thank you for your reply. and yes, i already stripped a usb cable of its 5V line, so that won't happen again. right now, i'm having a defect printer that needs repair and i'm not sure where to start. a new mainboard was destroyed instantly (without usb), so there's another device that has a short circuit. is it the display? is is the PSU? is it one/all of the stepper motors, is it CR-touch, ... is it a combination? i'm pretty close to just buying a new printer -.-