
Yes I know what the problem is the Kress spindle is inducing mains hum,
try the following
1. Mount stepper drivers in a metal box and earth the box (connect
the box to the 0v on the PSU)
2. Do not feed mains and stepper driver wires together.
3. Use screened cable from the breakout board to the drivers.
3. Make sure that you keep motor outputs separate from inputs on the
drive board (do not bundle them together or run them together keep them
physically separated.)
Thanks
Best Regards
Mike Gaylor