Are you replacing your overhead bulbs too often?

[Keith Dzura <kdzura@SOUTHEASTERN.STOKES.K12.NC.US>]

We spend too much money on these bulbs and I found the following article to
be useful.  Anyone have any other tips/resources for preventing premature
failure in projector bulbs?

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.


Keith Dzura
Media Coordinator
Southeastern Stokes Middle School
www.southeastern.stokes.k12.nc.us

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