LG Electronics. Inc. All rights reserved.
LGE Internal Use Only
Only for training and service purposes
SAFETY PRECAUTIONS
IMPORTANT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in
the
Exploded
View.
It is essential that these special safety parts should be replaced with the same components as recommended in this manual to
prevent
Shock, Fire, or other
Hazards.
Do not modify the original design without permission of
manufacturer.
General Guidance
An isolation Transformer should always be used during
the
servicing of a receiver whose chassis is not isolated from the
AC
power line. Use a transformer of adequate power rating as
this
protects the technician from accidents resulting in personal
injury
from electrical
shocks.
It will also protect the receiver and it's components from
being
damaged by accidental shorts of the circuitry that may
be
inadvertently introduced during the service
operation.
If any fuse (or Fusible Resistor) in this TV receiver is
blown,
replace it with the
specified.
When replacing a high wattage resistor (Oxide Metal Film
Resistor,
over 1 W), keep the resistor 10 mm away from
PCB.
Keep wires away from high voltage or high temperature
parts.
Before returning the receiver to the customer,
always perform an AC leakage current check on the
exposed
metallic parts of the cabinet, such as antennas, terminals, etc.,
to
be sure the set is safe to operate without damage of
electrical
shock.
Leakage Current Cold Check(Antenna Cold Check)
With the instrument AC plug removed from AC source, connect
an
electrical jumper across the two AC plug prongs. Place the
AC
switch in the on position, connect one lead of ohm-meter to the
AC
plug prongs tied together and touch other ohm-meter lead in turn
to
each exposed metallic parts such as antenna terminals,
phone
jacks,
etc.
If the exposed metallic part has a return path to the chassis,
the
measured resistance should be between 1 MΩ and 5.2
MΩ.
When the exposed metal has no return path to the chassis
the
reading must be
infinite.
An other abnormality exists that must be corrected before
the
receiver is returned to the
customer.
Leakage Current Hot Check
(See below
Figure)
Plug the AC cord directly into the AC
outlet.
Do not use a line Isolation Transformer during this
check.
Connect
1.5 K / 10 watt resistor in parallel with a 0.15 uF
capacitor
between
a known good earth ground (Water Pipe, Conduit,
etc.)
and the
exposed metallic
parts.
Measure the AC voltage across the resistor using AC
voltmeter
with 1000 ohms/volt or more
sensitivity.
Reverse plug the AC cord into the AC outlet and repeat AC
voltage
measurements for each exposed metallic part. Any
voltage
measured must not exceed 0.75 volt RMS which is corresponds
to
0.5
mA.
In case any measurement is out of the limits specified, there
is
possibility of shock hazard and the set must be checked
and
repaired before it is returned to the
customer.
Leakage Current Hot Check circuit
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