LG 55LM6400 Service Manual

The LG 55LM6400 is a 55-inch LED TV with Full HD 1080p resolution, built-in digital tuner, Smart TV capabilities with webOS platform, multiple HDMI inputs, USB connectivity, built-in Wi-Fi, Ethernet port, component/composite inputs, optical audio output, and energy-saving features. Below are key sections for safety, technical specifications, disassembly procedures, troubleshooting, and replacement parts.

1. Product Overview 2. Technical Specifications 3. Safety Precautions 4. Disassembly Procedures 5. Main Board Replacement 6. Power Supply Board 7. LCD Panel Assembly 8. Troubleshooting Guide 9. Error Codes 10. Parts List 11. Wiring Diagrams

Product Overview

Key components: 55-inch LED panel, main board, power supply board, T-Con board, LED backlight system, speakers, and various input/output connectors.

ComponentDescription
Main BoardEAX64419304 - Processes all inputs and controls TV functions
Power Supply BoardEAY64419301 - Provides power to all components
T-Con BoardControls timing and data to LCD panel
LED BacklightEdge-lit LED system with multiple strips
Speakers2 x 10W stereo speakers
Inputs/OutputsHDMI x3, USB x2, Component, Composite, Ethernet, Optical Audio

Technical Specifications

Safety Precautions

Before servicing, ensure proper safety procedures are followed.

  1. Disconnect power cord before disassembly
  2. Use anti-static wrist strap when handling circuit boards
  3. Discharge capacitors before working on power supply
  4. Handle LCD panel with care to avoid damage
  5. Use proper tools and equipment

WARNING! High voltage present in power supply section. Only qualified technicians should perform repairs.

Disassembly Procedures

Step-by-step instructions for accessing internal components.

  1. Remove stand (if attached) by loosening screws
  2. Remove rear cover screws (12 total)
  3. Carefully separate rear cover from front bezel
  4. Disconnect all cables from main board
  5. Remove main board mounting screws
  6. Remove power supply board mounting screws
  7. Access T-Con board by removing metal shield

CAUTION! LCD panel is fragile. Handle with care during disassembly.

Main Board Replacement

Procedure for replacing the main control board (EAX64419304).

  1. Disconnect all cables from main board
  2. Remove 6 mounting screws securing main board
  3. Carefully lift main board from chassis
  4. Install new main board and secure with screws
  5. Reconnect all cables according to labels
  6. Test TV operation before reassembling

Note: Main board contains firmware specific to this model.

Power Supply Board

Troubleshooting and replacement of power supply board (EAY64419301).

SymptomPossible CauseTest Point
No powerFuse, main capacitorCheck F901, C907
Standby LED onSecondary circuitsCheck 12V, 24V outputs
Intermittent powerCold solder jointsInspect all solder points
Backlight issuesLED driver circuitCheck LED voltage

LCD Panel Assembly

Handling and replacement of the LCD panel and LED backlight system.

  1. Remove front bezel carefully using plastic tools
  2. Remove diffuser sheets and optical films
  3. Access LED strips along edges
  4. Test individual LED strips for failure
  5. Replace damaged LED strips as needed
  6. Reassemble in reverse order, ensuring cleanliness

WARNING! Do not touch LCD surface or optical films with bare hands.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
No powerPower supply, main boardCheck power supply voltages, replace main board
No picture, sound OKT-Con board, LCD panelCheck T-Con voltages, replace T-Con board
No backlightLED strips, power supplyTest LED strips, check backlight voltage
No soundSpeakers, audio ICCheck speaker connections, replace main board
Wi-Fi not workingWi-Fi module, main boardCheck Wi-Fi module connection, update firmware

Error Codes

Common error codes and their meanings for the LG 55LM6400.

Error CodeDescriptionSolution
E1Main board communication errorReplace main board
E2Power supply errorCheck power supply board
E3T-Con board errorReplace T-Con board
E7Backlight errorCheck LED strips and driver
E8Panel errorReplace LCD panel

Parts List

Replacement parts for LG 55LM6400 service.

Part NumberDescriptionQty
EAX64419304Main Board Assembly1
EAY64419301Power Supply Board1
EAX64419302T-Con Board1
6871Q-0583ALED Backlight Strip4
AH74409301Remote Control1
6841Q-2028ALCD Panel Assembly1

Wiring Diagrams

Connection diagrams for internal components and external inputs.

  1. Main board to power supply connections
  2. T-Con board to LCD panel ribbon cables
  3. LED backlight connector wiring
  4. Speaker connections to main board
  5. Input/output port connections
  6. Button board and IR sensor wiring

Note: Refer to schematic diagrams for detailed wiring information.

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