Motorola MTX series - Except those with PCB 8486473 Z04; Troubleshooting Flow Chart for Receiver, for All Models; Troubleshooting Flow Chart for Receiver, for All Models Except those with PCB 8486473 Z04 (Sheet 1 of 2)

Maintenance: VHF Troubleshooting Charts 8-29
8.12.3 Troubleshooting Flow Chart for Receiver, for all models
except those with PCB 8486473Z04 (Sheet 1 of 2)
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
21 U3220?
Activity on
U3220 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