3D Printer (RepRap) Monitor

My wife and I were sitting together in my office recently and as usual the 3D Printer was churning away. Much to our surprise, and this has not happened before or since, the electronics stack started to smoke quite actively! It turns out that one of the fuses at the top of the board had blown. Puzzling as they are supposed to be self-resetting and they are not supposed to smoke to the point of flames! It did NOT reset and it DID smoke!”