5-36 Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 4
3
Remove shield, SH4.
Measure RF levels at the
RF switch, U402, and
compute switch loss.
700: output side of C402 &
input side of C409.
Loss < 1 dB?
No
Measure RF levels at the SAW filter,
FL401, and compute filter loss.
700: Output side of C409 and input
side of C413.
Loss < 3 dB?
No
Replace
FL401
Measure RF levels at the RF
switch, U404, and compute switch
loss.
700: output side of C413 & input
side of C423.
Loss < 2 dB?
No
Yes
Measure RF levels at LNA
and compute LNA gain.
700: input side of C423 and
output side of R406.
Gain about
10 dB?
Yes
Yes
No
Yes
Yes
Measure RF levels at the
RF switch, U403, and
compute switch loss.
700: output side of R406 &
input side of C411.
Loss < 1 dB?
No
Measure RF levels at the SAW filter,
FL402, and compute filter loss.
700: Output side of C411 and input
side of C415.
Loss < 3 dB?
No
Measure RF levels at the RF
switch, U405, and compute switch
loss.
700: output side of C415 & input
side of C430.
Loss < 1 dB?
No
Yes
Measure RF levels at LNA
and compute LNA gain.
700: input side of C430 and
output side of R412.
Gain about
10 dB?
Yes
No
Yes
Replace
FL402
5
7
6
Check digital logic
to the RF switch
and replace U403 if
needed.
Check digital logic
to the RF switch
and replace U405 if
needed.
Check digital logic
to the RF switch
and replace U402 if
needed.
Check digital logic
to the RF switch
and replace U404 if
needed.
Note: RF Test frequency used:
VHF: 154.275 MHz
UHF1: 424.975 MHz
UHF2: 485.075 MHz
700: 769.0625 MHz
800: 860.0625 MHz
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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