A friend will be debugging a malfunctioning turntable soon and is seeking an example or two of "typical" turntable control wiring diagrams for AC-drive and DC-drive turntables where the controller allows a variety of speed selections for each direction of travel.

The only thing I've found on-line thus far is a multi-speed AC-drive schematic from the N&W Historical Society.

Can anyone provide any leads which may lead to quick acquisition?

Regards,
Bob Milhaupt

You're gonna have to give more details. Is it DC, AC,single or 3 phase, has the controls been upgraded to a modern soft start or VFD? DC would just be a motor and resistor with a reversible field. AC 3 phase might be a wound rotor motor with a selectable resistor grid on the rotor brushes, and 2 of the 3 phases swap to reverse. Wouldn't be a stretch to find ones with a modern AC 3 phase motor driven by a VFD which should work pretty slick. Or like our transfer table, driven by a 3 phase motor with a current limiting soft start.

My friend has been told that the turntable is reported as "DC, I think". The turntable apparantly retains its "historical" (as equipped, when acquired) controls - no VFD or other "modernized" control circuits. It is apparantly equipped with a "controller" which has several "speed notches" for each direction of turntable rotation.

The info from N&W Hist. Soc. provides what appears to be an adequate example for 2-phase AC motor, with notes describing connections when used with a 3-phase AC motor. That example diagram appears to be appropriate for a "wound-rotor with slip rings"-type AC motor, and shows a controller capable of 6 "speeds" for each rotational direction.

Regards,
Bob Milhaupt

DC and AC antique variable speed drives are completely different animals.

One thing that would make a DC system stand out in most any case I could imagine, is somewhere will be a AC to DC converter. Might be an old rotary converter, or a more modern rectifier. If you lack one, you will have to make/buy one. If your shop is like mine, there was a power plant on site that made the DC voltage locally back in the railroad days, and when it was dismantled, the DC equipment was left powerless.

120 DC is no joke to mess with, an unusually nasty animal, it can hurt you more then you might think.

First step, especially with a DC drive, would be to make sure the converter works and that power is making it all the way to the turntable controls, and that voltage doesn't vanish when you try to engage the drive, due to a bad connection.