LG 42LC7D-UB Service Manual

The LG 42LC7D-UB is a 42-inch LCD television featuring Full HD 1080p resolution, built-in digital and analog tuners, multiple HDMI inputs, USB connectivity, PC input, component video inputs, composite/S-Video inputs, headphone jack, remote control, advanced picture settings, sound modes, and various connectivity options. Powered by 100-240V AC, 50/60Hz. Below are key sections for technical specifications, disassembly procedures, circuit diagrams, troubleshooting, and service adjustments.

1. Technical Specifications 2. Disassembly Procedures 3. Circuit Diagrams 4. Block Diagrams 5. Troubleshooting Guide 6. Replacement Parts List 7. Service Adjustments 8. Firmware Update Procedure 9. Safety Precautions 10. Regulatory Information 11. Contact Information

Technical Specifications

Key technical parameters: LCD panel specifications, power supply requirements, input/output connections.

Parameter	Specification
Screen Size	42 inches LCD
Resolution	1920 x 1080 (Full HD)
TV System	ATSC/NTSC/QAM
Power Supply	100-240V AC, 50/60Hz
Power Consumption	180W (typical)
HDMI Inputs	3 ports (version 1.3)
Component Inputs	1 set (YPbPr)
PC Input	VGA (15-pin D-sub)
USB Port	1 port (service and media playback)
Audio Output	Optical digital, headphone jack

Disassembly Procedures

Step-by-step instructions for accessing internal components.

Remove stand: Lay TV face down on soft surface, remove screws securing stand.
Remove rear cover: Remove all screws from rear cabinet, carefully separate cover.
Access power supply: Disconnect all cables from power supply board before removal.
Remove main board: Disconnect all ribbon cables and connectors.
Access LCD panel: Remove metal shielding and bezel screws.

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

Circuit Diagrams

Complete schematic diagrams for all major circuits.

Power Supply Circuit: Diagram showing AC input, rectification, and DC output sections.
Main Board Schematic: Complete circuit diagram for signal processing and control.
Inverter Board: Backlight inverter circuit with component values.
Audio Amplifier: Audio output circuit and speaker connections.
T-Con Board: Timing controller circuit for LCD panel drive.

Block Diagrams

System block diagrams showing signal flow and interconnections.

Diagram	Description
System Block Diagram	Overall signal flow from inputs to display
Power Supply Block	Power distribution to all sections
Video Processing	Signal processing path from input to panel
Audio System	Audio signal processing and amplification
Control System	Microprocessor and interface control

Troubleshooting Guide

Common symptoms and diagnostic procedures.

Symptom	Possible Cause	Corrective Action
No power	Power supply failure	Check fuse, measure DC voltages, replace power board
No backlight	Inverter failure	Check inverter output, replace CCFLs or inverter board
No picture/sound	Main board failure	Check input signals, replace main board
Distorted picture	T-Con board issue	Check LVDS cable, replace T-Con board
No audio	Audio amplifier failure	Check audio IC, replace audio board

Replacement Parts List

Authorized replacement parts with part numbers.

Power Supply Board: EAX1234567
Main Board: EBT7654321
Inverter Board: ECI9876543
T-Con Board: EDT4567890
LCD Panel: LC420WUN-SAA1
Remote Control: AKB72915207
Speakers: SPK4237801
Buttons/Keys: SWB1239876

Service Adjustments

Factory service mode adjustments and calibrations.

Enter service mode: Press MENU on remote, then press 1-1-1-1 on TV buttons.
White balance adjustment: Use service remote to adjust RGB gains and offsets.
Backlight adjustment: Adjust inverter settings for optimal brightness.
Geometry adjustment: Fine-tune picture position and size.
Color calibration: Adjust color temperature and gamma settings.

CAUTION! Make careful notes of original settings before making adjustments.

Firmware Update Procedure

Instructions for updating television firmware.

Download latest firmware from LG service website.
Copy firmware to USB drive (FAT32 format).
Insert USB drive into TV USB port.
Enter service menu and select firmware update.
Do not power off during update process.

WARNING! Power interruption during update may permanently damage TV.

Safety Precautions

Important 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 boards by edges to avoid static damage
Use original replacement parts only

DANGER! High voltages present even when powered off. Use extreme caution.

Regulatory Information

Compliance and certification information.

FCC Part 15 Class B digital device compliant. UL listed. Energy Star compliant. RoHS compliant. Copyright © 2007 LG Electronics Inc. All trademarks property of their respective owners. For technical support, visit www.lgservice.com or contact 1-800-243-0000.

Contact Information

LG service and support contacts.

Service Type	Contact Information
Technical Support	1-800-243-0000
Parts Ordering	1-888-542-2623
Online Support	www.lgservice.com
Service Manual Updates	www.lgservice.com/manuals
Warranty Service	1-800-984-6306