I have a Gottlieb Volcano (model 667, system 80)
I had it all working great... MPU reset modification. Booting great. I previously had an issue where the RAM appeared to be flaky because it was not retaining anything consistently and random scores coming up. Then I fixed several problems with the 110 VAC coming into the machine and I had no more of those weird issues for last several days.
Today I socketed the 5101 (Z5) Ram chip so I could install an NVRAM from PinballElectronics.com. (I remembered to remove the memory capacitor)
The NVRAM chip went in and seemed to work, but every time I start a new game, the high score is wiped out and replaced with the default high score 790,000. Credits are retained and other bookkeeping appears to work. The score is retained correctly through a power down/up cycle. It's just starting a new game that wipes it out. I went through bookkeeping and zeroed everything out; makes no difference.
I put my original 5101 back in and now that's doing the same thing. So whatever is happening apparently has nothing to do with the RAM chip itself.
I checked the new strip socket carefully and see no issues there.
Suggestions? I don't even know where to start. Thank you!