Here is a comparison between the 2 boards. new board on the left, old on the right...\\
notice there is an extra pin where the empty "key" slot should be... thought it was for forward compatibility or whatever...remove the key plug in my connector. nope. Doesn't work.
STORY TIME!
A call to stern yields... It seems the issue with the machine is that the interlock switch contacts for the 50V get stuck together. when the door opens, the 50 volt stays active. bla bla bla board locks on the coil and fries it. (likely the cheap contacts are welding themselves together.)
So instead of replacing the interlock switch and fixing the root of the issue, they designed and spun a new board to deal with the problem. So now if the 50 volt line stays on, the disabled 20 volt line will keep it from operating.
classic electronic engineer problem solving. Don't FIX the issue, just DEAL with the issue.
So in order to get the new style board to work, you have to steal 20 volts from a nearby flasher or something and punch it into the IDC connector and remove the plug. Stern has a kit with connector and whatnot to plug and play this board. whatever, I can wire this. NBD.
Still, would be nice if there was a technical bulletin about this.