Section Il. TROUBLESHOOTING DIGITAL VOLTMETER AN/GSM-64A

TM 11-6625-2616-14

h. Jumpering. Whenever an electrical connec-

wire or clip lead, If this fixes the problem then,

tion is suspected of being faulty, it is usually

of course the connection must be repaired.

possible to parallel the connection with a jumper

Section Il. TROUBLESHOOTING DIGITAL VOLTMETER AN/GSM-64A

b. Connect the unit to a 115 vac power source

6-4. General

as required.

The foregoing has provided the organization and

general techniques of the troubleshooting pro-

c. Connect the test equipment as specified for

cess. The following paragraphs provide detailed

each particular test (para 6-8 through 6-15).

troubleshooting information which, coupled with

a thorough understanding of the functioning data

6-7. Localizing Troubles

described in chapter 5, should enable the repair-

a. General. In the troubleshooting chart ( d

man to isolate the cause of the trouble and, with

below) procedures are given for localizing troubles

reference to chapter 7, to effect repair.

to a circuit or a specific component. Parts loca-

tions and test points are shown in figures 6-1

6-5. Equipment Required

and 6-2. Integrated circuits are not called out

a. DC voltage standard, John Fluke Model

on the figures since their reference designations

332A ( FSN 66252398924), or equivalent.

are etched on the printed circuit board,

b. Oscilloscope, AN/USM281.

b. Resistor and Capacitor Color Code Diagrams.

c. Multimeter, IS189

Color code diagrams for resistors and capacitors

(fig. 9-1 and 9-2) provide pertinent resistance,

d. Variac, Superior Electric Co. Type 3PN.

capacitance, voltage rating, and tolerance infor-

mation.

6-6. Initial Preparation

c. Use of Chart. When an abnormal symptom

a. Disassemble the instrument only so far as

has been observed in the instrument, look for a

is required to perform the specified checks or

description of this symptom in the Trouble symp-

tests (para 7-2a).

Figure 6-1. Main board assembly.

6-3