Motorola GP580 Service Information - Page 23
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1.0
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
Yes
B
Check 2nd LO Control Voltage at C3279
B
A
START
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
A
udio
Yes
at pin 27 of
U3220?
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Audio
heard?
No
Yes
VCO
locked?
No
16.8 MHz
Yes
at pin 21
U3220?
No
Check FGU
TROUBLESHOOTING CHARTS
Check Controller
Check Q3270 bias
circuitry for faults.
Rotate Freq. Knob
Activity
on U3220
LVZIF_SEL
pin?
Yes
Before replacing U3220, check 2nd
VCO Q3270. Check VCO O/P level,
C3272, C3273.
Chapter 3
A
No
Check controller