I would think that this could be caused by a bad power supply or/and by bad y sustainer and z sustainer boards. Check the fuses on the y/b will give you a good idea where to start. If they are bad then you'll have a easy fix, if not, i would try replacing the y board first. Also check on your LED's and see if you get an error code. The service manual is available right here Good Luck and I hope that this will help you out.