Motorola XTS 2500 Service Manual page 184

6.1-18
6.1.19VHF Frequency Generation Unit Troubleshooting Chart
D251&D252(RX VCO)
R273, R274 and R275
February 14, 2012
VHF Troubleshooting Charts: VHF Frequency Generation Unit Troubleshooting Chart
FGU NoLO
Injection/TX
Unlock
Is Vdc at
No
D270(Tx VCO)
0.4<Vdc<12?
Yes
Is Vdc at
R259,
Take a continuity
No
High for Tx,
check of traces
Low for Rx mode
to U201
Yes
For TX only pin 3 of Q216 (TX)
For RX check C263,
L258, C267, C261,
R293 and R294 for
continuity.
Replace
No
For TX check C278,
suspected
L274, C276, C279,
component
Yes
Change U250
Is Vdc
Do a continuity
No
at C218 3V?
check and refer to
and C211
DC switch chart
5V?
Yes
Is there
a voltage reading
No
Replace
at R204, R205, C206,
C207 directed
to U202?
Yes
Do a continuity
Is Vdc
No
at Y200 pin 4 check and refer to
DC switch chart
3V?
Yes
Do you
see 16.8MHz at
Replace Y200
No
pin 3 of Y200 and C214
and/or C214
connection to Xtal
K9 pin of
U202?
Yes
Do
No
you see
16.8MHz at
U201 circuitry
C245?
Yes
Fix/replace
Do
you see
No
~11.5 Vdc at pin 2
of D202?
Yes
Check components
Replace
D201, D202, C206,
U202
C207, C208
and C209
U202
Yes
Check Replace
U202
No
U201
Is
No
3Vdc at
pin 4 of
D201?
Yes
MAEPF-27346-O
6816985H01-F