Motorola GP340 - Chapter 3 TROUBLESHOOTING CHARTS; Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)

Chapter 3
TROUBLESHOOTING CHARTS
1.0 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
16.8 MHz
at pin 22
U301?
VCO
locked?
Audio
at pin 27 of
U301?
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
Ye s
No
Check 2nd LO Control Voltage at C363
B
Ye s
Activity
on U301
LVZIF_SEL
pin?
Check FGU
No
No
A
A
Ye s
Check Q320 bias
circuitry for faults.
Rotate Freq. Knob
Check controller
Before replacing U301, check 2nd
VCO Q320. Check VCO O/P level,
C351, C352.
Ye s
No