LG 50PJ350 Service Manual

The LG 50PJ350 is a 50-inch Plasma TV featuring HD resolution, built-in digital/analog tuner, multiple input options including HDMI, component, composite, and PC inputs, USB connectivity, energy saving features, and advanced picture settings. This service manual provides technical information for service personnel including safety precautions, specifications, disassembly instructions, troubleshooting, and circuit diagrams.

1. Safety Precautions 2. Product Specifications 3. Disassembly Instructions 4. Main Board Overview 5. Power Supply Unit 6. Control Board Functions 7. Panel Components 8. Troubleshooting Guide 9. Test Patterns 10. Replacement Parts 11. Circuit Diagrams

Safety Precautions

Before servicing, read all safety instructions. Disconnect power before working on unit.

Warning	Description
High Voltage	Plasma panels contain high voltage circuits - discharge properly before servicing
ESD Protection	Use anti-static wrist strap when handling circuit boards
Power Supply	Unplug unit before disassembly; capacitors may retain charge
Panel Handling	Plasma panel is fragile; handle with care to avoid breakage
Ventilation	Ensure proper ventilation during operation to prevent overheating

Product Specifications

Screen Size: 50 inches Plasma
Resolution: 1366 x 768 HD
Tuner: ATSC/NTSC/QAM
Inputs: 3x HDMI, 2x Component, 1x Composite, 1x PC Input, 1x USB
Sound Output: 10W x 2
Power Consumption: 280W (typical)
Power Supply: 100-240V AC, 50/60Hz
Dimensions: 1212 x 780 x 89.5 mm (with stand)
Weight: 28.5 kg

Disassembly Instructions

Follow these steps for proper disassembly:

Remove stand: Lay TV face down on soft surface, remove screws securing stand.
Remove rear cover: Remove all screws from rear cover, carefully separate from chassis.
Disconnect cables: Note cable positions before disconnecting from main board.
Remove boards: Remove screws securing main board, power supply, and control boards.
Access panel: Remove metal shielding to access plasma panel components.

WARNING! Handle plasma panel with extreme care - it is fragile and expensive to replace.

Main Board Overview

The main board processes all input signals and controls TV functions.

Component	Function
IC100	Main processor - signal processing and system control
IC200	Memory controller - DDR memory management
IC300	Video processor - handles video scaling and enhancement
IC400	Audio processor - audio decoding and processing
CN100	LVDS connector - connection to panel control board
CN200	Power supply connector - receives power from PSU

Power Supply Unit

The PSU provides all necessary voltages to TV components.

VS Voltage: 195V - Plasma sustain voltage
VA Voltage: 55V - Plasma address voltage
5V STBY: 5V - Standby power
12V: 12V - Main board and audio power
15V: 15V - Logic board power
VE Voltage: 95V - Panel erase voltage

CAUTION! High voltages present - discharge all capacitors before servicing.

Control Board Functions

Front control board and remote control functions.

Front Controls: POWER, MENU, VOLUME UP/DOWN, CHANNEL UP/DOWN, INPUT

Remote Control: POWER, Numeric buttons, MENU, GUIDE, INPUT, VOLUME, MUTE, CHANNEL, COLOR buttons, SETTINGS

Service Functions: - Service Menu: Press MENU on TV and remote simultaneously - Factory Reset: Service menu option - Panel Test: Service menu option for panel diagnostics

Panel Components

Plasma panel assembly and related components.

Plasma Panel: 50-inch HD plasma display
Y-Sustain Board: Generates scan pulses for panel
X-Sustain Board: Generates sustain pulses for panel
Control Board: Processes LVDS signal from main board
Logic Board: Controls timing and driving of panel
Buffer Boards: Top and bottom buffer boards for electrode driving

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No Power	Power supply failure	Check fuse F101; measure standby voltage; replace PSU if necessary
No Picture/Sound	Main board failure	Check main board voltages; replace main board if no LVDS output
Sound No Picture	Panel or sustain boards	Check VS/VA voltages; test Y-sustain and X-sustain boards
Picture Abnormalities	Sustain boards or buffers	Check for bad buffer boards; replace sustain boards if needed
No Backlight	Inverter board	Check inverter voltages; replace inverter board if faulty
HDMI No Signal	HDMI port or main board	Test different HDMI ports; replace main board if all ports fail

Test Patterns

Use these patterns for panel testing and calibration:

Red Pattern: Tests red subpixels and uniformity
Green Pattern: Tests green subpixels and uniformity
Blue Pattern: Tests blue subpixels and uniformity
White Pattern: Tests overall brightness and white balance
Gray Scale: Tests gray scale reproduction
Convergence: Tests pixel alignment and focus

Access through service menu: Pattern Test option

Replacement Parts

Part Number	Description	Notes
EAY61712201	Main Board Assembly	Complete main processing board
EAY61712202	Power Supply Unit	Complete power supply assembly
EAY61712203	Y-Sustain Board	Y-sustain circuit board
EAY61712204	X-Sustain Board	X-sustain circuit board
EAY61712205	Control Board	Panel control board
EAY61712206	Logic Board	Timing control board
6871QDH011A	Plasma Panel	Complete 50-inch plasma panel

Circuit Diagrams

Reference diagrams for circuit analysis and repair:

Power Supply Schematic: Complete PSU circuit diagram
Main Board Schematic: Main processing board circuits
Audio Section: Audio processing and amplification
Control Section: Front panel and remote control circuits
Panel Drive: Sustain boards and buffer circuits
Input Section: HDMI, component, and other input circuits

Note: These diagrams are for qualified service personnel only.