Motorola LB3 (42.0 - 50.0MHz) 서비스 정보 - 페이지 19

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Motorola LB3 (42.0 - 50.0MHz) 서비스 정보
Troubleshooting Flow Chart for Receiver

Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)

B
Inject RF into J1401
IF
Signal at
pin 2 of
U1051
?
No
RF
Signal at
pin 3 of
U1051
?
No
RF
Signal at
C1017
?
No
RF
Signal at
C1013
?
No or
weak RF
RF
Signal at
C1002
?
No
Check harmonic filters J1401
and ant.switch
Trace IF signal
Yes
from C1036 to
Q1106. Check for
bad XTAL filter.
Yes
1st
LO level OK?
Locked
?
Yes
Yes
Check filter between
C1017 & mixer U1051
Yes
Check RF amp (Q1001)
Stage.
Yes
Check preselector
and RF amp.
No
Check FGU
Check for detailed mixer.
IF
signal at
Yes
Q1106
collector
?
Before replacing
U1103, check
U1103 voltages.
No
Is
Yes
9V3 present
?
No
Check Supply Voltage
circuitry. Check U0681,
U3211 and U0641.
3-3
A