LG 24LH4830, Service Manual

- 3 -

LGE Internal Use Only

Copyright  © 

 ~ 

 LG Electronics. Inc. 

All right reserved. 

Only for training and service purposes

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 

1W

), keep the resistor 10mm 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 1M

Ω

 and 5.2M

Ω

. 

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 1.5K/10watt resistor in parallel with a 0.15uF 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 

0.5mA.

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

1.5 Kohm/10W

0.15µF

To Instrument's

exposed 

METALLIC PARTS

Good Earth Ground

such as WATER PIPE,

CONDUIT etc.

AC Volt-meter

When 25A is impressed between Earth and 2nd Ground

for 1 second, Resistance must be less than 0.1

*Base on Adjustment standard

IMPORTANT SAFETY NOTICE

SAFETY PRECAUTIONS