Troubleshooting Flow Chart For Vco - Motorola GM328 Service Manual

Troubleshooting Flow Chart for VCO

4.0

Troubleshooting Flow Chart for VCO

Low or no RF Signal
RX VCO
at TP5003
Visual check
of board
OK?
4.5V DC
at U5301 Pin 14 & 18
OK ?
35mV DC at
U5301 Pin 19
Are Q5301
Base at 2.4V
Collector at 4.5V
Emitter at 1.7V
Is RF available
at base of Q5332
Are Q5332
Base at 0.7V
Collector at 4.5V
Emitter at 110mV
If all parts from collector
of Q5332 to TP5003 are
OK, Replace U5301
NO
YES
Make sure Synthesizer is
NO
working correctly and runner
between U5201 Pin 28 and
U5301 Pin 14 & 18 are OK
YES
NO
between U5201 Pin 2
and U5301 Pin 19
OK?
YES
NO
YES
NO
If all parts from U5301 Pin 8
to Base of Q5332 are OK,
YES
NO
If all parts associated
with the pins are OK,
YES
Power OK but
no modulation
NO
Correct
Problem
NO
Check runner
NO
Replace Q5301
replace U5301
If all parts from U5301 Pin 10
replace Q5332
Audio =180mVrms
at "-" S
at CR5321
If C5321 and R5321 are OK,
then replace CR5321
Low or no RF Signal
TX VCO
at input to PA
Visual check
of board
OK?
YES
4.5V DC
at U5301 Pin 14 &18
OK ?
YES
4.8V DC at
U5301 Pin 19
OK?
YES
Are Q5311
NO
Base = 1.9V
Collector = 4.5V
Emitter = 1.3V
YES
Is RF available
NO
at U5401
Pin 16
YES
U5401 Pin 16 are OK,
replace U5301
NO
Replace C5325
ide of
C5325
YES
NO
4.5VDC
Replace C5322
YES
3-5
Replace
Q5311
If R5361 and
L5361 are OK,
replace U5301