S e c t i o n Ill. TROUBLESHOOTING

TM 11-6625 -537-14-1

6-4. Special Tools and Equipment for General

Support

No special tools and equipment are required for

general support maintenance.

S e c t i o n Ill. TROUBLESHOOTING

(1) Troubleshooting chart. The symptoms

6-5. Organization

of Troubleshooting Pro-

listed in the troubleshooting chart (table 6-1) will

cedures

aid in isolating the fault to a specific component.

a . General. The first step in servicing a

(2) Intermittent troubles. The possibility of

defective electronic voltmeter is to sectionalize

intermittent troubles should not be overlooked

t h e fault by tracing the fault to the circuit

w h e n trying to isolate faults. I n t e r m i t t e n t

r e s p o n s i b l e for the abnormal operation. The

troubles can often be made to appear by gently

second step is to localize the fault by tracing the

tapping or jarring the equipment. Wiring and

fault to a defective part responsible for the ab-

internal connections are typical sources of in-

normal condition. Some faults, such as burned

termittent troubles.

out resistors and arcing or shorted transformers,

can often be located by sight, smell, or hearing.

6-6. Troubleshooting Sequence

The majority of faults however must be isolated

Troubleshooting of the electronic voltmeter is

by checking voltagea and resistances.

a c c o m p l i s h e d using the overall schematic

b. Sectionalization. The electronic voltmeter

diagram (fig. FO-6), the voltage and resistance

can be divided into four circuits; the dc vtvm, the

measurements

(fig.

FO-5),

and

the

O- to 500-volt dc reference, the ac-to-dc con-

troubleshooting chart (table 6-1 ). Component

verter, and the low voltage supply. The first step

locations are shown in figures 6-2 through 6-12.

in tracing trouble is to locate the circuit at fault

Man y troubles in the electronic voltmeter can be

by the following methods:

quickly isolated by scanning the list of symptoms

(1) Visual inspection. Visual inspection is

in the troubleshooting chart.

used to locate faults with testing or measuring

6-7, Troubleshooting Chart

circuits. All meter readings or other indications

T h e troubleshooting chart (table 6-1) lists

should be observed and analyzed in an attempt to

probable causes corresponding to malfunction

isolate the fault to a particular circuit. An un-

i n d i c a t i o n s noted during operational checks.

derstanding of the operation of the electronic

Voltage and resistance measurements should be

voltmeter is particularly helpful when analyzing a

used to supplement the troubleshooting chart and

fault.

isolate the trouble to a particular part.

(2) Operation tests. O p e r a t i o n a l t e s t s

NOTE

frequently indicate the general location of trouble.

In many instances the tests will help to determine

When the probable cause for malfunc-

tion cannot be isolated during operational

the exact nature of the fault,

r e f e r e n c e to

` `out of

checks,

the

c. Localization. After the trouble has been

calibration" indicates that a higher level

sectionalized to a particular circuit, the next step

of maintenance is required, and that the

is to localize the specific component or com -

e q u i p m e n t should be returned to the

ponents responsible for the improper operation.

depot for maintenance.

The tests listed below will aid in isolating the

trouble.

Table 6-1, Troubleshooting

Corrective action

Probable cause

Malfunction

Insure that correct jumpers are

a. Improper fuse installed

1. Power fuse F1 blown

installed on power transformer

terminals and that proper fuse is

installed (fig. 5-6).

b. Short within instrument

b. Make resistance reading at the

following points. Readings below

the values noted in figure FO-5

are indications of short circuits.

6-2