Hi Dan,
Sorry to say but I have never seen Emco ATC that is solenoid driven, the one I have been playing with is DC driven with toolchange rotation clockwise seen from the chuck and locking counterclockwise with a ratchet/pawl. If you have the original mechanics I suggest you stay with the original setup as intended as you will get problems with the gearing ratio so the stepper will probably not hold the tool in position without mechanical aid = reversing - using the ratchet/pawl for locking up the tool in position.
The macro was written for PC-Turn 50 so it is possible that you have to modify the code. Sorry to say I do not have the lathe anymore so I cannot not help you on this.
The DC motor goes full voltage clockwise and reduced voltage with polarity change in reverse as it holds the tool in position all the time it is powered up, this is how it works on the PC-Turn 50.
Hope this helps
Cheers Bengt