Film-Tech Forum ARCHIVE: Potts platter will rewind but not payout properly

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Posted by Stephen Frazza (Member # 2320) on 09-08-2004, 04:20 PM:

I have an old potts platter.The top 2 platters work fine and have been.The bottom tier hasn't worked since I started here.It had a blue cfs motor on it that just didn't respond at all.It wasn't the brushes or anything I could see.So i took a motor out of a mut we don't use and wired it to the bad motor.I've done this before using a grainger motor and had no problems.The top 2 tiers have the newer motors not the blue ones ,just to note.

Anyway I can rewind to this tier fine from either other tier, the variac stays at the right height and is constant, but when I try to payout from this tier it just wont keep up.I put a new microswitch in but it still wont payout quick enough.

So I'm not sure where to go next.Any ideas on what to try or look for?

Posted by Dustin Mitchell (Member # 372) on 09-08-2004, 05:02 PM:

Have you timed the deck recently?

Posted by Stephen Frazza (Member # 2320) on 09-08-2004, 05:22 PM:

The deck is timed fine I believe.Even when a close the microswitch all the way with my hand it still wont turn quick enough.It seems like it just isn't telling the motor to spin fast enough.

Posted by Tim Sherman (Member # 569) on 09-08-2004, 05:49 PM:

I know they used two different sized output shafts on the motor. If you were to buy a new motor from them they come with both shafts. I can't remember the two sizes off the top of my head. The older platters used 1 size and the newer ones the other. I can get the sizes if you need them. Also make sure that the new motor has the diode inside of it, witch doesn't come on the motors from grainger.

Posted by Dustin Mitchell (Member # 372) on 09-08-2004, 08:30 PM:

Putting the larger drive shaft on the motor might help, but having the incorrect one would likely cause problems with rewind also.

Posted by Stephen Frazza (Member # 2320) on 09-08-2004, 09:07 PM:

Yes it already has the large shaft on.I don't think it is an issue with that or with the timeing because it rewinds so well.

Also, yes the diode is still on I just took everything off the old motor and connected it to the new one.

It seems like it might be an electrical problem to me but something outside my knowledge.

Posted by Dustin Mitchell (Member # 372) on 09-08-2004, 09:28 PM:

Do you have a multi-meter? You can probably narrow the problem down by downloading a wiring schematic from this site and using your multimeter to test for faults.

Posted by Ken Layton (Member # 133) on 09-10-2004, 01:43 AM:

The blue motors have TWO large resistors inside. One is a 2 ohm 25 watt and the other is 10 ohm 25 watt. One of those resistors could be open or off value. The toggle switch could have a bad set of contacts in it too.

Posted by Dustin Mitchell (Member # 372) on 09-10-2004, 03:23 AM:

*slaps forhead*
Never even thought of the selector switch. Usually when I've had a switch go bad it was just the make up selector.

Only other thing I'll to that though is it would be wierd to have a selector switch go bad in this manner. Perhaps some corrosion would cause a bad connection but I've never seen that before.

*shrugs* Worth checking out at least.

Posted by Tim Reed (Member # 137) on 09-10-2004, 08:55 AM:

Ken's on the right track with the payout resistor. Just short past it, it's not really necessary. And, if memory serves, that'll be the 2 ohm, since the scheme was to ensure that the payout deck always moves slightly faster than the takeup platter.

Posted by Ken Layton (Member # 133) on 09-10-2004, 11:44 AM:

If I remember correctly, the old Potts motor had one resistor in it. The Blue CFS motor has two resistors. The selector toggle switch goes bad because the contacts burn and pit causing poor internal connection. Generally only one section of the switch goes bad from what I've seen.

Posted by Dustin Mitchell (Member # 372) on 09-10-2004, 12:46 PM:

Yeah, whenever I've had one go bad its always been the 'make up' selection. My point was that although its a possibility I've never seen one go bad where the deck would still work but slower-its always been all or nothing in my experience.

Posted by Stephen Frazza (Member # 2320) on 09-11-2004, 01:01 AM:

Ok, I tested both resistors with a multimeter and they both checked out fine.One was 10 ohm and one was 2 ohm.So then I took Tim's advice and bypassed the 2 ohm one.That theater was the last to get out tonight so I didn't get to test it fully but just by holding the microswitch with my hand it looked like it was much faster and that it would work.So I am pretty sure this solved it but i am going to test it fully in the morning and post back

Thanks

Posted by Stephen Frazza (Member # 2320) on 10-31-2004, 01:58 AM:

Just to post back on this in the event it might help someone in the future. Even though the 2 ohm resistor tested fine with the multimeter only after bypassing it did the motor work properly.It has been running fine since I did that so that definitely was the problem.

Posted by Tim Reed (Member # 137) on 10-31-2004, 10:45 AM:

Good, glad it's working okay for you.