LG 47LG90 Service Manual

47LG90

Direct View LCD

LED Backlights

Updated 12/03/2009

Original February 2009

OUTLINE

Section 1

Section 2

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

Circuit Board Operation, Troubleshooting of :

• Switch mode Power Supply

NEW

• LED Backlight System

• Main Board

•T-CON Board NEW: Two control connections to the

Inverters for Global and Local Dimming

• Ft Control Board

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Overview of Topics to be Discussed

47LG90 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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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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(Electrostatic Static Discharge)

ESD

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 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.

NOTICE

(Electrostatic Static Discharge)

assembly by its edges only. When

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LG CONTACT INFORMATION

Customer Service (and Part Sales) (800) 243-0000 Technical Support (and Part Sales) (800) 847-7597 USA Website (GCSC) aic.lgservice.com Customer Service Website us.lgservice.com LG Web Training lge.webex.com

LG CS Academy lgcsacademy.com

LCD-DV:

PLASMA:

Also available on

the Plasma page

Published February 2009 by LG Technical Support and Training

http://136.166.4.200

LG Learning Academy

32LG40, 32LH30, 37LH55, 42LG60, 42LG70, 42LH20, 42LH40, 42LH50, 47LG90 42PG20, 42PQ20, 50PQ30, 50PG20, 50PS80, 50PS60

Plasma Panel

Alignment Handbook

LG Electronics Alabama, Inc.

201 James Record Road, Huntsville, AL, 35813.

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New Training Materials on

the Learning Academy site

LCD DV 47LG90

SECTION 1: LCD OVERVIEW

Safety and Handling Regulations

1. Approximately 20 minute pre-run time is required before any adjustments are performed.

2. Refer to the Voltage Sticker on the Switch Mode Power Supply silk screening. (+/- ½ volt).

3. Be cautious of electric shock from the Backlight section, it uses high voltage AC. Check that the Power Supply and Drive Circuits are completely discharged because of residual current stored before Circuit Board removal.

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

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

6. 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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Basic Troubleshooting Steps

Define, Localize, Isolate and Correct

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

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.

•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.

After carefully checking the symptom and determining the circuits to be

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

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

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47LG90 Product Information

This section of the manual will discuss the specifications of the 47LG90

LCD Direct View Display Panel.

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Basic Specifications

• Full HD 1080p Resolution (1920 x 1080)

• 1,000,000:1 Dynamic Contrast Ratio

• TruMotion 120Hz

• 4x HDMI™ V.1.3 with Deep Color

• Intelligent Sensor

• 24p Real Cinema

• AV Mode (Cinema, Sports, Game)

• Clear Voice

• LG SimpLink™ Connectivity

• Invisible Speaker System

• USB 2.0 (JPEG, MP3)

• ISFccc

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Basic Specifications (LOGO Familiarization) Page 1

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

TruMotion 120Hz

Advance 120Hz panel provides clear, smooth images, even during fast action scenes creating a stable structure for a crisper picture.

Intelligent Sensor

Unlike other sensors which can only sense brightness of ambient light, LG’s “Intelligent Sensor” uses 4,096 sensing steps to evaluate its surroundings. Using a sophisticated algorithm, the LG processes picture quality elements including brightness, contrast, color, sharpness and white balance. The result is a picture optimized for it’s surroundings, more pleasing to watch and which can also save up to 50% in power consumption.

24p Real Cinema

Hi-def movies run at exactly 24 frames per second speed that they were originally filmed in, making your home-cinema experience one step closer to a “Real Cinema” experience.

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Basic Specifications (LOGO Familiarization) Page 2

Clear Voice Technology

Automatically enhances and amplifies the sound of the human voice frequency range to provide high-quality dialogue when background noise swells.

SIMPLINK

Allows for convenient control of other LG SimpLink products using the existing HDMI connection.

Invisible Speaker System

A new invisible speaker system tuned by renowned audio expert, Mr. Mark Levinson. This unique system incorporates speaker actuators around the perimeter of the entire bezel, eliminating traditional speaker drivers and associated grills. This not only allows for a sleek, finished look, but also

offers a wider “sweet spot” by creating a virtual “wall” of sound.

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Basic Specifications (LOGO Familiarization) Page 3

LED BACKLIGHTING SYSTEM

Using LEDs for backlighting pushes picture quality to our best levels ever. Experience deep blacks through a 1,000,000:1 dynamic contrast ratio. LED backlighting also results in more natural color representation and faster response time for smoother, more natural picture motion.

USB

Viewing Photos and for Software Upgrades

ISF

Allows expert alignments to be saved.

Swivel Stand

Allows the TV to rotated 20 degrees either side.

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Remote Control Familiarization

TOP PORTION

BOTTOM PORTION

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Accessing the Service Menu

REMOTE

TOP PORTION

To access the Service Menu.

1) Turn the Set On

2) Simultaneously, Press and “Hold” the Menu Key on the Side Key pad and Press and “Hold” the Menu Key on the Remote approximately 5 seconds.

3) If Customer’s Menu appears, continue to hold until it disappears.

SIDE KEYS

4) The Service Menu appears

Note: It is possible, dependant upon the Software Version,

a Password may be required to enter the Service Menu.

If a password is required, enter

0000

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Rear and Side Input Jacks

Rear Input Jacks

Main PWB

Orientation

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Side Input

Jacks

LCD DV 47LG90

Weight w/o Stand 56.9 lbs

Weight with Stand 67.2 lbs

30.1"

764.54mm

47LG90 Dimensions

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

44.9"

1140.46mm

7.9"

200mm

16"

406.5mm

9.96"

253mm

5.0"

127mm

32.4"

822.96mm

2.2"

56mm

Weight w/o Stand 56.9 lbs

Weight with Stand 67.2 lbs

15.59"

396mm

5.7"

145mm

11.65"

296mm

Center

27.5"

698.5mm

17

7.9"

200mm

Model No.

Serial No.

Label

Remove 4 screws to

remove stand for

wall mount

13.5"

342.9mm

DISASSEMBLY SECTION

This section of the manual will discuss Disassembly, Layout and Circuit Board Identification, of the 47LG90 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 circuit boards and be able to identify each board.

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Removing the Back Cover

The Stand does not need to be removed

Remove the 26 screws indicated.

Pay attention to

the size and

type of screw

as there are many

different types.

Putting in the

improper screw

When reassembling

may Cause damage.

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Power Supply PWB Removal

P2

4

0

Step

1

Remove the 4 screws indicated by the arrows and remove the shield.

Step

2

Disconnect P201, P204, P205 and AC In.

P205

P201

Remove the 4 screws indicated by the arrows.

A

C

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I

n

LCD DV 47LG90

Main PWB Shield Removal

Remove the two screws holding the Decorative plastic piece on the right side. Remove the plastic piece.

Remove the three pieces of tape on the left and top side that are shielding the cables as shown.

Remove the remaining 10

TAP

Warning: The Tape shown Is Conductive. Do not allow to touch electrically charged components.

T

A

P

E

ve

i

t

a

r

co

e

D

c

i

ast

l

P

screws indicated by the arrows.

It is possible that your unit may have the Chocolate (Heat Transfer) material over the two large ICs. (See white squares) Maybe even behind the ICs. If so, pay attention to the location and return when reassembling.

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TAP

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MAIN PWB Removal

Disconnect P1000, P1001, P800, P404 and P501 Note: In the top right is a connector P200. This is an open connection.

Remove the 2 screws securing the Main PWB.

Note: The top 2 and bottom 2 screws were removed during the shield removal process.

P800

P404

P1000

P1001

P200

No Connection

NOTE: Look carefully on

top and behind the BCM and Micronas Chip, look

for a piece of Chocolate

(Heat Transfer Material).

Be sure to transfer to new PWB if replaced.

P501

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CON (TFT Driver) PWB Removal

TT--CON (TFT Driver) PWB Removal

Look for Chocolate (Rubber like) Heat

transfer material under shield. Always

put back is same location.

Removing the T-CON shield.

“Chocolate Pads”

Heat Transfer Materials

Remove and save the tape

over the LVDS Cables

Warning: The Tape shown is Conductive. Do not allow to touch electrically charged components.

23

CN2

CN4

C

N

9

CN5

8

CN

CN1

CN7

n/c

Disconnect CN1, CN2, CN4 and CN5.

See next slide for details.

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CON (TFT DRIVE) PWB REMOVAL CONTINUED:

TT--CON (TFT DRIVE) PWB REMOVAL CONTINUED:

UNLOCKING CN1, CN2, CN4 and CN5

To remove the flex cables to the TFT Panel, CN4 or CN5: Place a soft sharp object like a fingernail underneath the black locking tab and gently lift upward.

(Shown by the arrows in Fig 1)

CN4 or CN5 Locked

Use your fingernail to release locks to avoid damage to locking mechanism.

Fig 1

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

Unlocked

Fig 2

The locking tab is flipped upward

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Fig 3

To remove the LVDS cables for CN1 or CN2; Press in on the two tabs and slowly rock the cable out of the connector.

(Shown by the arrows in Fig 3)

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CON (TFT Drive) CN8 or CN9 Unlocking

TT--CON (TFT Drive) CN8 or CN9 Unlocking

Lift

Evenly

From this

side

Unlocked

Lifted Up

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CN8

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T-CON PWB

Locations

CN9

Use same

procedure

LCD DV 47LG90

Inverters ““MM””

Inverters

and ““SS””

and

Inverter “M” Inverter “S”

PWB Removal Step 1 (Shield Removal)

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INVERTERS (BACKLIGHT LED DRIVE) PWBs

““MM””and

and ““SS””

Removal Step 2

CN3

4

/

CN5

6

/

To Backlight

LEDs

CN7

8

/

“M”

CN3

0

4

No

Co

n

e

t

c

o

i

n

CN1

All screws to PWBs have

been removed when

removing shields.

If attempting service PWB,

return screws before

attempting to turn on set.

CN8

CN5

“S”

0

4

0

1

CN5

1

/

0

9

0

/

8

0

7

To Backlight

LEDs

CN5

0

/

6

0

5

CN9

CN5

0

/

4

0

3

1

/

0

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TROUBLESHOOTING SECTION

This section of the manual will 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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Circuit Board Layout

T-CON p/n EAT56805201

T-CON Under Shield

LVDS

Cables

p/n 6917L-0006A p/n 6917L-0007A

Side

Controls

Inverter

“M”

Under

Shield

POWER SUPPLY

Tweeter

Ft Control

AC Input

Woofer

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Woofer

Main “Digital” Under Shield

Rear Inputs

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Inverter

“S”

Under

Shield

RF

Input

Side Inputs

Tweeter

LCD DV 47LG90

Power Supply (SMPS) PWB Layout

To “M”

Inverter

P204

P205

P201

To “S”

Inverter

To Main

F101

3.15A/250V Run 385.7V

Stby 155.8V

From Hot Gnd

Hot Ground

Shock Hazard

30

F100

8A/250V

AC IN

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