In a message dated 6/21/99 3:51:46 PM EST, cpl49@xxxxxxxxxxxxx writes:
<< Basically, rapid temp changes are bad for filament life. The 'fan only' is
there and should be used if a bulb blows during a show and you want to
cool it as fast as possible so you can handle it (paper towel or cloth so
you don't transfer oil to surface). HTH,
>>
It's kinda like your computer, it gets its most stress at startup,
but some things you can't avoid altogether.
Generally, the shock required to break a hot filament is much less
than the shock required to break a cold filament. This is because the hotter
the temperature of the filament, the easier it stretches, or deforms; and as
such, it will stretch to a point where it breaks. Let's say your filament is
cold, you'd probably have to drop the projector all the way to the floor to
break the filament. But, aside from normal aging, the filament will break
with just jostling the projector if the filament has reached incandesence
(being lit). So, I would still run the "fan only" for a few minutes after a
slide show, no matter if the projector is from the '70s or '90s, regular
incandescent bulb, or halogen bulb. The major difference between a regular
bulb and a halogen, is the halogen burns at a higher temperature (which is
possible due to the filament being tungsten). Higher temp.= easier to break,
BUT the tungsten filament is stronger than regular steel, so it's a wash as
per heat vs.strength, so I'd still try to cool the bulb (filament) as soon as
I could even though it's a halogen. The cooler it gets, the less likely it
will be to break easily. Why keep it hot longer? Cool that sucker- fast.
George S.
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