CPS2 B board Troubleshooting Illegal interrupt

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    • CPS2 B board Troubleshooting Illegal interrupt

      Hi guys,

      I'm trying to troubleshoot this CPS B board (Super Street Fighter 2 Turbo) that is crashing after the warning screen. If i leave it off for 30min to an hour or so, It'll get to the intro, and you can start a game, but eventually it will crash to a black screen, usually with random letters and numbers flashing in random places on the screen. If I restart the board after this, it will sometimes make it halfway through the warning before crashing, or right at the start of the warning screen.

      We had a phoenix version of the game lying around with the same board revision, so i installed an infinikey on that and swapped the roms (program roms, and mask roms, and pal roms) over to test the roms. Board works great, roms ok. Cut off the battery on the original board, shorted exc5, and installed the phoenix romset.

      Phoenix romset has the same behavior, but when it crashes it shows an illegal interrupt screen. This screen is sometimes corrupted, and changes frequently, but the most common addresses are 0037FA80 and 0037F5DE. Occasionally, it will crash hard and show read/write data on lines, but no address.

      Looking at the mame source for CPS2, seems like this address is in the program rom, possibly SFX.09. I'm not terribly good with hex addresses, so please correct me if I'm wrong.

      SFX.09 is a 27c4096 EEPROM. Checked the pins with an oscope, there's activity on each Q and A address line, as well as the /CE and /OE lines unless it does the hard crash mentioned above.

      Anywhere else I should be looking?

    • If all the socketed chips checked out when you moved them to the other board, it sounds like something faulty on the B board itself. Was there any acid damage in the battery area?

      Cab: Namco Exceleena 1
      Darksoft Multi: CPS2/3, F3, ST-V, NEO
      Scan Converter: Micomsoft XRGB2+, Silicon Optix ImageAnyplace
      Monitor: Amiga 1080, BenQ RL2460, Pioneer KRP-500M