Plasma televisions hold many advantages over traditional cathode-ray tube sets. Plasma TVs are much thinner, sometimes only extending 6 inches, and use a series of pixels to create a vibrant display by combining red, blue and green hues together to form the coloured picture. They can last for years, but rely on gas inside the set to achieve their picture quality, and plasma TVs can go bad over time or due to mechanical failure. Determining if a plasma set is going bad requires some observation.
Turn on the set and look for "ghosting" in the display, which is a greyish effect often caused in plasma sets due to static images being left on the screen for too long. If the display is showing signs of ghosting, it likely won't improve and will only get worse.
Examine the pixels on the set. If you start seeing white spots in the picture, the pixels could be starting to fail. Turn off the TV and restart it to see if the pixelation goes away.
Listen for a loud humming or static sound. A low hum is normal on plasma TVs, but a louder crackling sound coming from the upper portion of the set in the back indicates a failed circuit board that needs replacement.
Change channels several times and leave the TV on for several hours to see how the display reacts. If the display starts going black or the pixels start malfunctioning, the TV is likely beginning to fail.