Motorola Professional GP680 - Synthesizer

3-4 TROUBLESHOOTING CHARTS
4.0 Synthesizer
Visual
check of the
Board OK?
+5V at
U205 Pin’s
13 & 30?
Is information
from uP U409
correct?
Is U205
pin 18 at
4.54 V DC
?
Is U205
Pin 47 at
>12 V DC
In receive, is
Pin 1 < .7 V and Pin 2 >
3 Vplus in transmit is
Pin 1 > 3 V and Pin 2 <
.7 V?
Start
Correct
Problem
Check 5V
Regulator
Is 17.0 MHz
Signal at
U205 Pin 19?
Check Y201,CR211,
C236,C237,C242,
R219
Signal
at Pin 14 and
15 of U205?
Replace U205
Replace or
resolder
necessary
components
Is RF level at
U205 Pin 32
>-30 dBm?
Are loop filter
parts R224, R225,
R227, R228, R229,
C256, C257, C259
and C260
OK?
Replace U201
If R234, R238 and C297
are OK, then see VCO
troubleshooting chart
Do Pins 7,8 & 9
of U205 toggle
when channel is
changed?
Check programming
lines between U409
and U205 Pins 7,8 & 9
Replace U205
Check uP U409
Troubleshooting
Chart
NO
YES
NO
YES
NO
NO
YES
NO
YES
YES
NO
YES
YES
YES
NO
NO
NO
NO
YES
NO
YES
YES
Check C247, C249,
C283-C286,
D210, D211,
R285 and R286
3.3V at U205
pins 5, 20, 34
& 36
Check U400
and L225
Is
17.0MHz
signal at
U201 pin
23?
Replace
U205
YES
NO
NO
YES