I have been using my MiniMill with a CNC xPRO V3 board successfully for the past several months without any problems. I recently hooked up an accessory board (made by a friend) containing MOSFETS to control my spindle (i.e. router) and solenoid valve for coolant. I tried hooking up the spindle signals first. The xPRO worked fine with the accessory board and a relay to turn the spindle on and off. I used the exact same parts and configuration shown on the Github site. I proceeded to hookup the solenoid (yes I used a flyback diode). When turning the power back on to the board after connecting the solenoid through the accessory board, I think I heard a pop and smelled something burning. I noticed I no longer had lights on for the stepper drivers, but the 24V, 5V and USB comm lights were on. I could still turn the spindle on and off, and I could now activate and deactivate the solenoid. However, I still had no lights on for the stepper drivers and I could not move my stepper motors at all. I tried everything I could think of by disconnection and reconnecting things. I checked voltages and all are correct. I can still turn the spindle on and off and activate/deactivate the solenoid, but no power to the stepper drivers. Did I just fry my xPRO? If everything else is working, what could have happened? Can anyone suggest some diagnostic techniques to help me? Please keep in mind I'm not very electrically inclined.