Section II. DIRECT SUPPORT TROUBLESHOOTING

TM 11-5820-477-30

Section Il. DIRECT SUPPORT TROUBLESHOOTING

Page

Para.

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Preliminary Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Dc Resistance of Transformers and Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Remote Control Unit Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Local Control Unit Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-3. General

The first step in troubleshooting is to trace the fault to a specific system or subsystem. The next step is to localize

the fault to a particular assembly, such as a printed circuit card. The final step is to isolate the fault by tracing it to

a defective component, such as a resistor, transformer or switch. Fault isolation is limited to those items which

may be repaired or replaced at direct support level. This primarily includes replacement or repair (by component

replacement) of the chassis assembly and panel assembly on each of the control units that make up the

AN/GRA-39(*).

Some faults, such as burned-out resistors, arcing and shorted relay coils and transformer windings, can often be

identified by sight, smell or hearing. Visual inspection is used to locate faults without testing or measuring circuits.

Most faults, however, must be isolated by checking voltages and resistances. Dc resistance of transformers and

coils (paragraph 2-5) will isolate a malfunction to a defective component on the chassis. The voltage

measurements given in tables 2-1 and 2-2 provide the data needed to check operating voltages of specific major

circuits.

The troubleshooting tables are designed to supplement the operational checks detailed in the equipment

performance checklist in TM 11-5820-477-12. If previous operational checks have resulted in reference to a

particular item on the troubleshooting table, go directly to the referenced item.

This section has two troubleshooting tables. Table 2-3 pertains to the remote control unit. Table 2-4 pertains to

the local control unit. Each table lists the common malfunctions that may occur during operation and maintenance

of the AN/GRA-39(*) and after unit maintenance has been performed. Each malfunction is followed by a list of

tests or inspections and corrective actions. These test or inspections and corrective actions should be performed

in the order listed. This manual cannot list all malfunctions that may occur. If you encounter a problem that is not

listed or cannot be corrected by the listed corrective action, notify your supervisor.

Refer to the Maintenance Allocation Chart in the operator's and unit maintenance manual TM 11-5820-477-12 for

a list of equipment required for direct support troubleshooting.

WARNING

Do not press RINGER button (of either the local or the remote unit) when touching line

binding posts. Electrical shock may result.

CAUTION

When a corrective action entails component replacement, refer to the applicable

maintenance paragraph, paying particular attention to all pertinent cautions and notes,

before attempting replacement.

2-2