Motorola 6864115B62-C - 5.0 Troubleshooting Flow Chart for VCO

Troubleshooting Flow Chart for VCO 3-5
4.0 Troubleshooting Flow Chart for VCO
Low or no RF Signal
at U1051
Visual Check
of Board
OK?
8.5V DC
Pin 3
<,1 V DC at
U1377 Pin 2
8.5V DC AT
U1378 PIN 4
Correct
Problem
NO
YES
Make sure Synthesizer is
working correctly and
runner between U1201 Pin
3 of U1377 & U1378.
Check runner
between U1201 Pin 2
and U1377 Pin 2
Is RF
Q1304 ?
Troubleshoot
Oscillator Stage
Is RF
Check parts between
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
Low or NO RF Signal
at Input to PA
Visual Check
of Board
OK?
8.5V DC at
U1378 Pin 3
4.5V DC at
U1377 Pin 2
8.5V DC at
U1377 Pin 4
Is RF
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
U1051 and Q1305
Q1305 ?
Troubleshoot
Buffer Stage
Make sure U1377 and U1378
are working correctly.
Is RF
Q130 8 ?
NO
YES
Check parts between
U1401 and Q1308
RX - VCO
TX - VCO
at U1378
available at Base of
available at Base of
Q1307 ?
available at Base of
available at Base of
Q1303
Circuitry
Q1304
Circuitry
Oscillator Stage
Troubleshoot
Troubleshoot
Q1306
Circuitry
Q1307
Buffer Stage
Circuitry