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Posted by Dave Ganoe (Member # 53) on 07-28-2002, 02:27 AM:
I just picked up a used potts platter for my home setup. Got it all setup and works fine. However, I don't understand the work lights for the middle and bottom decks. THe brightness of the lamps change with the position of the variac. Other identical potts platters that I have used on the job are not like this. Has anyone come across this before? Ideas? Thanks so much.
Posted by Kenneth Wuepper (Member # 1174) on 07-28-2002, 06:47 AM:
Hello, Dave,You have a wire switched in your re-connection process. The lamps operate from the direct AC not the variable output from the takeup controlled variac supply.
Did you have to remove the wires from any of the system to move it?
If you need to verify the connections to your unit, please access the Manuals section where there is a clear print of your wiring diagram.
Happy spinning
KEN
Posted by Dave Ganoe (Member # 53) on 07-28-2002, 09:05 AM:
THere were only the two wires sticking up through each support arm which I hooked up. I looked at that diagram but don't quite understand it. The colors that I hooked up were, bottom and middle deck, blue and red. Top deck red and white. All where hooked to the micro normally open connections. I took the light holder off of the end of the support arms to see if there were different wires in there and there was nothing extra to hook up or nothing different.
Posted by Ken Layton (Member # 133) on 07-28-2002, 12:35 PM:
How old is the platter? Later ones have an 8 digit serial number with the first 4 digits being the month and year of manufacture. Earlier platters only had a 4 digit serial number (no date code). Does it have white rollers or black rollers? Does it have drop-in control plates or did you have to remove some screws and disconnect the wires to the microswitch to remove the control plates?
Posted by Kenneth Wuepper (Member # 1174) on 07-28-2002, 08:29 PM:
Dave,Was your platter ever converted from cloth covered wire to plastic coated wire? It sounds like these are not the original wires.
Also had a thought that the owner might have become tired of changing the lamps and rewired them to the lower voltage output from the variac.
KEN
Posted by Dave Ganoe (Member # 53) on 07-29-2002, 01:37 PM:
The serial number of the unit is 37L5. I took the cover off of the variac and someone had done some rewiring and I found the 120v supply to the work lights was taken from the side of the variac that has changes in voltage depending on the position of the arm. Moving it to the 120 supply side took care of the problem. Now I've got another question. There is a problem with one of the motors. It runs in payout position (runs slow)even though the micro switch is not activated, if you activate the micro switch it runs fast. This is with the tension bar of the variac locked in its upper position. THe other two motors run either in rewind(as they should) or in payout but only when you activate the micro switch. I moved the problem motor around and it does the same thing no matter what deck it is on. The problem motor looks different than the other two. It has a shiny front on it with the diode sticking out the bottom, the other two are like cans and have the same gray finish as the rest of the platter. I checked all the brushes and they are like new. The odd ball motor has an extra resistor inside where the other two motors have only one and the diode in them in inside the front cover. The control plates are held in place by 2 screws and the rollers are white. The wiring is plastic coated. Hope my explaination of what is happening makes sense. Any ideas? Thanks so much.
Posted by Kenneth Wuepper (Member # 1174) on 07-29-2002, 09:51 PM:
Hello again, Dave,The motor is one of a number which were "improved" by adding an extra resistor across the outside terminals of the mode switch. The purpose of the second resistor is to allow the payout function to keep the motor running slowly. The microswitch shorts out that resistor and makes the motor run at full speed. Essentially they were trying to get away from the RUN STOP RUN STOP payout and get a smoother more constant payout.
I am happy that you found the variac terminals and corrected the deck lights. The earliest Potts were fitted with rubber and cloth insulated wiring. The later version and all field modified machines have a plastic type of wire insulation. Yours was probably of the modified type.
The maximum payout speed is determined by the variac setting which is regulated by the tension roller positioning the variac rotor.
Hope this was helpful.
KEN
Posted by Richard Fowler (Member # 893) on 07-29-2002, 10:28 PM:
The early Potts did use rubber type SJ type of wiring which after five years would be a problem as the rubber would dry out.....rewired many early ones with THHN teflon appliance wire which they use today. Gee, almost 30 years have past since I installed the first one in a 14 hour a day grind house......
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com
Posted by Ken Lackner (Member # 1002) on 07-30-2002, 11:41 AM:
Kenneth,Are you saying that with that new type of motor, the platter is always runnning - slow when the microswitch is open and fast when the switch is closed?
Posted by Paul G. Thompson (Member # 655) on 07-31-2002, 08:11 PM:
When you are screwing around with the old Potts and CFS platters, be advised there was a major wiring snafu in the masts. Black wire may not be the "Hot wire" - but neutral. And the white wire may be actually "hot."You will discover that when you get knocked on your ass even when you change the light bulb. (been there)
Posted by Richard Fowler (Member # 893) on 07-31-2002, 09:00 PM:
Paul,
zapped by the early wiring also............
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com
Posted by Paul G. Thompson (Member # 655) on 07-31-2002, 09:54 PM:
Richard, did you invent a few new words like I did when it gotcha too? 
Posted by Ken Lackner (Member # 1002) on 08-01-2002, 09:16 AM:
Where's the weenie!?
Posted by Paul G. Thompson (Member # 655) on 08-01-2002, 03:56 PM:
Ken, the "weenie" is coming back by popular demand.
Posted by Kenneth Wuepper (Member # 1174) on 08-02-2002, 08:03 PM:
Ken,
"Are you saying that with that new type of motor, the platter is always runnning - slow when the microswitch is open and fast when the switch is closed?"
Yes, but remember that the speed is controlled by the TAKEUP platter. Therefore the speed would always be less than the takeup. (The 2 ohm resistor in series with the takeup provides some drop in power to the TU motor and also is a current limiter while the motor is stalled waiting for the show to start) 
Although that is the result of the added resistor, my pipe organ experience would say that the resistor was to reduce the arcing inside the microswitch and extend its life. A capacitor across the microswitch contacts would extend their life also..BUT the consequence of a shorted capacitor is a guaranteed brain wrap. 
KEN