Service manual

3-28 800 MHz Troubleshooting Charts
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Audio at
pin27of
U351?
Check Controller
Yes
No
Spray or inject 1st IF into XTAL
Filter
IF Freq: 109.65 MHz
Audio heard?
B
Yes
No
Check 2nd LO Control
Voltage at R365
VCO locked?
B
Yes
16.8 MHz
check at pin
21 of U351?
Activity
on U351
pin 19?
Check FGU
No
No
A
A
Yes
Check Q350 bias cir-
cuitry for faults
Rotate Freq. Knob
Check controller
Before replacing U351, check
2nd VCO Q350. Check VCO O/P
level, C385, C387
Yes
No
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)