LG 37LC7D Service Manual

The LG 37LC7D is a 37-inch LCD television featuring Full HD 1080p resolution, built-in digital and analog tuners, multiple HDMI inputs, USB connectivity, PC input capability, and advanced picture processing technologies. This service manual provides comprehensive technical information for qualified service personnel including disassembly instructions, circuit diagrams, troubleshooting procedures, and replacement part specifications.

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

Product Overview

The LG 37LC7D LCD TV features a 37-inch widescreen display with 1920x1080 resolution, 5000:1 dynamic contrast ratio, and 178-degree viewing angle. Key components include main board, power supply board, T-CON board, LCD panel, and backlight system.

ComponentDescription
Main BoardModel: EAX36153801 - Handles signal processing and system control
Power SupplyModel: EAY40419301 - Provides various DC voltages to system
T-CON BoardTiming controller for LCD panel drive signals
LCD Panel37-inch LCD with LED backlight system
Inputs/Outputs3x HDMI, 2x Component, 1x VGA, 1x Composite, 1x S-Video
Tuner SystemIntegrated digital/analog tuner with CI slot
Audio System10W x 2 speaker output with Dolby Digital processing

Technical Specifications

Disassembly Procedures

Follow these steps carefully for proper disassembly of the LG 37LC7D LCD TV.

  1. Remove stand: Lay TV face down on soft surface, remove 4 screws securing stand.
  2. Remove rear cover: Remove all visible screws from rear cabinet.
  3. Separate front/back cabinets: Carefully pry apart using plastic opening tools.
  4. Disconnect cables: Note positions before disconnecting all internal cables.
  5. Remove main board: Remove mounting screws and disconnect all connectors.
  6. Remove power supply: Disconnect AC input and all output connectors.
  7. Access LCD panel: Remove metal chassis screws to access panel assembly.

WARNING! Always disconnect power before disassembly. Handle LCD panel with care to avoid damage.

Circuit Diagrams

Complete circuit schematics for all major boards and systems.

DiagramDescriptionReference
Main BoardComplete schematic with IC pinoutsFig. 5-1
Power SupplySMPS circuit with voltage outputsFig. 5-2
T-CON BoardTiming controller and LVDS interfaceFig. 5-3
Audio SectionAmplifier and audio processing circuitsFig. 5-4
Tuner SectionDigital/analog tuner and demodulatorFig. 5-5

Note: All diagrams include component values and test points.

Main Board Replacement

Procedure for replacing the main system board (EAX36153801).

  1. Disconnect all external cables and power cord.
  2. Remove rear cabinet as described in disassembly section.
  3. Document all cable connections with photos or diagrams.
  4. Remove 6 mounting screws securing main board.
  5. Carefully disconnect all ribbon cables and connectors.
  6. Install new main board and reconnect all cables.
  7. Reassemble cabinet and test all functions.

Important: After replacement, enter service menu to configure settings.

Power Supply Board

Troubleshooting and service information for power supply board EAY40419301.

VoltageValueTest PointTolerance
Standby 5V5.1V DCCN201 Pin 1±5%
Main 12V12.0V DCCN201 Pin 3,4±5%
Main 24V24.0V DCCN201 Pin 5,6±5%
Inverter 24V24.0V DCCN202 Pin 1,2±5%
Audio 15V15.0V DCCN203 Pin 1,2±5%

Safety: High voltage present on primary side - exercise caution.

LCD Panel Service

Service procedures for LCD panel and backlight system.

  1. Panel removal: Remove bezel and disconnect LVDS cables.
  2. Backlight replacement: Remove diffuser sheets and LED strips.
  3. Inverter board: Test and replace if backlight fails to illuminate.
  4. Panel testing: Use test patterns to identify defective pixels.
  5. Reassembly: Ensure proper alignment of all optical components.

CAUTION! LCD panels are fragile and easily damaged by pressure or static electricity.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
No powerPower supply failureCheck standby voltage, replace power board if necessary
No picture/soundMain board failureVerify input signals, replace main board if needed
Backlight failureInverter/LED issueCheck inverter output, replace backlight if dark
No videoT-CON board failureTest LVDS signals, replace T-CON board
Audio distortionAmplifier/speaker issueCheck audio IC, test speakers, replace as needed
Tuner problemsTuner module failureReplace tuner module or main board

Replacement Parts List

Authorized replacement parts for LG 37LC7D service.

Part NumberDescriptionQty
EAX36153801Main Board Assembly1
EAY40419301Power Supply Board1
EAX40419401T-CON Board1
6871Q-0583ALCD Panel Complete1
AGG73325001Remote Control1
3840ER1002BSpeaker Set2
3840ER1001ABacklight LED Strip4

Safety Precautions

Essential safety information for service technicians.

WARNING! High voltage present even when unit is unplugged.

Service Tools Required

Recommended tools for servicing LG 37LC7D LCD TV.

ToolSpecificationPurpose
Digital MultimeterAuto-ranging, CAT IIIVoltage and continuity testing
Oscilloscope100MHz, dual channelSignal analysis and troubleshooting
ESD Wrist Strap1M ohm resistanceStatic protection for components
Torx Screwdriver SetT8-T15 sizesDisassembly of cabinet and chassis
Plastic Opening ToolsVarious sizesSafe cabinet separation
Soldering StationESD safe, temperature controlComponent-level repairs
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