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Topic: Strong Alpha Platter Motor

Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-13-2002 07:16 PM

I have a dead platter motor on my Strong Alpha platter. Testing has confirmed it is indeed the motor and not a wiring problem with that deck. There is no response from the motor; ie, its not that its burning up and turning slowly, its just plain DEAD.

I'd like some advice on how to go about changing this motor. I've never done it before and our theatre tech is currently out in N. Dakota. Thanks in advance.

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Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 11-13-2002 08:27 PM

Who performs your service, If you dont mind my asking?

Josh

P.S. Never had a strong alpha platter so I don't know

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-13-2002 08:34 PM

Have you checked the brushes?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 11-13-2002 08:36 PM

It's been too long for me to be able to draw a picture, but I do remember the procedure is pretty simple. Whatever you do, if you opt for a new motor make SURE that you "time" it! If all 3 platters don't spin at right at the same speed, you're looking to make a frisbee out of your films.

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Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-13-2002 08:41 PM

Josh, Dan Jorgenson, formerly of MTS.

Steve, I'm a dummy when it comes to these things. Explain to me how to check the brushes.

Brad, yes, I've discovered the wonders of timing my decks.

BTW, if anyone is in contact with Ken Layton can you ask him to check this thread out? I remember him posting a part number for a motor from Granger that you can use on the Strong platter, but I can't find it.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 11-13-2002 08:49 PM

here

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Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-13-2002 09:07 PM

Thank you, sir.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 11-13-2002 09:14 PM

The brushes are also available from Grainger as well, and alot cheaper too. At CLACO we repair all types of platter motors in house and then run thenm in for 48 hours bfore shipment back to the customer. Typical repair for an Alpha Motor is about $50 to $60, and they will run for another 10 years just fine.
Mark @ CLACO here

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 11-13-2002 10:12 PM

There is a resistor and diode inside the motor shell. I would recommend you check those components before you condemn the motor. The wires have been known to break off now and then.

The A-3 had two different style shells on them. One was with a toggle switch (the older ones) and newer one did not. The motor without the switch on the shell had a rotary switch to control the platter functions on the pod.

Which one do you have?

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Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-13-2002 10:45 PM

Rotary switch.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 11-13-2002 11:11 PM

OK. There are two screws that bolt 1/2 of the shell to the motor frame. Take the cover off, and look around for the doide and resistor. Unplug the motor from the platter, and check the resistor with an ohmmeter. If I recall correctly, it is a 2-ohm 10 watt (maybe 25) wire wound resistor. Check specifically for broken wires.

The diode is mounted to a small "L" bracket and that bracket is pop-riveted to the other half of the motor shell. Use the doide checker facility on the meter if it is equipped with it. If not, use a very low ohm scale on the ohmmeter function, and if the diode is good, it'll read a very low resistance in one direction, and a very high resistance (extremely high) in the opposite direction. If the diode is open, it'll show an extremely high resistance in both directions, and that will prevent the motor from running. A shorted diode will show a low resistance in both directions, but it will not prevent the motor from running. It just won't have any torque.

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Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-13-2002 11:43 PM

The resistor is reading 2.9 ohms, the diode is open.

So how do I go about replacing the diode? And is the reistor performing withing acceptable limits or does that need to be replaced too?

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 11-14-2002 12:08 AM

Yes on the resistor, it is OK. The diode can be obtained at most any electronic parts house, probably for 3 or 4 bucks, if that.

But also be advised that something may have blown the diode. If you hit the motor with 115vac, and if the motor is ok, it'll run (like a bat out of hell, I might add.) If the motor sounds OK, just go buy a new diode and put it in. I would not recommend powering the motor up for test purposes with the platter. If the motor is goofy, it could damage the platter's variac.

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Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 11-14-2002 12:23 AM

A few 'dumb' questions:

1) Are there different kinds of diodes? I mean, if I walk into Radio Shack and say, "I need a diode" will they know what I'm talking about?

2) How should I go about powering the motor up to test it? Which wires specificaly do I need to connect to a power source and how, and do I need to worry about polarity?

Thanks for all your help guys.

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Daryl C. W. O'Shea
Film God

Posts: 3977
From: Midland Ontario Canada (where Panavision & IMAX lenses come from)
Registered: Jun 2002

posted 11-14-2002 12:23 AM

You could probably safely use the MUT to test it with the motor's rotary switch in the Makeup position.

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