So I recently picked up a Nascar. The MPU definitely has some acid damage to it that was repaired in the past.
I cleaned up the game, fixed a few Optos, installed some new rubber and repaired the car mech.
It was playing fine for about a month but now it is possessed. The game will just start a random multiball but it's not actually in multiball. It will just kick out all 4 balls into play and continue to do that. I can just leave the machine sit and it will continue to kick the balls out but then at a certain point it will drain and go to the next ball and play fine.
I've played a 2 player game and one player it will do the crazy long fake multiball but then player 2 will play fine and it won't happen again.
I've tested the playfield switches, the voltage is at 5.10 measured on the MPU.
It is running Rom version 4.0 - so this is an odd thing - I suspected maybe the rom was corrupted so I burned version 4.5 from Stern's website and the game won't even boot with it. I've tried 2 separate chips and it just blinks like it's blanking anytime it tries to boot.
I'm at a loss here. Any help would be appreciated. I'm suspecting the acid damage is the issue. I just hate to go buy a new MPU if it's something I can repair since it's not the most desirable game.