Motorola Professional GP640 Service Information - Page 22

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Motorola Professional GP640 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 Þlters L101 & L102
and ant. switches CR101, CR102, L104
Trace IF signal
Yes
from L311 to
Q302. Check for
bad XTAL Þlter.
Yes
1st LO O/P
OK?
Locked?
Check T301, T302, CR306,
Yes
Yes
Check Þlter between
C310 & T301.
Yes
Check RF amp
(Q301) Stage.
Check Þlter between C301
Yes
& C307; program Þlter to
schematic test freq and
check varactor voltages.
No
Check FGU
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?
Yes
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 Þlter.
path.
A
A