My problem- My new A axis motor creeps in ONE direction when it should be stopped.
I haven't been here for a couple of years. My machine has been reliable and behaving
However, I just replaced my A axis motor NEMA 34 with a NEMA 17 motor'
I replaced the big stepper controller (DM860A) with a HY-DIV168N-3.5
I am using a computer power supply for the 12vdc input to the stepper controller.
This was a straight change over. No pin outs or other wiring changes.
The motor runs fine in one direction BUT in the other direction it continues to creep until direction is changed.
This happens from both a jog command or a g-code command.
Motor signals come from an optical isolated breakout board connected to the printer port.
Things I have checked. Wiring is identical to the old controller. have tried almost all dip switch settings on the controller.
I have tried mach3 motor tuning parameters from 1-5ms on the signals.
I even tried to reverse the pin out signal logic in mach3 (that did not go well.)
Any helpful suggestions would be appreciated.
Thanks

You made two major changes and now have a problem you didn't have before. First, why did you swap motors and controllers if the machine was working ok? Its now a process of elimination.  I would reinstall the original stepper controller and see if the problem disappears. Next reinstall the NEMA 34 motor if that cures the issue. Computer power supplies are switching type and aren't desirable for stepper controllers.   

I am using the machine for a different purpose. The old A axis is still installed. just unplugged. When the plugs are reinserted and the new axis unconnected, everything works just like it should. This is required to easily return the machine back into its main use.
NOW, that 12vdc computer power supply could be my problem.
Got any low budget suggestions to replace it? or modify its output?
Thanks.
Oh, My new NEMA 17 is max rated at 1.75 amps and winding voltage at something else that is lower than the rated output from the original DM860 stepper controller, the lowest setting on the DM860 is something over 2amps. I was afraid of smoking my NEMA 17 and my DM860 if I hooked them together. (Smoking the DM860 would cripple the machine when I tried to reuse it for its normal operation.)
It looked to me like I was about to plug a 120v motor into a 220v outlet.
That NEVER goes well.

You lft out one crucial detail:
When the system creeps, do the DROs in mach show any change? This is fundamental.

Change: something is telling Mach to creep along. I suspect this is not happening.

No Change: Mach is not putting out any Step pulses, but the hardware thinks it sees some. And it only sees the puses when the Dir line is in one state, not in the other state.
I would check the power supply to the controller - both the +5 V rail AND the 0 V rail. You want hard single-point (star) earthing. It sounds as though one of these lines, and i suspect the 0 V, is wobbling around.

Cheers
Roger

Thanks, No the DRO is not counting. HOWEVER you are on to something. Today I was trouble shooting other issues when I noticed the motor definitely turns unpredictably when the X axis gets either a JOG or g-code signal.
Only the X axis. So I definitely have a signal problem.
I intend to install new signal wires from the breakout board using different pin outs for this controller. Hopefully this will eliminate the cross talk.
Thanks again.