Probably a stupid question, but can anyone show me the grounding point for a Gottlieb System 80B alpha numeric display board (20 characters-MA644)? I have added grounds to all of the other boards, but due to my deficiency in reading schematics, I am not sure where to attach a ground. I haven’t found an answer on PInwilki or other internet sites. Do people ground the display? If so, can anyone can share/suggest the location to attach a ground to the display?