Film-Tech Forum ARCHIVE: STRONG Phase Control Weirdness

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Posted by Joe Redifer (Member # 3) on 12-22-2002, 02:05 AM:

I had my Strong A3 platter (about 3 months old) spaz out on me tonight. This is the system that is in our biggest house. I was feeding off of the bottom deck and it was spinning waaaaay faster than it should have been, resulting in a reverse brainwrap which engaged the wrap detector and shut down the projector. Setting the payout arm on the brain to zero percent slowed it down a bit, but it was still spinning faster than it needed to spin. The brain was threaded correctly, the switch was set to "Payout". I tried adjusting the brain in it's little hole (moving it around, etc)... made no difference. I had to run the rest of the show with the switch set to "Rewind" for the rest of the show while periodically stopping and making sure it didn't wrap.

After the show was done, I removed the brain and set it back in the deck. It started spinning super fast again when set to payout, with the brain resting at 0%. I put another brain in the bottom deck and it was fine. Worked as it should. I put the "problem" brain into the top deck and it worked as it should. I put the "problem" brain back into the bottom deck and all of a sudden it worked as it should. What the hell?

This platter system was purchased brand new and is still under warranty. Is it normal for these things to spaz out without warning during a show? Should I have the whole thing replaced just to be safe? I do not feel confident with this thing anymore. It could easily decide to spaz without warning during a sold out show.

If anyone has any questions about this situation, please ask. Solutions would be appreciated as well.

Posted by Shaun Flichel (Member # 1435) on 12-22-2002, 03:21 AM:

Almost sounds to me like you have the carbon switches, its been awhile for me, but I believe if you lightly snug up the allen screw to "re-pack" the carbons, then back off til adjusted right may solve this, if you have the phase controls, maybe the arm that covers the LED is not moving, check to make sure the little spring is in place.

Shaun

Posted by Paul G. Thompson (Member # 655) on 12-22-2002, 05:05 AM:

Two things come to mind, Joe.

1. A leaky (defective) SCR.

2. The return spring on the light shutter is sticking. (This is what I would look for)

By the way, where is the elevator riding? If it is riding too low, it will definately "over power" the pay-out. A pay-out problem with the A-3, CFS, and Potts could actually be a take-up problem, such as tracking pressure on the take-up drive wheel, or a jammed/sticking elevator.

However, you mentioned that even with the pay-out at "0", the deck was still turning. Where was the elevator at this time? It should not do that, even if the carriage is pinned in the threading hole. This leads me to believe you have a sticking light shutter in the phase control since the problem "went away" after you rattled the pay-out head around a little.

And yes, they can spaz out without warning - just like anything else. Seems the booth machinery "knows" when to spaz. It waits for you to have a full house! [Eek!]

Sometimes I am greeted with a "Duh, it worked yesterday"....and my answer is usually "That was yesterday - today is today."

Another thing that could cause this, but I don't think it is your problem. If the doide in the motor shorts out during pay-out, it will cause the carriage to drop a little, and over-power the pay-out. But if the doide is shorted, you would know when you used that motor in pay-out. It probably would not keep up with the demand, hence one big under-feed.

In short, I think it could have been a slipping take-up drive wheel. But more than likely, there is an electrical or mechanical problem within the phase control unit of the pay-out head.

Posted by Mark Gulbrandsen (Member # 72) on 12-22-2002, 09:25 AM:

JOe, While U have the cover off to check the spring check for proper alignment of the small shutter at the one extreme end the curved tip should line up with the radius of the light cell. The spring comming off and improper alignment form kiddies abuse seems to be two very common problems.
Mark @ CLACO

Posted by Joe Redifer (Member # 3) on 12-22-2002, 10:48 AM:

I looked at the "light cover" and it was springing back into place. My first thought was that perhaps the little metal "arm" that moves the plastc light cover got knocked over to the other side of the piece. But it was bouncing back just fine. The elevator was running normally, and when I was testing it I had it locked into the bottom hole...the threading position. It was flying even at 0%!

When I moved brains from deck to deck, all I did was lift them as normal. I did no surgery and I didn't rattle them around at all. I just moved them. Even if the spring came off of the plastic piece inside, I don't think it could put itself back on, could it?

Either the motor was going nuts (it stopped the second the brain was removed, though) or it was an LED problem. I just want to know how to prevent it in the future. Should I have this brain replaced under the warranty?

Posted by Gordon McLeod (Member # 33) on 12-22-2002, 10:55 AM:

Check the connector on the base of the unit and the one it mates into on the arm
I have seen those amp pins dislodged slightly makeing very bizare things happen on certain decks only

Posted by Paul G. Thompson (Member # 655) on 12-22-2002, 01:03 PM:

Don't trust that pay-out head. Something is amiss. Get it replaced under warrenty.

Posted by Joe Redifer (Member # 3) on 12-22-2002, 07:35 PM:

Gordon, nothing is visably wrong with the connector or the socket. What should I be checking for?

Posted by Rick Long (Member # 213) on 12-22-2002, 09:14 PM:

Joe is that control unit still doing it or was this a one-time thing?. Would normally have agreed with Paul that the shadow mask got stuck in the open position, but you say it closes ok right?

Posted by Joe Redifer (Member # 3) on 12-22-2002, 09:18 PM:

It was a one time thing, more or less. It's fine now, or so I am hoping. It wasn't until I put that brain into a different deck and/or put a different brain into that deck and switched them back that the problem went away. And yes, the "shadow mask" as you call it (is that the proper term?) was swiveling back and forth like it normally does, happy as could be.

Posted by Paul G. Thompson (Member # 655) on 12-22-2002, 10:12 PM:

Joe, I have had a few stick on me for no apparent reason. Inspect it very closely.

Posted by Gordon McLeod (Member # 33) on 12-22-2002, 11:03 PM:

I have seen the pins inside the amp connector on the bottom of the pay out getting pushed partially out of there connector and that can cause all sorts of wierdness depending on contact
the brass ends should all be the same distance back

Posted by Pat Moore (Member # 380) on 12-23-2002, 08:44 AM:

Intermittent problems are the toughest of all to troubleshoot. It's difficult at best to find it on site, let alone duplicate the problem and circumstances elsewhere. The fact that Joe can plug that feed assembly into another platter, and then into the same platter where the problem first occurred, and have it work fine is frustrating. The payout will probably work fine 99 times out of 100, and if it's been in regular use at Joe's theatre it's rate of failure is far less than that.

Now if it was Holloween maybe we'd have an answer... [Wink]

Pat

Posted by Joe Redifer (Member # 3) on 12-23-2002, 11:34 AM:

The only possible other clue I can give is that we don't use the bottom deck as often to run actual movies... but we use it a lot for build up. Not sure why that would have any significance, but you never know. Maybe the bottom deck only likes to spin f-a-s-t! [Smile]

Posted by Rick Long (Member # 213) on 12-24-2002, 12:08 AM:

I shouldn't think that would do it, but have you checked the timing on these platters lately?