Text preview for : lg_42ld840-sa_chassis_lj03b.pdf part of LG lg 42ld840-sa chassis lj03b LG LCD 42LD840 Chassis LJ03B lg_42ld840-sa_chassis_lj03b.pdf
Back to : lg_42ld840-sa_chassis_lj0 | Home
Internal Use Only
North/Latin America http://aic.lgservice.com
Europe/Africa http://eic.lgservice.com
Asia/Oceania http://biz.lgservice.com
LCD TV
SERVICE MANUAL
CHASSIS : LJ03B
MODEL : 42LD840 42LD840-SA
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL63261822 (1010-REV01) Printed in Korea
CONTENTS
CONTENTS .............................................................................................. 2
PRODUCT SAFETY ................................................................................. 3
SPECIFICATION ....................................................................................... 6
ADJUSTMENT INSTRUCTION .............................................................. 10
EXPLODED VIEW .................................................................................. 18
SVC. SHEET ...............................................................................................
Copyright LG Electronics. Inc. All right reserved. -2- 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
Schematic Diagram and 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 Leakage Current Hot Check (See below Figure)
Plug the AC cord directly into the AC outlet.
An isolation Transformer should always be used during the
servicing of a receiver whose chassis is not isolated from the AC Do not use a line Isolation Transformer during this check.
power line. Use a transformer of adequate power rating as this Connect 1.5 K / 10 watt resistor in parallel with a 0.15 uF capacitor
protects the technician from accidents resulting in personal injury between a known good earth ground (Water Pipe, Conduit, etc.)
from electrical shocks. and the exposed metallic parts.
Measure the AC voltage across the resistor using AC voltmeter
It will also protect the receiver and it's components from being with 1000 ohms/volt or more sensitivity.
damaged by accidental shorts of the circuitry that may be Reverse plug the AC cord into the AC outlet and repeat AC voltage
inadvertently introduced during the service operation. measurements for each exposed metallic part. Any voltage
measured must not exceed 0.75 volt RMS which is corresponds to
If any fuse (or Fusible Resistor) in this TV receiver is blown, 0.5 mA.
replace it with the specified. In case any measurement is out of the limits specified, there is
possibility of shock hazard and the set must be checked and
When replacing a high wattage resistor (Oxide Metal Film Resistor, repaired before it is returned to the customer.
over 1 W), keep the resistor 10 mm away from PCB.
Leakage Current Hot Check circuit
Keep wires away from high voltage or high temperature parts.
Before returning the receiver to the customer, AC Volt-meter
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 Good Earth Ground
shock. such as WATER PIPE,
To Instrument's CONDUIT etc.
0.15 uF
Leakage Current Cold Check(Antenna Cold Check) exposed
With the instrument AC plug removed from AC source, connect an METALLIC PARTS
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 1.5 Kohm/10W
plug prongs tied together and touch other ohm-meter lead in turn to
each exposed metallic parts such as antenna terminals, phone
jacks, etc. When 25A is impressed between Earth and 2nd Ground
If the exposed metallic part has a return path to the chassis, the for 1 second, Resistance must be less than 0.1
measured resistance should be between 1 M and 5.2 M.
*Base on Adjustment standard
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.
Copyright LG Electronics. Inc. All right reserved. -3- LGE Internal Use Only
Only for training and service purposes
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service 2. After removing an electrical assembly equipped with ES
manual and its supplements and addenda, read and follow the devices, place the assembly on a conductive surface such as
SAFETY PRECAUTIONS on page 3 of this publication. aluminum foil, to prevent electrostatic charge buildup or
NOTE: If unforeseen circumstances create conflict between the exposure of the assembly.
following servicing precautions and any of the safety precautions on 3. Use only a grounded-tip soldering iron to solder or unsolder ES
page 3 of this publication, always follow the safety precautions. devices.
Remember: Safety First. 4. Use only an anti-static type solder removal device. Some solder
removal devices not classified as "anti-static" can generate
General Servicing Precautions electrical charges sufficient to damage ES devices.
1. Always unplug the receiver AC power cord from the AC power 5. Do not use freon-propelled chemicals. These can generate
source before; electrical charges sufficient to damage ES devices.
a. Removing or reinstalling any component, circuit board 6. Do not remove a replacement ES device from its protective
module or any other receiver assembly. package until immediately before you are ready to install it.
b. Disconnecting or reconnecting any receiver electrical plug or (Most replacement ES devices are packaged with leads
other electrical connection. electrically shorted together by conductive foam, aluminum foil
c. Connecting a test substitute in parallel with an electrolytic or comparable conductive material).
capacitor in the receiver. 7. Immediately before removing the protective material from the
CAUTION: A wrong part substitution or incorrect polarity leads of a replacement ES device, touch the protective material
installation of electrolytic capacitors may result in an to the chassis or circuit assembly into which the device will be
explosion hazard. installed.
CAUTION: Be sure no power is applied to the chassis or circuit,
2. Test high voltage only by measuring it with an appropriate high and observe all other safety precautions.
voltage meter or other voltage measuring device (DVM, 8. Minimize bodily motions when handling unpackaged
FETVOM, etc) equipped with a suitable high voltage probe. replacement ES devices. (Otherwise harmless motion such as
Do not test high voltage by "drawing an arc". the brushing together of your clothes fabric or the lifting of your
3. Do not spray chemicals on or near this receiver or any of its foot from a carpeted floor can generate static electricity
assemblies. sufficient to damage an ES device.)
4. Unless specified otherwise in this service manual, clean
electrical contacts only by applying the following mixture to the General Soldering Guidelines
contacts with a pipe cleaner, cotton-tipped stick or comparable 1. Use a grounded-tip, low-wattage soldering iron and appropriate
non-abrasive applicator; 10 % (by volume) Acetone and 90 % tip size and shape that will maintain tip temperature within the
(by volume) isopropyl alcohol (90 % - 99 % strength) range or 500