LG 42LH20 Series Bedienungsanleitung

42LH20

Direct View LCD

Original: March 2009

Updated: February 11, 2010

February 2009 42LH20

OUTLINE

• 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

• Side Keys

February 2009 42LH20

42LH20 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

February 2009 42LH20

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)

February 2009 42LH20

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 or PLASMA 2009 Model

Contact Information

Also available on the

Plasma page

Plasma page New Training Materials on

New Training Materials on

the Learning Academy site

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

LG Electronics Alabama, Inc. 201

James Record Road, Huntsville,

AL, 35813.

http://136.166.4.200

Published March 2009 by LG Technical Support and Training

32LG40, 32LH30, 37LH55, 42LG60, 42LG70, 42LH20, 42LH40, 42LH50, 42LH90, 42SL80,

47LG90,47LH85

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

LCD-DV:

PLASMA:

Plasma Panel

Alignment Handbook

Presentations

with Audio/Video

and Screen Marks

February 2009 42LH20

Safety and Handling Regulations

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

2. SMPS adjustments are factory sealed. They are VR301 (Frequency) and VR302 (Current)

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. Always handle the circuit boards on the

outside edges while using ESD protection.

5. Exercise care when making voltage and waveform checks to prevent costly short circuits

from damaging the unit.

6. Be cautious of loose screws and other metal objects to prevent a possible short in the

circuitry.

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…

Observe the following items

LCD Direct View Overview

February 2009 42LH20

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 Diode Check 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.

February 2009 42LH20

This section of the manual will discuss the specifications of the 42LH20

LCD Direct View Display Panel.

42LH20 Product Information

February 2009 42LH20

Basic Specifications

Key Features

•42" Screen

•720p HD Resolution

•Two (2) HDMI(TM) (V.1.3 with Deep Color)

•ISFccc Ready

•Smart Energy Saving

•LG SimpLink (TM) (32-inch and above)

•LG Core Technologies (32-inch and above)

•Dynamic Contrast Ratio 12,000:1

•Response Time (G to G) 8ms

•Brightness 500 cd/m2

•Viewing Angle 178º / 178º

•Life Span (Typical) 60,000 hr

•Built-in Tuner ATSC/NTSC/Clear QAM

•HDMI™/HDCP Input 2 v1.3

•Cabinet Color Glossy Piano-Black

•Limited Warranty 1 Year Parts/Labor

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