Well my PCB is having all sorts of issues. Once I replaced 15C the game went into game mode (hurrah!!) but the game was going nuts like it was overclocked. I went into test mode and it acts like a coin switch is stuck on during certain tests. I went into the DIP switch test mode and I noticed that one of the dip switches is rapidly switching on and off. Further investigation shows that DIP switch 2 is not changing state like it should. Looks like I have more work cut out for myself with this PCB!
The positive thing is I found a fully working PCB for $85. I’m going to buy that and put it in the game so I can play it and fix this one at my leisure. It will be a good spare once I have figured out what is wrong.
