I recently built a printer designed roughly on a Prusa i3. I managed to get a few prints out of it (about 18 hours of printing time) and flipped the direction of the Y axis because I realized my parts where a mirror of what I was sending. I am using repetier as my host and firmware, so I went back into their configuration tool and uploaded my previous configuration.h file and only changed the direction of the y axis. When I powered the printer back up and went to print again I smelled something burning and saw smoke coming from what looked like the voltage regulator for the hot end heating element. I am not certain that is where the smoke was coming from as I killed power as soon as I saw it, but it was coming from that area. I am using a ramps 1.4 motherboard on an Arduino mega clone as my controller. The bed still seems to heat fine and all the motors can be manually controlled without a problem. As soon as my hot end temp is reading about 200 degrees C I start to see the smoke. Any recommendations on troubleshooting would be greatly appreciated.