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Chapter 3
TROUBLESHOOTING CHARTS
1.0
Troubleshooting Flow Chart for Receiver, for all models except
those with PCB 8486473Z04 (Sheet 1 of 2)
Activity
on U3220
LVZIF_SEL
pin?
16.8 MHz
at pin 21
U3220?
Check 2nd LO Control Voltage at C3279
A
udio
at pin 27 of
U3220?
VCO
locked?
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Check Controller
Yes
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 45.1MHz
Audio
heard?
B
Yes
No
B
Yes
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
Summary of Contents for GP1280 Series
Page 1: ...Professional Radio GP Series VHF 136 174MHz Service Information Issue November 2004 ...
Page 24: ...2 14 THEORY OF OPERATION ...
Page 34: ...3 10 TROUBLESHOOTING CHARTS ...
Page 38: ...4 4 VHF PCB SCHEMATICS PARTS LISTS ...
Page 50: ...4 16 VHF PCB 8486062B12 Parts List Intentionally Left Blank ...
Page 54: ...4 20 VHF PCB 8486101B09 Schematics GP1280 Intentionally Left Blank ...
Page 64: ...4 30 VHF PCB 8486062B14 Parts List Intentionally Left Blank ...
Page 108: ...4 74 VHF PCB 8486473Z04 Radio Parts List Intentionally Left Blank ...