Written by Valerie Henson, December 1997.
A projector is basically a lamp, a lens, and a computer hookup. The lamp is very powerful and generates a lot of waste heat, so the fan has to run for a few minutes after lamp shutoff or else the projector or lamp can be damaged from the excess heat. For this reason, you should never cut the power to a projector, just put it on “standby”. If the lamp is left on for more than a few hours, it seriously shortens the life of the bulb.
When a lamp fails, it often does not fail completely. The lamp will still shine dimly, start flickering, or go dark after a minute. You must leave the lamp on long enough (a minute or so) for it to reach its maximum temperature because the lamps expand as they get hotter. The lamp may work when it is cold and fail when it is hot.
You need to bring a remote with you when you are checking the projectors (just in case the remote in the room is dead). Remember, leave the projector on for about a minute to fully test the lamp, and return the projector to standby after you test it!