Motorola APX 5000 Service Manual page 151
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- Service manual (318 pages) ,
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- User manual (45 pages)
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Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 11
15
Remove shield, SH3.
Measure RF levels at first
preselector filter and
compute filter loss.
UHF: Input side of C2035
& output side of C2039.
Loss < 3.5
dB?
Measure RF levels at LNA
and compute LNA gain.
UHF: Input side of C2033
and output side of C2044.
Gain about
18 dB?
Measure RF levels at second
preselector filter and compute
filter loss.
UHF: input side of C2059 &
output side of C2061.
Loss < 5
dB?
Remove shield, SH5A. Measure
RF levels at the filter and
compute filter loss. Output
side of C2061 and output side
of C510.
Filter Loss
< 3 dB?
8
Check components
No
and replace defective
parts.
Autotune the radio.
Yes
No
Yes
Check components
No
and replace defective
parts.
Autotune the radio.
Yes
Visually inspect
No
and replace
components if
necessary.
Yes
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
UHF2: 485.075 MHz
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 LNA:
Check DC bias voltages of
U2032 at the base (pin 1) &
collector (pin 3).
Is base voltage =
0.787 V? Collector
voltage = 1.56 V?
Yes
Check DC bias voltages of
Q2022 at the base (pin 2 or
5), collector (pin 3) & emitter
(pin 4).
Is base voltage = 1.022
V? Collector voltage =
0.787 V? Emitter
voltage = 1.561 V?
Yes
Check DC input line voltages
and visually inspect and
replace defective
components if needed.
5-45
No
Replace
U2032
No
Replace
Q2022
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Troubleshooting
