LG 50LB5900 Service Manual

The LG 50LB5900 is a 50-inch LED TV featuring Full HD 1080p resolution, webOS smart TV platform, built-in Wi-Fi, triple XD engine, LED Plus technology, Magic Remote compatibility, multiple HDMI inputs, USB connectivity, and energy-saving features. This service manual provides technical information for qualified service personnel including disassembly instructions, circuit diagrams, troubleshooting procedures, and replacement parts information.

1. Product Overview 2. Specifications 3. Disassembly Instructions 4. Circuit Diagrams 5. Main Board Replacement 6. Power Supply Board 7. LED Backlight System 8. Troubleshooting Flowcharts 9. Error Codes 10. Parts List 11. Safety Precautions

Product Overview

Key components: LED panel with webOS smart platform, main board, power supply board, T-CON board, LED backlight system, and various input/output interfaces.

Component	Description
Main Board	EAX65406604 - Processes video/audio signals and controls TV functions
Power Supply Board	EAY64927601 - Provides power to all components
T-CON Board	EAE65509301 - Timing controller for LCD panel
LED Driver Board	Controls LED backlight operation
Wi-Fi Module	Integrated wireless connectivity
Input Ports	3x HDMI, 2x USB, Component, Composite, RF Antenna
Output Ports	Digital Audio Out, Headphone Jack

Specifications

Screen Size: 50 inches LED
Resolution: Full HD 1920x1080
Smart Platform: webOS 2.0
Connectivity: Built-in Wi-Fi, Ethernet
Processor: Triple XD Engine
Backlight: LED Plus with Local Dimming
Power Consumption: 65W typical, 0.3W standby
Inputs: 3 HDMI, 2 USB, Component, Composite, RF
Sound: 10W x 2, Clear Voice II
Dimensions: 1127.7 x 655.8 x 59.9 mm (without stand)

Disassembly Instructions

Follow these steps to safely 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 casing, carefully separate cover.
Disconnect cables: Note cable positions before disconnecting from main board.
Remove main board: Unscrew mounting points, lift board carefully.
Access power supply: Remove screws and disconnect power cables.
Remove LCD panel: Extreme care required to avoid damage to fragile panel.

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

Circuit Diagrams

Complete schematic diagrams for all major circuits including power supply, main board, and T-CON board.

Diagram	Description	Reference
Power Supply	AC input to DC output circuits	PS-65406604
Main Board	Video processing and control circuits	MB-65406604
T-CON Board	LCD panel timing control	TC-65509301
LED Driver	Backlight control circuits	LD-64927602
Audio Circuit	Amplifier and output stages	AU-65406605

Main Board Replacement

Procedure for replacing the main board (EAX65406604).

Disconnect all cables from main board, noting positions.
Remove 6 mounting screws securing main board to chassis.
Carefully lift main board from mounting posts.
Install new main board, ensuring proper alignment.
Secure with mounting screws.
Reconnect all cables according to original configuration.
Test all functions before reassembling.

NOTE: Main board replacement may require software update for full functionality.

Power Supply Board

Troubleshooting and replacement of power supply board (EAY64927601).

Input: 100-240V AC, 50/60Hz
Outputs: +12V, +24V, +3.3V STBY
Common Issues: No power, intermittent operation, backlight issues
Test Points: TP1 (+12V), TP2 (+24V), TP3 (+3.3V STBY)

CAUTION! High voltage present even when unplugged. Discharge capacitors before servicing.

LED Backlight System

Diagnosis and repair of LED backlight system.

Check LED driver board output voltage (should be 100-150V DC).
Test individual LED strips for open circuits.
Replace faulty LED strips or entire backlight assembly.
Calibrate backlight uniformity after replacement.

WARNING! LED backlight operates at high voltage. Use proper insulation and safety procedures.

Troubleshooting Flowcharts

Step-by-step diagnostic procedures for common issues.

Symptom	First Check	Next Steps
No Power	Check AC input and standby voltage	Test power supply outputs, check main board
No Picture/Sound	Check main board power inputs	Test video processing circuits, replace main board
No Backlight	Check LED driver voltage	Test LED strips, replace driver board
Intermittent Operation	Check for overheating components	Reseat connectors, check solder joints
Wi-Fi Issues	Check wireless module connection	Update software, replace Wi-Fi module

Error Codes

Diagnostic error codes and their meanings.

ERR-01: Main board communication failure
ERR-02: Power supply fault
ERR-03: T-CON board error
ERR-04: LED backlight failure
ERR-05: Wi-Fi module error
ERR-06: Memory initialization failure
ERR-07: Software corruption

Parts List

Replacement parts and their part numbers.

Part Description	Part Number	Supplier
Main Board	EAX65406604	LG Electronics
Power Supply Board	EAY64927601	LG Electronics
T-CON Board	EAE65509301	LG Electronics
LED Backlight Strips	EBL65214701	LG Electronics
Wi-Fi Module	EMW65046702	LG Electronics
Remote Control	AKB75915201	LG Electronics
Stand	AGS48889901	LG Electronics

Safety Precautions

Essential safety procedures for service technicians.

Always disconnect power before servicing.
Use insulated tools when working with high voltage.
Discharge large capacitors before handling.
Work on anti-static mat to prevent ESD damage.
Handle LCD panel with extreme care to avoid breakage.
Reassemble completely before applying power.
Test all safety features after repair.

IMPORTANT! This manual is for qualified service personnel only. Incorrect repairs may create safety hazards.