Quoted from nerdygrrl:OK back at it today. First thing on the agenda was to sort out what got nuked here. Oddly enough this is the "cabinet Wiring" harness. Typically these are all of the lines that run from the body of the cab: coin door lights, flipper button, credits buttons, volume, etc.
The connector you are holding in your first picture likely burned because it was plugged into the black mating connector, which would be wrong. It is hard to believe Williams did not ever think anyone would swap the black and white connectors, even by accident. They easily could have used a different size connector to prevent this.
So with that said, you may have some board repairs to do.