LG 46LD550 Service Manual

The LG 46LD550 is a 46-inch LED TV featuring Full HD 1080p resolution, built-in digital tuner, multiple HDMI inputs, USB connectivity, Smart TV capabilities, energy saving technology, and advanced picture and sound settings. 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. Technical 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

Main components: LED panel, main board, power supply board, T-CON board, LED backlight system, speakers, and remote control.

ComponentDescription
Main BoardEAX61732401 - Main processing unit with HDMI, USB, and tuner inputs
Power SupplyEAY62733301 - Provides power to all components
T-CON BoardEAX61732701 - Timing controller for panel driving
LED BacklightEdge-lit LED system with 4 strings
Speakers2 x 10W stereo speakers
Remote ControlAKB72915207 - Infrared remote with Smart TV functions
Panel46-inch LCD with LED backlight, 1920x1080 resolution
Inputs4x HDMI, 3x USB, Component, Composite, RF, Ethernet
OutputsDigital Audio Optical, Headphone, RS-232

Technical Specifications

Disassembly Instructions

Follow these steps carefully for safe disassembly of the TV unit.

  1. Remove stand: Lay TV face down on soft surface, remove 4 screws securing stand.
  2. Remove rear cover: Remove all screws from rear cover, carefully separate cover from chassis.
  3. Disconnect cables: Note positions of all cable connections before disconnecting.
  4. Remove main board: Remove mounting screws and disconnect all cables from main board.
  5. Remove power supply: Disconnect AC input and all output connectors, remove mounting screws.
  6. Remove T-CON board: Disconnect LVDS cables and remove mounting screws.
  7. Access LED backlight: Remove bezel and panel to access LED strips.

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

Circuit Diagrams

Complete circuit schematics for all major boards and systems.

DiagramDescription
Power Supply CircuitEAY62733301 complete schematic with voltage outputs
Main Board CircuitEAX61732401 processor, memory, and input/output circuits
T-CON Board CircuitEAX61732701 timing control and panel driver circuits
LED Driver CircuitBacklight driver and current regulation circuits
Audio Amplifier Circuit20W stereo amplifier and speaker output circuits
Input/Output CircuitsHDMI, USB, tuner, and other interface circuits

PCB Layouts

Printed circuit board layouts showing component placement and test points.

  1. Main Board Top/Bottom View: Component locations and reference designators
  2. Power Supply Board: Primary and secondary side component placement
  3. T-CON Board: IC and connector locations
  4. LED Driver Board: Backlight control components
  5. Key Panel Board: Front control button circuits

Note: All layouts include component designators matching schematic diagrams.

Troubleshooting Procedures

SymptomPossible CauseCorrective Action
No powerPower supply failureCheck AC input, fuse F101, standby voltage (+5VSTBY)
No backlightLED driver failureCheck LED driver IC, backlight enable signal, LED strings
No picture/soundMain board failureCheck main voltages, main processor, reset circuit
No soundAudio circuit failureCheck audio IC, speakers, audio input signals
HDMI not workingHDMI circuit failureCheck HDMI IC, +5V supply, data lines
USB not recognizedUSB circuit failureCheck USB power, data lines, USB controller
Remote not workingIR sensor failureCheck IR sensor, +5V supply, remote signal

Replacement Parts List

Authorized replacement parts with manufacturer part numbers.

Part DescriptionPart Number
Main Board AssemblyEAX61732401
Power Supply BoardEAY62733301
T-CON BoardEAX61732701
LED Backlight StripsELL46W015A
LCD Panel AssemblyLC460EUN
Remote ControlAKB72915207
Speakers (Pair)AGS36300101
Stand AssemblyATS48010502
IR Sensor BoardEAX61732801
Key Panel BoardEAX61732901

Adjustment Procedures

Factory adjustment procedures for proper TV operation.

  1. White Balance Adjustment: Using service remote, adjust R/G/B gains and offsets
  2. Backlight Adjustment: Set backlight level to factory specifications
  3. Color Temperature: Adjust color temperature settings (Cool/Normal/Warm)
  4. Geometry Adjustment: Check and adjust picture position and size
  5. Sound Adjustment: Set audio levels and equalizer settings
  6. Software Update: Procedure for updating TV firmware

Note: Service remote required for most adjustment procedures.

Safety Precautions

Critical safety information for service personnel.

WARNING! High voltages present in power supply and backlight circuits can cause serious injury or death.

Block Diagrams

System block diagrams showing signal flow and interconnections.

  1. Overall System Block Diagram: Complete TV system overview
  2. Main Board Block Diagram: Signal processing flow
  3. Power Supply Block Diagram: Power distribution system
  4. Audio System Block Diagram: Audio signal processing
  5. Video System Block Diagram: Video signal processing
  6. Backlight System Block Diagram: LED driver and control

Test Points & Voltages

Test PointNormal VoltageDescription
TP101 (+5VSTBY)+5.0V ±5%Standby power supply
TP102 (+12V)+12.0V ±5%Main 12V supply
TP103 (+24V)+24.0V ±5%Backlight power supply
TP201 (VCC_CORE)+1.2V ±3%Main processor core voltage
TP202 (VCC_DDR)+1.5V ±3%Memory power supply
TP301 (VGH)+18V to +25VT-CON gate high voltage
TP302 (VGL)-5V to -7VT-CON gate low voltage
TP401 (LED+)+80V to +120VLED backlight anode voltage

Reset Procedure: Enter service menu > Factory Reset if available.

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

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