LG 20lc1r Service Manual

							LCD TV
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
CHASSIS : CL-81
MODEL : 20LC1R-ZG
website:http://biz.LGservice.com
e-mail:http://www.LGEservice.com/techsup.html
 
						

							- 2 -
CONTENTS
CONTENTS .............................................................................................. 2
PRODUCT SAFETY ..................................................................................3
DISASSEMBLY ..........................................................................................6
SPECIFICATION ........................................................................................7
ADJUSTMENT INSTRUCTION ...............................................................12
SVC REMOCON ......................................................................................14
TROUBLE SHOOTING ............................................................................15
BLOCK DIAGRAM...................................................................................19
WIRING DIAGRAM ..................................................................................21
EXPLODED VIEW .................................................................................. 22
REPLACEMENT PARTS LIST ............................................................... 24
SVC. SHEET  ...............................................................................................
 
						

							- 3 -
SAFETY PRECAUTIONS
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
Shock, Fire, or other Hazards. 
Do not modify the original design without permission of manufacturer.
General Guidance
An isolation Transformer should always be usedduring 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 its 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 checkon 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 1MΩand 5.2MΩ. 
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
To Instruments
exposed 
METALLIC PARTSGood Earth Ground
such as WATER PIPE,
CONDUIT etc.
AC Volt-meter
IMPORTANT SAFETY NOTICE
0.15uF
 
						

							- 4 -
CAUTION: Before servicing receivers covered by this service
manual and its supplements and addenda, read and follow the
SAFETY PRECAUTIONSon page 3 of this publication.
NOTE: If unforeseen circumstances create conflict between the
following servicing precautions and any of the safety precautions on
page 3 of this publication, always follow the safety precautions.
Remember: Safety First.
General Servicing Precautions
1.  Always unplug the receiver AC power cord from the AC power
source before;
a.  Removing or reinstalling any component, circuit board
module or any other receiver assembly.
b.  Disconnecting or reconnecting any receiver electrical plug or
other electrical connection.
c. Connecting a test substitute in parallel with an electrolytic
capacitor in the receiver.
CAUTION:A wrong part substitution or incorrect polarity
installation of electrolytic capacitors may result in an
explosion hazard.
2.  Test high voltage only by measuring it with an appropriate high
voltage meter or other voltage measuring device (DVM,
FETVOM, etc) equipped with a suitable high voltage probe.
Do not test high voltage by drawing an arc.
3.  Do not spray chemicals on or near this receiver or any of its
assemblies.
4. Unless specified otherwise in this service manual, clean
electrical contacts only by applying the following mixture to the
contacts with a pipe cleaner, cotton-tipped stick or comparable
non-abrasive applicator; 10% (by volume) Acetone and 90% (by
volume) isopropyl alcohol (90%-99% strength)
CAUTION:This is a flammable mixture.
Unless specified otherwise in this service manual, lubrication of
contacts in not required.
5.  Do not defeat any plug/socket B+ voltage interlocks with which
receivers covered by this service manual might be equipped.
6.  Do not apply AC power to this instrument and/or any of its
electrical assemblies unless all solid-state device heat sinks are
correctly installed.
7.  Always connect the test receiver ground lead to the receiver
chassis ground before connecting the test receiver positive
lead.
Always remove the test receiver ground lead last.
8. Use with this receiver only the test fixtures specified in this
service manual.
CAUTION:Do not connect the test fixture ground strap to any
heat sink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid-state) devices can be damaged easily
by static electricity. Such components commonly are called
Electrostatically Sensitive (ES) Devices.Examples of typical ES
devices are integrated circuits and some field-effect transistors and
semiconductor chip components. The following techniques
should be used to help reduce the incidence of component
damage caused by static by static electricity.
1.  Immediately before handling any semiconductor component or
semiconductor-equipped assembly, drain off any electrostatic
charge on your body by touching a known earth ground.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, which should be removed toprevent potential shock reasons prior to applying power to the
unit under test.
2.  After removing an electrical assembly equipped with ES
devices, place the assembly on a conductive surface such as
aluminum foil, to prevent electrostatic charge buildup or
exposure of the assembly.
3.  Use only a grounded-tip soldering iron to solder or unsolder ES
devices.
4. Use only an anti-static type solder removal device. Some solder
removal devices not classified as anti-static can generate
electrical charges sufficient to damage ES devices.
5.  Do not use freon-propelled chemicals. These can generate
electrical charges sufficient to damage ES devices.
6.  Do not remove a replacement ES device from its protective
package until immediately before you are ready to install it.
(Most replacement ES devices are packaged with leads
electrically shorted together by conductive foam, aluminum foil
or comparable conductive material).
7.  Immediately before removing the protective material from the
leads of a replacement ES device, touch the protective material
to the chassis or circuit assembly into which the device will be
installed.
CAUTION: Be sure no power is applied to the chassis or circuit,
and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged
replacement ES devices. (Otherwise harmless motion such as
the brushing together of your clothes fabric or the lifting  of your
foot from a carpeted floor can generate static electricity
sufficient to damage an ES device.)
General Soldering Guidelines
1.  Use a grounded-tip, low-wattage soldering iron and appropriate
tip size and shape that will maintain tip temperature within the
range or 500
oF to 600oF.
2.  Use an appropriate gauge of RMA resin-core solder composed
of 60 parts tin/40 parts lead.
3.  Keep the soldering iron tip clean and well tinned.
4.  Thoroughly clean the surfaces to be soldered. Use a mall wire-
bristle (0.5 inch, or 1.25cm) brush with a metal handle.
Do not use freon-propelled spray-on cleaners.
5.  Use the following unsoldering technique
a.  Allow the soldering iron tip to reach normal temperature.
(500
oF to 600oF)
b.  Heat the component lead until the solder melts.
c.  Quickly draw the melted solder with an anti-static, suction-
type solder removal device or with solder braid.
CAUTION: Work quickly to avoid overheating the
circuitboard printed foil.
6.  Use the following soldering technique.
a.  Allow the soldering iron tip to reach a normal temperature
(500
oF to 600oF)
b.  First, hold the soldering iron tip and solder the strand against
the component lead until the solder melts.
c. Quickly move the soldering iron tip to the junction of the
component lead and the printed circuit foil, and hold it there
only until the solder flows onto and around both the
component lead and the foil.
CAUTION:Work quickly to avoid overheating the circuit
board printed foil.
d. Closely inspect the solder area and remove any excess or
splashed solder with a small wire-bristle brush.
SERVICING PRECAUTIONS
 
						

							- 5 -
IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat against the
circuit foil. When holes are the slotted type, the following technique
should be used to remove and replace the IC. When working with
boards using the familiar round hole, use the standard technique
as outlined in paragraphs 5 and 6 above.
Removal
1.  Desolder and straighten each IC lead in one operation by gently
prying up on the lead with the soldering iron tip as the solder
melts.
2.  Draw away the melted solder with an anti-static suction-type
solder removal device (or with solder braid) before removing the
IC.
Replacement
1.  Carefully insert the replacement IC in the circuit board.
2.  Carefully bend each IC lead against the circuit foil pad and
solder it.
3.  Clean the soldered areas with a small wire-bristle brush.
(It is not necessary to reapply acrylic coating to the areas).
Small-Signal Discrete Transistor
Removal/Replacement
1.  Remove the defective transistor by clipping its leads as close as
possible to the component body.
2.  Bend into a U shape the end of each of three leads remaining
on the circuit board.
3.  Bend into a U shape the replacement transistor leads.
4.  Connect the replacement transistor leads to the corresponding
leads extending from the circuit board and crimp the U with
long nose pliers to insure metal to metal contact then solder
each connection.
Power Output, Transistor Device
Removal/Replacement
1.  Heat and remove all solder from around the transistor leads.
2. Remove the heat sink mounting screw (if so equipped).
3.  Carefully remove the transistor from the heat sink of the circuit
board.
4.  Insert new transistor in the circuit board.
5. Solder each transistor lead, and clip off excess lead.
6.  Replace heat sink.
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.
Circuit Board Foil Repair
Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
board causing the foil to separate from or lift-off the board. The
following guidelines and procedures should be followed whenever
this condition is encountered.
At IC Connections
To repair a defective copper pattern at IC connections use the
following procedure to install a jumper wire on the copper pattern
side of the circuit board. (Use this technique only on IC
connections).
1.  Carefully remove the damaged copper pattern with a sharp
knife. (Remove only as much copper as absolutely necessary).
2.  carefully scratch away the solder resist and acrylic coating (if
used) from the end of the remaining copper pattern.
3.  Bend a small U in one end of a small gauge jumper wire and
carefully crimp it around the IC pin. Solder the IC connection.
4.  Route the jumper wire along the path of the out-away copper
pattern and let it overlap the previously scraped end of the good
copper pattern. Solder the overlapped area and clip off any
excess jumper wire.
At Other Connections
Use the following technique to repair the defective copper pattern
at connections other than IC Pins. This technique involves the
installation of a jumper wire on the component side of the circuit
board.
1.  Remove the defective copper pattern with a sharp knife.
Remove at least 1/4 inch of copper, to ensure that a hazardous
condition will not exist if the jumper wire opens.
2.  Trace along the copper pattern from both sides of the pattern
break and locate the nearest component that is directly
connected to the affected copper pattern.
3.  Connect insulated 20-gauge jumper wire from the lead of the
nearest component on one side of the pattern break to the lead
of the nearest component on the other side.
Carefully crimp and solder the connections.
CAUTION:Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
 
						

							- 6 -
DISASSEMBLY
#1#2 Detached stand assy (Remove the screws)
#3 Disassembly stand assy#4 Detached Backcover (Remove the screw)
#5 Open the Backcovers latch with jig#6 Unlock latch between Cabinet and Backcover
 
						

							- 7 -
SPECIFICATION
1. Application range
This specification is applied to CL-81 chassis.
2. Requirement for Test
Testing for standard of each part must be followed in below
condition.
(1) Temperature: 25°C ± 2°C
(2) Humidity: 65% ± 10%
(3) Power: Standard input voltage (AC 100-240V, 50/60Hz)
(4) Measurement must be performed after heat-run more than
30min.
(5) Adjusting standard for this chassis is followed a special
standard.
3.General Specification
4. Mechanical Specification
No.
Item
Specification Remark
1TFT Color LCD Module
20.1 inches(510.54mm) diagonal
0.2125mm(H)x0.6375mm(V)xRGB
TTL
8BIT, 16,777,216 colors
432(H) x 331.5(V) x 25(D)
Anti-Glare, Hard Coating(3H) 
Normally Black
6 CCFL(6 lamps)
25ms(R.T.:12ms + F.T.:13ms)LPL
NOTE : Specifications and others are subject to change without notice for improvement.
No.
1 Product Width(W) Lengh(D) Height(H)
Dimension Before Packing 492.4 272.8 483.3
After Packing 574.0 225.0 627.0
2 Product Only SET 8.7Kg
Weight With BOX 11.1Kg Type
ActiveDisplay Area
Pixel Pitch [mm]
Electrical Interface
Color Depth
Size [mm]
Surface Treatment
Operating Mode
Back light Unit
R/T Typ.
Item ContentRemark
 
						

							- 8 -
6.Optical Character
ItemRemark Specification
Viewing Angle

Luminance
Contrast Ratio
CIE Color CoordinatesAll White/All Black
In AV Input
PSM : Dynamic
White
(100 IRE) R/L, 
U/D
Luminance(cd/
)
Variation
CRTyp
88/88
88/88
450
350
0.313
0.329
0.283
0.298
0.274
0.286 Min
85/85
85/85
380
280
0.283
0.299
0.253
0.268
0.244
0.256 WHITE
(Warm)
WHITE
(Normal)
WHITE
(Cool)Wx
Wy
Wx
Wy
Wx
WyMax
1.3
0.343
0.359
0.313
0.328
0.304
0.316 No.
1
2
3
4
5. Reference table-Function
No.
ItemSpecification
Remark
1 Teletext TOP, FLOF TOP(option)
2 REMOCON NEC Code PAL
3 AV Input 1 Rear
4 S-Video Input 1 Rear
5 Component Input X
6 PERI TV Connector Full SCART : 1 Rear
7 Ear-phone output 1
8 2 Carrier Stereo BG, DK
9 NICAM Stereo BG, I, LL
10 2 Carrier Daul BG, DK
11 NICAM Daul BG, I, LL
12 DW(Double Window) Mode X
13 MW(Multi Window) Mode X
14 Film Mode X
15 Noise Reduction X
16 Progressive Scan O
17 Motion Detection X
18 SRS WOW X
19 Swivel Speaker X
20 EZ-pip X
21 ARC X
22 DRP X
23 DCDI X
24 HDCP X
 
						

							- 9 -
7. Outgoing Condition
No Item Condition Remark
1 Power Off
2 Volume Level 30
3 Main Picture Input TV
4 Main Last Channel Pr 01
5 Mute Off
6 Station Auto Program
Manual Program
Program Edit
Favorite Program None
7 Picture PSM Dynamic
CSM Normal
Dynamic Contrast 100
Brightness 50
Colour 70
Sharpness 50
Tint 0 NTSC OPTION
8 Sound SSM Flat
AVL Off
Balance 0
9 Special Input TV
Child Lock Off
Power Indicator On
Language English(Area Management)
10 Time Clock -- : --
Off Time -- : -- Off
On Time -- : --
Pr. 1
Vol. 30
Off
Auto Sleep Off
 
						

							- 10 -
8-1.General Specification
8.Engineering Specification
1
2
3Power Supply
Normal
Stand By
Cut-off Switch off
ITEM
D-SUB Pin   Configuraion
Control FunctionH/V Sync
On/On
Off/Off
-
Spectification
1: RED
3: Blue
5: S.T(GND)
7: Green GND
9: N.C
11: ID0(GND)
13: H-Sync
15: SCL
1) Contrast/Brightness/Colour/Sharpness/(Tint)
2) Power On/Off, Input select, Menu, OK
Volume(
,), PR(,)2: Green
4: ID2(GND)
6: RED GND
8: Blue GND
10: D-GND
12: SDA
14: V-Sync
Shell: GNDRemark
For SVC Only Video
Active
Off
-Power Consumption
≤65W
≤1W(110V)
≤1W(220V)
0W Item Specification Remark No.
LED Color
BLUE
ORANGE
OFF