Troubleshooting Flow Chart For Receiver (Sheet 1 Of 2) - Motorola Professional Radio Service Manual

900 MHz Troubleshooting Charts
B
B
Check FGU

Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)

START
Bad SINAD.
Bad 20dB Quieting.
No Recovered Audio.
Audio at
pin 27 of
U351?
No
Spray or inject 1st IF into XTAL
Filter.
IF Freq: 109.65 MHz
Yes
Audio heard?
No
Check 2nd LO Control
Voltage at R365
Yes
VCO locked?
No
16.8 MHz
No
check at pin
21 of U351?
Yes
A
Yes
Check Controller.
Check controller
A
Check Q350 bias cir-
cuitry for faults
Rotate Freq. Knob
No
Activity
on U351
pin 19?
Yes
Before replacing U351, check
2nd VCO Q350. Check VCO O/P
level, C385, C387.
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