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Internal Use Only
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LCD TV
SERVICE MANUAL
CHASSIS : LA05E
MODEL : 37LV555H 37LV555H-UA
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL67121705 (1111-REV00) Printed in Korea
CONTENTS
CONTENTS .............................................................................................. 2
SAFETY PRECAUTIONS ......................................................................... 3
SPECIFICATION ....................................................................................... 6
ADJUSTMENT INSTRUCTION .............................................................. 12
EXPLODED VIEW .................................................................................. 21
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 1.5K/10watt resistor in parallel with a 0.15uF 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, 0.5mA.
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 1W), keep the resistor 10mm away from PCB.
Leakage Current Hot Check circuit
Keep wires away from high voltage or high temperature parts.
AC Volt-meter
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 Good Earth Ground
shock. such as WATER PIPE,
To Instrument's CONDUIT etc.
0.15uF
Leakage Current Cold Check(Antenna Cold Check) exposed
METALLIC PARTS
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 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.
If the exposed metallic part has a return path to the chassis, the
measured resistance should be between 1M and 5.2M.
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 unit under test.
manual and its supplements and addenda, read and follow the 2. After removing an electrical assembly equipped with ES
SAFETY PRECAUTIONS on page 3 of this publication. devices, place the assembly on a conductive surface such as
NOTE: If unforeseen circumstances create conflict between the aluminum foil, to prevent electrostatic charge buildup or
following servicing precautions and any of the safety precautions on exposure of the assembly.
page 3 of this publication, always follow the safety precautions. 3. Use only a grounded-tip soldering iron to solder or unsolder ES
Remember: Safety First. devices.
4. Use only an anti-static type solder removal device. Some solder
General Servicing Precautions removal devices not classified as "anti-static" can generate
1. Always unplug the receiver AC power cord from the AC power electrical charges sufficient to damage ES devices.
source before; 5. Do not use freon-propelled chemicals. These can generate
a. Removing or reinstalling any component, circuit board electrical charges sufficient to damage ES devices.
module or any other receiver assembly. 6. Do not remove a replacement ES device from its protective
b. Disconnecting or reconnecting any receiver electrical plug or package until immediately before you are ready to install it.
other electrical connection. (Most replacement ES devices are packaged with leads
c. Connecting a test substitute in parallel with an electrolytic electrically shorted together by conductive foam, aluminum foil
capacitor in the receiver. or comparable conductive material).
CAUTION: A wrong part substitution or incorrect polarity 7. Immediately before removing the protective material from the
installation of electrolytic capacitors may result in an leads of a replacement ES device, touch the protective material
explosion hazard. to the chassis or circuit assembly into which the device will be
installed.
2. Test high voltage only by measuring it with an appropriate high CAUTION: Be sure no power is applied to the chassis or circuit,
voltage meter or other voltage measuring device (DVM, and observe all other safety precautions.
FETVOM, etc) equipped with a suitable high voltage probe. 8. Minimize bodily motions when handling unpackaged
Do not test high voltage by "drawing an arc". replacement ES devices. (Otherwise harmless motion such as
3. Do not spray chemicals on or near this receiver or any of its the brushing together of your clothes fabric or the lifting of your
assemblies. foot from a carpeted floor can generate static electricity
4. Unless specified otherwise in this service manual, clean sufficient to damage an ES device.)
electrical contacts only by applying the following mixture to the
contacts with a pipe cleaner, cotton-tipped stick or comparable General Soldering Guidelines
non-abrasive applicator; 10% (by volume) Acetone and 90% (by 1. Use a grounded-tip, low-wattage soldering iron and appropriate
volume) isopropyl alcohol (90%-99% strength) tip size and shape that will maintain tip temperature within the
CAUTION: This is a flammable mixture. range or 500