Film-Tech Forum ARCHIVE: projector stops when lamp strikes

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Posted by Rob van Ede (Member # 1457) on 11-22-2002, 06:16 PM:

The problem introduced itself last week and shows up more frequently now. The projector runs fine until the lamp strikes. Then stops as if someone has pushed the stop-button. Sometimes the projector stops when the lamp strikes only to start again (automatically). When this happens, the lamp strikes again and most of the time the projector runs fine this second time.
Last night it took four tries to get the projector running (sold out HP). What might be the cause?

Projector: Ernemann 15
Lamphouse: Xenosol 2000

Posted by Pat Moore (Member # 380) on 11-22-2002, 07:07 PM:

Rob-- What is the automation system? Something in the ignition pulse is knocking out the control system that runs the projector motor. Does the lamp light and stay lit when this happens?

Pat

Posted by Gordon McLeod (Member # 33) on 11-22-2002, 07:38 PM:

Most of the european ernamans run on the ernaman base with there logic control. The odds are that the EMI from the ignitor is causing a glitch on the motor control in the base.
Check the grounding and also the condition of the spark gap in the ignitor

Posted by Rob van Ede (Member # 1457) on 11-23-2002, 02:37 AM:

The automation is an Ernemat (800?).

The lamp goes off along with the projector when it happens.

I actually thought about the EMI from the ignitor because that causes some DMX controlled dimmers in the theatre (at another projector) to go on sometimes. The cables are too close together. That problem was solved by switching off the dimmers while not in use.

The strange thing here is that nothing was changed in the last months and the projector has run fine for nine years now. This says me that something must have broken. Earth sounds like a possiblitity, i'll check it. What would be the effect of a faulty spark gap? A too high ignition voltage causing more EMI?

Rob

Posted by Gordon McLeod (Member # 33) on 11-23-2002, 06:20 AM:

The length of the spark gap in cojunction with the caps determins the frequency of the pulse also check for corrosion on the mounting of the ignitor I have seen that happen once causing the ignitor to be above ground

Posted by Pat Moore (Member # 380) on 11-23-2002, 10:27 AM:

I think Gordon is correct. Electrical RF noise is getting into the controller and causing some sort of reset. Grounding -- or lack of it -- is a potential cause and it can be a real pain to trace and isolate. Finding it is one thing, and correcting it is another.

Not knowing the Ernaman igniter circuit, you might try a small, high voltage capacitor, something like .1mfd, from the DC plus or minus side to ground. That type of noise suppression should already be there, I would think, so assuming the system has worked correctly in the past you might have lost such a noise suppression cap somewhere in the circuit.

Pat

Posted by Rob van Ede (Member # 1457) on 11-26-2002, 02:19 AM:

We've put the control board in another projector and had no troubles with both projectors during the weekend. Hope it stays that way. It might have been a bad contact on the control board?...
Thanks for the suggestions.

Rob