Troubleshooting Flow Chart For Vco - Motorola CDM Series Detailed Service Manual

Troubleshooting Flow Chart for VCO

4.0 Troubleshooting Flow Chart for VCO
Low or no RF Signal
RX VCO
at TP3001
Visual check
of board
OK?
5V DC at U3301
Pin 14 & 18 OK?
4.5V DC at
U3301 Pin 3 OK?
35mV DC at
U3301 Pin 19
OK?
Are Q3304
Base at 2.4V
Collector at 4.5V
Emitter at 1.7V
Are Q3301
Base at 0.7V
Collector at 4.5V
Emitter at 110mV
Is RF available
at base of Q3301
Check parts between
T3001 and Q3301
NO
Correct
Problem
YES
Make sure U3211 is working
NO
correctly and runner
between U3211 Pin 1 and
U3301 Pin 14 & 18 is OK
YES
Make sure Synthesizer is
NO
working correctly and runner
between U3201 Pin 28 and
U4301 Pin 3 is OK
YES
NO Check runner
between U3201 Pin 2
and U3301 Pin 19
YES
NO
If all parts associated
with the pins are OK,
replace Q3301
YES
NO
If all parts associated
with the pins are OK,
replace Q3301
YES
NO
If all parts from U3301 Pin 8
to Base of Q3301 are OK,
replace U3301
YES
Low or no RF Signal
at input to PA
NO
Visual check
of board
OK?
NO
5V DC at U3301
Pin 14 & 18 OK?
NO
4.5V DC at
U3301 Pin 3 OK?
NO
4.8V DC at
U3301 Pin 19
OK?
Are U3301 Pins
13 at 4.4V
15 at 1.1V
10 at 4.5V
16 at 1.9V
Is RF available
at TP3401
If all parts from TP3401 of
U3401 Pin 16 are OK,
replace U3401
Audio =180mVrms
Power OK but
at "-" side of
no modulation
If C3362 and R3363 are OK,
Section 4: 3-7
TX VCO
YES
YES
YES
YES
If all parts
associated
NO
with the pins
are OK,
replace U3301
YES
If R3402 and
NO
C3315 are OK,
replace U3301
YES
NO
Replace R3364
D3362
YES
NO
2.5VDC
Replace R3363
at D3362
YES
then replace D3362
66881091C63-F