mikejmoffitt
Member
This isn't a huge deal, and not a huge restoration, but it was a lot of work probing, documenting, and trying new things, and I'm pretty pleased with the result after hours of work.
I received a CPS-1 JAMMA board with Street Fighter 2' HF loaded on it. Game played blind. Visual inspection returned this:
That's one burnt to hell and back DAC section! Likely some chump miswired a JAMMA connector and sent power down the video lines.
Anyway, by probing around with a scope (and later a test-bench CRT) I figured out the following digital RGB bits:
I've figured out now that the ?? bits are ANDed with the RGB values to allow for screen fades in hardware (instead of palette manipulation in software).
I built a really ugly 4-bit DAC on the red channel just to verify that my theory was correct in how the video works:
And here's the red channel represented in greyscale:
Cool, it works!
I received a CPS-1 JAMMA board with Street Fighter 2' HF loaded on it. Game played blind. Visual inspection returned this:
That's one burnt to hell and back DAC section! Likely some chump miswired a JAMMA connector and sent power down the video lines.
Anyway, by probing around with a scope (and later a test-bench CRT) I figured out the following digital RGB bits:
I've figured out now that the ?? bits are ANDed with the RGB values to allow for screen fades in hardware (instead of palette manipulation in software).
I built a really ugly 4-bit DAC on the red channel just to verify that my theory was correct in how the video works:
And here's the red channel represented in greyscale:
Cool, it works!
