Motorola GP1280 Series Service Information - Page 24
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3-2
2.0
Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
B
Inject RF into J3501
IF Signal
at C3200?
No
RF
Signal
at T3301
?
No
RF
Signal
at R3313
?
No
RF
Signal
at C3306
?
No or
weak RF
RF
Signal
at C3302
?
No
Check harmonic filters L3531 & L3532,
C3532 and ant. switches D3521, D3551,
L3551, R3551,C3551, C3552, L3552.
Trace IF signal
Yes
from C3200 to
Q3200. Check for
bad XTAL filter.
Yes
1st LO O/P
OK?
Locked?
Check T3301, T3302, CR3301,
Yes
R3321, R3322, R3320
Yes
Check filter between
C3313 & T3301.
Yes
Check RF amp
(Q3302) Stage.
Check filter between
Yes
C3302 & C3306; program
filter to schematic test freq
and check varactor
voltages.
No
Check FGU
Are
varactor
voltages
OK
?
No
Check U404 voltage. U404
can be selected by MCU
before replacing U404.
TROUBLESHOOTING CHARTS
Q3200
collector OK?
Yes
IF signal
present?
Before replacing
U3220, check
No
U3220 voltages;
trace IF signal
Yes
Check for 2.9
VDC
No
Is R5
Yes
present
?
No
Check Q3721, U3701
(pin 48) voltages
and U3711
Yes
Check varactor filter.
path.
A
A