LG LH-CX640 Series Service Manual page 4

1-3
IMPORTANT
SAFETY
NOTICE
This
manual
was
prepared
for
use
only
by
properly
trained
audio-video
service
technicians.
When
servicing
this
product, under
no
circumstances
should
the
original
design
be
modified
or
altered
without
permission
from LG
Electronics
Corporation.
All
components
should be
replaced
only with
types identical
to
those
in
the
original
circuit
and
their
physical
location,
wiring
and lead
dress
must
conform
to
original
layout
upon
completion
of
repairs.
Special components are also
used to
prevent
x-radiation,
shock
and fire
haz-
ard.
These components are indicated
by
the letter
\"x\"
included in
their
compo-
nent
designators and
are
required to
maintain
safe
performance. No
deviations
are
allowed
without
prior
approval
by LG
Electronics
Corporation.
Circuit
diagrams
may
occasionally
differ
from
the
actual
circuit
used.
This
way,
implementation of
the
latest
safety
and
performance
improvement
changes
into
the
set
is
not
delayed until
the
new
service
literature
is printed.
CAUTION: Do not
attempt
to
modify this
product
in
any
way. Never
perform
customized
installations
without
manufacturer's
approval.
Unauthorized
modi-
fications
will not
only void
the
warranty, but
may
lead to
property
damage
or
user
injury.
Service work
should be
performed
only after
you are
thoroughly
familiar with
these
safety
checks
and
servicing
guidelines.
GRAPHIC
SYMBOLS
The
exclamation
point
within
an
equilateral
triangle
is
intended to
alert
the service
personnel
to
important
safety
information in
the
service
literature.
The
lightning flash
with
arrowhead
symbol
within
an
equilateral
tri-
angle is
intended to alert
the service
personnel
to
the
presence
of
noninsulated
\"dangerous
voltage\"
that
may be
of
sufficient
magni-
tude to
constitute
a
risk of
electric
shock.
The
pictorial
representation
of
a
fuse
and its
rating within
an
equi-
lateral
triangle
is
intended to convey to
the service
personnel
the
following fuse
replacement
caution notice:
CAUTION:
FOR CONTINUED
PROTECTION
AGAINST
RISK
OF
FIRE,
REPLACE ALL
FUSES
WITH
THE
SAME
TYPE
AND
RATING
AS MARKED
NEAR
EACH
FUSE.
SERVICE
INFORMATION
While
servicing,
use
an
isolation
transformer
for
protection
from
AC line shock.
After
the
original
service
problem
has
been
corrected,
make
a
check
of
the fol-
lowing:
FIRE
AND
SHOCK
HAZARD
1. Be
sure
that all
components
are
positioned
to
avoid a
possibility
of
adjacent
component shorts.
This
is
especially
important
on
items
trans-ported
to
and
from
the repair
shop.
2.
Verify
that
all
protective
devices
such
as
insulators,
barriers,
covers, shields,
strain reliefs, power
supply
cords,
and other
hardware
have
been
reinstalled
per
the
original
design.
Be
sure
that
the
safety
purpose
of
the
polarized line
plug
has
not been defeated.
3.
Soldering
must
be
inspected to discover
possible
cold
solder
joints,
solder
splashes, or
sharp
solder
points.
Be
certain to remove
all
loose
foreign
par-
ticles.
4.
Check
for
physical
evidence
of
damage
or
deterioration to
parts
and
compo-
nents,
for
frayed
leads
or
damaged
insulation
(including
the
AC
cord),
and
replace
if
necessary.
5. No
lead
or
component
should touch a
high
current
device
or
a
resistor rated
at
1
watt or
more.
Lead
tension
around
protruding
metal
surfaces must be
avoided.
6.
After
reassembly
of
the set,
always
perform
an AC leakage
test on
all
exposed
metallic
parts
of
the
cabinet (the channel
selector
knobs,
antenna
terminals,
handle
and
screws)
to be
sure
that
set is
safe to operate
without
danger
of
electrical shock. DO
NOT
USE
ALINE
ISOLATION
TRANS-
FORMER
DURING
THIS
TEST.
Use
an
AC
voltmeter
having
5000
ohms
per
volt or
more sensitivity
in
the
following manner:
Connect
a 1500
ohm,
10
watt
resistor,
paralleled by
a .15
mfd
150V
AC
type
capacitor
between a
known
good
earth
ground
water pipe, conduit, etc.)
and
the
exposed metal-
lic
parts,
one at a time. Measure
the AC
voltage
across
the
combination of
1500
ohm resistor
and
.15
mfd
capacitor.
Reverse
the AC
plug by
using
a
non-polarized
adaptor
and repeat AC voltage
measurements
for
each
exposed metallic
part.
Voltage
measured must not
exceed
0.75
volts
RMS.
This corresponds to 0.5
milliamp
AC.
Any value
exceeding
this limit
consti-
tutes a
potential
shock
hazard
and
must
be
corrected
immediately.
TIPS
ON
PROPER
INSTALLATION
1. Never install
any
receiver
in
a
closed-in recess,
cubbyhole,
or
closely
fitting
shelf
space
over,
or
close to, a heat duct,
or in
the
path of
heated air
flow.
2. Avoid
conditions
of
high
humidity
such
as:
outdoor
patio
installations
where
dew
is
a
factor,
near
steam
radiators
where
steam leakage is a
factor,
etc.
3. Avoid
placement
where draperies
may
obstruct
venting. The
customer
should
also
avoid
the
use
of
decorative
scarves
or
other
coverings that
might
obstruct
ventilation.
4.
Wall-
and
shelf-mounted
installations
using a commercial
mounting
kit
must
follow
the
factory-approved
mounting
instructions. Aproduct mounted to a
shelf
or platform
must
retain
its
original feet
(or
the
equivalent
thickness
in
spacers)
to
provide
adequate
air flow
across
the
bottom.
Bolts or
screws
used
for
fasteners
must not touch
any
parts or wiring. Perform
leakage
tests
on
customized
installations.
5.
Caution
customers
against
mounting
a
product
on
a
sloping
shelf or in
a
tilt-
ed
position,
unless
the
receiver is properly
secured.
6.
Aproduct
on a
roll-about
cart
should be stable
in
its
mounting to
the
cart.
Caution
the
customer on
the
hazards of
trying to
roll
a
cart
with
small
cast-
ers
across
thresholds
or
deep
pile
carpets.
7.
Caution
customers
against
using
extension cords.
Explain
that
a
forest of
extensions,
sprouting from
a
single outlet, can lead to disastrous
conse-
quences
to
home
and
family.
A.C. Voltmeter
1500
OHM
10
WATT
Place
this probe
on
each
exposed
metal part.
Good
Earth
Ground
such
as
the
Water
Pipe,
Conduit, etc.
0.15uF
PRODUCT
SAFETY
SERVICING
GUIDELINES
FOR
VIDEO
PRODUCTS