, ±
do
1 0 %, Yr. watt, not insulated,
part No. 8B28530. Part of Ns
cup.
do
Fixed, carbon, 220,000 ohms, ±
10 %, Yr. watt, not insulated.
type 997-A, part No. 6B5571.
Fixed, carbon, 1 m!')gohm, ± 1 0 %
.. do .. .. .. .. .. .. .. .. .. ..
% watt, not insulated, part No.
8B2853 1 . Part of N4 cup.
do .. .. .. .. .. .. .. .. .. .. .. Fixed carbon, 6,800 ohms, ±
10 % , % watt, not insulated,
part No. 8B28530.
Part of N4
cup.
do
Fixed, carbon, 330,000 ohms, ±
1 0 %, H watt, insulated, type
MB 73 INS, p art No. 6B6366.
do
Fixed, carbon, 22,000 ohms, ±
1 0 %, Ys watt, insulated) type
MB Ys INS, part No. 6Bo370.
do
Fixed, carbon, 220,000 ohms, ±
1 0 %, �� watt, insulated, type
MB � INS, part No. 6B6349 .
Resistor
_
..
..
_
_
_ _ _ _ _ _ _ _ _ _
_
_
_ _ _ _ _ _ _ _ _ _
_
_ _ _ _ _
_ _ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_ _ _ _ _
Avc filter
_ _ _ _
'_
_
_
_
_
Plate dropping, V 1
_
_ _
_
_
_
_
(*)
_
_
_
_
_
_
_
_
_
_
_
-
4
- ---- -
-
_
_
_
_
_ _ _ _
_
_ _
_
_
_
•
PIa te dropping, V5 -
_
4
Screen grid dropping V3 - Detector filter, V4Detector load, V4
_
_ _ _
Plate dropping, V3
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
Screen grid dropping, Vs
_
Screen grid dropping, V2
Screen grid dropping, V1
( *)
3
( *)
_
4
•
-
_
_
- - -
4
_
_
4
_ _ _
- - --
- - -
(*)
_
_ _
_
-
_
-
""1,
_
--
-
_
_
- -
_ _
- - - -
-
-
- -
_ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
•
•
•
•
R1o
_ _ __
R20
_
_ _
3Z681 0-6
_ _
R,1-- - - -
R22
3Z6768-3
_
_ _ _ _
_
_
_
_
_
_
_
_
_
_
_ _ _
__ _
_
_
_
_
_
_ _ _ _ _ _
_
_ _ _ _ __
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
do
do
do
do
_ _ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_ _
_ _ _ _ _ _ _
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
•
�3----- 3Z6803A3-L
R24
R 2S
_
_
_
_
_ _ _
_
_ _
�6R27
_ _ _
_
_
_
_
_ _
3Zfl390
_
_
3Z6568-9
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
3Z6804A7-L
3Z6747-6
_
_
3Z8318/LL
3Z8318/L2
_
2S536A/ Al
_
_
2C5351A/A6
_
_
_
_ _ _ _
_
_
_
_
_
_
do
do
do
do
do
_
_
_ _
_
_ _ _ _ _ _ _ _ _
_ _ _
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_ _ _ _ _
_
_
_
_
_
_
_ _ _ _
_
_
_
_
_
_
_
Arm, switch lever
(long) .
Arm, switch lever
(short) .
Assembly, antenna
cap and chain.
Assembly, bracket
and grommet.
Fixed, carbon, 680,000 ohms, ±
10%, � watt, insulated, type
M B )� INS, part No. 6B6388.
Fixed, carbon, 10 megohm, ±
10%, Ya watt, insulated, type
EB INS, part No. 6B5572.
Fixed, carbon, 3.3 me � ohm, ±
1 0 %, Ya watt, not �nsulated,
Part of N4
part No. 8B28531 .
cup.
Fixed, carbon, 1 megohm, ± 10 %,
7� watt, not insulated, part No.
8B2853 1 . Part of N, cup.
Fixed, carbon, 3.3 megohm, ±
l O % Ya watt, insulated., type
M B Va INS, part No. flBti364.
Fixed, carbon, 3,900 ohms, ±
1 0% , � watt, insulated, type
MB Ya INS, part No. 6B5573.
Fixed, carbon, 6,800 ohms, ±
Ya watt, insulated, type
LO%
,
M E Ya INS, part No. 6B6350.
Fixed, carbon, 4.7 megohm, ±
1 0 % , . Ya watt, insulated, type
EB INS, part No. 6B6391 .
Fixed, carbon, 470,000 ohms, ±
1 0% , Ya watt, insulated, type
M B Ya INS, part No. 6B6338.
Metal, 2" long, % 6" wide, part 1\0.
45B27215.
Metal, 1 Ya" long, %6" wide, part
No. 45A25998.
Aluminum cap, 1 % 6 / 1 diameter,
3%" high, beaded chain 4/1
long, part No. lX28690.
Aluminum, %" x Yz " , %6" hole
with rubber grommet, part No.
1 X30139.
·Denotes part made for or by Gaiyin Mfg. Corp., Chicago, Ill .
•
•
Plate dropping, V 6Grid Bias, V4-
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
4
2
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
•
�creen grid dropping, V4
Plate load, V4
Grid bias, Vs
_
_
_
_
_
_
_
_
_
_
_
_
_
•
_
_ _ _ _
_
_
_
_
_
_
_
(*)
- - -
( *)
4
i:Jcreen grid decoupling,
Vs .
Rensitivity controL
Avc filter
Damping
_
_ _ _
_ _
_
_
_
_
_
_
_ _
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Cover for antenna
2
4
_
(*)
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Holds VT-172 and VT­
. 174 in socket.
4
_
_
P a r t 0 f push-to-talk
switch lever assembly.
do �
_
4
-
-
_
_
-- --
---
_
-
--
-
-
_ _ _ _ _ _
_
_
_
_
.. _
_
_
_
_ _
_ _
_
_
_
_
_
_
_ _
_
_
_ _ _ _ _
-
-
-
(*)
--
(*)
- --
(*)
-
-
- -
-
_ _ _
_
_
- - - - -
- - -
-
_
_ _
- --
--
-
--
- - -
-
-
-
,
•
Radio receiver and transmitter BC-61 1-(*)
Ref. NO. 1
---
100
_
1 0L
102
_
_
_
_
_
_
_
_
_
_
Signal Corps stock No.
_
_
_
_
1 05 _
_
_
_
_
_
_
2C536A/A3/3_ _
----
--
Assembly, bottom
cover.
_ _
A s s e m b ly , a n d
plate.
_ _
2C536A/A3/4 _ _ _ _ j A s s e m b I y , filler
and clips.
I
2853tlA/ A3/L
104
Name of part
----. ----
2853 6 A/A3
Description
_
_
_
Assembly, spade
bolt and cover.
28536A/A2 _ _ _ _ _ _ Assembly, strap
28536A/A4
_
_
_
_
_
_
_
_
Assembly, top
cover.
_
•
106 _ _ _ _ 2A292-2/3 _ _ _ _ _ _ _ Ball end, antenna_
10i _ _ _ 2C5351 A/ J2/2
_
_
108 _ _ _ _ 3Z8318/B1
109
110
_
_
llL
_
_
_
_
_
_
_ _ _
_
_
2Z11 100.1/L
_
_
_
_
_
_
_
Bezel, data plate
_
1
_
_ Bracket, switch
stop.
Bracket, tl'be re­
tainer.
_
_
·_-
_·
_·
__
--
Continued
---·
---
Metal, 3%6" X 3%", complete with
battery contactor plate and
springs, part No. 1 X28692.
Bakelite, 3X6" x 1J.j;" complete
with terminals and contacts
part No. 1 X2866i.
Fiber, 1 W ' wide, 1 1 W ' long, clip
riveted on each end, part No.
1 X29056.
W' spade bolt with %" diameter,
knurled edge nut, part No.
1X29661.
Olive drab strap, 114" wide, 30"
long, part No. 1X2869 1 .
Aluminum, 3X" x 3%" complete
with battery spacer and springs,
antenna insulator, moisture seal
and strap hanger, part No .
1 X28688.
Marblette ball, W' diameter, olive
drab finish, part No. 6i A2i209.
Aluminum frame 2�{6" x W', part
No. 13A285i1.
Metal %" x %", with a . 144"
diameter hole, part No. iA31332.
Aluminum, %" x W' with %6"
hole, part No. i A,25988.
,
2 C535U.jA2/L . _ Cap, phone, and Molded bakelite, 2%" diameter,
p art No. 6iB25B32.
microphone.
2Z2626.3 __
__
Clamp, capacitoL _ Brass, semicircular, %" radius,
part No. 42A28454.
_ _ _
_
1
---
Galvin
drwg. No.
Mfr.
Function
---_·_---
--
--1--- 1 ·---·--
Bottom cover of housing
and batterv contactor.
-
( *)
..
_
- - - - - -
•
End plate of chassis_ _ _
_
( *)
_
Used to fill space between
battery BA-38 and
housing.
Holds bottom cover shut Carrying strap
_
_
_
_
_
_
_
_
_
(*)
Part of push-to-talk
switch, lever top.
Holds tube shield for
VT-174, VT-1i1, and
VT-1i3.
Cap for mouthpiece and
earpIece.
Holds capacitor C30- - - _ _
•
_
-
-
(*)
_
_
_
_
- - - - - -
- - - - - - -
(*)
Top cover of housing _ _ _ _ _
-
- - - - - - -
(*)
_
On tip of antenna to aid
in pulling antenna out.
Frame for data plate _ _ _ _ _
-
_
_
_
---
_
_
( *)
- ---
(*)
( *)
-
-
- - - - -
_ _ _ _ _ _
---
-
-
- - - - - -
( *)
(* )
- -
-
-
- - - - - -
- - -
- - - - - -
---
-- -
- -
- - - - -
- - - - -
•
..
I
•
•
1 12
_
_
_
_
2Z2645 _ _ _ _ _ _ _ _ _ Clamp, crystaL _
_
113 _ _ _ _ 2C5351 A/J2/L _ _
1 14_ _
1 15
_
_
_
_
_
_
1 1 6_ _ _ _
•
2Z3401 . L
_
3Z8318/C2
_
_
_
3Z8318/QL
_
_
_
_
_
Cover, data plate _ _
Cover r-f choke
_
_
Cover, switch _ _
_ _ _ _
_
_
_
_
_
Cover, swit c h
mechanism.
1 1 7 _ _ _ _ 3Z8318/FL _ _ _ _ _ F r a m e , c o v e r
clamping.
118
_
_
_
_
_ _ _ _ _
3Z8318/ ML
_ _
_
_
Fulcrum, hinge _ _
_
_
_
1 19 _ _ _ _ 2A292-2/4 _ _ _ __ _ _ Guide, antenna _ _ _ _
120 _ _ _ _ 2C5351A/J2.L _ _ _ Housing
_ _
_ _
_
_
_
_
_
_
•
121122
_
123_
124-
_ _
_
_
_
_
_
_
_
_
_
_
3Z8318/L3 _ _ _ _ _ _ Link, sliding hinge_
No number to be Nameplate
assigned.
2C5351A/N1 _ _ Nut, chamfered
_
_
2S5351 A/ A3/2
_
125_ _ _ _ 3Z8318/PL _ _
_
1 26_
_ _ _
3Z8318/P2
_
_
_
_
_
_
_
_
_ _ _ _ _ _
_
_
_
Pin, groove
_
_
_
_
_
Pin, hinge
_
_
_
_
_ do
_
_
_
_
_
_ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _
127 _ _ _ _ 2C5351 A/J2/L _ _ Plate, data
I
_
_
_
_ _ _ _ _
i
l
L"
wide
Phosphor bronze %"
shaped, part No. 42A28543.
Clear vinylite, 1 %" x 1%6", part
No. 6 1 A28456.
Bakelite, I " long, W ' outside diam­
eter, part N o . 67 A30885.
Acetate celluloid, 1Ys" x 1 0%,',
part No. 6 1 B28450.
Molded rubber). 1 %" x 4", part
No. 37C272 11:s.
Aluminum frame 1 %" x 4" with
6 holes . 156" diameter for­
mounting part No. 42B25987 .
Alcoa metai, one . 156" hole for
mounting .067" hole for hinge
pin, part No. 45A272 19 .
Molded 7%6" long .282" diam­
eter groove, part No. 67B27214.
Housing, less all parts, l lW ' x 3 "
X 3%2", p art No. 62D27227 .
Metal, 1 W ' x % 6" , slotte d, hole at
end for hinge pin, part No.
45B2722 1 .
Vinylite, 1%" x 3W', black back­
ground, p art No. 13K34950.
Brass, nickel plated, %6-23 x % 6",
part No. 2A30408.
%" long, .093" diameter, metal,
part No. 47 A28460.
W' long, 0. 125" diameter, 4-36
thread on one end, part No.
47A25997.
0. 672" long x 0.062/1 diameter,
part No. 47 A25999.
Vinylite plate, 1%/1 x 1 %6" part
No. 13A28455.
Holds crystals
_ _ _ _ _ _
_
_
_
_
(*)
--
( *)
-
_
Transparent cover for
data plate.
Cover for r-f choke La- _ .
_
( *)
_
Cover for change-over
switch assembly .
Cover for push-to-talk
switch assembly.
Frame for push-to-talk
switch cover.
(*)
( *)
Housing for unit
_
_
___
_
_ _
_ _
( *)
M odel, order and serial
number data plate.
Tank capacitor mounting_
( *)
Hinge pin for mounting
spade bolt and nut.
Part of
push-to-talk
switch; holds long and
short levers together.
Part of push-to-talk
switch assembly.
Frequency, channel and
battery date informa­
tion plate.
(.*)
-
- -
- - -
•
- -
•
-
-
- -
- -
- - - -
- - -
- - - -
..
-
- - ...
- - - -
-
-
- - - -
-
-
-
-
-
-
-
•- - ­
- ---- -
-
- - - - - - - - -
- - - - - - -
-- -
- - - - - -
-- - - .... -
-
- -
13B28503
(*)
-
- -
- - -
P art o f p u s h - t o - t a l k
switch assembly.
These reference numbers do not appear on parts in illustrations nor in reference to parts throughout this manual.
"Denotes part made for or by Galvin Mfg. Oorp., Ohic�go. Ill.
-
(*)
_
-
-
--
Guide for antenna _
--
-
( *)
-
---
- --- -
--
(*)
_ _
-
-
- - - -
( *)
P art o f p u sh - t o - t a l k
switch assembly.
_
-
-
-
-
-
- - - -
- - -
-
-
--
-
- -
- - -
•
,
..
Radio receiver and transmitter BC-61 1-(*)
Ref. No. I
Signal Corps stock No.
128 _ _ _ _ 2C5351AjSL
_
_
_
_
Plug, jumper _
___
_
'i
Molded bakelite over wire jumper,
%6" x W', part No. 28A28535.
_ _ _ _
2S536AjA2j3
_
_
_
_
_
_
Seal, rubber ring_ Sponge rubber ring, Ys", 3Ya2" X
3?{6", part No. 37 A25986.
2-crystal receptacle, part No.
133 _ _ _ _ 2Z8761-10 _ _ _ _ _ _ Socket, crystaL
9A2598 1.
2C5351AjS L _ Spring, coil re- Phosphor bronze, %" x W ' with
134_
tainer.
. 127" diameter hole for mount­
ing, part No. 41A25995.
Phosphor bronze, Ya" x %" spring,
135 _ _ _ _ 3Z8318jS2_ _ _ _ _ _ _ Spring, cushion _
part No. 41 A28452.
136 _ _ _ _ 3Z8318jSL ___ _ _ _ S p r i n g , s wit ch Stainless steel spring, part No.
41A27203,
lever.
132_ _ _ _
2S536A/A3j5_ _
_
_
_
_
_
_ _
_
_
_
_
_ _ _
•
1 37 _ _ _ _ 2Z8669-6 _ _ _ _ _ _ _ Tube socket
138 _ _ _ _ 2Z8669-6
_
_
_
_
_ _ _
_ _ _ _ _
•
do
_ _ _
_
_ _ _
_
_
_
_
_
_ _ _ _ _
7 prong miniature
6
_
_
_
prong miniature,
9K6796 .
_
_
_
_
_
_ _ _ _ _ _ _
part
No.
Galvin
drwg. No.
Mfr,
Function
Rod, housing and 2" long, %2" diameter, threaded
at one end, part No. 46K27220.
strap su pport
(long) .
130_ _ _ 2S536Aj A2/2_ _ _ Rod; housing and 1%" long, %2" diameter, threaded
at one end, part No. 46A25849.
strap support
(short) .
13L _ _ _ 2S536A/A4/L _ _ _ Seal, moisture _ _ _ _ _ Rubber, %6" diameter, W' hole,
part No . 37 A27308.
129
Continued
Description
Name of part
,
Jumper for plate meter
--terminals when meter
is not used.
Bottom cover hinge rod - - - - - - and strap support.
- -
-
-
-
Top cover hinge rod and - - - strap hanger support.
- - -
-
-
-
- - - -
- - ----
- -
-
- - - - - -
Weatherproofing at an­ - - - - - - tenna t hrough top
cover.
Top and bottom cover - - -rubber seal.
�ocket for two crystals _ ( *) - - - -
-
_
-
-
( *)
P art o f pu sh-to-talk
switch assembly.
Lever return spring, part
of push-to-talk switch
assembly .
VT-171, VT-172, VT173, tube ·socket.
VT-174 tube socket
( *)
_
_
_
- - - - -
-
_
Tank coil retainer spring _
_
-
( *)
_
- - - - -
- -
-
-
-
- -
- -
--- - -
-
-
- - - - -
- -
-
-
-
-
-- -
( *)
9A6794
( *)
9A6794
1
These reference numbers do not appear on parts in illustrations nor in references to parts throughout this manual.
· Denotes part made for or by Galvin Mfg. Corp., Chicago, Ill.
•
RADIO
SETS
seR
5 3 6-A, -B, AND --c
80
80. Names and addresses of manufacturers.
.
Mfg.
No.
Street address
Name
1
Centralab
2
Allen Bradley Co
Carborundum Corp
3
_ _ _ _ _ _ _ _ _ _ _ _
_
_
_
_
_
_
_
_
City
State
900 E. Keefe
Ave.
Milwaukee
-Globar DiviSlOn.
Elk County
Milwaukee
Niagara Falls
- - - - - - - - - -
- -
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Wisconsin.
Wisconsin.
New York.
•
4
Stackpole Carbon Co
_
_
_ _ _
St. Mary's
_ _ _
_
Pennsylvania.
•
-- --
,
•
•
•
•
81
,
•
INDEX
Adjustments:
Alinement _
Presetting
Paragraphs
•
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _
.
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
.
.
_
_
_
_
_
_
_
_ _
_
_
Antenna coil :
Replacement
.
T unlng
BattRries:
Installation_
Life
_
_ _
Testing
Type used
_
Bias, adjustmenk
Change of frequency
Change-over switch:
Adjustment
____
Functioning
Coils:
Frequency range of (chart IL _
Replacement
Components :
1) cscnp
. t·lon
Weights and dimensions
Controls :
Location
Operation
_
Power swit.ch
�
Push -to-tnlk switch
Crystal activity test
CrYRtal earphonc
_
Crystal microphone
_ _
CrYRtals, replacement oL
Current readings:
. .
ReceIVlDg
. .
T ransmlSslon
Description of components
Difference between SCR-536-A, B, and C
Dimemdons of components
DiRtance range
Earphone :
Crystal
Inductor
Employment
Frequency coverage
Frequency presett.i n g
Functioning of parts
. _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
__
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
40, 54
33, 36,
50, 51
- -- - - - 55, 70
58, 72
29, -l4
33, 50
11
4
63
4
78
54, 69
6
3
40
3
·64
28, 43
78
37
64
70
55, 70
44
29, 44
9
2
5
3
8
13, 16
13
15
57
9
9
55, 70
5
7, 9
7
8
33
5
5
29, 44
58
59
9
1
2
5
33
36
5
2
3
4
9
9
10
6
54, 69
24-38
5
5
6
4
28, 43
11
_
_
•
_ _
62, 74
58, 59, 72, 73
_ _
_
_
_
Pages
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
•
_
_
_
_
_
_
_
_
_ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_ _ _ _ _
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
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_
_
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_
_
_
_
_
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_
_
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I f<
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INDEX
Paragraphs
I-f amplifier:
Alinement _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 62, 74
Functioning____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
28
Input power_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
4
Locating trouble ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23, 47, 48, 78
Manufacturers' addresses__ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
80
Measurements, voltage (chart III).
Microphone,35
Amplifier, circuit_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Crystal___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
9
Inductor_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
9
Modes of transmission and reception_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
7
Modulation:
Percentage _____ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ 59, 73
Circu� _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
36
�etting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
18
Operation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
13
Oscillator, circuit _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
33
Parts :
79
List of replaceable_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Rcplacement _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55, 70, 77
Poor reception and transmission _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23, 47
Power amplifier :
Circuit_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
34
Tuning_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 58, 73
Preparation for use_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
12
72
Presetting receiver with IE-I5-A___ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
PreRet,ting receiver with IE-17-(*) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
58
Presetting transmitter with IE-I5-A_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
73
Presetting transmitter with IE-17-(*) ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
59
Procedure in locating trouble ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23, 47, 48, 78
22
Rain, operation in_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Receiver :
Alinement_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 62, 74
Characteristics (chart V) .
24
Functioning_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Presetting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55-58, 69-72
Sensitivity ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
78
Receiving_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
14
77
Removal of eyelet_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Repairs _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 39, 77, 78
Replacement ofAntenna coiL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55, 70
11
Batteries _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Crystarn _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ 55, 70
45
Earphone___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
77
I-f transformer ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
44
Microphone ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. _ _ _ _
77
Power switch _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
R-f tank coiL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55, 70
77
Resistor-capacitor cups ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_
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•
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83
Pages
40, 54
14
3
10, 23, 64
81
17
5
5
5
36, 51
17
9
7
17
70
29, 44, 60
10, 23
17
33, 51
7
50
33
51
36
10, 23, 64
10
40, 54
11
29, 43
64
8
60
22, 60, 64
29, 44
6
29, 44
23
60
23
60
29, 44
60
•
INDEX
•
Paragraphs
Setting up test equipment IE-I5-A_ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
71
Setting up test equipment IE-17-(*) __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
56
Starting set _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ - - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _
13
Switch, change-over :
AdjustmenL__ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ _
78
_ ___ ___ _ _ _ ____ ____ ____
Function _ _ _ _ _ _ _ _ _ _ _ _ _ _
37
Operation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
15
Test case C8-81-(*) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 50, 51, 64, 65
Test equipment IE-15-A_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
64
Test equipment IE-15-A, presetting with _ _ _ _ _ � _ _ _ _ _ _ _ _ _ _ _ _
69
Test equipment IE-17-(*) _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
50
Test equipment IE-17-(*) , presetting with _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
54
Test harness_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _
67
Test set 1-56-(*) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ �_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
68
Test stand FT-252-(*) ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 50, 52, 64, 66
Test unit 1-135- (*) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 50, 53, 56, 62, 63
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Testing batteries_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
63
3
Total weighL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Transmitter :
Characteristics (chart IIL- _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _
78
Circuit _ _ _ _ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 31, 32
Presetting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55, 56, 57, 59, 70, 71, 73
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32
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42
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28
43
43
24, 42
24,
25, 32, 40
. 40
3
•
64
15
29,
32, 33, 36,
44, 45, 51
Tral)Bmitting_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
15
8
Trouble, location _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23, 47, 48, 78 10, 23, 64
Tubes, vacuum:
60
77
Base connections (fig. 24) ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Replacement_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
41
23
Vacuum tube base connections (fig. 24) ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
60
77
41
Vacuum tubes, replacement oL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
23
Voltage measurements (fig. 25 and chart III) _ _ _ _ _ _ _ _ _ _ _ _ _
78
64
47
Weak signals, cause oL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
23
Weights:
2
COlnponents _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ __ _
3
TotaL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _
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[A. 0. 062.11 (1-29-43).)
By ORDER OF THE SECRETARY OF WAR :
OFFICIAL :
J. A. ULIO,
G. C. MARSHALL,
Ohief of Staff·
Major General,
The Adjutant General.
DISTRmUTION :
B 5 (2) ; R 7 (3 ) ; Bn 7 (5) ; I Bn 5, 44 (5) ; I e 5 ( 10), 4, 7, 44,
(5) and 1 1 (4).
(For explanation of symbols see FM 21-6 .)
84
U. s. GOVER N M E N "J
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8
24, 42
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P H I N T I N G O F F I C E : ....!
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