I don't know about the theory on this one, but I do know that all the commecial projectors I have used run the fan on cooldonwn for a few minutes after the bulb is turned off and give a warning in the instruction manuals not to pull the plug before the fan shuts down or bulb dammage could result.

Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!