LG 55UF6450 Service Manual

The LG 55UF6450 is a 55-inch Ultra HD LED TV with 3840x2160 resolution, built-in digital tuner, webOS smart TV platform, multiple HDMI inputs, USB connectivity, Wi-Fi capability, built-in speakers with audio enhancements, remote control, energy saving features, and advanced picture settings. Powered by 120V AC, 60Hz. Below are key sections for technical specifications, disassembly procedures, circuit diagrams, troubleshooting, and repair instructions.

1. Technical Specifications 2. Disassembly Procedures 3. Circuit Diagrams 4. Board Replacement 5. Power Supply Section 6. Main Board Section 7. T-Con Board Section 8. Panel Components 9. Troubleshooting Flowcharts 10. Error Codes 11. Safety Precautions

Technical Specifications

Key components: 55-inch LED panel, main board, power supply board, T-Con board, LED backlight system, and various connectors.

Specification	Details
Model	55UF6450-UB
Screen Size	55 inches
Resolution	3840 x 2160 (Ultra HD)
Panel Type	LED LCD
Smart TV Platform	webOS 2.0
Inputs	3x HDMI, 2x USB, Component, Composite, RF
Wireless	Built-in Wi-Fi
Power Consumption	Approx. 85W typical
Power Supply	120V AC, 60Hz
Standby Power	< 0.5W

Disassembly Procedures

Proper disassembly sequence for service access and component replacement.

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.
Access internal boards: Identify main board, power supply, T-Con board locations.
Disconnect cables: Note cable positions before disconnecting ribbon cables and connectors.

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

Circuit Diagrams

Complete schematic diagrams for all major circuits and boards.

Power Supply Circuit: EAX65457601 power board schematic with voltage outputs.
Main Board Circuit: EBT65428902 main board with processor and memory circuits.
T-Con Board: 6870C-0596A T-Con board timing controller circuit.
LED Backlight: LED driver circuit and backlight string configuration.
Input/Output: HDMI, USB, and audio input/output circuits.

Board Replacement

Step-by-step procedures for replacing major circuit boards.

Power Supply Board: Disconnect all cables, remove mounting screws, replace with EAX65457601.
Main Board: Remove all connectors and ribbon cables, replace with EBT65428902.
T-Con Board: Handle ribbon cables carefully, replace with 6870C-0596A.
LED Driver Board: Disconnect LED strings, replace driver board if backlight issues.

CAUTION! Use anti-static precautions. Verify board compatibility before replacement.

Power Supply Section

Detailed analysis of power supply board operation and troubleshooting.

Voltage Outputs: +12V, +24V for LED backlight, +3.3V standby, +5V for signal processing.

Power Supply IC: L6599D for PFC circuit, FSFR2100 for main switching.

Troubleshooting: Check fuse F101 (6.3A), measure standby voltage (+3.3VSTBY), verify PFC voltage (390V DC).

Main Board Section

Main board components and signal flow analysis.

Main Processor: LG own chip with quad-core CPU for webOS operation.

Memory: 1.5GB DDR3 RAM, 4GB eMMC flash storage.

Input Processing: HDMI receivers, tuner module, Ethernet controller.

Video Processing: Ultra HD upscaling, motion processing, color management.

T-Con Board Section

Timing controller board operation and LVDS signal analysis.

LVDS Input: Check LVDS cable from main board to T-Con.
Gamma Voltumes: Measure VGH, VGL, VCOM voltages.
Panel Voltages: Verify VCC, VDD, VEE supplies to panel.
Gate/Source Drivers: Check output to panel row and column drivers.

Tip: Use LVDS pattern generator for T-Con board testing.

Panel Components

LCD panel internal components and backlight system.

LED Backlight: 4 strings with multiple LEDs per string.
Optical Films: Diffuser sheets, prism films, reflective sheets.
LCD Glass: TFT array with liquid crystal material.
Polarizers: Front and rear polarizer films.
Driver Circuits: Source and gate driver ICs on panel edges.

WARNING! Do not disassemble panel without proper training. Risk of permanent damage.

Troubleshooting Flowcharts

Systematic troubleshooting procedures for common problems.

Symptom	First Check	Next Steps
No Power	Check AC input, fuse	Measure standby voltage, check PFC circuit
No Backlight	Check LED voltages	Test LED strings, check driver IC
No Picture	Check T-Con voltages	Verify LVDS signal, test gamma voltages
No Sound	Check audio output	Test audio IC, check speaker connections
No Boot	Check main board power	Verify processor operation, check eMMC

Error Codes

Diagnostic error codes and their meanings for service diagnosis.

Error 1: Main board communication failure
Error 2: T-Con board not detected
Error 3: Power supply fault
Error 4: Backlight failure
Error 5: Temperature sensor fault
Error 6: EEPROM data corruption

Safety Precautions

Important safety information for service technicians.

High Voltage Warning: Power supply contains lethal voltages even when unplugged. Discharge capacitors before servicing.

ESD Protection: Use grounded wrist strap when handling circuit boards.

Panel Handling: LCD glass is fragile and easily damaged by pressure or impact.

Service Contact: LG authorized service centers only. Unauthorized service voids warranty.