I have an 8" I3v. I was experiencing an issue where the steppers were not turning but were making a HMMM sound. I believe I traced it to a failed stepper controller and I ordered some A4988 Stepper Motor Driver Carrier, Black Edition (Bulk, Header Pins Soldered) directly from Pololu, my reasoning being that the stepper board had failed due to heat, and the Pololu 'black' a4988 board would be less prone to fail due to its claimed superior heat dissipation. (I do intend to add active cooling.)

What I am experiencing is that on the axis with the replacement stepper controller is that the step (from pronterface) is substantially larger than sent. I tell it to move 10mm...it moved 20. What is going on? I wouldn't think that it would be voltage.. but what do I know..

Thanks for any tips!

chip kigar