Troubleshooting Charts: RX RF Failure 5-43
RX RF Failure – Page 9
TP602(Vdc) TP601 (MHz) Fvco
0.00 102.70
1.47 107.40
4.16 111.90
5.00 112.80
11
Measure control
voltage at TP602
Fvco too low?
<107.4 MHz
TP602 =
5 Vdc?
TP602 = 0
Vdc?
10
10
Remove Abacus
shield, SH6A, and
inspect second LO
VCO.
Visual
examination
OK?
Repair
defects
Replace
Varactor
VR602
No
No
Yes
No
Yes
Yes
No
Yes
12
Remove IF filter shield,
SH2. Check IF filter and
LC matching networks.
Visual
inspection
OK?
Repair
Defects
Replace IF
filter, FL501.
No
Yes
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
UHF2: 485.075MHz
700: 769.0625MHz
800: 860.0625MHz
Measured with a high impedance probe for
relative comparisons and troubleshooting only.
Actual S21 gain or loss may differ if the
test point is not 50 ohms.
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