Right before Christmas, my three-year-old Grizzly G0720 (AKA SIEG SX4) milling machine's main controller board released some of it's magic smoke. In the previous post I went over the initial troubleshooting steps that led me to believe that my failure was due to a blown output transistor. This appears to be a very common failure point of these brushless motor controllers and the replacement boards are very costly. Since the cost of output transistor replacement is less than 1/10th of the replacement board I decided to attempt it before buying a new board. If you find yourself in a similar situation, this post will guide you through the replacement process.
