I am trying to build small CNC based on GRBL. I've bought GRBL shield on ebay and wired everything. When I try to run stepper it vibrates a lot. I've set current on driver, and numbers of steps in configuration. I'am using 12V ATX power supply. You can hear it in following video: First I thought it was motor problem, but then I've connected same motor to RAMPS 1.4 board with Marlin software. It uses same drivers (A4988). When I run it in this configuration it works perfectly. I've tried swapping drivers and power supplies between boards, but same thing happens. Does anyone have any idea what could be the problem?