Hi jazz,

The machine is a momus design belt driven, il post pics ASAP. Motors are 381oz in from keling inc. I will check the parallel cable thanks, that is one I've overlooked. Looking at the circuit of the bob the output current (74hc244d schmitts) can only source just over 7mA current and the optical isolators on the drivers expect up to 16mA so I think it's definitely out of spec there and needs to be addressed, I think I have a solution using logic level mosfets to sink the optical isolator GND on dir step and ena so I will try today and report back. There is probably a few things going on, always the way so far, I may have too much preload on the bearings too.