Motorola GP540

3-6 TROUBLESHOOTING CHARTS
4.0 Troubleshooting Flow Chart for Synthesizer
5V
at pin 6 of
D3701
Is
information
from mP U409
correct
?
Is
U3701 Pin
18 AT 4.54
VDC?
Is U3701
Pin47 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
Regulator
+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 toggle
when channel
is changed
?
Check prgramming
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
Is
16.8MHz
signal at
U3701 pin
23?
Replace
U3701
YES
NO
NO
YES
NO
YES
Replace
Check
U3201,
L3731