GROSS TROUBLESHOOTING PRELIMINARY INSTRUCTIONS.

TM 11-5820-401-34-3/0967-LP-432-3060

4-11.

GENERAL. (CONT)

The troubleshooting charts are designed to locate the cause of the performance degradation by using

procedures more complex than those utilized for gross troubleshooting. Added complexity is due to the

fact that the troubleshooting tests must evaluate the quality of the signals at various test points, instead

of merely confirming the presence of signals as is usually the case in gross troubleshooting.

OVERALL TROUBLESHOOTING APPROACH

Both kinds of troubleshooting charts contained in this section are intended for use based on the

following assumptions in connection with the R-442/VRC:

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

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

isolated using the schematics located in the back of this manual.

4. Troubleshooting procedures for germanium and silicon versions of the R-442/VRC are the

same.

4-12. GROSS TROUBLESHOOTING PRELIMINARY INSTRUCTIONS.

The gross troubleshooting charts in this section are based on the assumption that the receiver fails the

VOLUME control test at any frequency setting of the MC-TUNE-KC control. However, certain defects

in the crystal reference system can result in loss of audio at some frequencies while the receiver can

function normally at other frequency settings.

Before proceeding with the steps given in the gross troubleshooting charts, determine whether or not

the failure of the volume control test conforms to any of the following failure modes.

CAUSE

FAILURE MODE

CORRECTION

Replace A2000 assembly.

Crystal Y2012 (5.65 MHz)

No audio on all

in A2000 assembly

channels ending in

"0", (eg, 30.00,

30.10,30.20,etc)

Crystal Y2011 (5.60 MHz)

No audio on all

Replace A2000 assembly.

in A2000 assembly

channels ending in

"5", (eg, 30.05,

30.15,30.25,etc)

Defective interpolation

No audio on the same

Replace A2000 assembly.

oscillator crystal

100-kHz segment for

See interpolation oscilla-

each MHz of tuning

tor crystal chart.

4-31