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Author
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Topic: Christie MUT Motor Brush Source?
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Jim Cassedy
Phenomenal Film Handler
Posts: 1661
From: San Francisco, CA
Registered: Dec 2006
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posted 01-13-2009 11:17 PM
quote: Mark Gulbrandsen 30 years of use is a LONG TIME on any brush type motor
Well, yes and no. I suppose it depends on how you look at it.
This MUT is located in a 'single' booth, not at multiplex. So if you think about the amount of time the MUT was actually used over that 30 year period (one day a week or less for about an hour's worth of intermittant duty)- - the motor, although 'old', doesn't have all that many hours on it, relatively speaking.
This particular booth is also equipped for change-over operation and I personally know of at least one 3 year period of time where the MUT wasn't used at all, since all shows were being run off of reels. There may have been other long periods of disuse also that I'm not aware of.
Your advice about dissassembly and checking the commutator for carbon build up and 'scoring' is well taken. I ran carbon acrs off of motor-generator sets for many years and did this sort of stuff as routine maintenance, and I'd planned on disassembling and cleaning/checking the MUT motor when replacing the brushes just because it made good sense to do so.
As for damaging any control card circuitry, that's not an issue with this particular set up. The MUT and the AW3 platters were extensively modified and re-wired many years ago by a local tech who bypassed everything in the AW3's.
Instead of being powered from the AW3, the MUT plugs directly into a wall socket for power, and then you've got to plug a cable from the MUT directly into the platter motor to drive the platter when making up a show.
As for the MUT, it does not have one of the new solid state speed controls. Only a variable autotransformer and rectifier. (and a large wattage resistor) So while a motor short would blow a fuse in the MUT, no real "electronic' circuitry would burn out. About two years ago, I replaced the contact brush in the variable autotransformer, and other than that the darn thing has been working fine.
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