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website:http://biz.LGservice.com
e-mail:http://www.LGEservice.com/techsup.html
LCD TV
SERVICE MANUAL
CHASSIS : ML-024E
MODEL : RM-15LA70
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
R
CONTENTS
Contents .................................................................................................. 2
Safety Precautions ..................................................................................3
Servicing Precautions ............................................................................ 4
Description of Controls .......................................................................... 6
Adjustment Instruction ............................................................................9
Block Diagram.........................................................................................11
Exploded View ...................................................................................... 13
Exploded View Parts List .......................................................................14
Replacement Parts List ........................................................................ 15
SVC. Sheet .................................................................................................
-2-
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 Replacement Parts List.
It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent
X-RADIATION, Shock, Fire, or other Hazards.
Do not modify the original design without permission of manufacturer.
General Guidance Before returning the receiver to the customer,
An isolation Transformer should always be used during the always perform an AC leakage current check on the exposed
servicing of a receiver whose chassis is not isolated from the AC metallic parts of the cabinet, such as antennas, terminals, etc., to
power line. Use a transformer of adequate power rating as this be sure the set is safe to operate without damage of electrical
protects the technician from accidents resulting in personal injury shock.
from electrical shocks.
Leakage Current Cold Check(Antenna Cold Check)
It will also protect the receiver and it's components from being With the instrument AC plug removed from AC source, connect an
damaged by accidental shorts of the circuitry that may be electrical jumper across the two AC plug prongs. Place the AC
inadvertently introduced during the service operation. 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
If any fuse (or Fusible Resistor) in this TV receiver is blown, each exposed metallic parts such as antenna terminals, phone
replace it with the specified. jacks, etc.
If the exposed metallic part has a return path to the chassis, the
When replacing a high wattage resistor (Oxide Metal Film Resistor, measured resistance should be between 1M and 5.2M.
over 1W), keep the resistor 10mm away from PCB. When the exposed metal has no return path to the chassis the
reading must be infinite.
Keep wires away from high voltage or high temperature parts. An other abnormality exists that must be corrected before the
receiver is returned to the customer.
Due to high vacuum and large surface area of picture tube,
extreme care should be used in handling the Picture Tube. Do not Leakage Current Hot Check (See below Figure)
lift the Picture tube by it's Neck. Plug the AC cord directly into the AC outlet.
Do not use a line Isolation Transformer during this check.
X-RAY Radiation Connect 1.5K/10watt resistor in parallel with a 0.15uF capacitor
between a known good earth ground (Water Pipe, Conduit, etc.)
Warning: and the exposed metallic parts.
Measure the AC voltage across the resistor using AC voltmeter
The source of X-RAY RADIATION in this TV receiver is the High with 1000 ohms/volt or more sensitivity.
Voltage Section and the Picture Tube. Reverse plug the AC cord into the AC outlet and repeat AC voltage
For continued X-RAY RADIATION protection, the replacement measurements for each exposed metallic part. Any voltage
tube must be the same type tube as specified in the measured must not exceed 0.75 volt RMS which is corresponds to
Replacement Parts List. 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.
To determine the presence of high voltage, use an accurate high
impedance HV meter. Leakage Current Hot Check circuit
Adjust brightness, color, contrast controls to minimum. AC Volt-meter
Measure the high voltage.
The meter reading should indicate
23.5 1.5KV: 14-19 inch, 26 1.5KV: 19-21 inch,
29.0 1.5KV: 25-29 inch, 30.0 1.5KV: 32 inch
If the meter indication is out of tolerance, immediate service and Good Earth Ground
correction is required to prevent the possibility of premature such as WATER PIPE,
To Instrument's CONDUIT etc.
component failure.
exposed 0.15uF
METALLIC PARTS
1.5 Kohm/10W
-3-
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service semiconductor-equipped assembly, drain off any electrostatic
manual and its supplements and addenda, read and follow the charge on your body by touching a known earth ground.
SAFETY PRECAUTIONS on page 3 of this publication. Alternatively, obtain and wear a commercially available
NOTE: If unforeseen circumstances create conflict between the discharging wrist strap device, which should be removed to
following servicing precautions and any of the safety precautions on prevent potential shock reasons prior to applying power to the
page 3 of this publication, always follow the safety precautions. unit under test.
Remember: Safety First. 2. After removing an electrical assembly equipped with ES
devices, place the assembly on a conductive surface such as
General Servicing Precautions aluminum foil, to prevent electrostatic charge buildup or
1. Always unplug the receiver AC power cord from the AC power exposure of the assembly.
source before; 3. Use only a grounded-tip soldering iron to solder or unsolder ES
a. Removing or reinstalling any component, circuit board devices.
module or any other receiver assembly. 4. Use only an anti-static type solder removal device. Some solder
b. Disconnecting or reconnecting any receiver electrical plug or removal devices not classified as "anti-static" can generate
other electrical connection. electrical charges sufficient to damage ES devices.
c. Connecting a test substitute in parallel with an electrolytic 5. Do not use freon-propelled chemicals. These can generate
capacitor in the receiver. electrical charges sufficient to damage ES devices.
CAUTION: A wrong part substitution or incorrect polarity 6. Do not remove a replacement ES device from its protective
installation of electrolytic capacitors may result in an package until immediately before you are ready to install it.
explosion hazard. (Most replacement ES devices are packaged with leads
d. Discharging the picture tube anode. electrically shorted together by conductive foam, aluminum foil
2. Test high voltage only by measuring it with an appropriate high or comparable conductive material).
voltage meter or other voltage measuring device (DVM, 7. Immediately before removing the protective material from the
FETVOM, etc) equipped with a suitable high voltage probe. leads of a replacement ES device, touch the protective material
Do not test high voltage by "drawing an arc". to the chassis or circuit assembly into which the device will be
3. Discharge the picture tube anode only by (a) first connecting installed.
one end of an insulated clip lead to the degaussing or kine CAUTION:Be sure no power is applied to the chassis or circuit,
aquadag grounding system shield at the point where the picture and observe all other safety precautions.
tube socket ground lead is connected, and then (b) touch the 8. Minimize bodily motions when handling unpackaged
other end of the insulated clip lead to the picture tube anode replacement ES devices. (Otherwise harmless motion such as
button, using an insulating handle to avoid personal contact with the brushing together of your clothes fabric or the lifting of your
high voltage. foot from a carpeted floor can generate static electricity
4. Do not spray chemicals on or near this receiver or any of its sufficient to damage an ES device.)
assemblies.
5. Unless specified otherwise in this service manual, clean General Soldering Guidelines
electrical contacts only by applying the following mixture to the 1. Use a grounded-tip, low-wattage soldering iron and appropriate
contacts with a pipe cleaner, cotton-tipped stick or comparable tip size and shape that will maintain tip temperature within the
non-abrasive applicator; 10% (by volume) Acetone and 90% (by range or 500 F to 600 F.
volume) isopropyl alcohol (90%-99% strength) 2. Use an appropriate gauge of RMA resin-core solder composed
CAUTION: This is a flammable mixture. of 60 parts tin/40 parts lead.
Unless specified otherwise in this service manual, lubrication of 3. Keep the soldering iron tip clean and well tinned.
contacts in not required. 4. Thoroughly clean the surfaces to be soldered. Use a mall wire-
6. Do not defeat any plug/socket B+ voltage interlocks with which bristle (0.5 inch, or 1.25cm) brush with a metal handle.
receivers covered by this service manual might be equipped. Do not use freon-propelled spray-on cleaners.
7. Do not apply AC power to this instrument and/or any of its 5. Use the following unsoldering technique
electrical assemblies unless all solid-state device heat sinks are a. Allow the soldering iron tip to reach normal temperature.
correctly installed. (500 F to 600 F)
8. Always connect the test receiver ground lead to the receiver b. Heat the component lead until the solder melts.
chassis ground before connecting the test receiver positive c. Quickly draw the melted solder with an anti-static, suction-
lead. type solder removal device or with solder braid.
Always remove the test receiver ground lead last. CAUTION: Work quickly to avoid overheating the
9. Use with this receiver only the test fixtures specified in this circuitboard printed foil.
service manual. 6. Use the following soldering technique.
CAUTION: Do not connect the test fixture ground strap to any a. Allow the soldering iron tip to reach a normal temperature
heat sink in this receiver. (500 F to 600 F)
b. First, hold the soldering iron tip and solder the strand against
Electrostatically Sensitive (ES) Devices the component lead until the solder melts.
Some semiconductor (solid-state) devices can be damaged easily c. Quickly move the soldering iron tip to the junction of the
by static electricity. Such components commonly are called component lead and the printed circuit foil, and hold it there
Electrostatically Sensitive (ES) Devices. Examples of typical ES only until the solder flows onto and around both the
devices are integrated circuits and some field-effect transistors and component lead and the foil.
semiconductor "chip" components. The following techniques CAUTION: Work quickly to avoid overheating the circuit
should be used to help reduce the incidence of component board printed foil.
damage caused by static by static electricity. d. Closely inspect the solder area and remove any excess or
1. Immediately before handling any semiconductor component or splashed solder with a small wire-bristle brush.
-4-
IC Remove/Replacement Circuit Board Foil Repair
Some chassis circuit boards have slotted holes (oblong) through Excessive heat applied to the copper foil of any printed circuit
which the IC leads are inserted and then bent flat against the board will weaken the adhesive that bonds the foil to the circuit
circuit foil. When holes are the slotted type, the following technique board causing the foil to separate from or "lift-off" the board. The
should be used to remove and replace the IC. When working with following guidelines and procedures should be followed whenever
boards using the familiar round hole, use the standard technique this condition is encountered.
as outlined in paragraphs 5 and 6 above.
At IC Connections
Removal To repair a defective copper pattern at IC connections use the
1. Desolder and straighten each IC lead in one operation by gently following procedure to install a jumper wire on the copper pattern
prying up on the lead with the soldering iron tip as the solder side of the circuit board. (Use this technique only on IC
melts. connections).
2. Draw away the melted solder with an anti-static suction-type
solder removal device (or with solder braid) before removing the 1. Carefully remove the damaged copper pattern with a sharp
IC. knife. (Remove only as much copper as absolutely necessary).
Replacement 2. carefully scratch away the solder resist and acrylic coating (if
1. Carefully insert the replacement IC in the circuit board. used) from the end of the remaining copper pattern.
2. Carefully bend each IC lead against the circuit foil pad and 3. Bend a small "U" in one end of a small gauge jumper wire and
solder it. carefully crimp it around the IC pin. Solder the IC connection.
3. Clean the soldered areas with a small wire-bristle brush. 4. Route the jumper wire along the path of the out-away copper
(It is not necessary to reapply acrylic coating to the areas). pattern and let it overlap the previously scraped end of the good
copper pattern. Solder the overlapped area and clip off any
"Small-Signal" Discrete Transistor Removal/Replacement excess jumper wire.
1. Remove the defective transistor by clipping its leads as close as
possible to the component body. At Other Connections
2. Bend into a "U" shape the end of each of three leads remaining Use the following technique to repair the defective copper pattern
on the circuit board. at connections other than IC Pins. This technique involves the
3. Bend into a "U" shape the replacement transistor leads. installation of a jumper wire on the component side of the circuit
4. Connect the replacement transistor leads to the corresponding board.
leads extending from the circuit board and crimp the "U" with
long nose pliers to insure metal to metal contact then solder 1. Remove the defective copper pattern with a sharp knife.
each connection. Remove at least 1/4 inch of copper, to ensure that a hazardous
condition will not exist if the jumper wire opens.
Power Output, Transistor Device Removal/Replacement 2. Trace along the copper pattern from both sides of the pattern
1. Heat and remove all solder from around the transistor leads. break and locate the nearest component that is directly
2. Remove the heat sink mounting screw (if so equipped). connected to the affected copper pattern.
3. Carefully remove the transistor from the heat sink of the circuit 3. Connect insulated 20-gauge jumper wire from the lead of the
board. nearest component on one side of the pattern break to the lead
4. Insert new transistor in the circuit board. of the nearest component on the other side.
5. Solder each transistor lead, and clip off excess lead. Carefully crimp and solder the connections.
6. Replace heat sink. CAUTION: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as
possible to diode body.
2. Bend the two remaining leads perpendicular y to the circuit
board.
3. Observing diode polarity, wrap each lead of the new diode
around the corresponding lead on the circuit board.
4. Securely crimp each connection and solder it.
5. Inspect (on the circuit board copper side) the solder joints of
the two "original" leads. If they are not shiny, reheat them and if
necessary, apply additional solder.
Fuse and Conventional Resistor Removal/Replacement
1. Clip each fuse or resistor lead at top of the circuit board hollow
stake.
2. Securely crimp the leads of replacement component around
notch at stake top.
3. Solder the connections.
CAUTION: Maintain original spacing between the replaced
component and adjacent components and the circuit board to
prevent excessive component temperatures.
-5-
DESCRIPTION OF CONTROLS
Remote Control Buttons
MUTE
TV/VIDEO
MUTE POWER
Select: TV, VIDEO, S-Video,
Component, PC(PC only POWER
available for RM-15LA70) TV/VIDEO MULTIMEDIA MTS
MTS
FCR EXIT MENU
FCR MENU
MULTIMEDIA
EXIT
Select: TV,Component,
CH
PC(PC only available for
RM-15LA70) ENTER
VOL VOL
CHANNEL ( ) CH
VOLUME ( )
1 2 3
NUMBERS 4 5 6 APC
7 8 9 REVIEW
DASP APC : Press this button to return
DASP 0 to the last channel you
CAPTION REVIEW SLEEP
were watching.
CAPTION
SLEEP
-6-
Front of the TV
Side Control Panel
Channel Buttons
CH
VOL
Volume Buttons
ENTER
Enter Button
MENU TV/VIDEO
R
Menu Button
TV/Video Button
On/Off Button
/I ON/OFF
Remote Control Sensor
Power/Standby Indicator
Glows red in Standby mode,
Glows green when the TV is turned on.
-7-
Back of the TV
* Kensington
Security System
Connector
RM-15LA70 PC Input PC sound Input
Y PB PR H/P S-VIDEO VIDEO (MONO) L AUDIO R PC INPUT ANT IN PC
AC INPUT
COMPONENT(480i/480p/720p/1080i) 75 SOUND
VIDEO IN
DVD/DTV IN
AC Input Headphone Audio/Video Input
Jack
DVD/DTV Input S-Video Input Antenna Input
RM-20LA70
Y PB PR H/P S-VIDEO VIDEO (MONO) L AUDIO R ANT IN
AC INPUT
COMPONENT(480i/480p) VIDEO IN 75
DVD/DTV IN
-8-
ADJUSTMENT INSTRUCTION
1. Application Object (8) At this time the adjustment starts automatically changing
This instruction is for the application to the LCD TV/Monitor, the number in order of RO --> GO --> BO --> RD --> GD --
ML-024E. > BD.
Finally, when the number of BD is changed the adjustment
is completed.
2. Notes (9) Press the MENU or EXIT key to come out of the
adjustment mode.
(1) This LCD TV has power within set. Connect the power
correctly, then start the adjustment.
(2) The adjustment must be performed under the correct 4. COMPONENT Adjustment
sequence. (Only CMO MODULE)
(3) The adjustment must be performed in the circumstance of
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