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Author Topic: Strong Platter Switches
Richard Tucker
Film Handler

Posts: 15
From: Austin, TX, USA
Registered: Apr 2001


 - posted 07-20-2003 11:42 PM      Profile for Richard Tucker   Email Richard Tucker   Send New Private Message       Edit/Delete Post 
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?

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Jack Ondracek
Film God

Posts: 2348
From: Port Orchard, WA, USA
Registered: Oct 2002


 - posted 07-21-2003 12:19 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
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.

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