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What causes early projection lamp failure?

Early lamp failure in your a/v equipment
by Bob Carlson

One of the more frequent questions I get in the service department at United Visual is what causes early projection lamp failure. A lot of people are making simple mistakes that are costing them a lot in burned-out lamps. For instance, did you know...

  • Moving the machine while the lamp is on or even shortly after turning it off can cause premature failure. A hot lamp filament will fall apart if the machine is handled roughly.

  • Average lamp life means just that. In a test done by GTE/Sylvania on 10 ENX lamps, the range of life was 34.3 hours to 76 hours. The average lamp life for this batch was 68.7 hours, higher than the published average of 65 hours. However, the lamp that lasted only 34.3 hours is not considered to be defective.

  • If an overhead projector lamp does not burn out immediately, but burns out within an hour, the lamp is probably defective, not the projector. In recent years diode failures (a component in most newer overheads) have been the cause of many burned out lamps. However, a diode failure will always cause a lamp to burn out instantly!

  • You should never move a lamp changer lever (if your machine is so equipped) while the on/off switch is in the "On" position. This will jar the lamp and cause a hot lamp filament to fall apart. Moving it when the power is off will assure the lamp filament is cool and able to handle rougher treatment.

  • Excessive heat will shorten lamp life. A fan running slow due to lack of lubrication or a dirty motor will not cool a lamp sufficiently. Regular maintenance at United Visual will prevent this from occurring.

  • You should never allow anything to block the airflow of your projector's cooling fan. The intake and output grills must not be obstructed or overheating will occur, shortening the lamp life.

  • A higher than normal AC line voltage will tremendously decrease lamp life. Whereas higher voltage might not affect other appliances, an increase of only two volts will shorten lamp life by as much as 20%, five volts as much as 58%! If you notice a problem with short lamp life, it's worth having an electrician test your lines.

  • A lamp that is not properly seated in its socket may seem burned out. Not only may the lamp not make good enough contact to light, it may make enough contact to arc and burn its pins or the contacts of the socket. If arcing occurs, the lamp may not light even after it is seated correctly.

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