I had the same thing happen to me. It was my fault as I tried to work on the hotend while powered on. I smoked the stepper motor driver. It's on the main board. If you follow the wiring from the motor to the main board you can see which one it is. If you want to be sure you can swap the one form the working side. I used the printer while I ordered a new one by taking out the bad driver.
If you look on the USA FF site they sell them for 16 bucks ( I bought 2 as I'm prone to blowing things up). No soldering, it's just a plug in module.