Digital light processing (DLP) is the most common technology behind rear-projection HDTVs. A DLP television produces an image using a collection of microscopic mirrors mounted on a chip, a color wheel or other color-processing device, and a white lamp. The lamp is user-replaceable and usually gives off warning signs as it wears out before burning out completely.
Loss of Brightness
When a DLP lamp is nearing the end of its life, the brightness of the television picture will degrade. This may go undetected at first because the human eye tends to adjust to a slowly dimming image. When the loss of brightness becomes apparent, the DLP lamp is likely close to burning out. Turning up the brightness on the TV will likely have little effect on the picture when the lamp is on the verge of burning out.
In addition to a darker picture, the television may display a noticeable flicker from time to time, which indicates either a faulty DLP lamp or a lamp that is burning out.
Muddy or Faded Color
If your DLP television uses color-wheel technology, you may notice that colors are either faded somewhat or no longer display accurately. This is a frequent symptom of a bad DLP bulb, as the bulb loses its ability to fully project accurate color onto the DLP mirror chip.
DLP Lamp Indicator
Many DLP televisions feature a lamp indicator light on the front of the unit that turns on and stays on when the lamp requires replacement. The TV display will still work until the lamp burns out completely, but with increasingly noticeable flicker and fade.