Motorola APX 3000 Detailed Service Manual page 125

Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 9
(For reference only)
TP603 (Vdc)
11
0.00
1.33
3.89
Measure control 5.00
voltage at TP603
Fvco too low?
No
7/800/ UHF1
UHF2/ VHF:
<107.4 MHz
Yes
No
TP603 = 5 Vdc?
Yes
Remove Abacus
2nd LO shield,
SH4, and inspect
second LO VCO.
Visual
No
Repair defects
examination
Yes
Replace
Varactor
VR602
TP601 (MHz) Fvco
102.70
107.40
111.90
112.75
No
TP603= 0 Vdc?
10
Yes
10
Note: RF Test frequency used:
UHF1: 424.975MHz
UHF2: 485.075MHz
VHF: 154.275MHz
12
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.
Remove IF filter shield,
SH1. Check IF filter and
LC matching networks.
Visual
No
Repair
inspection
Defects
OK?
Yes
Replace IF
filter, FL502.
5-35