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Author Topic: Potts Platter Takeup Problem Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 02-05-2009 11:35 AM                     An arts center that I run film for every now and again has a Potts Platter (or an early knock off) that has developed a problem. Occasionally the takeup platter stops, or does not start. It has happened 3 times, 2 of which were at startup, last night it happened about 15 minutes into the feature. As their is no automation or safety interlocks on the projector, it merrily drops film on the floor, the "yo-yo" takeup rollers drop to the bottom cutting power to the entire platter, causing a brain wrap on the feed. Fortunately, I was in the booth when this happened and by chance caught it in what appears to be under a minute (judging by the amount of film dumped on the floor). I shut down, fixed everything, and the remaining 2 hours ran fine. I'm not a happy camper when film is damaged or dumped on the floor during my watch, and although I have been in the booth, I have not actually seen it happen. As a result, I haven't been able to determine exactly what the problem is. These platters are not exactly high tech. It has to be one of: 1) The power rheostat has a dead spot. After the show I tried to find it moving the "yo-yo" manually, but no dead spots were found. 2) The takeup motor intermittently stops or loses speed, but motors tend to either work or not, and it ran fine for the next 2 hours. 3) The "yo-yo" is sticking, causing the takeup to run too slow, then "yo-yo" lets go and drops to the bottom cutting the platters power. Again, I can find no evidence of this happening. I'm at a loss on how to proceed. Any help would be appreciated.  |  IP: Logged John T. Hendrickson, Jr Jedi Master Film Handler Posts: 889 From: Freehold, NJ, USA Registered: Apr 2001 posted 02-05-2009 01:38 PM                     Mitch- You may have a bad microswitch in the variac assembly. Any idea how old it is? Try replacing it and see what happens.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-05-2009 02:15 PM                     It is more likely worn-out brush on the variac assembly. The problem will get worse fast if you don't fix it soon. As long as you replace it before the top of the windings where the brush slides gets burned, it is a simple and relatively inexpensive fix. If you wait too long and fry the variac, don't waste money on the part from Potts or Strong. You can buy the same variac at a good electronics store and swap the shaft assembly (which is a unique piece but interchangeable with a stock variac.) Contact Mark G at CLACO, I think he stocks the parts and can give instructions for the swap.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-05-2009 04:03 PM                     I vote with Tony. Check your variac.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 02-05-2009 09:13 PM                     We do stock all the variac parts... Stator, Brush, Rotor, and center contact... usually the center contact comes off and what's left of it rubs on the rotor and the consequent arcing destroys the brass in a small area. The platter then becomes erratic. 801-355-1250  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-05-2009 09:20 PM                     Thanks Mark..now do I get a bonus check for the referral?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 02-06-2009 01:34 AM                     The book keeper has to approve all sales comission checks Mark  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 02-06-2009 02:44 AM                     Yea, had to replace a variac in one of our A-3 units. You oughta see that collector ring where the brass button makes contact at - all the chrome gone and horribly pitted. I was experiencing the same, irratic rewind. the "W" roller assembly was having fits keeping steady.  |  IP: Logged Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 03-05-2009 10:31 AM                     This platter is becoming the bane of my existence. The above problems have been resolved, but I have now have a different issue. The theatre's tech director decided to take the variac apart to check the brushes and clean it one day when I was not there. He put it back together, and timed the platter according to the manuals instructions. However, now the takeup platter stops when the yo-yo is about an inch from the top, and comes up to full speed about 2 to 3 inches from the top. The problem is that when I start the show, the yo-yo drops almost to the bottom, causing the takeup to to spin very fast and not have time, due to momentum, to slow down before the yo-yo hits the top and snaps the film (acetate threading leader). We tried lowering the "off" spot on the yo-yo in relation to the variac, but that caused the yo-yo to hit bottom during startup killing the power to the platter. What I have been doing is starting the projector and running over to the platter to manually slow the momentum of the takeup so the film does not snap. Once done, it runs fine for the rest of the show. Unfortunately, I'm not always there for film show, and I would like to get this fixed of other who may run shows. To summarize this long winded post, the range of the variac, from stop to fast, seems to be taking place within 3 inches of each other, which does not allow for takeup momentum at the top of the yo-yo. Any suggestions on how to proceed?  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 03-05-2009 11:35 AM                     quote: Mitchell Dvoskin Any suggestions on how to proceed? Shoot the tech who screwed up the platter !  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-05-2009 12:53 PM                     What the reason why the tech had to fubar the thing in the first place? Obviously, he didn't get the adjustments right to let the variac go back to mechanical zero.  |  IP: Logged Adam Fraser Master Film Handler Posts: 499 From: Houghton Lake, MI, USA Registered: Dec 2001 posted 03-06-2009 09:40 AM                        Mark, do you carry the Staco 291 variac for the early TECO platters? I have heard they are a Potts knockoff. The one I need is for the moving arm on the tree. The variac has an open frame, the only ones I can find have a dial on and are enclosed in a box for other uses. Sorry to the OP for going off course.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-06-2009 10:03 AM                     Most of the TECCO's used a smaller variac than the potts  |  IP: Logged Jarret Chessell Master Film Handler Posts: 288 From: London, Ontario, Canada Registered: Jan 2009 posted 03-06-2009 08:38 PM                     Just one thought to put out... I've seen similar problems with platters that have become warped, the motor isn't making contact with the platter, so if the platter happens to be in the dead zone when it starts it just wont take up the film. (The motor usually spins wildly as the yo-yo drops before it hits the stop micro switch)  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-08-2009 03:03 AM                     quote: Jarret Chessell I've seen similar problems with platters that have become warped, the motor isn't making contact with the platter, so if the platter happens to be in the dead zone when it starts it just wont take up the film ... and this is when you either crawl under the deck, or take it off the spindle, lay it face down on the smooth floor, get a pair of vise-grip pliers, pinch them on the deck support arms and pull sideways on them to straighten the arms out to square. This usually gets the decks back to level since the aluminum isn't bent itself-just pulled down by the bent support arms. But, if there is a crease in the aluminum, then good luck in getting things straighten out. You just have to tell the people not to lean heavy on the decks, or splice on the decks themselve being so flimsy. Christie decks - you can stand on them .... -Monte  |  IP: Logged

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