Motorola ASTRO Digital Spectra Plus Detailed Service Manual page 235

Troubleshooting Charts
START
Check Module Gain: Inject
Measure Transceiver On-Channel Signal
Sinad by Injecting (851-870 MHz) of -20dBm
Signal at J9127 at J9127: Measure Level 109.65
MHz Out at IF Output Pad
No Problem with
Yes
Sinad
RX Front End or
<- 119
? RF Board
No
Measure RF Board
Sinad: Inject
109.65MHz into RF
Board at J350
Sinad
Troubleshoot Measure RF Level
No
<- 119
RF Board at Base of Q8126
?
Yes
Check DC
Voltage at IF
Output Pad
Troubleshoot
Check Inject Level
~ _
No
9.6V
DC Feed from
at Injection Input Pad
?
RF Board
Yes
Check Biasing
on Q8126:
Vcollector ~ _ 8.0V
Vbase = 0.4 to 0.8V
Check Bias Circuit Troubleshoot
No
OK
and Associated RF Injection or
?
Components Carrier Board
Yes
Chart C.22 800 MHz Receiver Front-End Hybrid
6881076C25-E
-10 dBm
Yes Check Beta
to -14 dBm
of Q8126
?
No
No
B = <60
Replace Q8126
?
Yes
Recheck RF BD
and Transceiver
Sinad
Measure Level of
Yes
~ _
-1 dBm On-Channel Signal
? at Preselector
Input Pad
No
Check Components
in Output Network
Yes
-20 to -23 dBm
C8129, 30, 31, 36:
?
L8129, 30, 31:
R8129, 30, 31:
Replace as
No
Necessary
Yes Replace
> _
+ 3 dBm
RXFE Board
?
No
START
Check Module Gain: Inject
Measure Transceiver Signal -20dBm at J9127
Sinad by Injecting Measure at IF Output Pad
Signal at J9127
-20 dBm
No Problem with
Yes
Sinad
RX Front End or to -17 dBm
<- 120
?
? RF Board
No
Measure RF Board
Sinad: Inject
109.65MHz into RF
Board at J350
Sinad
Troubleshoot Measure RF Level
No
<- 120
RF Board at Base of Q9125
?
Yes
Check DC
Voltage at IF ~ _
-10 dBm
Output Pad ?
Troubleshoot
Check Injection Level
~ _
No
12V
DC Feed from
at Injection Input Pad
?
RF Board
Yes
Check Biasing
on Q9125:
> _
+ 10dBm
Vcollector ~ _ 10V
?
Vbase = 0.4 to 0.8V
Check Bias Circuit Troubleshoot
No
OK
and Associated RF Injection or
?
Components Carrier Board
Yes
Yes Check Beta
of Q9125
No
No
B = >60
Replace Q9125
?
Yes
Recheck RF BD
and Transceiver
Sinad
Yes
Measure Level
at Preselector
Input Pad
No
Check Components
Yes
in Output Network
~ ~ ~ -20 dBm
Replace as
?
Necessary
No
Yes Replace
RXFE Board
No
Chart C.23 UHF Receiver Front-End Hybrid
September 5, 2008
5-17