Motorola APX 1000 Detailed Service Manual page 789

Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 4
3
Remove shield, SH16.
Measure RF levels at the
RF switch, U402, and
compute switch loss.
700: output side of C402 &
input side of R451.
No
Check digital logic
to the RF switch
Loss < 1 dB?
and replace U402 if
needed.
Yes
Measure RF levels at the SAW filter,
FL401, and compute filter loss.
700: Output side of R451 and output
side of C413.
No
Replace
Loss < 3 dB?
FL401
Yes
Measure RF levels at the RF
switch, U404, and compute switch
loss.
700: output side of C413 & output
side of C487.
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U404 if
needed.
Yes
Measure RF levels at LNA
and compute LNA gain.
700: input side of C423 and
output side of R406.
No
Gain about
6
10 dB?
Yes
Measure RF levels at the
RF switch, U403, and
compute switch loss.
700: output side of R406 &
input side of R453.
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U403 if
needed.
Measure RF levels at the SAW filter,
FL402, and compute filter loss.
700: Output side of R453 and input
side of R455.
No Replace
Loss < 5 dB?
FL402
Yes
Measure RF levels at the RF
switch, U405, and compute switch
loss.
700: output side of R455 & input
side of C430.
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U405 if
Yes
Measure RF levels at LNA
and compute LNA gain.
700: input side of C430 and
output side of R412.
No
Gain about
7
10 dB?
Yes
5
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
UHF2: 485.075MHz
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.
needed.
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