Overhead projector problem

Hello all,
I've been having a problem with an overhead projector for the last few days.
It runs fine for approx. 3mins 10secs then the bulb cuts out for approx. 45secs.
The fan continues running throughout.

I tested this for about 40mins and the times never varied more than 10secs from the approximate figures I gave.
I've tried with a couple of brand new bulbs and got the same problem.

Unfortunately there are no manufacturers marks anywhere on the machine but I believe these projectors are quite standard items. I'm not too hot on electronics but I think I can identify the key items in this photo (transformer, fan/motor, power connections/switches):

I had assumed there would be a thermistor in there somewhere but I can't locate it.

Any help appreciated.

Post edited by: JonnyD, at: 2007/07/21 18:33

Welcome to the forum, JonnyD

Although you can't locate the thermistor, it does seem to me like a problem of the thermal-protection circuit - while bulb gets overheated...

using the correct bulb? i have a lightbox projection unit that does this when the bulb is going bad or if i put the wrong bulb in it. i.e. try a higher wattage same cofiguration bulb if not the protection circuit is faulty