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

3-10
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 U301?
No
Induce or inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Yes
Audio heard?
No
Check 2nd LO Control
Voltage at C363
Yes
VCO locked?
No
16.8 MHz
No
check at pin
22 U301?
Yes
A
Yes
Check Controller
Check controller
Before replacing U301, check 2nd
VCO Q320. Check VCO O/P level,
C351, C352
UHF Troubleshooting Charts
A
Check Q320 bias
circuitry for faults
Rotate Freq. Knob
No
Activity on
U301 sel pin?
Yes