The ribbon doesn’t carry power. It only carries TTL data.
Installing it backwards shouldn’t have hurt anything. I’m sure that I’ve done that at least once.
The component on the background sound board that uses -12V is shorted. Off hand, I don’t know what that part would be.
—
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://www.PinWiki.com - The new place for pinball repair info