LCD Overheating: Backlight Turns On Then Off

by David Casselbury

Liquid Crystal Display TVs and monitors are lighter, thinner and more energy-friendly than CRTs or rear-projection TVs. LCDs are very durable, but if you are having flickering or a complete display outage, a faulty backlight could be to blame. The backlight is responsible for generating enough light for you to see the images created by the liquid crystals. Regulated by capacitors, the backlight controller must operate at optimal temperatures for proper illumination. If it overheats, the backlight can act erratically or completely shut itself down.

Capacitors

Similar to batteries, capacitors are cylindrical electronic components that store and regulate energy. This energy is transferred at a consistent level to chips on the monitor motherboard, including the backlight controller. LCDs do not contain internal fans, so this regulation keeps the other components at the proper operating temperatures. However, throughout the 2000s, capacitors created in Taiwan were incorrectly formulated, causing a premature degradation and recall on many monitors by their manufacturers, according to PC Tools.

Degrading and Overheating

When a capacitor degrades, its ability to regulate voltage wanes, causing other components to overheat -- including the backlight controller, which then shuts down. You can spot degraded capacitors by the once-flat tops and bottoms bulging into a dome. The capacitor might also begin to release its electrolyte filling, a rust-colored, gooey liquid on top of these domes. In extreme cases, degraded capacitors can dome to such a degree they disconnect from the motherboard.

Short-Term Fix

When the backlight goes out, you can still read the on-screen menu, as long as the room is bright enough. Adjust the brightness of the monitor screen to less than 50 percent and then restart the LCD. Doing this lowers the amount of power the capacitor has to regulate, resulting in the display remaining backlit. This may seem like a miracle fix; however, it's only a short-term solution as the capacitor will continue to degrade, potentially causing damage to other components.

Long-Term Fix

To repair this issue properly, you need to replace the degraded capacitor(s). Acquiring the schematic diagram for your LCD is best for obtaining the exact capacitor for replacement; however, once you remove the faulty capacitor, you can read the specs off the component itself. Capacitors are soldered onto the motherboard directly, so you will need soldering equipment and experience to safely and properly repair the part. Call a professional to repair these parts if you are untrained, as soldering irons can damage the motherboard when used incorrectly.

About the Author

David Casselbury received a degree in general electronics in 2001 and currently serves as the IT supervisor for a large regional library system. He is A+, N+ and Windows 7 Enterprise Desktop Support-certified.

Photo Credits

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