Motorola MTX series - Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)

8-44 Maintenance: 800 MHz Troubleshooting Charts
8.14.3 Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
RF Signal at
the input of
FL300?
IF Signal at
L353?
No
RF Signal at
pin 8 of U301?
RF Signal at
CR300?
No
No or
Check harmonic filter L101 &
L102 CR101, CR102, and
CR300
Inject RF into J101
No
Ye s
Check RF amp
(Q302) Stage.
Replace filter
FL301
Ye s
Check U301, R320,
R321, R322
Ye s
1st LO O/P
OK?
Locked?
Ye s
Check FGU
Ye s
Trace IF signal from
L353 to U352.
Check for bad XTAL
filter.
No
Ye s
Is the level of the
IF signal of the
output of U352 as
indicated?
Before replacing
U351, check U351
voltages; trace IF
signal path.
Ye s
Is the biasing of
U352 OK?
Is R5 present?
Check Q210, U201
(pin 48) voltages
and U247
No
No
No
Ye s
Ye s
A
B
weak RF
RF Signal at
C317?
No
Replace
U352.
Are the
AGC voltages
without RF as
indicated?
Ye s
Check U302,
U350, and CR301
Replace
FL300.
No or
weak RF