Simultaneously, press and hold the button on the remote control.

Diagnostic Flowchart for "Audio Present, No Video (Black Screen)"

: A safety test to ensure no exposed metallic parts pose a shock hazard. This involves measuring AC voltage across a resistor (typically 1.5 K / 10 watt) connected between ground and exposed parts. Isolation Transformer

Houses the primary system-on-chip (SoC), video processing units, HDMI/tuner inputs, and EEPROM/Flash memory.

Depending on the specific screen size, the T-CON is either a standalone board or integrated directly into the bottom panel source driver tabs. It translates the standardized LVDS or V-by-One signals from the LJ7 mainboard into raw data pixel streams for the LCD panel. 3. High-Frequency Failure Modes & Troubleshooting

Use an LED tester on the panel connector. If one LED is open, none will light.

Ensure the main board sends a signal (~3.3V) to the PSU to start up the 12V and 24V rails. If P-ON is low: Main board issue. If P-ON is high but no 12V/24V: PSU board failure. Scenario 3: Sound But No Picture (Backlight Failure)

Standard LG service manuals typically include the following technical sections:

The primary side of the PSU contains large electrolytic capacitors that hold lethal charges (300V–400V DC) long after the TV is unplugged. Always discharge these capacitors using a dedicated discharge tool or a high-wattage resistor before touching the board.

Disconnect one side of the flat flexible cables (FFC) leaving the T-CON board to the panel at a time. If half the screen displays a clean white or clear image with the other side disconnected, the panel itself has an internal short circuit on the side that caused the system to crash.

If PWR-ON stays low, the Main Board SoC is not executing its boot code. This often indicates corrupted EEPROM/NAND flash memory or a failing SoC BGA solder joint.

If the backlights are on, but there's no image and no on-screen display, the issue could be with the T-Con board or the main board. The manual provides the detailed schematics of the T-Con board and the LVDS signals, allowing a technician to probe data lines and verify the main board is sending the correct signals.

Solder an EEPROM programmer (such as a CH341A) to the chip pins, or desolder the chip entirely.

To repair an LJ7 chassis TV, you will need the specific PDF manual. Search for the model number of your TV (e.g., 32LJ500B, 43LJ5500) followed by "service manual".

. Technicians use the manual to perform a "Leakage Current Cold Check," ensuring that no metallic part of the TV—like the antenna terminal—is accidentally carrying live voltage that could harm a user. Common Chapters in the Manual

In many LJ7 configurations, the T-CON is integrated into the panel itself, or attached via a single ribbon cable from the main board. D. LED Backlight Strips Direct-lit LEDs located behind the LCD panel. 4. Troubleshooting Guide & Flowcharts