This is topic AP-3 Phase Control in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Paul Stevens (Member # 4016) on 02-16-2007, 11:31 AM:
 
These things are getting tired! Anyone refurbished the phase control module without having to purchase an entire new one? This is the LED/Photo Cell version.
 

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Posted by Dennis Benjamin (Member # 1137) on 02-16-2007, 12:14 PM:
 
Hmmmmm...

Cardinal Sound & Motion Picture Systems
in Elkridge, Maryland.

At least I think they do....

www.cardinalsound.com


 

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Posted by Jack Ondracek (Member # 1466) on 02-16-2007, 12:15 PM:
 
There's a guy over here that still does them, I think. I'll ask & send you and email.
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-16-2007, 04:54 PM:
 
Its best to replace them with a microswitch kit. Much more stable operation will result.

Mark
 

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Posted by Paul Stevens (Member # 4016) on 02-16-2007, 07:54 PM:
 
I was thinking in terms of available components for refurbishing the devices myself. LED's, photo detector or that stiff wire spring. I have looked over some of the early posts on this subject and did not see this course of action suggested. I am sure there is a good reason.

Paul

[ 02-16-2007, 09:09 PM: Message edited by: Paul Stevens ]
 

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Posted by Frank Dubrois (Member # 3042) on 02-16-2007, 10:48 PM:
 
Back to the microswitch? OMG no. I prefer the LED version so much more.
 

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Posted by Richard May (Member # 2627) on 02-17-2007, 07:16 AM:
 
Have had very very few problems with phase control. Much more with microswitch.
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-17-2007, 03:23 PM:
 
Guys, Things such as motor age, "O" ring condition, line voltage fluctations, and drift within the phase control itself from LED fade as it ages makes them one of the worst methods of controling a strong(or Potts) platter in existance. Replace your micros every two years and as long as no one bends the tang... IE: It clicks in the center of the swing arm travel the platter will work fine no matter what the motor age, "O" Ring condition, or line voltage cares to do. I've been thourgh this literally at dozens of complex's and all of them have switched back to Micros and had zero problems after words.

Mark
 

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Posted by Ken Lackner (Member # 1002) on 02-17-2007, 04:11 PM:
 
It makes sense to me that things like motor condition, o-ring condition, line voltage, etc., would affect platter timing. So why does this not happen with the microswitches but it does with the phase control?
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-17-2007, 04:45 PM:
 
The Phase controls supply a maximum available preset amount of drive to the motors that is not automatically compensatable for motor drofe and other parts wear like the Digital drive is. A phase control platter HAS to hold timming to be operationally consistant, and thats impossible with the motors that are used. As motors age and "O"-rings become glazed the timing changes and nothing in the Phase control automatically compensates for that aging and speed difference unless you adjust the phase control or the motor timming again. For instance... Try timming a set of motors on any given platter and a couple of days later(hours later in some circumstances) they will all be different. Microswitch operation is such that it keeps the motor turned on until the film is fed out to a certain point and the swing arm travels back and shuts it off... strictly a demand system and one in that even much aging of components still affords adaquate operation. The SCDC digital drive looks at the individual motor speed by counting the brush commutation pulses which signifies actual motor speed and makes corrections through an mpu(according to Design And Manufacturing) as needed.... A much better but more expensive idea but one that works really well. This can all be observed with the appropriate Strong Software while the platter is in operation. I would love to see the SCDC system working on an AW-3... that would be a really great platter system... One that would never go out of adjustment!

If anyone here can elaborate in simpler terms or correct something posted here be my guest! I can't always explain things in a simple manner but I think you'll get the point.

Mark
 

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Posted by Steve Guttag (Member # 268) on 02-17-2007, 09:37 PM:
 
Think of the phase control thing as something else in the system that ages, almost instantly. And just like the @%@%#$ red LED readers, some seem to stay stable for a long time while others seem like they have one anode in the grave the moment they are put into operation.

Since the microswitch method is strictly an on/off thing...other than the switch itself becoming unreliable, the payout system does not age.

The motors do and can to the point that retiming is required. On a non-SCDC system, the take up circuit puts a resistor in series with the motor. The payout circuit does not receive this resistor so the payout is give an advantage in addition to the fact that the film that has left the payout platter that has not arrived at the take up platter gives the payout a speed advantage since its ID will be larger than the take up's OD.

AW-3s have the same issue with LEDs and sensors not being stable with some being rock solid for some time and others not so good. However, with the AW3, all three decks are completely independent (aside from the power transformer) so the drift in LED is not as pronounced in its effect until it is substantially out.

The SCDC can indeed work well though the best I've seen by far is Kinoton's E series. It is the best of all worlds. There is no calibration since it is a matter of "faster" or "slower" like a microswitch but without any of the moving parts to wear out. Also the film never deflects more than a couple of degrees before the speed is immediately corrected. Payout and takeup are independent. While some may not like it, the fact it is tied to the motor start of the projector means it does not have to deal with reacting to the film starting either.

Anyway...as to the "payout as a function of the take up speed" platters go...SPECO definately has the best design with the LP270. Their payout has three speeds. Coast, Take-Up speed, Full speed. This also ensure that no motor timing is ever necessary. They use a magnet and a pair of reed switches to switch modes. Generally, the full-speed is only used for thread up and when the show first starts. The platter decks are so heavy they naturally prevent jerky operation much the same as a flywheel would. On the negative side, since the decks are so heavy, they are slow to start and many give them a "push start" though if they are set up properly, that isn't necessary. They have extended their take up path to further make this unnecessary.

I don't know if I explained this better than Mark but I definately used more words!

Steve
 

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Posted by Richard May (Member # 2627) on 02-18-2007, 10:29 AM:
 
All of those points make sense. In my experiences though, I have had very little problems with the phase controls. The theater that I am a projectionists at has 4 platters with phase controls. I have only changed 2 or 3 units since 1989. Same with all the theaters I service. I have had many problems with the microswitched brains. The problems though, are usually from the operators bending the arms. Personally I would use the phase controls.
 

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Posted by Dustin Mitchell (Member # 372) on 02-18-2007, 02:26 PM:
 
I will say again that my experience (6 platters worth) has to agree with Richards.

I do believe someone once mentioned that were different phases of production for these units and that some were lacking significantly in quality. This could be the explanation for the wide variation in observed reliability.
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-18-2007, 02:36 PM:
 

quote: Dustin Mitchell

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This could be the explanation for the wide variation in observed reliability.

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