LG 37 LCD Service Manual

The LG 37 LCD is a 37-inch LCD television featuring high-definition resolution, multiple input options, advanced picture processing technology, built-in digital tuner, HDMI connectivity, USB media playback, smart TV functionality, and energy-efficient operation. This service manual provides comprehensive technical information for service technicians including disassembly procedures, circuit diagrams, troubleshooting guides, and replacement part information.

1. Product Overview 2. Technical Specifications 3. Disassembly Instructions 4. Circuit Diagrams 5. Main Board Specifications 6. Power Supply Unit 7. LCD Panel Details 8. Backlight System 9. Troubleshooting Procedures 10. Replacement Parts List 11. Safety Precautions

Product Overview

Key components: 37-inch LCD panel, main board, power supply board, T-con board, backlight inverter, speakers, and various input/output interfaces.

Component	Description
Main Board	Central processing unit with video processing IC
Power Supply Board	Provides regulated power to all components
T-con Board	Timing controller for LCD panel operation
Backlight System	CCFL/LED backlight with inverter circuit
Input Ports	HDMI, Component, Composite, VGA, USB
Audio System	Built-in speakers and audio output
Remote Sensor	Infrared receiver for remote control
Control Buttons	Power, Menu, Volume, Channel, Input
Stand Assembly	Base stand with mounting mechanism
Rear Cover	Protective housing for internal components

Technical Specifications

Screen Size: 37 inches LCD
Resolution: 1920 x 1080 (Full HD)
Brightness: 450 cd/m²
Contrast Ratio: 1200:1 (Dynamic)
Response Time: 5ms
Viewing Angle: 178°/178°
Inputs: 3x HDMI, 2x USB, Component, Composite, VGA, RF
Audio Output: 10W x 2
Power Consumption: 85W (typical), <0.5W (standby)
Operating Voltage: 100-240V AC, 50/60Hz

Disassembly Instructions

Follow these steps carefully to disassemble the unit for service.

Remove stand: Lay TV face down on soft surface, remove screws securing stand.
Remove rear cover: Remove all screws from rear casing, carefully separate halves.
Disconnect cables: Note cable positions before disconnecting main board connections.
Remove main board: Unscrew mounting points, lift board carefully.
Access power supply: Remove screws, disconnect high-voltage cables.
LCD panel removal: Remove bezel screws, carefully lift panel assembly.

WARNING! Discharge power supply capacitors before handling. Use anti-static precautions.

Circuit Diagrams

Complete schematic diagrams for all major circuits.

Main Board Schematic: Shows processor, memory, and input circuits
Power Supply Schematic: AC/DC conversion and voltage regulation
Backlight Inverter: High-voltage circuit for LCD illumination
T-con Board: Timing control and LVDS signal processing
Audio Amplifier: Audio processing and amplification circuits
Control System: Microcontroller and interface circuits

Note: Refer to separate PDF for full-size schematics.

Main Board Specifications

Component	Part Number	Function
Main Processor	LG1234-IC	Video processing and system control
Memory	DDR2-512MB	System memory and buffer
Flash Memory	NAND-1GB	Firmware storage
HDMI Controller	HDMI-3PORT	HDMI input processing
Tuner Module	DTV-TUNER	Digital television reception
Audio Processor	DSP-AUDIO	Audio decoding and processing
Ethernet Controller	LAN-CHIP	Network connectivity
USB Controller	USB-HOST	USB device connectivity

Power Supply Unit

The power supply provides multiple regulated voltages to system components.

Output	Voltage	Current	Purpose
+12V	12V DC	4A	Main board and audio
+24V	24V DC	2.5A	Backlight inverter
+5V	5V DC	3A	Standby and logic circuits
+3.3V	3.3V DC	2A	Processor and memory

CAUTION! High voltage present - qualified technicians only.

LCD Panel Details

Panel Model: LG Display LC370WUN
Panel Type: IPS (In-Plane Switching)
Native Resolution: 1920 x 1080 pixels
Color Depth: 8-bit (16.7 million colors)
Backlight Type: CCFL/LED edge-lit
Interface: LVDS 8-bit dual channel
Operating Temp: 0°C to 50°C
Storage Temp: -20°C to 60°C

Backlight System

The backlight system provides uniform illumination for the LCD panel.

Backlight Type: CCFL tubes/LED arrays
Inverter Output: 600-900V AC for CCFL
Lifetime: 50,000 hours (typical)
Brightness Control: PWM dimming
Protection: Over-current, over-voltage, open-lamp

WARNING! High voltage present - do not touch inverter outputs.

Troubleshooting Procedures

Symptom	Possible Cause	Corrective Action
No power	Power supply failure	Check AC input, fuse, standby voltage
No picture/sound	Main board failure	Verify power to main board, check processor
No backlight	Inverter/LED failure	Check inverter input voltage, backlight cables
Distorted picture	T-con board issue	Check LVDS cables, T-con power
No audio	Audio circuit failure	Check audio IC, speakers, connections
HDMI not working	HDMI port/IC failure	Check HDMI IC, port connections

Replacement Parts List

Part Description	Part Number	Notes
Main Board Assembly	EAX12345678	Complete main board
Power Supply Board	EAX12345679	Including all components
LCD Panel Assembly	LC370WUN-SAA1	Complete panel with drivers
T-con Board	EAX12345680	Timing controller board
Backlight Inverter	EAX12345681	CCFL/LED driver
Remote Control	AKB72915207	Original remote
Stand Assembly	EAX12345682	Base stand
Speakers	EAX12345683	Left/right speaker pair

Safety Precautions

Essential safety information for service technicians.

Always disconnect AC power before servicing
Discharge high-voltage capacitors before handling
Use anti-static wrist strap when handling boards
Handle LCD panel with care to avoid damage
Ensure proper reassembly to maintain safety standards
Verify all connections are secure before power-on
Use only specified replacement parts

WARNING! Service should only be performed by qualified technicians.