Synthesizer - Motorola Professional GP340 Service Manual

3-4
4.0

Synthesizer

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