I've been struggling with this machine for a while now... It had some erratic behavior that seems like it couldn't possibly be related. The first thing it did was the volume would go up on its own, in a game or attract mode and the flippers would actuate on their own. It's a -1 PDB in that game so it does have the flipper relay for non-opto flippers. I checked the dedicated ground switches and the cabinet flipper switches, all test good. Next, it started showing row 1 ground short on boot, but it was intermittent. Sometimes it would boot fine. The MPU had some battery damage and work done by the previous owner, and it was all at U20 and the LM339's so it was suspect. We put a rottendog MPU in the game, same issues. I replaced the LM339's on both opto boards as well. Next we tried isolating the issue by unplugging ALL of the switch connectors to the MPU and it still showed the row 1 ground short. Then, all of the MPU controlled lamps just quit. Every one of them. I pulled the board and put it in my STTNG. Both the row 1 ground short and the lack of controlled lamps followed the board to STTNG. So PDB for sure right? I noticed that the 12vr pin has no voltage and led 1 is off if the ground short shows up on boot but if it boots to attract mode, the led is on. The volume up and freaky flippers has not come back since I replaced the LM339's on the opto boards but I don't know what that would have to do with that. I hate to let this PDB win, my last resort is to send it our for repair. Any ideas?