be used in localizing the trouble to a functional
circuit in the suspected unit.
1. This equipment contains transis-
(1) O p e r a t i o n a l t e s t p r o c e d u r e .
tor circuits in both the test set and
simulator. Be sure that the test equip-
ment used is equipped with polarized
11-6625-601-12), in some cases, localize a trou-
ground plugs. If substitute test equip-
b l e to a specific circuit in the test set or
ment is used that does not have an iso-
lation transformer in its power supply
(2) Radio Set AN/ARC-54 test procedure. A
circuit, connect one in the input power
complete AN/ARC-54 Radio Set known to be in
circuit. (A suitable transformer is iden-
good operating condition is part of the test
tified by Federal stock number
equipment r e q u i r e d a t t h e d i r e c t s u p p o r t
m a i n t e n a n c e level. T o l o c a l i z e a t r o u b l e
2. Make test equipment connections
detected while performing the AN/ARC-54 test
with care so that shorts will not be
procedures, the repairman may duplicate the
caused by exposed test equipment con-
test wherein the fault occurred and, by use of
nectors. Tape or sleeves (spaghetti) test
schematic diagrams, v o l t a g e and resistance
prods or clips as necessary to leave as
charts, will localize a trouble to a functional cir-
little exposed as needed to make con-
tact to the circuit under test.
2-4. Voltage and Resistance Measurements
If none of the AN/ARC-54 test proce-
Normal voltage and resistance measurements
dures can be performed, there is a pos-
taken at the base, collector, and emitter of the
sibility that no power is being applied
audio amplifiers in the test set and simulator
are presented in the tables in paragraph 2-5.
( R T - 3 4 8 / A R C - 5 4 , C-3835/ARC-54, or
C U - 9 4 2 / A R C - 5 4 or CU-943/ARC-54)
under test. Refer to the power routing
When measuring voltages, use tape or
diagram (fig. FO-6) and make voltage
s l e e v i n g (spaghetti) to insulate the
checks at the appropriate pins on the
entire test prod, except for the extreme
tip. A momentary short circuit can ruin
d. Isolation. Once a trouble has been localized
a. Voltage Measurements. The voltage read-
to a functional circuit in the test set or
ings in the tables (para. 2-5) were obtained
simulator, f u r t h e r tests and measurements
under the conditions specified in (1) and (2)
must be made to isolate the trouble to a compo-
b e l o w . Always make voltage measurements
nent part. The most useful tool that a technician
under these same conditions, or the readings
has for troubleshooting any circuit is his com-
obtained may be inaccurate. Make all voltage
plete understanding of the circuit operation.
measurements with a vtvm that has an input
When a trouble has been localized to a func-
tional circuit, refer to chapter 1 and review the
Meter ME-30A/U, or equivalent). Connect the
principles of operation of the circuit. Chapter 1
dc common clip or the ac ground clip of the vtvm
contains functional and simplified schematic
to chassis ground of the unit under test.
diagrams of each test circuit. These schematic
diagrams omit the components and switches
a m p l i f i e r card A1 (part of Test Set, Radio
that are not directly involved with the circuit.
These diagrams make the circuit more easily
(a) Connect a 1 0 - o h m (¼-watt, ±10-
understood than does the overall schematic
p e r c e n t ) resistor between pins 2 and 4 of
diagram. Parts locations are indicated in figures
HEADSET jack J9.
2-1 through 29. The voltage and resistance
(b) Connect a 150-ohm (¼-watt, ±10-
tables (para 25) are valuable aids in isolating a
p e r c e n t ) resistor between pins 5 and 6 of
defective component. When making resistance
measurements, refer to figures FO-7, FO-8, and
RCVR/XMTR jack J11.
figures 2-14 through 222 as needed. Color code
(c) Apply +27.5 volts dc ±1 to POWER
diagram for coils, resistors, and capacitors (fig.
(d) Set the POWER circuit breaker to ON.
FO1), provides pertinent resistance, voltage
(e) S e t TEST FUNCTION SELECTOR
rating, and tolerance information.