LG 52LD550 Service Manual

The LG 52LD550 is a 52-inch LCD HDTV with Full HD 1080p resolution, built-in digital/analog tuner, multiple HDMI inputs, USB connectivity, Intelligent Sensor technology, Clear Voice II, Invisible Speaker system, and energy-saving features. This service manual provides comprehensive technical information for service technicians including disassembly instructions, circuit diagrams, troubleshooting procedures, and replacement part information.

1. Product Overview 2. Specifications 3. Disassembly Instructions 4. Circuit Diagrams 5. PCB Layouts 6. Troubleshooting Procedures 7. Replacement Parts List 8. Adjustment Procedures 9. Safety Precautions 10. Block Diagrams 11. Test Points & Voltages

Product Overview

The LG 52LD550 features a 52-inch LCD panel with 1920x1080 resolution, 120Hz refresh rate, and LED backlight technology. Key components include main board, power supply board, T-CON board, LCD panel, and various interface boards.

Component	Description
Main Board	EAX61753801 - Processes all input signals and controls TV functions
Power Supply	EAX61753802 - Provides power to all components
T-CON Board	EAX61753803 - Timing controller for LCD panel
LCD Panel	LG Display 52" LCD with LED backlight
Interface Board	HDMI, Component, Composite inputs
Inverter Board	Controls LED backlight operation
IR Board	Infrared receiver for remote control
Key Board	Front panel controls
Speaker System	Invisible Speaker with Clear Voice II

Specifications

Model: 52LD550
Screen Size: 52 inches diagonal
Resolution: 1920 x 1080 Full HD
Backlight: LED Edge Lit
Refresh Rate: 120Hz
Tuner: ATSC/NTSC/QAM
Inputs: 4x HDMI, 2x Component, 1x Composite, 1x PC Input, 2x USB
Sound Output: 10W + 10W
Power Consumption: 150W typical, 0.3W standby
Power Supply: 100-240V AC, 50/60Hz
Dimensions: 48.1" x 30.7" x 2.4" (with stand)
Weight: 47.4 lbs (with stand)

Disassembly Instructions

Follow these steps carefully to disassemble the TV for service.

Remove Stand: Lay TV face down on soft surface, remove screws securing stand.
Remove Rear Cover: Remove all screws from rear cover, carefully separate cover from chassis.
Disconnect Cables: Note cable positions before disconnecting from main board.
Remove Main Board: Remove mounting screws and carefully lift board from chassis.
Access Power Supply: Remove screws securing power supply board.
LCD Panel Removal: Remove bezel screws, carefully separate LCD panel from frame.
T-CON Board Access: Located behind LCD panel, accessible after panel removal.

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

Circuit Diagrams

Complete circuit diagrams for all major components.

Main Board Schematic: EAX61753801 complete circuit diagram
Power Supply Schematic: EAX61753802 power circuit details
T-CON Board Schematic: EAX61753803 timing controller circuits
Input/Output Circuits: HDMI, Component, Audio circuits
Control Circuits: Microprocessor and control signal paths
Backlight Circuits: LED driver and inverter circuits

Note: All schematics include component values, test points, and voltage specifications.

PCB Layouts

Printed Circuit Board layouts with component placement.

Board	Part Number	Layout Details
Main Board	EAX61753801	Top and bottom layer component placement
Power Supply	EAX61753802	Power component locations and heatsinks
T-CON Board	EAX61753803	Timing controller IC and related components
IR/Key Board	EAX61753804	Front panel control layout
Input Board	EAX61753805	HDMI and other input connectors

Troubleshooting Procedures

Systematic troubleshooting guide for common issues.

Symptom	Possible Cause	Corrective Action
No Power	Power supply failure, main board issue	Check AC input, measure standby voltage, test power supply outputs
No Picture/Sound	Main board failure, backlight issue	Check main board voltages, test backlight operation
No Backlight	Inverter failure, LED strips	Test inverter output, check LED continuity
Distorted Picture	T-CON board, LVDS cable	Check T-CON voltages, reseat LVDS cables
No Sound	Audio circuit, speaker connection	Test audio IC, check speaker connections
HDMI No Signal	HDMI port, main board	Test HDMI ports, check main board HDMI circuits
Remote Not Working	IR sensor, remote control	Test IR sensor voltage, check remote battery

Replacement Parts List

Authorized replacement parts with part numbers.

Component	Part Number	Description
Main Board	EAX61753801	Complete main processing board
Power Supply	EAX61753802	AC/DC power supply board
T-CON Board	EAX61753803	Timing controller board
LCD Panel	LC520EUN	52" LCD panel assembly
LED Strips	6871Q-0538A	LED backlight strips
IR Board	EAX61753804	Infrared receiver board
Speakers	20031468	Invisible speaker pair
Stand	AGT-516H	Table stand assembly

Adjustment Procedures

Factory adjustment and calibration procedures.

White Balance Adjustment: Use service remote to access white balance menu
Backlight Adjustment: Adjust LED current for proper brightness
Color Temperature: Calibrate color temperature settings
Geometry Adjustment: Adjust picture position and size
Sound Calibration: Set audio levels and equalization
Tuner Alignment: Fine-tune digital and analog tuners

Note: Requires service remote control and proper test equipment.

Safety Precautions

Critical safety information for service technicians.

Always disconnect AC power before servicing
Discharge capacitors before touching power supply
Use proper grounding when handling LCD panels
Handle LED backlights with care - high voltage present
Use approved replacement parts only
Follow ESD precautions when handling circuit boards
Ensure proper reassembly to maintain safety certifications

DANGER! High voltages present even when unplugged. Always discharge capacitors.

Block Diagrams

System block diagrams showing signal flow.

Overall System Block Diagram: Complete signal path from inputs to display
Main Board Block Diagram: Video and audio processing paths
Power Supply Block Diagram: Power distribution system
T-CON Block Diagram: LCD panel control system
Audio System Block Diagram: Sound processing and amplification
Tuner System Block Diagram: Digital and analog tuning circuits

Test Points & Voltages

Critical test points and expected voltage readings.

Test Point	Location	Expected Voltage	Tolerance
STBY 5V	Power Supply	+5.0V	±5%
+12V	Power Supply	+12.0V	±5%
+24V	Power Supply	+24.0V	±5%
+3.3V	Main Board	+3.3V	±5%
+1.8V	Main Board	+1.8V	±5%
VCC_CORE	Main Board	+1.2V	±5%
VCOM	T-CON Board	+6.5V	±5%
VGH	T-CON Board	+25V	±5%
VGL	T-CON Board	-7V	±5%

Service Support: LG Service Center 1-800-243-0000 | www.lg.com