Y/Ccircuit - LG LH-CX640 Series Service Manual

3-10
4.
Y/C
CIRCUIT
(1)
No
Video
in
EE
Mode,
No
Video
in
EE
Mode
Check
the
24Pin of
Tuner.
Doesthe
Video
signal
appear
at
the
IC301
Pin48?
Is
5V
applied
to
the
IC301
Pins18,
24,
42,
55,72,
91?
Does
the
Video
signal
appear
at
the
IC301
Pin65?
Does
the
Video
signal
appear
at
the
IC501
Pin19?
Does
the
Video
signal
appear
at
the
Emitter
termi-
nal of
the
Q307,
Q308?
Check the
5.2VT,
5.3VA
Line.
(Power
Circuit)
Is I2C
BUS
signal
applied
to
the
IC301
Pins68,
69?
Check
C316.
(AGC)
Chck
the
path
of
the
signal
betweenthe
IC301
Pin65
and
IC501
Pin17.
Replace
the
IC301.
Doesthe
12VT,
5.3VA
appear
at
the Emitter
termi-
nal of
the
Q804,
Q308.
Replace
t he
Q804,
Q308.
Check
the
12VT, 5.3VA
Line.
(Power
Circuit)
Check
the
System
Circuit.
(Refer to
'SYSTEM
I2C
BUS
CHECK
Trouble
Shooting')
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO