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3-22
Maintenance:
Low Band Troubleshooting Charts
Activity on
U303 sel pin?
Bad SINAD
Bad 20dB Quieting
No Recovered Audio
START
Audio at pin 27
of U303?
Check Controller
Yes
No
Spray of inject 1st IF into
XTAL Filter
IF Freq: 109.65 MHz
Audio heard?
B
Yes
No
Check 2nd LO Control
Voltage at C308
VCO locked?
B
Yes
17.0 MHz
check at pin 22
U303?
Check FGU
No
No
A
A
Yes
Check Q301 bias cir-
cuitry for faults.
Rotate Freq. Knob
Check controller.
Before replacing U303, check 2nd VCO
Q301. Check VCO O/P level, C315,
C316
Yes
No
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
Summary of Contents for PR860
Page 1: ...PR860 Two Way Portable Radio Detailed Service Manual ...
Page 2: ......
Page 5: ...iv Notes ...
Page 9: ...viii Table of Contents Notes ...
Page 13: ...Notes xii List of Figures ...
Page 17: ...1 4 Introduction Radio Model Information Notes ...
Page 51: ...2 34 Theory of Operation Voltage Control Oscillators VCO Notes ...
Page 81: ...4 4 Schematic Diagrams Overlays and Parts Lists Flex Layout Notes ...
Page 193: ...4 116 Schematic Diagrams Overlays and Parts Lists Low Band Section Notes ...
Page 196: ......