Film-Tech Forum ARCHIVE: Problem with platter timing

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Posted by Katie Smith (Member # 1594) on 03-06-2003, 03:51 PM:

We use potts alpha platters at my projection booth. For as long as I have worked there we have kept four strips of duck tape on the platters. to keep the film from being thrown is what i have been told. my question is how hard is it to get these platters running better? I hate having the tape on the platters because it makes a huge mess and i am not even sure we need it. i also know the tape damages the film. Any pointers for me when i take the tape off?

[ 06-09-2004, 01:25 AM: Message edited by: Katie Smith ]

Posted by Kara J. McVay (Member # 1285) on 03-06-2003, 04:15 PM:

I don't know how to help with the platter timing, but get a Bevan-poo (Cristie Film Retainer)see review section. If you keep them clean, they really stick to the platter and hold anything in place (see review). And only cost about $5.00 a piece.

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-06-2003, 06:12 PM:

Alpha Operation Manual

See 'Platter Timing' on page 4 of the manual (5 of the PDF).

I usually get the best results by either having no film on any of the decks, or having a print on each deck. Usually having no film works fine.

If you've never timed them before make sure you have lots of time to do it -- like after your last show.

Also, check to see if the decks are already timed before adjusting anything (loosening motors brackets). Since your prints are being thrown the timing is probably way out, but you don't want to mess them up if they are already timed.

Posted by Michael West (Member # 428) on 03-06-2003, 10:21 PM:

just as daryl had mentioned (and from my own experience) some time and patience is required but also check the variac adjustment it may also contribute some. also - you are not cleaning the platter decks with any thing that may leave a slippery surface, like wax.

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-06-2003, 10:30 PM:

Was in a hurry before, should have added to check the overall variac speed (that's why I mentioned checking timing before making any adjustments).

Like Mike led to, timing can be perfect but if the variac is adjusted so that the decks spin really fast the print can be thrown on startup (since those vaccuum cleaner motors will take off like a rocket). Adjust to the manual specs and you should be in good shape.

BTW, if you totally botch timing the platter system and find yourself at showtime, you can always spin the payout deck by hand (just disengage the motor first). It's almost as fun as hand winding a reel with a broken take-up belt -- but usually puts you in a position where you can't watch the show. [Frown]

And if you can run fast you can still run the other half dozen or so screens by yourself. [Smile]

Posted by Mark Maxwell (Member # 1355) on 03-06-2003, 10:46 PM:

You can take some masking tape and put it on the edge of the platters where no film touches it and make sure each piece in lined up from top to bottom. Let the motors spin the platters and make sure there you don't have a print on one of them because it will spin slower at first because it has to build momentum because of the weight. If after about five to ten revolutions one of the tape marks is way ahead of behind the other ones, that could be the problem. And try to remember if that is the platter that throws. If they seem to run the same speed, and your' prints are tossed from any platter, it could be the variac. Also, make sure the platters are level with a carpenters level, and make sure a platter isn't warped. I had bad platter because someone tried to reast their ass on the edge of a lower platter and made it slope by about a quarter of an inch, but it was enough.

Posted by Dustin Mitchell (Member # 372) on 03-07-2003, 09:25 AM:

Mark brings up a good point about warped decks, though in your case it appears to be a general problem throughout the booth so this may not be it (at least one hopes its not, unless you have a bunch of warped decks). Warping in a ceck, even slightly, can cause big problems. We have one deck that got warped in similar manner to what Mark describes. Despite our best efforts to straighten it out its still lower in that spot by an eigth of an inch. Its just enough to make prints that are less than 100 minutes get tossed. Considering a new platter deck costs about $500, suction cups or beavan poos are a more economical solution.

Another thing you might want to check is your payout heads (brains). Do you have microswitches or phase controls? If you have the microswitch variety you may need to replace some.

One question for you, do you have a brain for each deck? If not, how many do you have per platter?

Posted by Katie Smith (Member # 1594) on 03-07-2003, 10:35 AM:

Well as far as warped platters go, i dont think that is what the problem is. but i will check them all out.

I think it will probably be kind of a problem to figure out which platter systems are working well or not. As of right now we havent had a print thrown in a while. This is because we take the old movie pins (the rectangular ones the popcorn slingers wear) and fold them to a 90 degree angle and tape them to the platter with duct tape, up against the print. What can I say they love duct tape in my booth. [Eek!]

but I hate it. [Mad]

We have microswitches in our brains and a brain for each deck.

While we are on the subject of microswitches I have another question. Recenly I was replacing a switch and my manager told me that I might have to try several because they usually put the old ones back in the box. why you would have any reason to do this I do not know. Anyway my question is how do you tell if a microswitch is good or bad? They all make that clicky noise when you press them.

Thanks for all your help, i need it, sometimes i think our booth is the epitome of film done wrong. And besides you guys and the manuals i read, there is no one to teach me right. but i am learning alot.

Posted by David Stambaugh (Member # 1102) on 03-07-2003, 10:58 AM:

Microswitches are used extensively in pinball machines, which qualifies me to comment on this. [Wink]

Are these switches soldered in? If so, used ones should be obvious to pick out since the leads will have some solder and/or flux residue on them no matter how well the old solder was removed. Even if they're not soldered, a close inspection of the leads should tell you whether they've ever been used. This being a mission-critical application, I would stay away from used switches. Microswitches can and do flake out over time, even though they may "feel" fine, still make the clicking sound, etc. I've never taken a flaky one apart but my guess is the contacts become oxidized, or they lose their springiness and no longer can make solid contact.

When installing a microswitch, don't over-tighten the fasteners that pass throught the switch body. Too tight and the body will be squeezed enough to possibly interfere with smooth operation of the internal parts. Just snug.

Use known-new switches if you can.

Posted by Rick Long Jr (Member # 541) on 03-08-2003, 09:38 AM:

THe microswitches that Strong use are a fairly common. One thing a lot of people forget to do when replacing them is to remove the little spring behing the lever. If you don't, the force required to move the switch will be so great as to cause the film to possibly wrap around the head before triggering it, Which, in turn, will cause it to stay in the ON position longer, which will cause the disc to spin quite fast. Fast enough to throw the print if it's not centered. Without the spring, they work much better. The switch mechanism itself has enough springiness to push the lever back out.

Posted by Lance C. McFetridge (Member # 95) on 03-09-2003, 02:15 PM:

You may actually be able to smell a burnt and defective microswitch in your alpha brain. Usually a switch will start to work intermittently, so even if they still click, they could be on the way out.
lance

Posted by Darryl Spicer (Member # 711) on 03-09-2003, 02:23 PM:

if a switch is bad can you put a Multi-meter on them to check continuity thru the conection points?

Posted by Paul G. Thompson (Member # 655) on 03-09-2003, 09:12 PM:

There is a resistor that is shunting the micro-switchs. This resistor is inside the motor. To determine if this resistor is burned out, position the pay-out fingers so that the platter is not calling for more feed. Then, turn on that motor to the pay-out position. Then, use the elevator (or accumulator)and position it form one extreme to the other. If the platter does not move at all, the resistor is burned out.

By the way, if you have very small micrositches that came as stock, those switches will fail very quickly if the resistor is burned out. This will either be a stuck switch, intermitting, or just plain does not work. The small contacts in those micros cannot handle the surge current of the motor.

Lance has a point, and my last paragraph echos his comment.