Motorola CDM Series Detailed Service Manual page 248

Section 5: 3-6
3.0 Troubleshooting Flow Chart for Synthesizer
Correct
Problem
Check D4201,
C4202, C4203, &
C4206
YES
Is
NO
5V
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
6881091C63-F
NO
YES
Check C4381
NO
Is
U4201
YES
Pin 2 >4.5 VDC in
Tx & <40 mVDC
in Rx
?
NO
NO
Replace
U4201
If L4225, C4229 & C4227
NO
are OK, then see VCO
troubleshooting chart
Replace or
NO
resolder
necessary
components
Troubleshooting Flow Chart for Synthesizer
Start
Visual
check of the
Board
OK?
YES
Signal at U4201
+5V
at U4201
NO
YES
Pins
13 & 30
?
Check 5V
R e g u l a t o r
U4211
Are
signals NO
at Pins 14 &15
of U4201
?
YES
Is
there a short
between Pin 47 and
Pins 14 & 15 of
U4201
?
YES
Remove
Shorts
5V
NO
Check 5V
at U4201
Regulator
pins 5, 20, 34
U4211
& 36
YES
Is
Is
16.8MHz
16.8MHz NO
signal at
U4201 Pin
Pin 19
23?
?
YES
NO
Check
Y4261 / Y4262 and
associated parts
Are
Waveforms
NO
at Pins 14 & 15
triangular
?
YES
Do
Pins 7,8 & 9
NO
of U4201 toggle
when channel is
changed?
Check programming
YES
lines between
U0101 and U4201
Pins 7,8 & 9
Is
NO
information
from µP U0101
correct
?
Check µP U0101
Troubleshooting
Chart
Replace
U4201
Replace
U4201
YES
YES