Film-Tech Forum ARCHIVE: Potts Platter Take-Up Problem

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Posted by Patrick Matthews (Member # 2705) on 12-23-2005, 10:43 AM:

After getting a new brain and it not doing the trick when it came to irregular payout I have come to the conclusion (based on the fact that it happens to every deck so it probably isn't the motor brushes) that is has something to do with the take up system. I sat and watched as I ran a test reel today I noticed that the area that the take-up mechanism is able to engage the motor is a lot smaller than it used to be. This is to say that at the majority of points from the most northern part to the most southern part have the motor disengaged rather than engaged, leading to a very unsteady take up (the tree is never "level") Is there an easy adjustment for this?

Posted by Steve Scott (Member # 630) on 12-23-2005, 12:00 PM:

The start/stop points on the take up variac are probably dirty or out of alignment. Pull the power plug to the platter & inspect it, if you have another Potts, compare its settings to the malfunctioning one & set accordingly.

Posted by Patrick Matthews (Member # 2705) on 12-23-2005, 12:02 PM:

I talked with a tech guy that our owner knows (our tech is out of the country) and he said that I need to set the "Electronic Zero". He is faxing over instructions. Is this a hard procedure?

Posted by Monte L Fullmer (Member # 2797) on 12-24-2005, 02:43 AM:

Loosen the motor bracket bolts and raise the motor, or lower the motor a bit to find that "sweet spot".

This is how one adjusts the takeup tension and adjusts the platter RPM.

Posted by Dustin Mitchell (Member # 372) on 12-24-2005, 02:53 AM:

The platter 'drive tires' might need to be replaced too. These are the two rubber rings that actually make contact with the deck.

Posted by Mark Gulbrandsen (Member # 72) on 12-24-2005, 09:46 AM:

quote: Monte L Fullmer
Loosen the motor bracket bolts and raise the motor, or lower the motor a bit to find that "sweet spot".

Monte, What does this have to do with finding the zero voltage point?

Setting the zero voltage point is easy. Remove the variac cover and loosen the set screw in the center of the variac shaft to loosen the clamp(some older platters have two allen head screws there). Place one deck in "take up", then with the take up "tree" at a point that the microswitch is just not being activated be sure that the variac is not allowing any platters to turn at all. If the deck is turning just turn the variac shaft counterclockwise so the deck just stops. Then tighten down the locking screw(s). Your platter is now set for zero voltage with the tree at its lowest OPERATING point just before the microswitch turns off the power.

Also.... while you have the cover off take a flashlight and check the variac brishes, not so much the stator carbon brush as they rarely wear out but in particuluar the center rotor contact to be sure that its not worn out and also that its not broken off. There should be a contact button seen in there at the end of the piece making contact with the coppper area on the rotor. Broken center rotor contacts are quite common and will cause very erratic operation. Some platters will run for a long time with a broken rotor contact but will eventually wear through the copper ring on the rotor that it makes contact with. Then all hell breaks loose.

Hope this helps....

Mark

Posted by Aaron Mehocic (Member # 15) on 12-24-2005, 11:50 AM:

quote: Dustin Mitchell
The platter 'drive tires' might need to be replaced too. These are the two rubber rings that actually make contact with the deck.

Use Kirby vacuum cleaner belt K-159056 for best results (not kidding). I ordered a whole bag full last year from our local mom-and-pap sweeper store and got a substantial discount on each belt.

Changing the belts is a simple task and can be done in between shows. Two signs that belts need changed are shuttering decks and uncentered prints (usually resulting in thrown prints).

Posted by Monte L Fullmer (Member # 2797) on 12-24-2005, 12:46 PM:

HI Mark. I had a hunch that "electronic zero" IS the variac adjustments needed in the control arm in the control box, but to be safe thought I just chime in on the motor adjustment thingey to sorta help out.

Posted by Mark Gulbrandsen (Member # 72) on 12-24-2005, 02:46 PM:

Just don't want him to get confused over which is which.... you left it sounding like the motor height afjustment had something to do with the zero voltage adjustment.

Mark

Posted by Gordon McLeod (Member # 33) on 12-24-2005, 06:27 PM:

And be very carefull on some variacs the metal plate that holds the brush is live. Autotransformers under dead short conditions can act like a choke and current limit themselves so fuses don't blow and if they do they can provide a nasty kick from the collapsing field
If you are not sure of the correct sfety methods then call in your service engineer

Posted by Dustin Mitchell (Member # 372) on 12-25-2005, 01:18 PM:

Mark, is the Potts platter take-up that different from the Alpha platter take up? Either I'm mis-reading your post or you have your instructions backwards. When I read it it sounds like you're saying to set the take up assembly as low as it will go without tripping the microswitch. But on the Alpha platter you have to do the opposite-set is as high as it will go. From the Alpha manual (the Potts manual doesn't have instructions for setting the variac in it):

1) Raise the take up to the top of its travel and secure there with a rubber band around the pulleys.....

(further instructions in the manual found in the manuals section of this site)

Posted by Monte L Fullmer (Member # 2797) on 12-25-2005, 01:47 PM:

I had to do a couple of Alphas and I've done it with the accumulator in the down postion to get things centered and microswitch adjusted correctly (course, unplug the platter first from the wall..lol) in the variac box.

Not so sure on the Potts, but if like the Balco with that cable drawn variac to the accumulator, it could be the same as the Alpha.

Posted by Dustin Mitchell (Member # 372) on 12-25-2005, 02:56 PM:

On an Alpha the electric zero should be at the top. Why would it be at the buttom-that's what the microswitch is there for.

Posted by Gordon McLeod (Member # 33) on 12-25-2005, 02:59 PM:

The platter should be set for zero with the dancer in the top position

Posted by Mark Gulbrandsen (Member # 72) on 12-25-2005, 03:27 PM:

You guys are right... [thumbsup]

caught me with my pants down [Eek!]

!

Merry Xmas!

Mark

Posted by Dustin Mitchell (Member # 372) on 12-25-2005, 05:24 PM:

We all make mistakes sometimes Mark. I have a basic knowledge of booth operations (limited to the equipment I've worked with) so to be honest I really wasn't sure if I was right or not [Smile]

Posted by Mark Gulbrandsen (Member # 72) on 12-25-2005, 06:37 PM:

Christmas shoppers burn out is what I call it.....

You are correct though.... tree drops-platter spins faster till it falls far enough for the micro to shut it off.

Mark

Posted by Patrick Matthews (Member # 2705) on 12-27-2005, 09:50 AM:

I did manage to set the electronic zero based on a manual that I recieved from a tech that does other theatres in this area (i'm running a Potts Alpha platter btw). I also switched out the microswitch down there. It is still doing the same thing. While I could understand that it would be the position of the motors and the rubber on the drive wheels every deck is doing this and I find it hard to believe that they all just stopped working at the same time.

EDIT: I went up just a second ago to try disc timing and I read in the manual to turn all decks to the off position and then raise the take up plate to the lower hole and put in the pin in so it stays in place. I did this and then turned all the switches to rewind. Instead of all the decks spinning nothing happened. I hen lowered the take up plate about a half an inch and they all started spinning. So basically it looks like the center of where my take up plate is supposed to be engaging is lower than it should be.

Posted by Louis Bornwasser (Member # 3063) on 12-27-2005, 10:29 AM:

With the carriage in the lower hole (if you have 2), and the three decks in takeup....pardon me "Rewind," the variac should be adjusted so that the decks creep very slowly. Speed should be less than 6 inches per second.

New platters are adjusted this way so that when threading you put the platter into REWIND, and when the film tightens, the pin pops out and then the motor stops. Louis

Posted by Patrick Matthews (Member # 2705) on 12-27-2005, 10:55 AM:

Fair enough Louis, but they don't creep, they don't move at all. So once again I ask is there an adjustment that i'm missing or just not understanding so that I can make this so? I guess i'm just a little confused.

Posted by Gordon McLeod (Member # 33) on 12-27-2005, 11:18 AM:

You may also have a dead spot on the autotransformer

Posted by Mark Gulbrandsen (Member # 72) on 12-27-2005, 03:04 PM:

I agree... Bad autoformer(variac). Probably a broken statiionary rotor contact on it. The one down near the center of the rotor.... I wouldn't do any more work on it till you take a real close look at the variac.

Mark

Posted by Patrick Matthews (Member # 2705) on 12-27-2005, 03:52 PM:

I obviously don't have the original manual so I'm going off of the closest one I can find in the manuals section. If I'm looking at the right thing it is a black piece right behind the microswitch that has about 8 different wires going into it (sorry, I'm not very technical when it comes to machinery like this). Does this piece need to be replaced totally or is there a part of it that goes bad? If I have to replace the whole thing what is the difficulty and any estimated costs?

Posted by Mark Gulbrandsen (Member # 72) on 12-27-2005, 08:15 PM:

You can either replace the whole thing or repair it your self. Some dealers stock all the replacement parts for that particuluar Staco variac, model 1010. Brushes, rotor, stator, snap ring, etc. There are tens of thousands of those running daily! We stock all the 1010 parts and I'm sure that some other dealers do as well. New variacs are expensive from the factory but a new off the shelf 1010 can be modified very easily. Check with your local supply dealer or your local electrronics parts house if there's no cinema dealer in your area. Many of our customers swap out the variac themselves and then have the old one rebuilt to serve as a standby unit. No cinema technician in your area and you're unsure about what to do or afraid to work with electricity.... just call in any electrician he'd be able to fix it. Just be sure to print out Louis's instructions on setting the zero voltage point for him.

Or... Perhaps Monte could put together a step by step pict-o-graph of how to replace one..... He's pretty good at that.

Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 12-27-2005, 09:33 PM:

The only repairable item on a autotransformer is replacing the brush
A dead spot is an opening in the winding and is unrepairable
Often when the dancer oscilates up and down constantly it is an indication of a dead spot

Posted by Monte L Fullmer (Member # 2797) on 12-27-2005, 11:32 PM:

quote: Gordon McLeod
Often when the dancer oscilates up and down constantly it is an indication of a dead spot

I'm gonna chime in on this one even though Gord here has it right: (a side topic for you with my asking..)

With the "dancer" (that's a new term for me on this unit..I've always called it the "W" or the accumulator...WHATEVER..lol)

oscillating up and down .. is the platter deck bent causing the motor to pivot up and down on its mounting axis? This causes the film takeup speed to variate causing the "dancer" to oscillate up and down.

Cure on this (if this is what it is..)take the deck off, lay it flat on the floor, look at the "spider supports" and see of the "spider supports" are bent any. And if so, take a crescent wrench, close the opening gap to the width of the "spider", place the wrench in the spider and bend the spider supports back to vertical and this will raise that portion of the deck to be flat with the rest of the deck.

I've seen decks so warped that the "dancer" actually jam up to the top of the run and will pull the lower guidance roller on the projector over. Plus, with this variace, the payout deck will speed up and suddenly stop causing thrown prints like nobody's business.

How they get warped is when people hammer the splicer while the splicer is on the deck's edge fixing a break, or they lean like crazy over that part of the deck while threading the brain, or on rare occasions, moving prints by taking the deck off the support arm and moving the deck with the print (especially with huge prints...and I'm guilty on that one, but I make sure the the deck is lifted squarely with a helper and placed back on the receiving arm in the same manner...)

This "bending the spider support arms" to get decks flat is my usual treatment of oscillating "dancers."

Yea, I'm about ready to do some more shoots of "do-it-yourself- fixit tips"

quote: Patrick Matthews
I hen lowered the take up plate about a half an inch and they all started spinning. So basically it looks like the center of where my take up plate is supposed to be engaging is lower than it should be.

The brush arm that contacts the windings on the variac should be close to in the middle of the wind set. I wonder if the microswitch is way out of adjustment, (with the "dancer" all the way down, one motor switch to either "rewind" or "payout" and you barely lift up the "dancer", does this one deck start to take off full speed with the "dancer" raised about 2 inches? If so, then the microswith is adjusted correctly) the "electronic zero" isn't adjusted right...or a burnt spot on the windings itself... You may have to make up your own "electronic zero" to get this unit to function.

-Monte

Posted by Mark Gulbrandsen (Member # 72) on 12-27-2005, 11:47 PM:

quote: Gordon McLeod
The only repairable item on a autotransformer is replacing the brush

Actually I have only seen one dead spot in a 1010 winding over perhaps 30-40 failed units in 20 years.... but then we also don't have the drastic hydro problems you have up north in some areas.

quote: Gordon McLeod
A dead spot is an opening in the winding and is unrepairable

Not necessarily.... While an open stator is a dead stator the most common failure point I experince on a regular basis is the stationary contact and the ares of the rotor itself in which the stationary brush normally rides on. A missing contact button or broken contact that is still actually making rough contact will eventually arc and erode the brass contact area of the rotor away. This leaves the 1010 with intermittent operation at the common point of platter operation. As Monte said finding a new zero point might get you by... but the same variac is also used in the MUT so you could rob that one temporarily so you can run film. To see if the stationary contact is broken just remnove the cover of the variac and look into the variac between the windings and the rotor with a flashlight... it should be pretty obvious.....

The stationary brush, the most common part that fails is also available from Strong dealers as Strong part number 2103.

All 1010 parts are available as spares from STACO... but they do have a miminum order amount...

The replacement Staco Part numbers are as follows: Tele. # 513-253-1191

Brush set 808-0127-S
Contact plate 808-0147-S
Contact Assy. 841-0025-S
Rotor Assy. 942-0178-S

Hopefully this helps.....

Mark

Posted by Monte L Fullmer (Member # 2797) on 12-27-2005, 11:49 PM:

Thx Mark for these part numbers, for I need to rebuild some STRONG MUTS, since these "booth clowns" that I have to deal with love to tip over [Eek!]

the MUT at times..

-Monte

Posted by Mark Gulbrandsen (Member # 72) on 12-27-2005, 11:55 PM:

We stock all the 1010 parts if you need them Monte.... lots of stationary brushes and rotors!

Mark

Posted by Patrick Matthews (Member # 2705) on 12-28-2005, 09:20 AM:

quote: Monte L Fullmer
The brush arm that contacts the windings on the variac should be close to in the middle of the wind set. I wonder if the microswitch is way out of adjustment, (with the "dancer" all the way down, one motor switch to either "rewind" or "payout" and you barely lift up the "dancer", does this one deck start to take off full speed with the "dancer" raised about 2 inches? If so, then the microswith is adjusted correctly) the "electronic zero" isn't adjusted right...or a burnt spot on the windings itself... You may have to make up your own "electronic zero" to get this unit to function.

Monte - Just went up and checked and indeed the microswitch is adjusted correctly, when the dance is about 2 inches from the bottom the decks are going full speed. I was just up messing around with the dancer and when I usually thread it I lock the dancer in with the pin in the lower slot, which usually has the motor engaged and thus the brain paying out while I get me leader through, It no longer does this because this position isn't engaging the motor anymore, but it will begin spinning the decks when I put very light tension on it...not enough to unlock the pin, but enough that I have to push my hand up a little bit.

Posted by Monte L Fullmer (Member # 2797) on 12-28-2005, 08:34 PM:

quote: Patrick Matthews
but it will begin spinning the decks when I put very light tension on it...not enough to unlock the pin, but enough that I have to push my hand up a little bit.

..just wonder if you have a irratic variac, variac brush giving you fits, or just the pivot arm attached to the variac shaft needs to be adjusted more to where when the dancer is locked that the motor takes off for threading.

Posted by Mark Gulbrandsen (Member # 72) on 12-29-2005, 08:17 AM:

quote: Monte L Fullmer
..just wonder if you have a irratic variac, variac brush giving you fits

Of course thats whats wrong..... [Roll Eyes]