Vintage Varispeed

[tubologic]

It does look like three phase doesn't it?  And with center taps on each winding as well.  I'm not sure exactly what they are doing.

Yes,it certainly looks like a (delta-connected) three phase motor with center taps. The torque motors are also (star-connected) three phase motors. What we need here is some motor-expert advice.(which i'm not)  I've seen many small three phase low power motors running on single phase with a simple RC network though perfect 120° phase shift between inductor coils would not be possible. This is the case on the classic EMT 930 turntable which is fitted with a true 3-phase motor. I successfully converted many of these by using a SIEMENS "Micromaster" series inverter which is fully programmable (voltage,frequency,and all other electrical parameters). You only need a three wire connection and discard the original RC network. The results are (much) quieter operation and accurate speed control (by varying the frequency). I don't know how well it would work with your studer C37 motor,and some (careful) experimentation would be required but it looks it could be done. Motor schematics are sometimes misleading;for exemple vintage AMPEX capstan motors looks 3-phase but after closer examination appears to be actually bi-phase two speed motors. Same for the MAGNECORDER's. These can not be used with the above mentioned inverter. For 3-phase operation you allways need 3 wires going separately to the three motor inductor coils. Any motor expert on this board ?