Troubleshooting Flow Chart For Synthesizer - Motorola GM328 Service Manual

3-4
3.0

Troubleshooting Flow Chart for Synthesizer

Check D4201, C4202,
C4203, & C4206
YES
5V
NO
Is U4201 Pin 47
at pin 6 of
at = 13VDC
D4201
NO
Check
R4201
Is U4301 Pin 19
<40 mVDC in RX &
>4.5 VDC in TX? (at
VCO section)
YES
Is RF level at
U4201 Pin 32
-12 < x <-25
dBm?
YES
Are R4221,R4222,
R4223,C4221,C4222,
& C4223 OK?
YES
Replace U4201
NO
Correct
Problem
YES
Check C4381
NO
YES
Is U4201 pin 2
>4.5 VDC in Rx &
<40 mVDC in Rx
NO
Replace U4201
If L4225, C4229 & C4227
NO
are OK, then see VCO
troubleshooting chart
Replace or
NO
resolder
necessary
components
Start
Visual
check of the
Board OK?
YES
YES
+5V at U4201
NO
Pin's
13 & 30?
Check 5V
R e g u l a t o r
U4211
NO
Are signals
at Pin's 14 &
15 of U4201?
YES
Is there a short
NO
between Pin 47 and
Pins 14 & 15 of
U4201?
YES
Remove
Shorts
Troubleshooting Flow Chart for Synthesizer
NO
Check 5V
5V at U4201
Regulator
pins 5, 20, 34 &
U4211
36
YES
Is 16.8MHz NO 16.8MHz
Signal at signal at
U4201 Pin 19? U4201 pin
23?
YES
Check Y4261, C4261,
C4262, C4263, D4261
& R4261
NO
Are Waveforms
at Pins 14 & 15
triangular?
YES
NO
Check programming
lines between U0101
and U4201 Pins 7,8 & 9
NO
from
Check uP U0101
Troubleshooting
Chart
Replace U4201
Is
Replace
U4201
YES
NO
Do Pins 7,8 & 9
of U4201 toggle
when channel is
changed?
YES
Is information
µ
P U0101
correct?
YES