Hi RJR:
On PS3 electric engines (which this is), the red roller wire and a red pantograph wire meet at a selector switch on the frame, forward of the board assembly. I typically remove the red roller wire and selector switch, and feed the board directly with the pantograph.
I have to test the board again to be sure it is dead, but GGG's idea of DC getting in somewhere makes sense (especially if the board is dead), but I still cannot see any frayed wires coming off the board or anywhere else.
--Nate Murry