TM 11-6625-2946-14/TM 08168A-14/1
Table 5-1. Fault Isolation Chart
Symptom
Probable cause
Corrective action
a. Reset circuit breaker.
No meter indication when FUNCTION
a. Open RESET circuit breaker.
b. Faulty power source (battery or 24 vdc
b. Check output of battery or power
switch is placed in BAT position.
power supply).
supply being used. If no output, replace
power source.
c. Check continuity of power cable. If
c. Defective input power cable from ex-
open, replace or repair power cable.
ternal power supply.
d. Defective meter.
ohms scale. Observe polarity, momentarily
connect meter terminals. Meter is good if it
swings upscale. If not replace.
e. Check continuity of metering circuit,
e. Defective component or wiring in
replacing defective components or repairing
power input metering circuit.
wiring if required.
a. Check and replace.
No meter indication for all test modes
a. Defective meter.
b. Check and repair or replace.
b. Defective FUNCTION switch or meter
wiring,
a, Voltage regulator output level mis-
a. Adjust voltage regulator output poten-
Test set functions normally with battery
tiometer 1A1A1r24 for a reading of 7 divi-
but not with external 24 vdc power
adjusted
sion on test set meter.
source.
b. Replace meter function board.
b. Defective voltage regulator.
c. Check and replace or repair.
c. Defective POWER switch, circuit breaker,
or wiring.
a. Perform alignment procedure steps 1
a. Resistor 1A1A1R22 misadjusted.
Incorrect battery (BAT) test indications
through g of table 5-2.
b. Replace 1A1A1R22.
b. Defective 1A1A1R22`.
a. Faulty synthesizer module.
No, or incorrect, RCV mode test indications.
Remove VCO, press READ SENS button, and
with oscilloscope, measure waveform at TP 1.
(See Fig. 5-2. ) If improper waveform,
remove and replace synthesizer. If correct
reinstall vco and proceed to step b, below.
b. Using AN/USM-451, depress SENS
b. Faulty vco module
switch, measure 12-14.5 vdc at S7 lug 6. If
correct, proceed to step c. Remove syn-
thesizer and apply 2-11 vdc to TP3 while
monitoring TP4, with AN/USM-218C. The
output should vary in frequency and dc
voltage at TP3, If improper output occurs,
If correct, proceed to step c, below.
c. Remove synthesizer and apply 2-11 vdc to
c. Faulty vco module
TP3 while monitoring TP2, with AN/USM-
218C. While varying dc voltage at TP3, press
READ SENS button and monitor TP2 out-
put. If incorrect output occurs, (see fig. 5-2,
step c) remove and replace VCO. If correct,
proceed to step d, below.
d. Replace synthesizer module. Select code of
3001 on test set. Press READ SENS button
and measure the frequency at TP4 and
record. Measure the frequency at TP5. Fre-
quency at TP5 should be 12 MHz above that
at TP4, (see fig. 5-2, step d).
NOTE
Output of a double balanced mixer
(TP5) contains sum, difference and
fundamental. Frequency mixing at the
counter may be required to achieve a
reading of 54.05 MHz.
If TP4 is not 42.05 MHz, check panel
switch wiring. If frequency is correct at
TP4 and incorrect at TP5, remove and
replace rf generator hoard.
5-3
