Film-Tech Forum ARCHIVE: AP3 Film Transport unexplained behavior.

This is topic AP3 Film Transport unexplained behavior. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Eric Robinson (Member # 2966) on 03-14-2009, 12:09 AM:

A theatre I service uses Strong AP3 platters with phase control brains. They have a problem with film wrapping because the pay out is too slow, so they use a trick to speed the pay out up. The trick is to set the unused deck in take up mode. Then they put a rubber band holding the feed castor assembly in the on position, they also disengage the motor from the unused platter. So, in effect the unused platter motor just sits there and spins. For some reason, the payout platter becomes more aggresive. I have spoken with Design and Engineering and they commented that they have heard of this phenomena but dont know why it happens.

I know there's a real way to fix the platter properly and I know how to do it, so I'm not looking for advice about fixing the problem...I'm just curious why the trick works.

Posted by Monte L Fullmer (Member # 2797) on 03-14-2009, 01:01 PM:

Interesting.Does this happen with any brain inserted, or do they leave the brains alone-no brain switching?

Curious to see if you took a microswitch brain and tried this same trick to see what happens.

I'm pointing this towards tired P.C. units.

-Monte

Posted by Jim Cassedy (Member # 4115) on 03-14-2009, 01:19 PM:

Slightly off topic but I was doing some work on a Christie
AW3 recently that had been extensivly modified.

The push-buttons to select make-up mode had been replaced
by small toggle switches. While working on the deck with
the power unplugged and all 3 toggles in the "make up" mode,
I was suprised to see the other two platters move whenever I
spun the 3rd one by hand.

It took me a few seconds to figure out that the platter
motors were permanant magnet type, so the one was working
as a "generator" to turn the other two whenever I spun it.

Apparantly putting all 3 toggles into "make up" mode
connected the motors in parallel.

Posted by Jarret Chessell (Member # 5077) on 03-14-2009, 02:22 PM:

my guess would be.....

having the second motor running would put the two take up motors in parallel, which would make them both run a little slower... which would cause the yo-yo on the variac linkage to lower, which would make the variac try to speed up (since it thinks it isn't taking up fast enough). Both the payout and take up motors are powered by the output of the variac, so.... the payout platter would spin faster. (It would be similar to putting weight on the yo-yo to make it pay out faster)

Posted by Monte L Fullmer (Member # 2797) on 03-14-2009, 03:32 PM:

I'd also wonder if they got a castor switch going wacko, if the 2 ohm, 100w resistor in the tower having problems, if the variac is timed at mechanical zero, platter motors not too tight against the underside of the deck (with motor engaged, the tire should just be making contact with the undersurface and not raise the deck surface any)..et.al..

What happens if they simply unplug that one motor,would the other motor then pick up speed. If so, then it's a motor issue robbing current...

Tonnage of area to condemn... - Monte