Chapter 3
TROUBLESHOOTING CHARTS
1.0 Troubleshooting Flow Chart for Receiver, for all models except
those with PCB 8486473Z04 (Sheet 1 of 2)
Activity
on U3220
LVZIF_SEL
pin?
16.8 MHz
at pin 21
U3220?
Check 2nd LO Control Voltage at C3279
Audio
at pin 27 of
U3220?
VCO
locked?
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Check Controller
Ye s
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Audio
heard?
B
Yes
No
B
Yes
Check FGU
No
No
A
A
Yes
Check Q3270 bias
circuitry for faults.
Rotate Freq. Knob
Check controller
Before replacing U3220, check 2nd
VCO Q3270. Check VCO O/P level,
C3272, C3273.
Ye s
No
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