P3D Cooling fan protects projector, not slides

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

>From: lilindn@xxxxxxxxxxx (Rob)
>May I ask if the fan on your TDC is running?  

The function of the fan is mainly to cool the projector, not the slides.  

This is from an earlier posting in this list:

>Date: Thu, 5 Dec 1996 22:58:48 -0500 (EST)
>From: P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>
>Subject: Does the cooling fan protect slides in projection?
>
>The cooling fan is there to protect the projector and not the slides. 
>This is based on the observation that the temperature of the slide in
>the projection beam rises steadily as it absorbs radiation.  One would
>expect that the cooling stream of air will cause the temperature to reach
>an equilibrium point. However, my observation has been that the temperature
>is still rising in the short period of time that the slide remains in the
>beam's path.  The heat-absorbing filters or cold mirrors block the IR
>radiation from heating the slide and these are the ones that essentially 
>protect the slide.
>
>So:  - heat absorbing system (filter, mirror) protects slides
>     - cooling fan protects projector
>
>Those who have problems with melting RBT mounts should check the fitlers.  
>If the projector feels very hot and parts of the projector are cracking 
>from excessive heat then the fan is in fault.

George Themelis


------------------------------