What component did I kill?

[macua85 52]

When I was building up my second ultimaker, I was testing the fan 19v output with my multimeter and accidentally shorted the terminals. I heard a click, and everything was dead. I took the ardunio off, and that wasn't communicating with just a solid red light on it. So I installed a new Mega today, flashed firmware no problem. However, the ulticontroller screen is blank, with the backlight cycling between 3 brightness levels continuously. I try to run bed level wizard from cura, but says can establish connection. Any idea what the cause is? Or what I could have fried on the ultimaker board?

Thanks,

[macua85 52]

New bit of info...the stepper drivers are getting hot when its switched on. If I remove all of the drivers the ulticontroller screen stays with constant backlight (and a few characters on which fade away).