Servo Circuit - LG LH-CX640 Series Service Manual

3-7
3.
SERVO
CIRCUIT
(1)
UnstableVideo
in
PB
MODE
Unstable
Video
in
PB
Mode.
Does
the
Noise
level
of
the
screen
change
periodically?
Do
the CTL
pulses
appear
at
the
IC501
Pin8?
Is adjusting
the height of
the CTL
Head
accurate?
Readjust
the
height
of
the
CTL
Head.
Replace the
IC501.
Refer
to
\"When
the Y
signal
doesn't
appear on the
screen
in
PB
Mode\".
Does
the
CFG
waveform
appear
at
the
IC501
Pin9?
On
tracking
do the CTL
pulses move?
Does
the
Video
Envelope
waveform
appear
at
the
IC501
Pin24?
Replace
the
IC501.
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
(2)
When
the
Drum
Motor
doesn't
run.
Do
the
DFG
Pulses
appear
at
the
PMC01
Pin11?
Replace
t he
Cap
M.
Aren't
the
foil
patterns
and
the
Components
between
IC501
Pin104
and
PMC01
Pin11
short?
Replace
the
IC501.
Refer
to
\"(2)
No
12VAof
Power
section\"
Do the
Drum
PWM Pulses
appear
at
the
IC501
Pin107?
Aren't
the
foil
patterns
and
the
Components
between
IC501 Pin107
and
PMC01
Pin12
short?
Do
the
DFG
Pulses
appear
at
the
IC501
Pin104?
Do
the
Drum
PWM
Pulses
appear
at
the
IC501
Pin107?
Aren't
the
connecting
patterns
and
the
Components
between
IC501 Pin107
and
PMC01
Pin12
short?
When
the
Drum
Motor
doesn't
run,
Does
12V
appear
at
the
PMC01
Pin8?
Does
2.8V
appear
at
the
PMC01
Pin12?
Check
the
connector
(PMC01)
and
the
Drum
Motor
Ass'y.
NO
YES
YES
YES
NO
NO
NO
NO
NO
YES
YES
YES