not stepping

Hi,

I'm replacing a Nema23 dbl stack with a Nema34 single.
Gecko's, changed the resistor. to 21K
serial, (half winding)
1.7 volts, 4.7 amp motor. 6 wire, series (half coil)
35V power supply. over 10 amps, 68k cap.

I can hear the motor sound like it is stepping, but no shaft movement.
I tried starting at 100 and 1000 for the speed, but no shaft response.

I tried an 8 wire and a 6 wire NEMA34 and they both do the same thing.

any ideas ?

Dave