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  TM 55-4920-244-14
Table 4-1. Troubleshooting
Malfunction
Probable cause
Corrective action.
1. Galvanometers (GALVO-1)
a. Defective switch SW-6.
a. Replace switch.
does not respond to tem-
b. Defective potentiometer.
b. Replace potentiometer
perature selector knob
adjustments with switch
c. Incorrect reference voltage to
c. See figure 4-25 and test
SW-6 in RANGE posi-
potentiometer.
following components of
tion (all applicable modes
cable and printed circuit
of operation).
board assembly. Part No.
BH1766; T2, CR8, CR9,
CR10, CR11, CR12, CR13,
C9, R14, R16, and R18.
Replace defective compon-
ents (para. 4-17).
2. Tester inoperative in all
a. Defective power inlet con-
a. R e p l a c e power inlet connector
modes of operation.
nector.
3. POWER ON light inop-
a. Defective transformer T2.
erative.
b. Defective cable and printed
b. Replace cable and printed
circuit board assembly,
circuit board assembly
part no. BH1766.
c. Defective wiring or con-
c. Repair or replace wiring
nections.
4. Switch SW-1 in T/C posi-
a. Defective transformer T2.
a. Replace transformer (para.
tion; no light beam in
galvanometers (GALVO-
b. Redate cable and printed
b. Defective cable and printed
1).
circuit board assembly
circuit board assembly,
part no. BH1766.
c. Repair or replace wiring
c. Defective wiring or connec-
tions.
d. Replace switch .
d. Defective switch SW-1.
e. Repair or replace power lead.
e. Defective power lead cable to
c a b l e (para.
cable and printed circuit
and (9)).
board assembly, part no.
BH1766.
a. Defective galvanometers.
5. Galvanometers (GALVO-1)
cannot be set to zero with
mechanical zero knob.
a. Replace potentiometer
6. Galvanometers (GALVO-1)
a. Defective potentiometer.
deflects erratically when
reading in RANGE po-
sition.
7. Heater probes will not heat;
a. Replace fuse and excite
a. Temporary power line over-
20 amp fuse blown.
voltage.
heater probes with TEMP
REGULATOR knob.
Continue operation if
fuse does not blow.
b. Heater cable connector de-
4-47).
fective or short in wiring.
c. Replace voltage regulator
c. Defective voltage regulator.
4-8
Change 1
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