Motorola APX 2000 Detailed Service Manual

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

Motorola APX 2000 Specifications

General

IP Rating	IP67
Operating Temperature	-30°C to +60°C
GPS	Optional
Bluetooth	No
Frequency Range	700/800 MHz
Power Output	1-5 W (VHF), 1-3 W (700/800 MHz)
Channels	Up to 1, 000
Battery Life	Up to 10 hours (digital)
Digital Protocol	APCO P25
Frequency	VHF: 136-174 MHz, UHF: 380-470 MHz, 700/800 MHz: 764-870 MHz
Power	1-3W (700/800 MHz), 1-5W (VHF)