Table 3-4. Test Set Troubleshooting

TM 11-5895--1097-40

stick before making resistance measurements.

sistor. (For example, if the bias is shorted out, excessive

current would ruin the transistor between emitter and the

CAUTION

base.) Use resistor and capacitor color codes shown in

This equipment is transistorized:

figure FO-1 to find values of components, or refer to the

observe all cautions to prevent

component locations drawing.

transistor damage. Do not make

c. Intermittent Troubles. In all tests, the possibility

continuity checks other than those

of intermittent troubles should not be overlooked. If

spcecified in the tables. Damage to

present, this type of trouble may develop by tapping or

the transistors and microelectronic

jarring the assembly. Check the wiring and connections

devices, which can impair the

to the assemblies and subassemblies.

performance of the equipment, may

d. Test Points. The printed circuit card is equipped

result if improper battery voltages

with test points to facilitate connections of test

and polarities are applied.

instruments. The test points should be used whenever

b. Voltage Measurements. This equipment is

possible to avoid needless disassembly of the

transistorized. Observe all cautions to prevent transistor

equipment. These test points are shown on the

damage. Make voltage measurements in this equipment

schematic diagram (fig. FO-2).

only as specified. When measuring voltages, use tape or

sleeving to insulate the entire test prod, except for the

extreme tip. A momentary short circuit can ruin the tran

Table 3-4. Test Set Troubleshooting

Malfunction

Probable cause

Corrective action

1. POWER indicator fails to light when POWER

Defective POWER indicator as-

Connect test set to known good 120 Vac source. Set

switch is set to ON.

sembly.

test select switch to LAMP TEST and observe that

GO/NO GO indicator light. If correct, repair

wiring/replace defective POWER indicator.

Defective input power cord.

b. Disconnect test set from 120 Vac source. Using Mul-

timeter AN/USM-223, check for continuity of ac input

circuit (fig. FO-3). If incorrect, repair wiring/- replace

defective component.

Defective fuse assembly.

c. Same as b. above.

Defective POWER switch Sl.

d. Same as b. above.

Defective transformer TI.

e. Using Multimeter AN/USM-223, measure dc input of

T1.

(1) If correct, go to table 3-5, malfunction I.

(2) If incorrect, replace TI.

2. One or both test indicators (GO/NO GO) fail to Defective LAMP TEST circuit (indi-

Disconnect test set from 120 Vac source.

light with test select switch set to LAMP TEST.-

cator assembly or test select

Using Multimeter AN/USM-223, check for contin-

Power indicator is lit.

switch S2).

uity of LAMP TEST circuit (fig. 3-2 and FO-3). Re-

pair defective wiring/replace defective component.

3. No test indicator (GO/NO GO) lights to show

Defective XTAL TEST indicators

a. Set test select switch to LAMP TEST and observe

status of XTAL MODULE under test.

assembly or test select switch S2.

that both indicators light. If incorrect, disconnect test

set from 120 Vac source. Using Multimeter AN/USM-

223, check for continuity of indicators and S2 (fig. 3-

2 and FO-3). Repair defective wiring- /replace

defective component.

Defective xtal select switch 52.

b. Disconnect test set from 120 Vac source. Using

Multimeter AN/USM-223, check for continuity of xtal

select circuit (fig. 3-2 and FO-3). (1) If correct,

continue troubleshooting. If incorrect, repair

wiring/replace defective S3.

4. NO GO indicator always lights when XMIT MO- Defective XMIT XTAL MODULES,

Insert a known good XMIT XTAL into test socket. Test xtal

and observe indicators.

DULES are tested.

test socket (J7) or main circuit

a. If GO indicator lights, XMIT XTAL MODULES

card A1.

tested before were defective.

b. If NO GO indicator lights, disconnect test set from

120 Vac source. Using Multimeter AN/- USM-223,

check for continuity between test soc-

3-12