Motorola APX 3000

Troubleshooting Charts: RX RF Failure 5-35
RX RF Failure – Page 9
11
Measure control
voltage at TP603
Fvco too low?
7/800/ UHF1
UHF2/ VHF:
<107.4 MHz
TP603 = 5 Vdc?
TP603= 0 Vdc?
10
10
Remove Abacus
2nd LO shield,
SH4, and inspect
second LO VCO.
Visual
examination
Repair defects
Replace
Varactor
VR602
No
No
Yes
No
Yes
Yes
No
Yes
12
Remove IF filter shield,
SH1. Check IF filter and
LC matching networks.
Visual
inspection
OK?
Repair
Defects
Replace IF
filter, FL502.
No
Yes
Note: RF Test frequency used:
UHF1: 424.975MHz
UHF2: 485.075MHz
VHF: 154.275MHz
700: 769.0625MHz
800: 860.0625MHz
Measured with a High Frequency Probe for relative comparisons and troubleshooting
only. Actual S21 gain or loss may differ if the test point is not 50 ohms.
TP603 (Vdc)
TP601 (MHz) Fvco
0.00 102.70
1.33 107.40
3.89 111.90
5.00 112.75
(For reference only)