Motorola GP88s

9B-50 Troubleshooting Charts
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Audio at pin
27 of U3220?
Check Controller
Yes
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Audio heard?
B
Yes
No
Check 2nd LO Control
Voltage at C3279
VCO locked?
B
Yes
16.8 MHz
check at pin
22 U3220?
Activity
on U3220
LVZIF_SEL
pin?
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.
Yes
No
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)