2-2
TROUBLESHOOTING CHARTS
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Audio at
pin 27 of
U301?
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 C363
VCO locked?
B
Yes
16.8 MHz
check at pin
22 U301?
Activity on
U301 sel
pin?
Check FGU
No
No
A
A
Yes
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.
Yes
No
Figure 2-1
Troubleshooting Chart for Receiver (Sheet 1 of 2)
Summary of Contents for GP-688
Page 5: ...Compact Professional Portable Radios Service Maintainability Issue July 2007 ...
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Page 24: ...2 6 MAINTENANCE THIS PAGE INTENTIONALLY LEFT BLANK ...
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Page 64: ...3 12 CONTROLLER KEYPAD SCHEMATICS ...
Page 112: ...3 60 PCB and Schematic Drawings IP67 THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 116: ...3 64 PCB and Schematic Drawings IP67 THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 120: ...3 68 PCB and Schematic Drawings IP67 THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 147: ...Compact Professional Portable Radios VHF 136 174MHz Service Information Issue July 2007 ...
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Page 335: ...Compact Professional Portable Radios UHF2 450 527MHz Service Information Issue July 2007 ...
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Page 348: ...1 10 THEORY OF OPERATION THIS PAGE INTENTIONALLY LEFT BLANK ...
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