Motorola CDM Series Detailed Service Manual page 351

Troubleshooting Flow Chart for VCO
4.0 Troubleshooting Flow Chart for VCO
RX VCO
LOW OR NO RF SIGNAL
AT U1051
VISUAL CHECK
OF BOARD
OK?
YES
8.5V DC AT
U1378 PIN 3
YES
<,1 V DC AT
U1377 PIN 2
YES
8.5V DC AT
U1378 PIN 4
YES
IS RF AVAILABLE
AT BASE OF Q1304
YES
IS RF AVAILABLE
AT BASE Q1305
YES
CHECK PARTS BETWEEN U1051
AND Q1305
NO
CORRECT
PROBLEM
MAKE SURE SYNTHESIZER IS
NO
WORKING CORRECTLY AND
CHECK RUNNER BETWEEN
U1201 & PIN 3 of U1377 & U1378
CHECK RUNNER
NO
BETWEEN U1201 PIN 2
AND U1377 PIN 2
NO
MAKE SURE U1377 AND U1378
ARE WORKING CORRECTLY.
TROUBLESHOOT Q1303
NO
OSCILLATOR STAGE CIRCUITRY
NO
TROUBLESHOOT Q1304
BUFFER STAGE CIRCUITRY
TX VCO
LOW OR NO RF SIGNAL
AT INPUT TO PA
NO VISUAL CHECK
OF BOARD
OK?
YES
NO
8.5V DC AT
U1378 PIN 3
YES
NO
4.5V DC AT
U1377 PIN 2
YES
NO
8.5V DC AT
U1377 PIN 4
YES
IS RF AVAILABLE
AT BASE OF Q1307
YES
IS RF AVAILABLE
AT BASE OF Q1308
YES
CHECK PARTS BETWEEN
U1401 AND Q1308
Section 7: 3-5
NO
A
NO
B
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