OVERALL TROUBLESHOOTING APPROACH

TM 11-5820-670-30

2-24. GENERAL. (CONT)

When a radio set fails to meet a designated standard during a performance test, a reference is made

in the test procedure to a specific troubleshooting chart which can then be used to locate the cause of

the nonperformance. The results of in-aircraft tests may accompany the radio set when it is forwarded

by AVUM maintenance to the AVIM unit and can be used to select an appropriate troubleshooting

procedure in the event that saving time is essential. If trouble symptoms are unkown, begin with volt-

age distribution troubleshooting and proceed until symptoms are known. See applicable mode of

operation troubleshooting chart.

Troubleshooting procedures are based on the following assumptions:

1. Only one malfunction exists which is causing the symptom detected.

2. The troubleshooting charts do not isolate every possible defect.

3. Failure to locate a defect using the charts suggests a wiring-related problem which can be iso-

lated using the schematics in the back of this manual.

4. Troubleshooting procedures for germanium and silicon versions of the modules in the rt are

the same.

TOTAL FAILURE TROUBLESHOOTING

The rt will be completely inoperative if voltage distribution is interrupted by an open or a short in the rt

chassis wiring. The voltage distribution and primary power circuit troubleshooting charts will aid in

determining if there is a wiring problem or if power supply has been interrupted by a faulty power supply

assembly or its fuse, a faulty voltage regulator, or a defect in the control unit. Perform appropriate

repair or replacement as instructed and repeat the performance test after repair is made.

PERFORMANCE FAILURE TROUBLESHOOTING

If the rt is operational, but does not meet a performance standard, performance troubleshooting

charts will aid in determining the specific module or component that is malfunctioning. Performance

troubleshooting isolates problems when the radio components are functioning in the receive mode,

the transmit mode, or its homing mode. In each case, the first chart covers a gross failure; for

example, a complete failure to transmit. Subsequent charts cover performance degradation where the

rt may transmit, for example, but at low power or with excess distortion. The troubleshooting charts

isolate the problem to a module or component that is faulty. A faulty module may have failed completely

or partially, may be operating at less than standard performance due to damage or age, or may itself

contain an open or short. Repair or replacement instructions for a specific module or component is

given. After repair or replacement, aline unit if required, then repeat performance test.

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