Motorola APX 1000 Detailed Service Manual page 136

5-38
RX RF Failure – Page 5
Remove shield, SH16.
Measure RF levels at the
RF switch, U402, and
compute switch loss.
800: output side of C402 &
input side of R450.
Measure RF levels at the SAW filter,
FL401, and compute filter loss.
800: output side of R450 and output
Measure RF levels at the RF
switch, U404, and compute switch
800: output side of C412 & output
Measure RF levels at LNA
and compute LNA gain.
800: input side of C423 and
output side of R406.
Measure RF levels at the
RF switch, U403, and
compute switch loss.
800: output side of R406 &
input side of R452.
Measure RF levels at the SAW filter,
FL402, and compute filter loss.
800: output side of R452 and input
Measure RF levels at the RF
switch, U405, and compute switch
800: output side of R454 & input
Measure RF levels at LNA
and compute LNA gain.
800: input side of C430 and
output side of R412.
4
Check digital logic
No
to the RF switch
Loss < 2 dB?
and replace U402 if
needed.
Yes
side of C412.
No
Replace
Loss < 2 dB?
FL401
Yes
loss.
side of C487.
Check digital logic
No
to the RF switch
Loss < 2 dB?
and replace U404 if
needed.
Yes
No
Gain about
6
8 dB?
Yes
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U403 if
needed.
side of R454.
No
Replace
Loss < 3 dB?
FL402
Yes
loss.
side of C430.
Check digital logic
No
to the RF switch
Loss < 1 dB?
and replace U405 if
needed.
Yes
No
Gain about
7
8 dB?
Yes
5
Troubleshooting Charts: RX RF Failure
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
UHF2: 485.075MHz
700: 769.0625MHz
800: 860.0625MHz
900: 938.0625MHz
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.