Motorola APX 3000

5-30 Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 4
3
Remove shield, SH9.
Measure RF levels at the
RF switch, U402, and
compute switch loss.
700: o utput sid e o f C402
& input side of R451.
Loss < 1 dB?
No
Measure RF levels at the SAW
f ilter, FL401, and co mpute f ilter
loss.
700: Output side of R451 and
outp ut sid e of C413.
Loss < 3 dB?
No
Replace
FL401
Measure RF levels at the RF
switch, U404, and co mpute
switch loss.
700: o utput sid e o f C413 &
outp ut sid e of C487.
Loss < 1 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
No
Yes
Yes
Measure RF levels at the
RF switch, U403, and
compute switch loss.
700: o utput sid e o f R406
& input side of R453.
Loss < 1 dB?
No
Measure RF levels at the SAW
f ilter, FL402, and co mpute f ilter
loss.
700: Output side of R453 and inp ut
side of R455.
Loss < 6 dB?
No
Measure RF levels at the RF
switch, U405, and co mpute
switch loss.
700: o utput side of R455 & 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
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:
UHF1: 424.975MHz
UHF2: 485.075MHz
VHF: 154.275MHz
700: 769.0625MHz
800: 860.0625MHz
Measured with a High Frequency Prob e f or relative comp arisons and troub leshooting
only. Actual S21 gain or lo ss may d if f er if the test p oint is not 50 ohms.