Maybe my wording wasn't the clearest. I was suggesting getting the normal running temperature range of good ones to compare with suspected bad ones. It would help with basic troubleshooting I think.I don't think they die of heat, more like fujitsu poisoning inside the chip or dry joints / crap on the joints causing latch up / cooked state.
It's not bad if the sprites came back. There's probably a bad via or pad connection underneath the chip itself. Proceed as @stj described and check if the vias connected to the pads have continuity before resoldering the chip.So I found the guilty party, it's the sprite generator 055673 I pressed down on it while supporting it from the bottom and got some foreground sprites coming back. I went and head and fully reflowed the chip but it made no differenct, I am thinking it's bad or maybe some of the vias around it or traces are bad.
Unfortunately I’ve see early 16bit boards have the same issues.Early Konami 16bit seems stable in my experience, TMNT, Sunset, Crime Fight.
Its the later stuff, Simpsons, Mystics, Cowboys, TMNT2, Martial Champ that seem to develop various sprite layer issues.
Reflow the chips around the one you pressed on. You flexed the board when pressing.
Sprites would show but gliteched out, forgot to mention that.