This is topic Strong Alpha Platter Motor in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Dustin Mitchell (Member # 372) on 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.
Posted by Josh Jones (Member # 447) on 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
Posted by Steve Kraus (Member # 476) on 11-13-2002, 08:34 PM:
Have you checked the brushes?
Posted by Brad Miller (Member # 2) on 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.
Posted by Dustin Mitchell (Member # 372) on 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.
Posted by Brad Miller (Member # 2) on 11-13-2002, 08:49 PM:
here
Posted by Dustin Mitchell (Member # 372) on 11-13-2002, 09:07 PM:
Thank you, sir.
Posted by Mark Gulbrandsen (Member # 72) on 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
Posted by Paul G. Thompson (Member # 655) on 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?
Posted by Dustin Mitchell (Member # 372) on 11-13-2002, 10:45 PM:
Rotary switch.
Posted by Paul G. Thompson (Member # 655) on 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.
Posted by Dustin Mitchell (Member # 372) on 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?
Posted by Paul G. Thompson (Member # 655) on 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.
Posted by Dustin Mitchell (Member # 372) on 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.
Posted by Daryl C. W. O'Shea (Member # 1303) on 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.
Posted by Dustin Mitchell (Member # 372) on 11-14-2002, 12:38 AM:
By plugging the motor in though I run into the same problem. I think what Paul is suggesting is that I 'hot wire' the motor to bypass the bad diode.
Posted by Paul G. Thompson (Member # 655) on 11-14-2002, 12:52 AM:
Exactly. Use a jumper clip to bypass the diode. Since that motor is an AC/DC motor, you can also power it up with a car battery, and it'll run - but not very fast. It is a good way to check the integrety of the motor. 
If you want to try Daryl's method, you can...but be VERY careful. If the motor field or armature is shorted, you could damage the variac in the MUT if you gave the motor "too much balls". That's why I didn't suggest it.
Posted by Daryl C. W. O'Shea (Member # 1303) on 11-14-2002, 01:04 AM:
Yeah, I was just eating my dinner now and realized I had a bit of a brain gap there. Totally forgot about the variac in the table. How I don't know. If you have the ability to directly wire the motor go for it, if you're stuck (and you've got a spare MUT) try the MUT.
Posted by Paul G. Thompson (Member # 655) on 11-14-2002, 01:19 AM:
Been there, Daryl....I have had brain gaps, too...more than once! 
Posted by Ken Layton (Member # 133) on 11-14-2002, 01:25 AM:
Dustin:I have forwarded the photos and info to you via email.
Posted by Dustin Mitchell (Member # 372) on 11-14-2002, 01:52 AM:
Thank you very much Ken.Overall this has turned out very well, I should be able to have this deck going in time for Harry Potter.
Posted by Lance C. McFetridge (Member # 95) on 11-14-2002, 06:52 AM:
Hi,
Would the part number for the grainger motor be the same for a Potts 3 Alpha? I see where they list several models. Do the Strong and the Potts use the same motor?
thanks
lance
Posted by Ken Layton (Member # 133) on 11-14-2002, 08:47 AM:
Lance:Yes, the same Grainger motor 2M262 is used on Potts and Strong.
Posted by Lance C. McFetridge (Member # 95) on 11-14-2002, 09:10 AM:
Thanks Ken,
I appreciate the help.
lance
Posted by Pat Moore (Member # 380) on 11-14-2002, 09:27 AM:
I'm pretty sure Ken knows more on the platter than most, so trust him. Makes me miss the Northwest at times...Pat
Posted by Dustin Mitchell (Member # 372) on 11-14-2002, 10:52 AM:
Ok, I'm stumped. How the hell do you replace the diode? Everything seems to be in the way and I can't figure out how to get it out of there.
Posted by Dustin Mitchell (Member # 372) on 11-14-2002, 12:07 PM:
Just for clarification sake, Dan was always available to take my questions. I didn't post this on Film-Tech because he is a poor tech or hard to get a hold of, in fact the exact opposite is true, he is very knowledgable and thorough tech and available via cell phone at a moments notice.The reason I posted this here is because it is easier for me to follow instructions when they are written. Posting on this board also enables me to see pictures and diagrams of how things should be done. I just thought doing it this way would be easier.
Just to clarify.
Posted by Ken Layton (Member # 133) on 11-14-2002, 05:32 PM:
I've always used a small ignition wrench set (from SEARS) to unbolt the diode and of course a soldering iron and solder sucker. If it's too cramped for you work in the motor shell then carefully drill out the pop rivet that attaches the plastic L-bracket that holds the diode.
Posted by Paul G. Thompson (Member # 655) on 11-14-2002, 06:43 PM:
Be sure to use the new mica insulators and the new plastic spacer, too if the "L" bracket is made of metal. You certainly do not want any part of that diode case referenced to ground.Ken, is that bracket plastic or metal?
Posted by Ken Layton (Member # 133) on 11-15-2002, 12:32 AM:
Paul:All the diode brackets I have seen have been made of a piece of ABS plastic formed into an "L" shape.
Posted by Paul G. Thompson (Member # 655) on 11-15-2002, 12:59 AM:
Thanks, Ken. There should be no problem with mica insulators or other crap. All Dustin has to do is get some small wrenches and a smoldering iron and go to work. Dustin, when you solder the wire to the diode, use an alligator clip as a heat sink on the diode stem to prevent heat damage to the diode. Don't use a soldering iron that is too hot or too cold. Remember, 60/40 solder becomes a liquid at 370 degrees F. The optimum temperature for the soldering tip is 700 degrees F for what you are trying to accomplish. If the tip of the soldering device is clean as well as the parts being soldered, you should be able to make a good solder joint in about 5 seconds. Make sure you have a good mechanical connection before you start soldering, too.
When you touch the tip of the soldering iron to the parts being soldered, establish the heat bridge by touching the solder to the junction of the tip and the parts being soldered.