So not to long ago there was this huff on the internet about proper sync levels on the RGB cables on various Game Consoles.
And there these two competing standards for Csync on consoles, TTL Sync and 75Ω Sync (75Ω is named after the impedance on Consumer video displays).
Hence what spawned this post. The post here is copied from my Face Book post.
So I been looking into proper video attenuation for a Neo Geo MVS. I am posting my findings and hoping on some feedback.
I would post pics, but everything covered in heat shrink tubing and I do not feel like undoing everything now. And I didn’t have the foresight to photograph before hand.
[Edit] I No longer have the attenuation circuits in the Scart head.
So I neglected to mention I have a MVS board MVH-MV1T. Apparently different boards have different output levels.
The most common thing to do is just top add some 1k adjustable Pots to the RGB lines. This works mostly fine for the bulk of Superguns for overall/generic compatibility. But I want to get the precise attenuation Neo Geo MVS.
I found I got the proper RGB Video Balance when I had a 75Ω Resistor and a 220 µF capacitors to the RGB Lines. This gives the NEO GEO MVS video the right levels of brightness, and the Caps provide some AC current filtering so there no return voltage on the input RGB lines.
As for the Sync, I believe the sync comes in at 5 volts peek TTL Sync. To get the sync closer NTSC specs, I followed the same attenuation circuit that is used properly wired Sega Genesis/Megadrive and Sega Master System Scart Cables. 470Ω going into a 10µF cap.
This does nothing for the picture quality per say but rather it avoids future burn-out consumer video equipment by bringing the sync signal down to the 75Ω impedance that consumer video equipment and TVs use.
Sources I used for my findings includes
Voultar’s Poor SCART Cable Design w/ Analysis and Rework Tips
René’s dbGrafx Booster – Not Every SCART Cable is Created Equal