Troubleshooting Flow Chart For Vco - Motorola Commercial CM Series Service Information

3-8
4.0

Troubleshooting Flow Chart for VCO

Low or no RF Signal
RX VCO
at TP1
Visual check
of board
4.5V DC
at U201 Pin 14 & 18
35mV DC at
U201 Pin 19
Is RF available
at base of Q200
Are Q200
Base at 2.4V
Collector at 4.5V
Emitter at 1.7V
If all parts from collector
of Q200 to TP1 are
OK, replace Q200
NO
OK?
YES
Make sure Synthesizer is
NO
working correctly and runner
between U200 Pin 28 and
OK ?
U201 Pin 14 & and is OK
YES
NO
between U200 Pin 2
OK?
YES
NO
YES
NO
YES
Power OK but
no modulation
NO
Correct
Problem
NO
Check runner
and U201 Pin 19
Replace U201
If all parts associated
with the pins are OK,
replace Q200
Audio =180mVRMS
If R211 and R12 are OK,
then replace D205
TROUBLESHOOTING CHARTS
Low or no RF Signal
at input to PA
Visual check
of board
OK?
YES
4.5V DC
at U201 Pin 14&18
OK ?
YES
NO
4.8V DC at
U201 Pin 19
OK?
YES
Are U201 Pins
13 at 4.4V
15 at 1.1V
10 at 4.5V
16 at 1.9V
YES
NO
Is RF available
at C2060
YES
Check parts to pre-driver
NO
Replace R212
at "-" S
ide of
D205
YES
NO
4.5VDC
Replace R211
at D205
YES
TX VCO
If all parts
associated
NO
with the pins
are OK,
replace U201
If parts between
R109 & U201 Pin10
are OK, replace U201