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Troubleshooting Charts
Check D3701, D3702,
U3701, C3701 -
C3707
YES
5V
NO
at pin 6 of
Is U3701 Pin 47
D3701
13 VDC
NO
Check
L3701,
R3701
Is U3701 Pin 19
<0.7 VDC in RX &
>4.3 VDC in TX?
YES
Is U3701
Pin 18 at
4.54 VDC?
YES
Is RF level at
U3701 Pin 32
>-30 dBm?
YES
Are C3721,
C3722,C3724,
R3721, R3722,
R3723 OK?
YES
Replace U3701
NO
Correct
Problem
YES
Check R3829
NO
YES
U3701 pin 2 at
>3V in Tx and
<0.7V in Rx
NO
NO
Replace U3701
If R3727, C3726 & C3727
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 U3701
NO
Pin's
13 & 30?
Check 5V
Regulator
NO
Are signals
at Pin's 14 &
15 of U3701?
YES
Is there a short
NO
between Pin 47 and
Pins 14 & 15 of
U3701?
YES
Remove
Shorts
Troubleshooting Flow Chart for Synthesizer
NO
Check U3201,
3.3V at U3701
L3731
pins 5, 20, 34 &
36
YES
Is
Is 16.8MHz
NO
16.8MHz
Signal at
signal at
U3701 Pin 19?
U3701 pin
23?
NO
YES
Check Y3761, C3761,
C3762, C3763, D3761
& R3761
NO
Are Waveforms
at Pins 14 & 15
triangular?
YES
Do Pins 7,8 & 9
NO
of U3701 toggle
when channel is
changed?
Check programming
lines between U409
and U3701 Pins 7,8 & 9
NO
Is information
from
correct?
Check uP U409
Troubleshooting
Chart
Replace U3701
9B-53
Replace
U3701
YES
YES
µ
P U409
YES
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Table of Contents
Troubleshooting
