Reply To: Koryuu s-video interference

[Noctua]

@megari I’ll see if I can get some good footage of the problem tonight and will post it here. I suppose I yelled Eureka! to soon. The fact that s-video shouldn’t need a comb filter makes a lot of sense when you put it that way. Goes to show how much I know.

Noise like this is always hard to properly describe. What I’m seeing is kinda like the pictures leewrigley posted. Diagnoal lines going through the image. However on those pictures it almost looks like it effects the entire image. On my end it’s only showing on specific shades. For example. The red and yellow text on the Pokemon Stadium title screen as well as Psyduck’s head. The other parts of the image look pretty much fine. I should also note that using other s-video sources with the same cable are fine. Using my SNES for example shows a perfectly clean image with the Koryuu. Composite sources also look fine (at least as good as composite can look that is).

Due to this I thought maybe my N64 was faulty, so I tried another one with the same board revision and one with an earlier board revision. Both show the same issue.

I’ve used a bunch of different cables for this. Started with the consolegoods.co.uk PAL modified s-video cable. This one wasn’t to great. Poor shielding and such. I’ve also tried the official Nintendo cable (NTSC), retro-access.com (NTSC), and classicgamestore.ch (PAL). These don’t have the yellow composite RCA lead. For testing the NTSC cables I’ve soldered a 75 Ohm resistor between Luma and ground on the console motherboard. The latter two cables are built really well and perform otherwhise excellent.

Now I’m thinking that maybe it could be a crosstalk problem. But not caused by the cable bu by the console itself? The PAL N64 doesn’t look like it was supposed to even have s-video support. It seems more of a leftover that they wanted to omit but didn’t for whatever reason. The fact that later board revisions and french systems flat out don’t work when you hook up an s-video cable says enough. Maybe the fact that the RetroTink MINI’s “auto” comb filter solves the issue is a necessary evil? Even though s-video normally shouldn’t need it?