[Al Skierkiewicz]

What a marvelous picture! Wonder what might have been in the hole? There is a FET missing from the board. Once the shaving(s) were layed down and power applied, a hot spot/arc developed, then the FET set itself on fire or might have exploded. Then the board succumbed to the high heat. I bet it smells really bad as well. Conformal coatings are not meant for transistor packages that exist above the circuit board or those components that may get hot. In this case, a little insulation around the FET leads (as they entered the board) might have helped. Now you know why electrical guys are always complaining about metal shavings and inspectors are always watching for wiring errors and circuit breaker use. I bet the breakers were tripping but the wires leading to the controller were not damaged.