I looked at my Williams row wrong. Sinistar got angry because of it. Typical.
So been dealing with flaky rugs for a bit. The game itself has no trace of the original power supply. The plate shows evidence of ghosts past but the Williams PSU is long gone it seems. I acquired the game in '23 with a switcher.
Digressing, that switcher went bad. Voltage drops across the ROM board told me all I needed to know. I put a new switcher in. Direct wire connections to the terminal block, not the Arcadeshop adapter or whatever that is…consistent, crispy +5.04 following adjustment to all ROM chips. SPECIAL CHIPS though…4.35v..? Hmm. Not knowledgeable enough but that seems…wrong. Anyway, the CPU and ROM boards were serviced in the summer last year for what its worth. For a time, things were pretty solid until I discovered the faulty switcher.
ROM error codes are inconsistent, nothing to definitively point to, so my first thought continues to be power distribution. With a consistent +5v across all ROMs though, confusion. So perhaps back at the CPU, we're running 4114 RAM FWIW?
Monitor shows flaky rug, coloration changes, and periodic reset to the beginning of the boot sequence again where you see the rug "raster" across the screen again.