LG 42LK520 Service Manual

The LG 42LK520 is a 42-inch LCD television featuring Full HD 1080p resolution, built-in digital and analog tuners, multiple HDMI inputs, USB connectivity, Smart TV capabilities, energy-saving modes, and advanced picture processing technologies. This service manual provides comprehensive technical information for service technicians including disassembly procedures, circuit diagrams, troubleshooting guides, and replacement parts information.

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 Flowcharts 9. Error Codes 10. Parts List 11. Safety Precautions

Product Overview

The LG 42LK520 features a 42-inch LCD panel with LED backlighting, built-in Wi-Fi, multiple connectivity options, and LG's proprietary picture enhancement technologies.

Component	Description
Main Board	EAX61719301 - Processes all inputs and controls display functions
Power Supply	EAY61719301 - Provides power to all components
T-Con Board	Controls timing and signal distribution to LCD panel
LCD Panel	42-inch Full HD 1920x1080 resolution
Backlight Unit	LED edge-lit system
Input Board	Handles all external connections

Technical Specifications

Model: 42LK520
Screen Size: 42 inches diagonal
Resolution: 1920 x 1080 Full HD
Panel Type: LCD with LED Backlight
Tuner: ATSC/NTSC/Clear QAM
Inputs: 4x HDMI, 2x USB, Component, Composite, RF
Power Consumption: 85W typical, 0.3W standby
Operating Voltage: 100-240V AC, 50/60Hz
Dimensions: 38.2" x 23.6" x 3.2" (without stand)
Weight: 25.4 lbs (without stand)

Disassembly Procedures

Follow these steps carefully to disassemble the television for service.

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

WARNING! Always discharge capacitors before working on power supply. Handle LCD panel with extreme care.

Circuit Diagrams

Complete schematic diagrams for all major circuits.

Diagram	Description
Power Supply	Detailed schematic of EAY61719301 power board
Main Board	Complete EAX61719301 main board schematic
T-Con Board	Timing control board circuit diagram
Input Board	Input selection and processing circuits
Backlight Driver	LED backlight driver circuit schematic

Main Board Replacement

Procedure for replacing the main control board.

Disconnect power and remove rear cover.
Document all cable connections with photos.
Remove mounting screws securing main board.
Carefully disconnect all cables and ribbon connectors.
Install new main board and reconnect all cables.
Reassemble and test all functions.

Note: Main board part number EAX61719301 must match exactly.

Power Supply Board

Troubleshooting and replacement of power supply board EAY61719301.

Output Voltages: +12V, +24V, +5VSTB, +3.3V
Common Failures: Blown fuse, failed capacitors, shorted MOSFETs
Test Points: TP1 (+12V), TP2 (+24V), TP3 (+5VSTB)
Replacement: Part number EAY61719301 or compatible

CAUTION! High voltage present even when unplugged. Discharge large capacitors.

LCD Panel Service

Handling and replacement of the LCD panel assembly.

Remove bezel and protective covers.
Disconnect LVDS cables from T-Con board.
Remove panel mounting brackets.
Carefully lift panel avoiding pressure on screen.
Install replacement panel and reassemble.

WARNING! LCD panels are fragile and expensive. Handle with extreme care.

Troubleshooting Flowcharts

Step-by-step diagnostic procedures for common problems.

Symptom	Diagnostic Steps
No Power	Check AC input → Fuse → Standby voltage → Main power voltages
No Picture/Sound	Backlight test → Main board voltages → Input signal check
No Backlight	LED driver voltages → Backlight inverter → Panel connections
No Input Signal	Input board check → Main board processing → Cable integrity

Error Codes

Diagnostic error codes and their meanings.

Error Code	Description	Solution
E1	Main board communication failure	Check main board connections
E2	Power supply fault	Test power supply voltages
E3	Backlight failure	Check LED driver circuit
E4	T-Con board error	Replace timing control board
E5	Temperature sensor fault	Check thermal management

Parts List

Replacement parts and their part numbers.

Part	Part Number	Description
Main Board	EAX61719301	Main control board assembly
Power Supply	EAY61719301	Power supply board
LCD Panel	LC420EUN	42-inch LCD panel assembly
Remote Control	AKB72915207	Original remote control
Stand	42LK520-stand	Table stand assembly

Safety Precautions

Critical safety information for service technicians.

Always disconnect power before servicing
Discharge high-voltage capacitors
Use anti-static protection when handling boards
Handle LCD panels with care to avoid breakage
Follow all local electrical safety regulations
Use proper tools and test equipment

WARNING! Failure to follow safety procedures may result in injury or equipment damage.