Motorola APX 6000 Service Manual

Troubleshooting Charts: RX RF Failure 5-35
5.18 RX RF Failure – Page 1
Inject a carrier wave with -47dBm
into antenna port. Remove shield,
SH6A. Use a spectrum analyzer
and high-impedance RF probe to
measure the IF signal at the input
side of C601 going to the Abacus.
IF Frequency =
109.65 MHz?
Testing a
UHF1 or
UHF2?
Poor RX
sensitivity or
no RX audio
No
No
Remove shield, SH5A. IF level
at the mixer (output side of
series resistor, R511) about:
VHF: -44 dBm?
UHF1: -45 dBm?
UHF2: -45 dBm?
700: -48 dBm?
800: -45 dBm?
Yes
Yes
Yes
1
Yes
Yes
Remove shield, SH11.
Measure RF input level at the
antenna port (input side of
C1301).
RF level
about -49
dBm?
Remove shield, SH13 for 700/800
or SH10 for UHF1 and UHF2.
Measure RF levels at the input side
of C1301 and the input side of L1108,
compute RF switch, U1111 loss.
(Skip if VHF).
Yes
RF switch
loss ~ 1 dB?
Check digital logic
to the RF switch
and replace U1111
if needed.
No
Measure RF levels at the output side of L1108 and
the input side of C1122, compute RF switch, U1102
loss.
Note: The 15 dB attenuator in the RF switch will be
enabled.
RF switch
loss <17dB?
No
Yes
Yes
Testing a
VHF
radio?
Measure RF level at
output side of C1149
and Pin 3 on U1149.
Yes
Testing a
7/800
radio?
Testing a
radio?
Testing a
700
channel?
No
No
Yes
Yes
Loss ~ 15 dB?
No
2
No
3
4
Inspect coaxial
antenna connector
and cable
assembly
Visual
inspection
OK?
Replace
bad part
Bad antenna
connector.
Replace cable
assembly.
No
No
Yes
No
Check digital logic
to the RF switch
and replace U1102
if needed.
Check logic on
attenuator U1149
and replace
if needed.
UHF1 or UHF2
15
Remove SH5A.
Measure the LO
power going into the
mixer, U506, at the
output side of C599.
Remove shield, SH7.
Check the polarity
of T505 and check
to see that all pins
are grounded.
Visually inspect
windings
Remove SH7.
Measure the LO
power going into the
mixer, U506, at the
output side of C528.
Is the LO power
= -5 dBm?
Check FGU and
replace U506 if
needed.
Yes
Yes
No
Testing a
UHF1 or
UHF2?
No
Yes
Replace T505
Check FGU and
replace U506 if
needed.
Is
polarity correct,
all pins gounded
and
windings look ok?
No
Note : RF Test frequency used:
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.

Motorola APX 6000 Specifications

General

Brand	Motorola
Model	APX 6000
Category	Two-Way Radio
Language	English