LG 42LH30 Service Manual

The LG 42LH30 is a 42-inch LCD HDTV with 1080p resolution, built-in digital/analog tuner, multiple HDMI inputs, USB connectivity, PC input, component/composite video inputs, headphone jack, remote control, advanced picture settings, audio adjustments, and energy saving features. Powered by 120V AC, 60Hz. Below are key sections for safety, technical specifications, disassembly procedures, troubleshooting, and repair guidelines.

1. Product Overview 2. Technical Specifications 3. Disassembly Instructions 4. Main Board Components 5. Power Supply Board 6. LCD Panel Specifications 7. Troubleshooting Flowcharts 8. Voltage Measurements 9. Replacement Parts List 10. Wiring Diagrams 11. Safety Precautions

Product Overview

Key components: LCD panel with LED backlight, main board, power supply board, T-con board, speakers, remote control sensor, input/output connectors.

Component	Description
Main Board	EAX40353801 - Processes video/audio signals
Power Supply	EAY60137401 - Provides power to all components
T-Con Board	Controls LCD panel timing and drivers
LCD Panel	42-inch 1080p resolution with LED backlight
Speakers	2 x 10W stereo speakers
Inputs	3x HDMI, 2x USB, Component, Composite, PC VGA
Outputs	Digital audio optical, headphone jack

Technical Specifications

Screen Size: 42 inches LCD
Resolution: 1920 x 1080 (1080p Full HD)
Backlight: LED edge-lit
Tuner: ATSC/NTSC/QAM digital/analog
Inputs: 3x HDMI, 2x USB, Component, Composite, PC VGA, RF antenna
Sound Output: 20W total (10W x 2)
Power Consumption: 120W typical, 0.5W standby
Power Supply: 120V AC, 60Hz internal switching
Dimensions: 40.2" x 26.5" x 3.5" (with stand)
Weight: 35.3 lbs (with stand)

Disassembly Instructions

Required tools: Phillips screwdriver, plastic opening tools, anti-static wrist strap.

Remove stand: Lay TV face down on soft surface, remove screws securing stand.
Remove rear cover: Remove all screws from back panel, carefully separate plastic clips.
Disconnect cables: Note cable positions before disconnecting from main board.
Remove main board: Remove mounting screws and carefully lift board out.
Access power supply: Remove screws and disconnect power cables.
LCD panel removal: Extreme care required - use suction cups for handling.

WARNING! High voltages present even when unplugged. Discharge capacitors before servicing.

Main Board Components

Main board EAX40353801 contains primary ICs and connectors.

Component	Part Number	Function
Main Processor	MT5326	Video/audio processing
Memory	K4B2G1646E	2GB DDR3 system memory
Flash Memory	MX25L3206E	32MB firmware storage
Tuner Module	TDMF-001	Digital/analog TV tuner
HDMI Controller	PS321	HDMI input processing

Power Supply Board

Power supply board EAY60137401 provides multiple voltage rails.

Output	Voltage	Current	Purpose
Main 12V	12V DC	8A max	Main board, audio amp
LED Backlight	200V DC	300mA	LED driver circuit
Standby 5V	5V DC	1A	Standby power
3.3V	3.3V DC	2A	Logic circuits

CAUTION! High voltage present on LED backlight circuit - risk of electric shock.

LCD Panel Specifications

Panel Model: LC420EUN
Resolution: 1920 x 1080 pixels
Response Time: 6.5ms
Viewing Angle: 178°/178°
Backlight Type: White LED edge-lit
Interface: LVDS 8-bit dual port
Manufacturer: LG Display

Troubleshooting Flowcharts

Systematic approach to common failure modes.

No Power: Check AC input → Standby voltage → Main power supply → Main board
No Backlight: Check LED voltage → Inverter circuit → T-con board → Main board
No Video: Check input source → Main board output → T-con board → LCD panel
No Audio: Check audio settings → Audio amplifier → Speakers → Main board
Remote Not Working: Check batteries → IR sensor → Main board IR circuit

Voltage Measurements

Key test points for diagnostics (refer to schematic for exact locations).

Test Point	Normal Voltage	Tolerance
CN201 Pin 1-2	12V	±5%
CN201 Pin 3-4	5V STBY	±5%
LED Connector	180-220V	Varies with brightness
Main 3.3V	3.3V	±3%
T-con 12V	12V	±5%

Replacement Parts List

Common replacement components and part numbers.

Component	Part Number	Description
Main Board	EAX40353801	Complete main board assembly
Power Supply	EAY60137401	Complete power supply board
LCD Panel	LC420EUN-SEF1	42-inch 1080p LCD panel
Remote Control	AKB72915207	Original remote control
Stand	AYT63934001	Table stand assembly
Speakers	AYT63934002	Replacement speaker set

Wiring Diagrams

Interconnection diagrams between major components.

Power Distribution: AC input → Power board → Main board → Other components
Video Signal Flow: Input sources → Main board → T-con board → LCD panel
Audio Signal Flow: Input sources → Main board → Audio amplifier → Speakers
Control Signals: Remote sensor → Main board → Power management → Display control
Backlight Circuit: Power board → LED driver → LED strips → Dimming control

Safety Precautions

Essential safety procedures for service technicians.

Always disconnect AC power before servicing
Discharge large capacitors before handling power supply
Use anti-static protection when handling circuit boards
Handle LCD panel with care - glass is fragile
Ensure proper reassembly to maintain electrical safety
Verify all connections are secure before applying power
Use insulated tools when working with live circuits
Follow local electrical safety regulations

WARNING! Failure to follow safety procedures may result in electric shock, fire, or equipment damage.