I'm having an issue with my TOTAN that I'm unable to track down. The game boots up fine and I can play multiple games without issue however if I leave the game running for 15-20 minutes it starts bonging 2 times, indicating S2 failure, repeatedly and becomes unresponsive. If I shut the machine down and power it back on right away, it won't boot, providing the same 2 bongs. If I leave the machine alone for a bit and turn it on, it will boot and play normally.

It seems to me that a component is overheating and failing which is why the game will work fine if I let it cool down. That said, I'm not sure where to begin regarding diagnosis as I'm not too savvy when it comes to schematics and I've been unable to find any leads on this specific issue online.

As a sanity check, I have replaced the S2 ROM with a new one however the problem still persists.

Both sides of the A/V board look nice without any apparent hacks.

Any help would be greatly appreciated!

Bump for science.

I've reseated the asic as well as all other chips on the cpu board and this appears to have fixed the problem. I'll leave it running for a few hours to make sure it doesn't crop up again.

Thanks @astill!