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» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » AW3 MUT spinning super fast on teardown

   
Author Topic: AW3 MUT spinning super fast on teardown
Justin Hamaker
Film God

Posts: 2253
From: Lakeport, CA USA
Registered: Jan 2004


 - posted 12-29-2008 02:30 AM      Profile for Justin Hamaker   Author's Homepage   Email Justin Hamaker   Send New Private Message       Edit/Delete Post 
Tonight I started breaking down a movie and things were fine for the first reel. But when I turned the motor on for the second reel, it started spinning at top speed right away.

There was nothing obviously wrong: motor works, belt is fine, connections seem to be fine, no indication of fried wiring, switches all seemed to be functioning fine. The only think I can think of is I recently changed the brushes on this MUT, but it's been used several times for tear down since then.

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James Westbrook
Phenomenal Film Handler

Posts: 1133
From: Lubbock, Texas, Usa
Registered: Mar 2006


 - posted 12-29-2008 04:08 AM      Profile for James Westbrook   Email James Westbrook   Send New Private Message       Edit/Delete Post 
Is it one of those Bodine motors?
I had a platter motor on one of my AW3's surge into forward speed during breakdown, literally taking the reel back up onto the platter. I had to unplug the motor to finish tearing the movie down. I sent the motor off to Christie for repair, but was transferred to another theatre after that so I never got the diagnosis of what caused that motor to spin at top speed like that. Though this is a motor on your MUT, the problem sounds similar...

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 12-29-2008 04:21 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
Do you use the "Brake" switch when breaking down? If so, there could be a possibility that the circuitry in the speed control card on the MUT has shorted due to the sudden reverse of current when the "Brake" switch is engaged to reverse the platter motor, and this short is sending full voltage to the motor.

Even though it's a handy thing to have to slow down the platter, that "Brake" switch is the death to these MUTS due to the weak circuitry since the platter motor has to receive current from the MUT to slow it down.

I just use a rag to slow down the platter when the splices comes around and not touch that "Brake" switch.

-Monte

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James Westbrook
Phenomenal Film Handler

Posts: 1133
From: Lubbock, Texas, Usa
Registered: Mar 2006


 - posted 12-29-2008 06:05 AM      Profile for James Westbrook   Email James Westbrook   Send New Private Message       Edit/Delete Post 
I remember being told to leave the Brake switch alone on those MUTs, too. I had forgotten that.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-29-2008 06:34 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
It actually sounds like the speed control module on the MUT has taken a dump...does full-speed situation apply to both make up or break down?

Steve

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999


 - posted 12-29-2008 07:10 AM      Profile for Tim Reed   Author's Homepage     Send New Private Message       Edit/Delete Post 
Yep, that's a classic symptom: the speed control's shorted.

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99


 - posted 12-29-2008 09:28 AM      Profile for Mike Blakesley   Author's Homepage   Email Mike Blakesley   Send New Private Message       Edit/Delete Post 
quote: Monte L Fullmer
Even though it's a handy thing to have to slow down the platter, that "Brake" switch is the death to these MUTS due to the weak circuitry
Is that on newer AW3s? I have a 1980 model and have been using the brake switch on it from the start - never a problem. I think the switch has been replaced once or twice, but that's to be expected.

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Damien Taylor
Master Film Handler

Posts: 493
From: Perth, Western Australia
Registered: Apr 2007


 - posted 12-29-2008 09:58 AM      Profile for Damien Taylor   Email Damien Taylor   Send New Private Message       Edit/Delete Post 
Yeah, i'm using an AW3R, are the r generation in the clear of this problem?

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99


 - posted 12-29-2008 10:09 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
It is indeed shorted but before you install a new $75.00 controler check the MUT motor carefully. You may find that it either has a very worn commutator, worn brushes or that it may be full of carbon dost. Any of these will also kill a brand new controller. NOw if someone grabbed a reel while it's turning that will also kill em. Mut motors can be rebuilt by any competant motor shop.

Mark

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999


 - posted 12-29-2008 11:39 AM      Profile for John Walsh   Email John Walsh   Send New Private Message       Edit/Delete Post 
If I remember, the 'brake' switch only shorts the motor leads together thru a low-ohm resistor. It shouldn't affect the control card at all.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-29-2008 12:14 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Yeah, there shouldn't be a problem with using the brake switch, though most seem to not use it properly. I've never had a blown MUT from it.

Now blown controllers...they have gone from time to time. Don't over torque things, it is bad for the film and the equipment.

Steve

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