I have a Gottlieb Volcano (1981 system 80). Ground modifications were done long time ago. New electrolytic caps on most of the boards including the sound board. The big orange capacitor was replaced in the past.

Thanks to Chris Hibler for the suggestion, I successfully completed the MPU reset circuit modification using the equivalent chip (MCP130-460DI/TO from Microchip Technology).

Reset Modification

However, now when I click the power button, the first digit of the credit display very brightly flashes zero for maybe a second before booting normally. In the 9 years I've owned the machine, I have never seen a blip on the credit display during any successful boot. Only during boot failures would the displays show any bright random characters.

bright zero on credit display

For anyone with a system 80, is this normal?

Again, this has only started happening immediately after I did the MPU reset modification. How about anyone with a system 80 who has done the MPU reset modification... is this normal? I was reading that the original reset was 50ms, but when using this MCP130-460DI/TO reset chip, the reset timing goes up to 350ms (150ms min - 700ms max acc to spec) ... maybe this is the reason?

Thank you!

I read & followed PinWiki on this mod... there is nothing there about seeing a zero flash on the credit display, nor anything about the difference in reset timing.

Just to confirm, you are saying this is normal to see a zero-digit blip on the credit display after doing the MPU reset mod?

Yes, thank you.