Re: Fans on projectors

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Prof. Paul S. Boyer mentioned Kodak's recent advice not to use the fans
to cool down the projector after the lamps are turned off:

>This practice is no longer deemed advisable by no less an authority
>than the Great Yellow Father (Kodak).  When the projector is off, no
>further heat is being added, and there is little reason to run a fan.
> Running the fan simply cools the bulbs faster, adding to thermal
>stress on their filaments, and shortening bulb life.

This makes me wonder... Why did it take Kodak so many years to come up
with this simple recommendation?  For years and years projectors were
supplied with a fan that can be operated separately and we were advised
to use it to cool the system after the bulbs are turned off.  Has something
changed in the projector or lamp design recently?  I would expect that a
big company like Kodak making money from selling lots of projectors would
have conducted a simple study on the effect of running the fan and tell
us what the results are, long time ago.

I agree that what Great Yellow Father is saying now makes sense regarding
the filament of the bulbs but what about the other components?  I am
specifically worried about the bakelite lamp holders of the TDC 116
projectors which are reported to crack under the heat of the 750W bulbs.
Since these are air-cooled when the lamps are on, I believe that their
temperature will rise when the bulbs and fan are turned off together.
I will continue to run the fan with the 750W bulbs to cool the lamp
holders, lenses, filters and other projector components.  As for the
reduction in filament life, I don't know if there is any and I don't 
care much. 

George Themelis


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