LG LH-CX640 Series Service Manual page 28

3-11
(2)
When
the
Y(Luminance)
signal
doesn't
appear
on
the
screen
in
PB
Mode,
Is
5.2VT, 5.3VAapplied
to
the
IC301
Pins24,
42,
55, 72,
91?
Is the
I2C
Bus
siganl
applied
to
the
IC301
Pins68,
69 ?
Does
the
normal
RF
signal
appear at
the
IC301
Pin78?
Check
the
line
of
the
5.2VT,
5.3VALine.
(Power
Circuit)
Check
the
System
Circuit.
(IC501
Pin105)
Checkthe
V.H.S/W
level.
(Check
R303,
R304)
Replace
the
IC301.
Refer
to
'SYSTEM I2C
BUS
CHECK
Trouble
Shooting'.
Isthe
V.H.S/W
signal
applied
to
the
IC301
Pin70?
Is
V.H.S/W
\"H\"
about
3.4V
at
the
IC301
Pin70?
Clean
the
Drum.
Check
the
path of
the
Y(Luminance)
RF
signal.
(Check
C327)
Check
the path of
the
Y(Luminance)
RF
signal.
(Check
the
C312)
Does the
Y(Luminance)
RF
signal
appear
at
the
IC301
Pin76?
Is the
Y(Luminance)
Video
waveform
showed
up at
theIC301
Pin43?
Replace the
IC301.
NO
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES