5-46
Troubleshooting Charts:
VCO Failure
5.16 VCO Failure – Page 1 (VHF, UHF1, UHF2, 700/800 MHz, 900 MHz)
VCO Failure
Frequency
detected?
* Sniff * frequency
near VCO shield
(SH11).
Remove VCO shield
(SH11).
Check control
voltage at R705.
< 0.3Vdc or
> 10.6Vdc or
voltage drifting?
Check power on
prescaler buffer output,
C823 using field probe.
Is power at
C823 >-15dBm?
Check if VCO is lock at
desired frequency using
field probe.
VCO locked?
Check parts around
U702. If OK, replace
U702.
Check lock_det line
circuitry in controller
section. Check R2811 and
R2812 for continuity.
Check loop filter R701,
R705, R708, C703,
C707, C713 for
continuity. Fault found?
Replace suspected
components.
UHF1 Radio?
7/800 MHz
Radio?
No fault found.
1
2
Remove FGU shield
(SH5).
Yes
No
No
Yes
Yes
No
No
No
Yes
No
Yes
Yes
Yes
No
Sniff: Using an inductive field probe
as an antenna to measure
frequency. Place the probe
approximately ½ inch away from
components to be sniffed
UHF2 Radio?
VHF Radio?
3
4
No
Yes
Yes
No
900 MHz Radio?
5
Yes
No
Summary of Contents for APX 2000
Page 1: ...APXTM TWO WAY RADIOS APX 1000 APX 2000 APX 4000 APX 4000Li DETAILED SERVICE MANUAL ...
Page 4: ......
Page 6: ...iv Document History Notes ...
Page 8: ...Notes vi Commercial Warranty ...
Page 10: ...Notes ...
Page 22: ...xiv List of Figures Notes ...
Page 226: ...6 64 Troubleshooting Waveforms LF CW on Spectrum Analyzer Notes ...
Page 688: ...Index 4 Index Notes ...
Page 690: ...ii Notes ...
Page 700: ...xvi List of Figures Notes ...
Page 806: ...5 50 Troubleshooting Charts PA Failure Notes ...
Page 1008: ...8 178 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF2 84012621001 Notes ...
Page 1062: ...8 234 Schematics Boards Overlays and Parts Lists Keypad Board M2 and M3 PC000261A01 Notes ...
Page 1064: ...ii Notes ...
Page 1068: ...Notes A 4 EMEA Warranty Service and Technical Support Further Assistance From Motorola ...
Page 1090: ...Glossary 10 Glossary Notes ...
Page 1094: ...Index 4 Index Notes ...
Page 1095: ......