Troubleshooting Flow Chart For Receiver (Sheet 2 Of 2) - Motorola GP320 Service Information

3-2
2.0

Troubleshooting Flow Chart for Receiver (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
Yes
& C307; program filter to
schematic test freq and
check varactor voltages.
No
Check FGU
Check T301, T302, CR306,
R308, R309, R310
Are varactor
voltages OK?
No
Check U404 voltage. U404
can be selected by MCU
before replacing U404.
TROUBLESHOOTING CHARTS
Q302
collector OK?
IF signal
present?
Before replacing
U301, check
No
U301 voltages;
trace IF signal
Yes
Check for 2.6
VDC
No
Is R5
Yes
present?
No
Check Q210, U201 (pin
48) voltages
and U247
Yes
Check varactor filter.
Yes
path.
A
A