I don't think that anyone has mentioned KING OF THE ROAD (English Title),
an early film by Wim Wenders.  The main character is a projectionist and
travels a route in Germany maintaining many theater's projectors.  There
would be many good excerpts for what you need.
 
The funniest one was a short "experimental" film that toured the festival
cirkuit in the early 80s that mimiced every projector problem: lost loop,
out-of-focus, no sound, broken splices and ended up with the film burning
in the gate.  It was done so well that the auidence rarely realized that
it was a joke, they kept shouting at the projectionist.
 
Good Luck
 
Dan Bailey, University of Maryland Baltimore County
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