LG LH-CX640 Series Service Manual page 5

1-4
SERVICING
PRECAUTIONS
CAUTION:
Before
servicing
the
HOME
THEATER
COMBI
covered
by
this
service
data
and
its
supplements
and
addends,
read
and
follow
the
SAFETY
PRECAUTIONS.
NOTE:
if
unforeseen
circumstances
create
conflict
between
the
following
servicing
precautions
and
any
of
the
safety
pre-
cautions
in
this
publications,
always
follow
the safety
pre-
cautions.
Remember
Safety
First:
General
Servicing
Precautions
1.
Always
unplug
the
HOME
THEATER
COMBI
AC
power
cord
from
the AC power
source
before:
(1)
Removing
or
reinstalling
any
component,
circuit board,
module,
or any
other
assembly.
(2)
Disconnecting
or
reconnecting
any
internal
electrical
plug
or
other
electrical
connection.
(3)Connecting
a test
substitute
in
parallel
with an
elec-
trolytic
capacitor.
Caution:
Awrong
part
substitution
or
incorrect
polarity
installation of
electrolytic
capacitors
may
result
in
an
explosion
hazard.
2.
Do
not
spray
chemicals
on
or
near
this
HOME
THEATER
COMBI
or
any
of
its
assemblies.
3.
Unless
specified
otherwise
in
this
service
data,
clean
electrical
contacts
by
applying
an
appropriate
contact
cleaning
solution
to
the
contacts
with
a
pipe
cleaner,
cotton-tipped
swab, or
comparable
soft
applicator.
Unless
specified
otherwise
in
this
service
data,
lubrication
of
contacts is
not
required.
4.
Do
not
defeat
any
plug/socket
B+
voltage
interlocks
with
whitch
instruments
covered
by
this
service
manual
might
be
equipped.
5.
Do
not
apply
AC
power to
this
HOME
THEATER
COMBI
and/or
any
of
its
electrical
assemblies
unless
all
solid-state
device
heat
sinks
are correctly installed.
6.
Always
connect
the
test
instrument
ground
lead
to
an
appropriate
ground
before
connecting
the
test
instrument
positive
lead.
Always
remove the
test
instrument
ground
lead
last.
Insulation
Checking
Procedure
Disconnect
the
attachment
plug
from the AC
outlet
and
turn
the
power
on.
Connect
an
insulation
resistance
meter
(500V)
to the
blades of the
attachment
plug.
The
insulation
resis-
tance
betweeneach blade
of
the
attachment
plug
and
acces-
sible
conductive
parts
(Note
1)
should
be more
than
1M-
ohm.
Note
1: Accessible Conductive Parts
include
Metal
panels,
Input
terminals, Earphone jacks,etc.
Electrostatically
Sensitive (ES)
Devices
Some
semiconductor
(solid
state)
devices
can
be
damaged
easily
by
static
electricity.
Such
components
commonly
are
called
Electrostatically
Sensitive
(ES)
Devices.
Examples
of
typical
ES
devices
are
integrated
circuits
and
some
field
effect
transistors
and
semiconductor
chip
components.
The
following
techniques
should
be
used
to
help
reduce the
incidence
of
component
damage
caused
by
static
electricity.
1.
Immediately
before
handling
any
semiconductor
compo-
nent or
semiconductor-equipped
assembly,
drain
off
any
electrostatic
charge on
your
body
by
touching
a
known
earth
ground.
Alternatively,
obtain
and
wear
a
commer-
cially
available
discharging
wrist
strap
device,
which
should
be
removed
for
potential
shock
reasons
prior
to
applying
power
to
the
unit
under
test.
2. After
removing
an
electrical
assembly
equipped
with
ES
devices, place
the
assembly on
a
conductive
surface
such
as
aluminum
foil,
to
prevent
electrostatic
charge
buildup
or
exposure
of
the
assembly.
3.
Use
only
a
grounded-tip
soldering iron
to
solder or unsolder
ES
devices.
4.
Use
only
an
anti-static
solder
removal
device.
Some
solder
removal
devices
not
classified
as
\"anti-static\"
can
generate
electrical
charges
sufficient
to
damage
ES
devices.
5.
Do
not
use
freon-propelled
chemicals.
These
can
generate
an
electrical
charge
sufficient
to
damage
ES
devices.
6.
Do
not
remove
a
replacement
ES
device
from
its
protec-
tive
package
until
immediately
before
you
are ready to
install
it.
(Most
replacement
ES
devices
are packaged
with
leads
electrically
shorted
together
by
conductive
foam,
aluminum
foil,or
comparable conductive
material).
7.
Immediately
before
removing
the
protective
material
from
the
leads of
a
replacement
ES
device,
touch
the
protective
material
to
the
chassis
or
circuit
assembly
into
which
the
device
will
be
installed.
Caution:
Be
sure no power is applied to the
chassis
or
circuit,
and
observe
all
other
safety
precautions.
8.
Minimize
bodily
motions
when
handling
unpackaged
replacement
ES
devices.
(Normally
harmless
motion
such
as the
brushing
together
of
your
clothes
fabric
or
the lifting
of
your
foot
from
a
carpeted
floor
can
generate static
elec-
tricity
sufficient
to
damage
an
ES
device.)