LG 42LH90 Service Manual

1080P

Direct View LCD

Training

42LH90

LED Backlights

Original February 09, 2010

Updated July

28, 2010

OUTLINE

Preliminary Section:

Contact Information, Preliminary Matters, Specifications, LCD Overview, General Troubleshooting Steps, Signal Distribution, Disassembly Instructions and Voltages

Disassembly Section: Removal of Circuit Boards Troubleshooting Section:

• Switch Mode Power Supply

• Inverter Board (LED Backlight Driver)

• T-CON (TFT Controller) Panel Driver board

• Main Board

• Ft Control Board

•

Side Keys

• Speakers

Board Operation Troubleshooting of :

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February 2010

LCD DV 42LH90

Overview of Topics to be Discussed

42LH90 LCD Direct View Display

This Section will cover Contact Information and remind the Technician of Important Safety Precautions for the Customers Safety as well as the Technician and the Equipment.

Basic Troubleshooting Techniques which can save time and money sometimes can be overlooked. These techniques will also be presented.

Section 1

This Section will get the Technician familiar with the Disassembly, Identification and Layout of the LCD Display Panel.

At the end of this Section the Technician should be able to Identify the Circuit Boards and have the ability and knowledge necessary to safely remove and replace any Circuit Board or Assembly.

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LCD DV 42LH90

Preliminary Matters (The Fine Print)

IMPORTANT SAFETY NOTICE

The information in this training manual is intended for use by persons possessing an adequate background in electrical equipment, electronic devices, and mechanical systems. In any attempt to repair a major Product, personal injury and property damage can result. The manufacturer or seller maintains no liability for the interpretation of this information, nor can it assume any liability in conjunction with its use. When servicing this product, under no circumstances should the original design be modified or altered without permission from LG Electronics. Unauthorized modifications will not only void the warranty, but may lead to property damage or user injury. If wires, screws, clips, straps, nuts, or washers used to complete a ground path are removed for service, they must be returned to their original positions and properly fastened.

CAUTION

To avoid personal injury, disconnect the power before servicing this product. If electrical power is required for diagnosis or test purposes, disconnect the power immediately after performing the necessary checks. Also be aware that many household products present a weight hazard. At least two people should be involved in the installation or servicing of such devices. Failure to consider the weight of an product could result in physical injury.

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February 2010

LCD DV 42LH90

(Electrostatic Static Discharge)

ESD Notice

Today’s sophisticated electronics are electrostatic discharge (ESD) sensitive. ESD can weaken or damage the electronics in a manner that renders them inoperative or reduces the time until their next failure. Connect an ESD wrist strap to a ground connection point or unpainted metal in the product. Alternatively, you can touch your finger repeatedly to a ground connection point or unpainted metal in the product. Before removing a replacement part from its package, touch the anti-static bag to a ground connection point or unpainted metal in the product. Handle the electronic control assembly by its edges only. When repackaging a failed electronic control assembly in an anti-static bag, observe these same precautions.

Regulatory Information

This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a residential installation. This equipment generates, uses, and can radiate radio frequency energy, and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures: Reorient or relocate the receiving antenna; Increase the separation between the equipment and the receiver; Connect the equipment to an outlet on a different circuit than that to which the receiver is connected; or consult the dealer or an experienced radio/TV technician for help.

(Electrostatic Static Discharge)

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February 2010

LCD DV 42LH90

LG Contact Information

Customer Service (and Part Sales) (800) 243-0000

Technical Support (and Part Sales) (800) 847-7597

USA Website (GSFS) http://gsfs-america.lge.com

Customer Service Website us.lgservice.com

LG Web Training lge.webex.com

LG CS Academy lgcsacademy.com

LCD-DV:

PLASMA:

PDP Panel Alignment Handbook, Schematics with Bookmarks

32LG40, 32LH30, 37LH55, 42LG60, 42LG70, 42LH20, 42LH40, 42LH50, 42LH90, 42SL80, 47LG90, 47LH85, 47LE8500

42PG20, 42PQ20, 42PQ30, 50PG20, 50PJ350, 50PK750, 50PS80, 50PS60, 60PK750, 60PS11, 60PS60, 60PS80

Also available on the Plasma Page:

Plasma Control Board ROM Update (Jig required)

Published February 2010 by LG Technical Support and Training

LG Electronics Alabama, Inc.

201 James Record Road, Huntsville, AL, 35813.

Presentations with Audio/Video

and Screen Marks

http://136.166.4.200

New Training Materials on

the Learning Academy site

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February 2010

LCD DV 42LH90

LCD Direct View Overview

Safety and Handling Regulations

1. Approximately 20 minute pre-run time is required before making any picture performance adjustments from the Menu.

2. Refer to the Voltage/Current silk screening on the Switch Mode Power Supply.

3. C-MOS circuits are sensitive to static electricity. Use caution when dealing with these IC and circuits.

4. Exercise care when making voltage and waveform checks to prevent costly short circuits from damaging the unit.

5. Be cautious of lost screws and other metal objects to prevent a possible short in the circuitry.

Checking Points to be Considered

1. Check the appearance of the Replacement Panel and Circuit Boards for both physical damage and part number accuracy.

2. Check the model label. Verify model names and board model matches.

3. Check details of defective condition and history. Example: Oscillator failure dead set, etc…

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February 2010

LCD DV 42LH90

Basic Troubleshooting Steps

Define, Localize, Isolate and Correct

•Define the failure. Use your senses Sight, Smell, Touch and Hearing. Look for burned parts and check for possible overheated components. Capacitors will sometimes leak dielectric material and give off a distinct odor. Frequency of power supplies will change with the load, or listen for relay closing etc. Observation of the front Power LED may give some clues.

•Localize checked and after giving a thorough examination using your senses the first check should always be the DC Supply Voltages to those circuits under test. Always confirm the supplies are not only the proper level but be sure they are noise free. If the supplies are missing check the resistance for possible short circuits.

•Isolate Oscilloscope to make a final determination of the failure. Look for correct Amplitude Phasing and Timing of the signals also check for the proper Duty Cycle of the signals. Sometimes “glitches” or “road bumps” will be an indication of an imminent failure.

Look at the symptom carefully and determine what circuits could be causing

After carefully checking the symptom and determining the circuits to be

To further isolate the failure, check for the proper waveforms with the

•Correct check the DC Supplies for proper levels. Make all necessary adjustments and lastly always perform a Safety AC Leakage Test before returning the product back to the Customer.

The final step is to correct the problem. Be careful of ESD and make sure to

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February 2010

LCD DV 42LH90

42LH90 PRODUCT INFORMATION SECTION

This section of the manual will discuss the specifications of the

42LH90

LCD Direct View Display

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February 2010

LCD DV 42LH90

Basic Specifications

Key TV Features

• LED Backlight with Local Dimming

• TruMotion 240Hz

• Intelligent Sensor

• Full HD 1080p

• 2,000,000:1 Contrast Ratio

• 2.4ms Response Time

• 500 cd/m² Brightness

• Wide Color gamut

• Super IPS Panel

• XD Engine

• 24fps Real Cinema

• ISFccc Ready

• Picture Wizard

• AV Mode II (Cinema, Sports, Game)

• Audio Output Power 10W x 2

• Invisible Speaker system

• Clear Voice II

• SRS TruSurround XT™

• Smart Volume Controller

• Dolby® Digital 5.1 Decoder

• Backlight Control

• Video Mute

• ENERGY STAR® 3.0 Compliant

• 4 HDMI™ v1.3 with Deep Color

• SIMPLINK™ Connectivity

• 2 HD Component Video Inputs

• 2 Composite inputs

• 1 Digital Audio Out

• NTSC / ATSC / Clear QAM

• USB 2.0 (JPEG, MP3, MP4, Divx)

• PC Connectivity (D-Sub 15pin)

• RF Antenna Input

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February 2010

LCD DV 42LH90

Basic Specifications (LOGO Familiarization)

Full HD 1080p Resolution

Displays HDTV programs in full 1920 x 1080p resolution for a more detailed picture.

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February 2010

LCD DV 42LH90

Remote Control Familiarization

TOP PORTION

p/n MKJ61841701

BOTTOM PORTION

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February 2010

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Accessing the Service Menu

To access the Service Menu.

1) You must have the Service

2) Press “In-Start”

3) A Password screen appears.

Remote. p/n 105-201M

Note: A Password is required

to enter the Service Menu.

Enter; 0000

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February 2010

LCD DV 42LH90

TV Rear Input / Output Jacks

Rear In/Out Jacks

USB Port

Software Upgrades

Music, Photos

Side In/Out

MAIN BOARD

Rear and Side

Input/Output locations

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February 2010

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Software Download

1) Create an LG_DTV folder on the USB Flash Drive

2) Copy new software (xxx.epk) to "LG_DTV" folder. Make sure to have correct software file.

3) With TV turned on, insert USB flash drive.

4) You can see the message “TV Software Upgrade” (See figure to right)

5) Cursor left and highlight "START" Button and push “Enter” button using the remote control.

6) You can see the download progress Bar.

7) Do not unplug until unit has automatically restarted.

8) When download is completed, you will see “COMPLETE”.

9) Your TV will be restarted automatically.

Shows the

Currently

Installed

Version

Shows the

Software

Version

found on the

USB Flash

Drive

* CAUTION: Do not remove AC power or the USB Flash Drive. Do not turn off Power, during the upgrade process.

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February 2010

LCD DV 42LH90

42LH90 Product Dimensions

There must be at least 4 inches of Clearance on all sides

Wattage Average 210W Stand By <1W

42LH90 Dimensions

42"

1066.8mm 7-7/8"

200mm

3-11/16"

93.98mm

28-3/16"

716.28mm

30-5/8"

777.88mm

Model No.

Serial No.

Label

2-7/16"

61.6mm

16-15/16"

430mm

14-1/8"

357.98mm

21"

533.4mm

14-1/8"

357.98mm

Center

10-5/8"

270mm

9-5/8"

244mm

7-7/8"

200mm

Remove 4 screws to

remove stand for

wall mount

Weight without Stand: 43 lb Weight with Stand: 51.1 lb

17-7/8"

454mm

16

14-3/16"

360.68mm

DISASSEMBLY SECTION

This section of the manual will discuss Disassembly, Layout

(Circuit Board Identification) of the 42LH90 LCD Direct View Television.

Upon completion of this section the Technician will have a better

understanding of the disassembly procedures, the layout of the printed

Disassembly:

circuit boards and be able to identify each board.

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February 2010

LCD DV 42LH90

Removing the Back Cover

Remove the 23 screws indicated.

Pay attention to the size and type of screw

as there are many different types.

Putting in an improper screw when

reassembling may Cause damage.

Decorative Plastic

Cap (if used) must

be removed.

The Stand does not need to be removed before removing the back.

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February 2010

Bottom two screws do

not have to be

removed.

LCD DV 42LH90

Circuit Board Layout

INVERTER

p/n EAY60702001

Left LED

Connection

Side Keys

Intelligent

Sensor / IR

TFT Panel

EAJ60694101

POWER SUPPLY

p/n EAY58584001

AC Input

T-CON board

p/n EAT60665101

LVDS Cables

p/n EAD60679428

p/n EAD60679364

Right LED

Connection

Main Board

p/n EBR62151101

Side

Inputs

Rear Inputs

Power Button

Tweeter R

Moving

LED

Full Range

Speaker R

p/n EAB58534501

19

Full Range

Speaker L

February 2010

Tweeter L

p/n EAB58536001

LCD DV 42LH90

42LH90 Connector Identification Diagram

CN5 CN4

T-CON

CN305 N/C

CN306

CN307 N/C

CN1

INVERTER

TFT PANEL

CN2

P100

CN4

CN3

CN1

KEY BOARD

IR

Main

Power

LED

P103

P203

IR

P100

POWER

SUPPLY

SK101

P201

SK100

P101

J1

AC In

LED

20

P3500 P3502

P3501

P700

MAIN

BOARD

P1200 P600

Speakers (Front Left)Speakers (Front Right)

P101N/C

Power Supply

Board Removal

Disconnect

P201, P203,

AC In SK100

and SK101.

Remove the 6

P

2

3

0

P

2

1

0

P201

screws indicated

by the arrows.

21

SK

SK101

Power

Switch

February 2010

Press in

Two tabs

to release

lock

1

0

AC In

LCD DV 42LH90

CON Board Removal

TT--CON Board Removal

STEP (1)

Remove the 3 Screws in the T-CON

shield and remove the shield

The two screws shown in the picture

below are for the Service Position.

They would have been removed

when removing the shield. Be sure to reinstall them if

servicing the T-CON Board.

CN5 CN4

Note: Chocolate

(Heat Sink

Material)

STEP (2)

CN1 CN2

Disconnect CN1, CN2, CN4 and CN5.

See next slide for details about removing cables.

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February 2010

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CON Board Removal Board Continued (Unlocking CN1 and CN2 LVDS Ca

TT--CON Board Removal Board Continued (Unlocking CN1 and CN2 LVDS Ca

bles)

Press In

Press in on the two tabs and slowly rock the cable out of the connector.

(CN1) LVDS

Pull Out

To remove the LVDS cables CN1 and CN2;

(Shown by the arrows in Figure above)

Press In

(CN2) LVDS

Pull Out

Press In

Note: The tabs are fragile, use caution, they may break.

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February 2010

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CON Board Removal Board Continued (Unlocking CN4 and CN5 LVDS Ca

TT--CON Board Removal Board Continued (Unlocking CN4 and CN5 LVDS Ca

To remove the flex cables to the TFT Panel, CN4 or CN5, place a soft thin object like a fingernail underneath the black locking tab and gently pull forward.

(Shown by the arrows in Fig 1 and 2)

bles)

Fig 1

Fig 2

CN5 or CN4 Locked

Flip the lock up and back from the flex cable. Then the flex cable can be easily removed.

Unlocked

Fig 3

The locking tab is flipped down

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February 2010

LCD DV 42LH90

Removing the Main Board

Disconnect P3500,

P3501, P3502, P1200,

P700 and P600

P3501

Remove any tape holding

down any cables.

Remove the 6 screws

indicated by the arrows.

Remove decorative

plastic and remove the

board.

P700

P1200

Flip the locking tab upward, pull the LVDS ribbon out.

P3500 P3502

Press in on the top

and bottom release

tabs to remove.

Decorative

Plastic

(See a and b)

n/c

(b)

Lift Out Pull

Down

NOTE: Always check on

top and behind the Large

ICs. And look for a piece

of Chocolate

(Heat Transfer Material).

Be sure to transfer to

new Board if present.

P600

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February 2010

n/c

(a)

Slide

Right

LCD DV 42LH90

Removing the Inverter Board

Remove the 8 screws

indicated by the arrows.

Remove the Inverter Shield.

Use caution, do not allow screws to fall.

Disconnect CN1,

CN3, CN4 and CN306.

Remove the Inverter.

CN306

Inverter

NOTE: Always check for Chocolate

(Heat Transfer Material).

Be sure to transfer to new Board if present

and replace in the correct position.

There should be 8 pieces on the DC to DC

converter coils near the bottom right.

NOTE: If Servicing the Board, return the

screws into the board to provide stability

and grounding.

CN3

26

CN4

CN1

Chocolate

February 2010

LCD DV 42LH90

Removing the Inverter Board (Chocolate Notice) Back Side of the

On the back side of the

Inverter are 5 pieces of

Chocolate, (Heat Transfer

and Noise reduction pads).

Be sure to replace these on

the New Inverter if the board

is replaced.

Be sure they do not fall off if

the Inverter is removed.

Chocolate Close Up

Board

Chocolate

27

Chocolate Location

White Box Outline

February 2010

LCD DV 42LH90

Removing Front Boards (IR Board and Moving LED Board)

Disconnect P101 and P102.

Note P102 is behind the Power Switch.

p/n EBR62127501

Remove the IR board by removing the 1 screw and lift out the board.

Key board

p/n EBR62128101

P100

P102

The Power Switch has

been removed for easier

viewing of connectors and

screws.

IR board / Intelligent Sensor

101

P

100

P

J

Disconnect J1 or P100. Remove

the LED board by lifting up on

the two locking tabs and pull

backwards on the board.

Tab

1

Moving LED board

(Power LEDs)

p/n EBR61674001

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February 2010

LCD DV 42LH90

Removing Front Key Board

Key

Board

p/n EBR62127501

To Remove the Key

Board, Apply Pressure at

point (A) on the Key Board itself while using an object to slightly pry

out from the top.

(A)

Push In

Tab Tab

(B)

Push In

Tab

Slots

Tab

Slots

Apply Pressure at point

(B) on the Key Board

itself while using an

object to slightly pry out

from the bottom.

Disconnect

P100

and remove the

Key Board

P1

0

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February 2010

LCD DV 42LH90

TROUBLESHOOTING SECTION

Troubleshooting:

This section of the manual will also discuss

troubleshooting.

Upon completion of this section the Technician will have

a better understanding of how to diagnosis and resolve

problems.

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February 2010

LCD DV 42LH90