Troubleshooting Flow Chart For Receiver (Sheet 1 Of 2) - Motorola GP88s Service Manual

9B-50
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 U3220?
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Yes
Audio heard?
No
Check 2nd LO Control
Voltage at C3279
Yes
VCO locked?
No
16.8 MHz
No
check at pin
22 U3220?
Yes
A
Yes
Check Controller
Check controller.
Troubleshooting Charts
A
Check Q3270 bias
circuitry for faults.
Rotate Freq. Knob
Activity
No
on U3220
LVZIF_SEL
pin?
Yes
Before replacing U3220, check 2nd
VCO Q3270. Check VCO O/P level,
C3272, C3273.