Thank you so much--I did disconnect the J3 of the Opto board and fired it up and this is what messages I am getting. Maybe no power to the board? See the photo of the board with the game powered up. There is a Red Light on the board and is not lit...Supposed to be?
Quoted from Manny65:
Have you tested disconnecting J3 on the sw10 opto board (A-18159) to see the ground short disappears? The additional switch errrors (sw 31-33) are all on the sw10 opto board - the magnet opto is sw33. So this all points to the sw10 opto board and most likely the LM339 having failed.
The Battle Kicker opto and Mini PF bad error messages relate to sw36 which is not on the sw10 opto board, however I'd focus on troubleshooting the sw10 opto board first - remember that you can take the opto board from Indy 500 to confirm your fault finding
Note that the only thing relates to both the sw10 opto board switches and the sw24 opto board that handles the Battle Kicker opto (sw36) is the 12v power from J116-2. However you wouldn't see the ground short error if the opto boards weren't getting power.