Film-Tech Forum ARCHIVE: Strong Platter Switches

This is topic Strong Platter Switches in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Richard Tucker (Member # 812) on 07-20-2003, 11:42 PM:

I am having trouble with the microswitches on the Strong platters at one of my theater locations. The problem is the switch is sticking on, causing film wraps. After taking one switch apart to see why it is failing, I discovered a pit on one contact and a tit on the other, which occasionally fit together to cause the contacts to stick.
Without getting into a big discussion on the merits of one platter over another, has anyone else had this problem? I am used to seeing contacts like this on DC circuits, like old car distributor points and exciter lamp circuit relays; can this also happen on an AC circuit? Also, in my experience Strong platter switches usually last years, but these have died 6 months after I replaced all the original switches for the same reason.
Any thoughts?

Posted by Jack Ondracek (Member # 1466) on 07-21-2003, 12:19 PM:

From what I've seen in the motors (and the drawings) it IS a DC circuit. There's a diode in the motor housing.

Seems there could have been a cap across the switch contacts though. That might have taken care of any internal arcing problem.

On the other hand, the voltages should be fairly low. Even on startup the variac isn't wide open, so the switch shouldn't be working that hard to begin with.