General Instructions

TM 11-6625-667-45/NAVAIR 16-30APM123-2/TO 33A1-3-367-22

SECTION Ill. GENERAL TROUBLESHOOTING

TECHNIQUES USING AN/TPM-25A

3-12. General Instructions

(2) S e c t i o n a l i z a t i o n t e s t s . T h e s e c -

tionalization tests are operational type tests and

Troubleshooting at general support and depot

frequently indicate the general location o

maintenance categories encludes all techniques

trouble. In some instances, the tests will help in

outlined for organizational maintenance and any

determining the exact nature of the fault. Tests

special or additional techniques required to

are given in paragraph 3-15.

isolate a defective part. Section II of this chapter

c. Localization. Localization

procedures

provides intra unit within the unit) localizing and

should be performed after the trouble has been

isolating techniques to be used at the general

sectionalized (b above. Localization procedures

support maintenance category.

applicable to this equipment are described in

3-13. Organizational of Troubleshooting

paragraphs 3-5 and 3-6, and should be used in

Procedures

localizing the trouble to a stage in the suspects

module or subassembly,

a . General. The first step in servicing a

d. Isolation. Procedures for isolating troubles

defective test set is to sectionalize the fault.

are given in paragraph 3-7.

Sectionalization means tracing the fault to a

e. Techniques. When performing the sec-

particular module or subassembly (for example;

tionalization para 3-4), localization, and isolation

encoder module A4 or transmitter A16). The

procedures, one or more of the technique

second step is to localize the fault. Localization

described below may be applied. Apply these

means tracing the fault to a defective stage or

techniques only as indicated, and observe al

circuit responsible for the abnormal condition.

cautions.

The third step is isolation. Isolation means

(1) Voltage measurements. This equipmen

locating the defective part or parts.

is transistorized. When measuring voltages, use

b. Sectionalization. The daily maintenance

tape or sleeving (spaghetti) to insulate the entire

c h e c k s and services (TM 11-6625-667-12)

t e s t probe, except for the extreme tip. A

provides a satisfactory means of determining

momentary short circuit can ruin a transistor

w h e t h e r the transponder test set may be

Use the same or equivalent electronic multimeter

operating. Because of the nature of the self test

specified on the voltage and resistance diagrams.

operation, the exact cause of an internal fault

cannot be determined with this chart. The test set

NOTE

provides only an accept or reject indication;

Modules A4, A5, and A7 through A12

therefore, one or more internal circuits can cause

contain digital circuits. Do not attempt

an improper indication. To simplify the location

to analyze their operation with voltage

readings. Analyze their operation with

of a fault, consider that there are four main

the waveforms shown in figures 8-17

functional sections in Test Set, Transponder

through 8-23.

TS-1809/APM-23V. These functional sections

include the power supply, transmitter, receiver,

(2) Resistance

measurements. M a k e

resistance measurements in this equipment only

and decoder. The first step in tracing trouble is to

determine the module or subassembly of the

a s directed on the voltage and resistance

section that contains the fault.

diagrams. For transistorized circuits, use only

(1) Visual inspection. The purpose of visual

the ohmmeter ranges specified on figures 3-8

inspection is to locate faults that maybe evident

through 3-18; otherwise, indications will be

without testing or measuring. This includes

inaccurate.

broken wires, bent or corroded connector pins,

CAUTION

damage circuit boards, or loose RF jacks and

Before using an ohmmeter to test

plugs. All possible visible inspections should be

transistors or transistor circuits, check

performed before attempting operational tests.

Change 5

3-42