Service manual

800 MHz Troubleshooting Charts 3-29
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
Yes
Check RF amp
(Q302) Stage.
Replace filter
FL301
Yes
Check U301, R320,
R321, R322
Yes
1st LO O/P
OK?
Locked?
Yes
Check FGU
Yes
Trace IF signal from
L353 to U352.
Check for bad XTAL
filter.
No
Yes
Is the level of the
IF signal of the
output of U352 as
indicated?
Before replacing
U351, check U351
voltages; trace IF
signal path.
Yes
Is the biasing of
U352 OK?
Is R5 present?
Check Q210, U201
(pin 48) voltages
and U247
No
No
No
Yes
Yes
A
B
weak RF
Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
RF Signal at
C317?
No
Replace
U352.
Are the AGC
voltages
without RF
as indi-
cated?
Yes
Check U302,
U350, and CR301
Replace
FL300.
No or
weak RF