Mini 3d printer not working

Hi, i recently built a mini 3d printer from 3 dvdroms. When i tested first the x and z axis were not working properly and i started to set the vref on the a4988. After i set them to 240mv i started to test the printer again bot all the axis motor had too low power supply to work so i set the drivers to 450-500mv. When i tested the printer again only the y axis was working perfect but after 2 3 test the y axis stopped working. I checked the vref on all drivers but now its shows 0.07mv.. i thought i burned them but i tested the nema17 for the extruder and works great. Build(mega2560, ramps 1.4, 4xa4988, 12v 5a power supply, 1 nema17, 3 steppers from dvdrom).Does anyone know whats the problem?Thanks.

Update, 3/4 drivers work and i set x and y to 300mv and extruder to 800mv, but the motors still doesn't work...