LG 20LS7DC-UB User Manual
LCD TV
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
CHASSIS : LA74E
MODEL : 20LS7D(C) 20LS7D(C)-UB
website:http://biz.LGservice.com
- 2 -
CONTENTS
CONTENTS .............................................................................................. 2
PRODUCT SAFETY ..................................................................................3
SPECIFICATION ........................................................................................6
ADJUSTMENT INSTRUCTION ...............................................................10
TROUBLE SHOOTING ............................................................................14
BLOCK DIAGRAM...................................................................................19
EXPLODED VIEW ...................................................................................20
REPLACEMENT PARTS LIST ............................................................... 22
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 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 1MΩ and 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 Instrument’s
exposed
METALLIC PARTS
Good 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 PRECAUTIONS on 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 to
prevent 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°F to 600°F.
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 wirebristle (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°F to 600°F)
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 circuit
board printed foil.
6. Use the following soldering technique.
a. Allow the soldering iron tip to reach a normal temperature
(500°F to 600°F)
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 -
SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement
.
4. General Specification(TV)
No Item Specification Remark
1 Receiving System ATSC/64 & 256 QAM/ NTSC-M
2 Available Channel 1) VHF : 02~13
2) UHF : 14~69
3) DTV : 02-69
4) CATV : 01~135
5) CADTV : 01~135
3 Input Voltage 100-240V~, 50/60Hz
4 Market NORTH AMERICA
5 Screen Size 20 inch Wide For 20LC7D-UB
23 inch Wide For 23LC7D-UB
6 Aspect Ratio 16:9
7 Tuning System FS
8 LCD Module T200XW02 Wide, AUO
T230XW01 Wide, AUO
9 Operating Environment 1) Temp : 0 ~ 40 deg
2) Humidity : ~ 80 %
10 Storage Environment 1)Temp : -20 ~ 60 deg
2) Humidity : 0 ~ 90 %
1. Application range
1) This spec sheet is applied all of the 20/23" LCD TV with
LA74E chassis.
2) Not included spec and each product spec in this spec sheet
apply correspondingly to the following each country
standard and requirement of Buyer
2. Specification
Each part is tested as below without special appointment.
1) Temperature : 20±5°C
2) Relative Humidity : 65±10%
3) Power Voltage : Standard input voltage
(100-240V@50/60Hz)
* Standard Voltage of each product is marked by models
4) Specification and performance of each parts are followed
each drawing and specification by part number in
accordance with BOM.
5) The receiver must be operated for about 20 minutes prior to
the adjustment.
3. Test method
1) Performance : LGE TV test method followed
2) Demanded other specification
Safety : UL, CSA, IEC specification
EMC : FCC, ICES, IEC specification
5. Chroma & Brightness
5.1. FOR 23LC7D (CONDITION : EZ-Picture "Daylight")
- 7 -
No Item Min Typ Max Unit
1 White peak brightness 360 450 cd/m
260 450 cd/m
2 Contrast ratio 550 700
400 700 Refer to LCD SPEC.
3 Brightness uniformity 1.25
4 Color coordinate RED X Typ -0.03 0.638 Typ +0.03
5 Y Typ -0.03 0.337 Typ +0.03
6 GREEN X Typ -0.03 0.299 Typ +0.03
7 Y Typ -0.03 0.604 Typ +0.03
8 BLUE X Typ -0.03 0.145 Typ +0.03
9 Y Typ -0.03 0.059 Typ +0.03
10 WHITE X Typ -0.03 0.280 Typ +0.03
11 Y Typ -0.03 0.292 Typ +0.03
12 White Balance Target Cool X Typ -0.015 0.274 Typ +0.015
13 Y Typ -0.015 0.274 Typ +0.015
14 Medium X Typ -0.015 0.287 Typ +0.015
15 Y Typ -0.015 0.289 Typ +0.015
16 Warm X Typ -0.015 0.314 Typ +0.015
17 Y Typ -0.015 0.318 Typ +0.015
18 Viewing angle 140 176 Right / Left
19 140 176 Up / Down
20 Color Temperature Medium 8,300 9,300 10,300
Cool 11,000 12,000 13,000
Warm 5,500 6,500 7,500
- 8 -
5.1. FOR 20LC7D (CONDITION : EZ-Picture "Daylight")
6. Component Video Input (Y, CB/PB, CR/PR)
No Resolution H-freq(kHz) V-freq(Hz) Pixel clock Proposed
1. 720*480 15.73 59.94 SDTV ,DVD 480I
2. 720*480 15.73 60.00 SDTV ,DVD 480I
3. 720*480 31.47 59.94 SDTV 480P
4. 720*480 31.50 60.00 SDTV 480P
5. 1280*720 44.96 59.94 HDTV 720P
6. 1280*720 45.00 60.00 HDTV 720P
7. 1920*1080 33.72 59.94 HDTV 1080I
8. 1920*1080 33.75 60.00 HDTV 1080I
No Item Min Typ Max Unit Remark
1. White peak brightness 360 450 cd/m
2
250 450 cd/m
2
PSM : Daylight
2. Contrast Ratio 600 700
400 700 PSM : Daylight
3. Brightness uniformity 1.25 Refer to LCD SPEC.
4. Color coordinate RED X 0.640 +/- 0.03
Y 0.330 +/- 0.03
GREEN X 0.290 +/- 0.03
Y 0.600 +/- 0.03
BLUE X 0.150 +/- 0.03
Y 0.060 +/- 0.03
WHITE X 0.295 +/- 0.03
Y 0.305 +/- 0.03
5. White Balance Target Cool X 0.274 +/- 0.015
Y 0.274 +/- 0.015
Medium X 0.287 +/- 0.015
Y 0.289 +/- 0.015
Warm X 0.314 +/- 0.015
Y 0.318 +/- 0.015
6. Viewing angle 130 160 Right / Left
110 140 Up / Down
7. Color Temperature Medium 8,300 9,300 10,300 <Test Signal>
Cool 11,000 12,000 13,000 85 IRE
Warm 5,500 6,500 7,500
No. Item Content Remark
1 Product Dimension Width(W) Length(D) Height(H)
Before Packing 499.6 175.0 401.4 Head depth : 73.0mm
After Packing 563.0 173.0 423.0 (stand detachable, 3 piece type)
2 Product Weight Only SET 6.22 Kg
With Box 7.73 Kg
3 Container Loading Quantity Individual or Palletizing 20 ft 40 ft 40 ft_HC
Indi. Wooden Indi. Wooden Indi. Wooden
689 576 1443 1296 1665 1512
4 Appearance General
- 9 -
8. Mechanical specification
<20LC7D>
<23LC7D>
7. RGB input (PC/DTV)
No Resolution H-freq(kHz) V-freq.(Hz) Pixel clock(MHz) Proposed
PC
1 640*350 31.469 70.08 25.17 DOS O
2 720*400 31.469 70.08 28.32 DOS O
3 640*480 31.469 59.94 25.17 VESA(VGA) O
4 800*600 37.879 60.31 40.00 VESA(SVGA) O
5 1024*768 48.363 60.00 65.00 VESA(XGA) O
6 1280*768 47.776 59.87 79.50 VESA(WXGA) O
7 1360*768 47.712 60.01 85.50 VESA(WXGA) O
8 1366*768 60.023 60.00 80.00
No. Item Content Remark
1 Product Dimension Width(W) Length(D) Height(H)
Before Packing 581.5 198.8 458.3 Head depth : 82mm
After Packing 655.0 186.0 490.0 (stand detachable, 3 piece type)
2 Product Weight Only SET 7.9 Kg
With Box 9.8 Kg
3 Container Loading Quantity Individual or Palletizing 20 ft 40 ft 40 ft_HC
Ind. Wooden Indi. Wooden Indi. Wooden
468 396 1008 924 1176 1092
4 Appearance General
- 10 -
ADJUSTMENT INSTRUCTION
1. Application Object
These instructions are applied to all of the LCD TV, LA74E.
2. Notes
(1) Because this is not a hot chassis, it is not necessary to use
an isolation transformer. However, the use of isolation
transformer will help protect test equipment.
(2) Adjustments must be done in the correct order.
(3) The adjustments must be performed in the circumstance of
20±5°C of temperature and 65±10% of relative humidity if
there is no specific designation.
(4) The input voltage of the receiver be must kept 110V, 60Hz
when adjusting.
(5) The receiver must be operational for about 15 minutes
prior to the adjustments.
(6) Perform preliminary operation after receiving 100% White
Pattern (06CH). (Or 3. White Pattern status of Ez-Adjust)
- White Pattern entry method
1) Enter into Ez-Adjust by pressing the ADJ key on the
adjustment R/C.
2) 100% FULL WHITE PATTERN appears if pressing the
OK (
A
) key after selecting the 3.WHITE PATTERN with
the CH + / - KEY.
* It is possible to heat run the set without a separate signal
generator in this mode.
Caution : Care must be taken as afterimage phenomena
may occur about the black level part of screen If leaving
pause image turned on for more than 20 minutes
(especially inner digital pattern (13 CH), Cross Hatch
Pattern (09CH) with significant black/white contrast).
3. MICOM Download(Option)
3-1. Required Test Equipment
(1) JIG-LEVER TYPE for adjusting: 1EA
(2) PC & MONITOR: 2EA
(3) BOARD for INTERFACE: IIC & ISP BOARD: 2EA
(4) 15P D-SUB CABLE: 2EA
(5) Using the 12/15 line of D-SUB 15P
12-SDA/15-SCL
3-2. JIG Connection
3-3. Establishment Program
(1) Establish LGE Monitor Tools v1.1
(2) The program work and it is opened program window as
seen below.
(3) Click the first icon shown in fig.9. The window seen in
fig.10 should appear.
- 11 -
3-4. Set Method
(1) MCU Select: MTV512M64
(2) Option
R/W Option: Auto Write(Verity)
Jig Option: Myson
Transmit Speed: Medium
(3) Check: Just do it with blank micom.
(4) PORT
Chose Parallel Port (normal LPT1)
Attention:You must chose EPP when select Rom BIAS at LPT
3-5. Download Method
(1) Click the Load File.
(2) Locate and select the correct file from your computer.
(*.hex).
(3) Click the Send.
(4) When you see (ISP COMPLETE) the download is complete.
4. ADC-Set Adjustment
4-1. Synopsis
ADC-Set adjustment to set the black level and the Gain to
optimum.
4-2. Test Equipment
Service R/C, 801GF(802V, 802F, 802R) or MSPG925FA
Pattern Generator
(480i/1080i The Horizontal 100% Color Bar Pattern adjust to
within 0.7±0.1Vp-p)
4-3. Adjustment
(1) Select Component as the input with 100% Horizontal Color
Bar Pattern(HozTV31Bar) in 480i Mode
(2) After receiving signal for at least 1 second, press the ADJ
Key on the Service R/C to enter the ‘Ez - Adjust’ and select
the ‘2. ADC 480i Comp1’.
Pressing the Enter Key to adjust automatically.
(3) When the adjustment is over, 'MST3361 Component
Success’ is displayed. If the adjustment has errors,
'MST3361 Configuration Error’ is displayed.
(4) Select Component 1 as the input with 100% Horizontal
Color Bar Pattern(HozTV31Bar) in 1080i Mode.
(5) After receiving signal for at least 1 second, press the ADJ
Key on the Service R/C to enter the ‘Ez - Adjust’ and select
the ‘3. ADC 1080i Comp1/RGB’.
Pressing the Enter Key to adjust automatically.
(6) When the adjustment is over, 'MST3361 Component
Success’ is displayed. If the adjustment has errors,
'MST3361 Configuration Error’ is displayed.
(7) After the Component MST3361 adjustment is over, convert
the RGB-DTV Mode and display Pattern.
When the adjustment is over, 'MST3361 RGB_DTV
Success’ is displayed.
(8) Readjust after confirming the case Pattern or adjustment
condition where the adjustment errors.
(9) After adjustment is complete, exit the adjustment mode by
pressing the ADJ KEY.
Ez Adj ust
1. CVBS ACC Adjust
2. ADC 480i Comp1
3. AD C 108 0i Co m p1 / RGB
4. Reserved
5. Sub- Brightness/Contrast
6. Wh it e-Balance
7. Module Control
8. Temp erat ure Thre sho ld
9. Wh it e-Pattern
10. 2 Hour Off Opt ion
<Adjustment Mode>
<Adjustment Pattern: 480i/1080i 60Hz HozTV31Bar Pattern>
Loading...