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LG 49LJ55 Series User Manual

LG 49LJ55 Series
54 pages
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P/NO : MFL69963003 (1703-REV01)
CHASSIS : LA75M
MODEL : 49LJ55** 49LJ55**-U*
LED TV
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
CONFIDENTIAL
Any reproduction, duplication, distribution (including by way of email, facsimile or other electronic means),
publication, modification, copying or transmission of this Service Manual is STRICTLY PROHIBITED unless you
have obtained the prior written consent of the LG Electronics entity from which you received this Service Manual.
The material covered by this prohibition includes, without limitation, any text, graphics or logos in this Service
Manual.
Copyright © 2017 LG Electronics Inc. All rights reserved. Only training and service purposes.

Table of Contents

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LG 49LJ55 Series Specifications

General IconGeneral
BrandLG
Model49LJ55 Series
CategoryLED TV
LanguageEnglish

Summary

SAFETY PRECAUTIONS

General Safety Guidance

General safety guidelines for servicing, including isolation transformers, fuses, and wire placement.

AC Leakage Current Checks

Procedures for performing cold and hot checks to ensure electrical safety during servicing.

SERVICING PRECAUTIONS

General Servicing Precautions

Essential precautions for general servicing, including power disconnection, testing, and cleaning.

Handling Electrostatically Sensitive Devices

Procedures to prevent damage to sensitive electronic components from static electricity.

Soldering Best Practices

Guidelines for proper soldering techniques, tools, and materials for effective repairs.

COMPONENT REPLACEMENT AND REPAIR

IC and Transistor Replacement

Procedures for removing and replacing Integrated Circuits (ICs) and discrete transistors.

Diode, Fuse, and Resistor Replacement

Steps for safely removing and replacing diodes, fuses, and conventional resistors.

Circuit Board Foil Repair

Techniques for repairing damaged copper traces on printed circuit boards.

SPECIFICATIONS

Application Range and Test Conditions

Defines the application range and standard conditions for testing TV components.

Test Methods and General Specifications

Outlines approved test methods and provides general technical specifications for the TV.

EXTERNAL INPUT SPECIFICATIONS

Component 2D Input Formats

Lists supported resolutions and frequencies for Component 2D video input.

HDMI Input Formats (PC/DTV)

Details supported resolutions and frequencies for HDMI inputs for PC and DTV.

SOFTWARE UPDATE PROCEDURES

Updating via USB

Step-by-step guide for updating the TV software using a USB memory stick.

Updating via Network (NSU)

Instructions for updating the TV software over the internet using the NSU function.

SYSTEM BLOCK DIAGRAM

EXPLODED VIEWS

Exploded View of TV Assembly

Provides a visual breakdown of the TV's internal and external components for service.

Exploded View of Modules

Details the exploded view of the TV's internal modules and panel assembly.

DISASSEMBLY GUIDE

Initial Disassembly Steps

Guides through the initial disassembly process, including screw removal and tape detachment.

Cable and Component Removal

Instructions for removing various cables, IR assembly, and WiFi PCB assembly.

Board and Speaker Removal

Details the process of removing screws for boards and disassembling the speaker modules.

Final Screw Removal

Covers the final screw disassembly steps for specific components.

TROUBLE SHOOTING GUIDE

STANDARD REPAIR PROCESS: VIDEO ERRORS

No Video/Normal Audio

Troubleshooting flowchart for resolving "No Video/Normal Audio" issues.

No Video/No Audio

Troubleshooting flowchart for resolving "No Video/No Audio" issues.

Picture Broken/Freezing

Troubleshooting flowchart for resolving picture breaking or freezing problems.

Color Issues

Troubleshooting steps for color errors, including input checks and test patterns.

Bars/Image Artifacts/External Device Color

Diagnoses vertical/horizontal bars, residual images, and external device color issues.

STANDARD REPAIR PROCESS: VIDEO ERROR DETAILS

Checking LCD Backlight

Method to check the LCD backlight by visual inspection after disassembly.

White Balance Adjustment

Procedure for checking and adjusting the TV's White Balance settings.

Tuner Signal Strength Check

How to check tuner input signal strength using OSD menus and external tools.

Software Version Checking

Method to check the TV's software version via the IN START menu.

Tuner Component Check

Identifies the tuner component and outlines checking methods for signal strength.

External Input Connection Diagram

Illustrates the connection diagram for external inputs to check screen condition.

Link Cable Reconnection Check

How to check the contact condition of the Link Cable, ensuring proper reconnection.

Test Pattern Adjustment

Using the ADJ key to display test patterns for diagnosing pixel defects and module errors.

APPENDIX: MAIN BOARD EXCHANGE (1)

APPENDIX: MAIN BOARD EXCHANGE (2)

APPENDIX: POWER BOARD (PSU) EXCHANGE

APPENDIX: MODULE EXCHANGE (1)

APPENDIX: MODULE EXCHANGE (2)

STANDARD REPAIR PROCESS: POWER ERRORS

Checking Power Indicator and Menu

How to check the power indicator and adjust TV settings via the menu.

Power Input Voltage Check

Procedure to check power input voltage and ST-BY voltage levels.

Power Off Mode Check

Method to check the TV's power off modes and status via the IN START menu.

STANDARD REPAIR PROCESS: AUDIO ERRORS

Sound Settings Check

How to check sound settings in the menu, specifically the Sound Out and TV Speaker options.

Voltage and Speaker Verification

Procedure to check voltage supply and speaker connection for audio issues.

STANDARD REPAIR PROCESS: FUNCTION ERRORS

Remote Control Operation Verification

Steps to check IR/Eye sensor condition and standby voltage for remote control functionality.

WiFi Operation Verification

Procedure to check IR/Wifi cable condition and 3.5V on the terminal for WiFi operation.

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