Motorola Pro Series Elite - Troubleshooting Flow Chart for Synthesizer

3-14 VHF Troubleshooting Charts
5V
at pin 6
of
D3701
Is information
from μP U409
correct?
Is U3701
Pin 18 AT
4.54
VDC?
Is U3701 Pin
47
AT = 13 VDC
Is U3701 Pin
19
<0.7 VDC in
RX &
>4.3 VDC in
TX?
Start
Visual
check of the
Board OK?
Correct
Problem
Check
5V
+5V at
U3701
Pin’s
13 & 30?
Is 16.8MHz
Signal at
U3701 Pin
19?
Check Y3761,
C3761, C3762,
C3763, D3761 &
R3761
Are signals
at Pin’s 14 &
15 of
U3701?
Check
L3701,
R3701
Check Q260,
Q261 &
R260
U3701 pin 2
at >3V in Tx
and <0.7V in
Rx
Remove
Shorts
Is there a short
between Pin 47
and Pins 14 & 15
of U3701?
Replace or resolder
necessary
components
Is RF level at
U3701 Pin 32
>-30 dBm?
Are C3721,
C3722,C3723,
R3721, R3722,
R3723 OK?
Replace
U3701
If R3727, C3726 &
C3727 are OK, then
see VCO
troubleshooting chart
Are Waveforms
at Pins 14 & 15
triangular?
Do Pins 7,8 & 9
of U3701 tog-
gle
when channel
is
changed?
Check program-
ming lines between
U409 and U3701
Pins 7, 8 & 9
Replace
U3701
Check uP U409
Troubleshooting
Chart
NO
YES
NO
YES
NO
YES
NO
YES
NO
NO
NO
YES
YES
NO
YES
YES
NO
YES
YES
YES
NO
NO
NO
NO
YES
NO
YES
YES
Check D3701,
D3702, U3701,
C3701 - C3707
3.3V at
U3701 pins
5, 20, 34 &
36
Check
U3201,
L3731
Is
16.8MHz
signal at
U3701
pin
23?
Replace
U3701
YES
NO
NO
YES
NO
YES
Troubleshooting Flow Chart for Synthesizer
Replace
U3701