System/Key Circuit - LG LH-CX640 Series Service Manual

3-6
2.
SYSTEM/KEY
CIRCUIT
(1)
AUTO
STOP
(2)
The
unstable
loading of
a
Cassette
tape
Auto
Stop
Does
the
SW25
waveform
appear
at
the
IC501
Pin105?
Do
the
T-UP Reel
Pulses
appear
at
the
IC501
Pin49?
Is
12V
applied
to
the
PMC01
Pin8?
Check
the
Drum
Motor
signal.
Does
5.2V
appear at
the
RS501?
Check
the
Power
Circuit.
Check
the
Power.
Is
5.3V
applied
to
the
R544
?
Refer to
SMPS
5.3VA
troubleshooting.
Check
the
IC501
Pins68,
69,
70,
71.
Do
T/UP
Reel
Pulses
appear
at
the Q514
Base
terminal
?
Replace
the
T/UP
Reel
Sensor
(RS501).
Check
the
CST
SW
and
the
peripheral
circuitry.
Replace
the
IC501.
The
unstable
loading
of
a
Cassette
tape
Does
the
\"H\"
signal
appear
at
the
IC501
Pin30
during
inserting
the
CST
?
Does
the
\"L\"
signal
appear
at
the
IC501
Pin72
during
inserting
the
CST?
Check
the
Deck
Mechanism.
Caution
:
Auto
stop
can
occur
because
Grease
or Oil
is
dried
up
YES
YES
YES
NO
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES