Motorola APX 5000 Service Manual page 145

Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 5
Measure RF levels at the SAW filter,
FL401, and compute filter loss.
800: output side of C408 and input
Measure RF levels at the RF
switch, U404, and compute switch
800: output side of C412 & input
Measure RF levels at LNA
and compute LNA gain.
800: input side of C423 and
Measure RF levels at the SAW filter,
FL402, and compute filter loss.
800: output side of C410 and input
side of C414.
Loss < 3 dB?
Measure RF levels at the RF
switch, U405, and compute switch
800: output side of C414 & input
side of C430.
Loss < 1 dB?
Measure RF levels at LNA
and compute LNA gain.
800: input side of C430 and
output side of R412.
Gain about
10 dB?
Measure RF levels at the
800: output side of C402 &
Yes
side of C412.
No
Replace
Loss < 2 dB?
FL401
Yes
loss.
side of C423.
Check digital logic
No
to the RF switch
Loss < 2 dB?
and replace U404 if
needed.
Yes
Gain about
output side of R406.
Measure RF levels at the
RF switch, U403, and
compute switch loss.
800: output side of R406 &
input side of C410.
Yes
Loss < 1 dB?
No
Replace
FL402
Yes
loss.
Check digital logic
No
to the RF switch
and replace U405 if
needed.
Yes
No
7
Yes
5
4
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
UHF2: 485.075 MHz
Remove shield, SH3.
700: 769.0625MHz
800: 860.0625MHz
RF switch, U402, and
compute switch loss.
Measured with a high impedance probe for relative comparisons and
troubleshooting only.
input side of C408.
Actual S21 gain or loss may differ if the test point is not 50 ohms.
Check digital logic
No
to the RF switch
Loss < 2 dB?
and replace U402 if
needed.
No
6
11 dB?
Yes
Check digital logic
No
to the RF switch
and replace U403 if
needed.
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