Motorola APX 5000 Service Manual page 144

5-38
RX RF Failure – Page 4
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?
Measure RF levels at the RF
switch, U404, and compute switch
700: output side of C413 & input
side of C423.
Loss < 2 dB?
Measure RF levels at LNA
and compute LNA gain.
700: input side of C423 and
output side of R406.
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?
Measure RF levels at the RF
switch, U405, and compute switch
loss.
700: output side of C415 & input
side of C430.
Loss < 1 dB?
Measure RF levels at LNA
and compute LNA gain.
700: input side of C430 and
output side of R412.
Gain about
10 dB?
5
Remove shield, SH3.
Measure RF levels at the
RF switch, U402, and
compute switch loss.
700: output side of C402 &
input side of C409.
Yes
No
Replace
FL401
Yes
loss.
Check digital logic
No
to the RF switch
and replace U404 if
needed.
Yes
Gain about
10 dB?
Measure RF levels at the
RF switch, U403, and
compute switch loss.
700: output side of R406 &
input side of C411.
Yes
Loss < 1 dB?
No Replace
FL402
Yes
Check digital logic
No
to the RF switch
and replace U405 if
needed.
Yes
No
7
Yes
Note: RF Test frequency used:
3
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.
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U402 if
needed.
No
6
Yes
Check digital logic
No
to the RF switch
and replace U403 if
needed.
Troubleshooting Charts: RX RF Failure