LG 42LG70 Series Installationsanleitung

42LG70

Direct View LCD

LCD DV 42LG70

2Spring 2009

OUTLINE

•BallastBoard

• Main Board

•T-CONBoard

Circuit Board Operation, Troubleshooting of :

• Switch mode Power Supply

Section 1

Section 2

Contact Information, Preliminary Matters, Specifications,

LCD Overview, General Troubleshooting Steps,

Signal Distribution, Disassembly Instructions and Voltages

• Ft Control Board

LCD DV 42LG70

3Spring 2009

42LG70 LCD Direct View Display

Section 1

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.

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.

Overview of Topics to be Discussed

LCD DV 42LG70

4Spring 2009

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.

Preliminary Matters (The Fine Print)

LCD DV 42LG70

5Spring 2009

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.

ESD

ESD NOTICE

NOTICE

(Electrostatic Static Discharge)

LCD DV 42LG70

6Spring 2009

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 CS Academy lgcsacademy.com

LG Web Training lge.webex.com

Published March 2009 by LG Technical Support and Training

LG Electronics Alabama, Inc.

201 James Record Road,

Huntsville, AL, 35813.

LCD DV 42LG70

7Spring 2009

Safety & Handling Regulations

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…

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

Troubleshooting

SECTION 1:

SECTION 1: LCD OVERVIEW

LCD OVERVIEW

LCD DV 42LG70

8Spring 2009

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, or listen for

relay closing etc. Observation of the front Power LED may give some clues.

•Localize After carefully checking the symptom and determining the circuits to be

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

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

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.

LCD DV 42LG70

9Spring 2009

This section of the manual will discuss the specifications of the 42LG70

LCD Direct View Display Panel.

42LG70 Product Information

LCD DV 42LG70

10 Spring 2009

Basic Specifications

• Full HD 1080p Resolution (1920 x 1080)

• 50,000:1 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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