Chapter 2. TROUBLESHOOTING - TM-11-6625-564-450028

C2, TM 11-6625-564-45

CHAPTER 2

TROUBLESHOOTING

Section I. GENERAL TROUBLESHOOTING TECHNIQUES

Warning: During servicing of the maintenance kit, be careful when working with the +225-

and +175-volt dc plate supply circuits. The +175-volt dc plate supply voltage is not used in

the MK-731A/ARC-51X except at power converter 1A3 output.

(1) Visual inspection. The purpose of

2-1.

Introduction

visual inspection is to locate faults

Troubleshooting at general support and de-

without testing or measuring circuits.

pot maintenance levels includes all the techni-

All meter readings, lamp indications,

ques outlined for organizational maintenance

or other visual signs, should be ob-

and any special or additional techniques re-

served, a n d a n a t t e m p t m a d e t o

quired to isolate a defective part. The general

localize the fault to a particular

support maintenance and depot procedures

circuit.

are not complete in themselves but supplement

(2) Operational tests. Operational tests

the procedures described in TM 11-6625-564-

frequently indicate the general lo-

12. The systematic troubleshooting procedure,

calization of trouble. In many cases,

which begins with the operational checks that

the tests will help in determining

can be performed at an organizational level,

the exact nature of the fault.

must be completed by means of localizing and

(3) V o l t a g e a n d r e s i s t a n c e m e a s u r e -

isolating techniques. Paragraphs 2-2 through

ments. T h i s e q u i p m e n t i s p a r t i a l l y

2-9 provide intraunit (within the unit) trou-

transistorized. Observe all precau-

bleshooting procedures and describe the lo-

tions given to prevent transistor

calizing and isolating techniques that must be

damage. Make voltage and resistance

performed at general support level.

measurements in this equipment only

as specified. When measuring volt-

2-2. Organization of Troubleshooting

ages, use tape or sleeving to insu-

Procedures

late the test probe except for the

a. General. The first step in servicing a

extreme tip. A momentary short cir-

defective maintenance kit is to localize the

cuit can ruin a transistor. Use the re-

fault. Localization means tracing the fault to

sistor and capacitor color code charts

a defective stage or circuit responsible for the

(fig.

4-4

and

4-5)

find

the

abnormal condition. Some faults, such as

value of the parts. Use the voltage

burned-out resistors, arcing, and

shorted

and resistance diagrams (fig. 2-13

transformers, can often be located by sight,

through 2-16, and 4-13) to compare

smell, and hearing. The majority of faults,

normal values with readings taken.

however, must be localized by voltage and re-

(4) Troubleshooting chart. The trouble

sistance checks.

symptoms listed in the charts (para

2-5 and 2-8) will aid in localizing

b. Localization. The tests listed below will

trouble to a part or circuit.

aid in isolating the trouble. First, localize the

trouble to a single stage or circuit, and then

(5) I n t e r m i t t e n t t r o u b l e s . I n a l l t h e s e

isolate the trouble within that circuit by volt-

tests, the possibility of intermittent

age, resistance, and continuity measurements.

troubles should not be overlooked.