Troubleshooting Flow Chart For Receiver (Models With Pcb 8486686Z02) (Sheet 2 Of 2) - Motorola GP Series Detailed Service Manual

2-4
4.0 Troubleshooting Flow Chart for Receiver (Models with PCB
8486686Z02) (Sheet 2 of 2)
B
Inject RF into J101
IF Signal at
L311?
No
RF Signal
at T301?
No
RF Signal
at C310?
No
RF Signal
at C307?
No or
weak RF
RF Signal
at C301?
No
Check harmonic filters L101 & L102 and
ant. switches CR101, CR102, L104
Trace IF signal
Yes
from L311 to
Q302. Check for
bad XTAL filter.
Yes
1st LO O/P
OK?
Locked?
Yes
Yes
Check filter between
C310 & T301.
Yes
Check RF amp (Q301)
Stage.
Check filter between
C301 & C307; program
Yes
filter to schematic test
freq and check varactor
voltages.
No
Check FGU
Check T301, T302,
CR306, R308, R309
Are varactor
voltages OK?
No
Check U404 voltage.
U404 can be selected by
MCU before replacing
U404.
TROUBLESHOOTING CHARTS
Q302 collec-
Yes
tor OK?
IF signal
present?
Before replacing
U301, check
U301 voltages;
No
trace IF signal
Yes
Check for 3.0
VDC
No
Yes
Is R5
present?
No
Check Q210, U201
(pin 48) voltages and
U247
Yes
Check varactor filter.
path.
A
A