I picked up a nice Haunted House not long ago. It worked fine and is in nice shape, so I was hesitant to do anything with it. However, it needed a new power cord and didn't have any of the ground mods done. After each set of steps I tested the game to make sure all was working.
I started out replacing the power cord and adding a ground wire from the transformer base (where the power/filter ground is attached) to both the copper ground strap in the cabinet and to the metal base of the voltage regulator board in the head.
Next I ran a ground from the neg side of the voltage regulator cap to metal base after sanding the black from the contact areas.
Next I soldered a ground wire from the MPU cap to the voltage regulator base.
As with the voltage regulator board, I had to remove the MPU to do the solder work. I got the MPU ground wire in place and the board reinstalled. Once I powered up the game, the player 1 least significant digit was out. Thinking it was a connector problem I reseated the MPU connectors and fired up the machine again. Now I only get the below on the displays. Any ideas of where/what to check?