Neo Geo S-video - Expert mode!

[kendrick]

Anybody happen to have the fully symbolic, abstract schematic diagram of the Neo Geo S-video mod? There are no less than ten websites describing how to do the mod, but they're all versions 'for dummies' with pretty pictures and descriptions of pin bending and hole drilling. Strangely, my brain is wired to handle the schematic, but not to backward-engineer the diagram from those descriptions. Any help is appreciated.

-KKC, who is 24 hours away from owning an MV-1C board. Somebody stop me before I buy again!

[Segasonicfan]

I might be able to draw one up for you.  It's the same mod I did for my CDX (same encoder chip) and I could use the schematic myself.  I also made my own slight improvements to the mod.  I know what you mean about working with schematics...much easier than picture descriptions.

-Segasonicfan

[Segasonicfan]

Here ya go:

[kendrick]

Excellent, thanks very much for that. I owe you a beer. Anybody see any problems subbing a old reliable 2N3904 for the transistor? I usually see the NTE85 specifically used in 12 volt circuits, so I imagine it's a higher-power equivalent component.

Coming soon to my house: A JVC X'eye with S-video. A Master System Mark I with S-video. A 32x with S-video! <maniacal laugher></maniacal laughter>

-KKC, who wonders how people evoked irony in their writing before hypertext tags were invented.

[Segasonicfan]

sounds sweet but how are you going to get S-video out of the 32x?  The encoder ciruit for it is pretty much unknown....

-Segasonicfan

[kendrick]

I'm making what I hope is a reasonable assumption that the 32x outputs RGB as well as composite through said controller. If that turns out to be true, then I'm going to tap power from the cart slot and intercept the RGB to run through a second encoder, probably a CXA1645. I'm not particularly worried about 32x video quality, I just happen to have a bunch of them lying around.

-KKC, up too early.

[Segasonicfan]

oh I see what you're saying.  You're going to use a seperate comverter for RGB->S-video?  You can definitely do that.  The 32X does output full RGB I just don't think it has luma and chroma outputs available.

-Segasonicfan  

[D-Lite]

You need a lot more encoder to do that RGB->S-Video.  Like the entire circuit around the CXA1645.

[kendrick]

Well yeah, that's pretty self evident. I've seen pictures of people who have taken a saw to the Genesis/Megadrive board and pulled out the encoder circuitry whole hog, but that's a little less elegant than what I want to do. Ideally, I'd solder components directly to the CXAchip I've got and wrap the whole thing in shrink tubing to prevent shorts, kinda like the one-off mod chip packages they used to have for the original PSX. Probably I'll be stuck connecting the components on veroboard or some other perf board.

I do have another thought, which involves commonly-available custom connectors and component consolidation, but that's beyond the scope of this particular thread and I'll probably start another one to discuss it.

-KKC, who fell through the floor of his attic yesterday, which is also the ceiling of his garage. Do they call them garages in Australia? Car holds? Car parks?

[kendrick]

Crap. Looks like the photobucket links around here are starting to go stale. Can somebody out there confirm that this photo SSF posted original is the same one that's in the Wiki now at this link, please?

http://gamesx.com/wiki/doku.php?id=av:genesis_1_s-video_mod

[albino_vulpix]

Not sure if that's the 2005 picture, but it definitely works.

[RGB32E]

Here's a rough idea as to how Micomsoft used the CXA1145P to generate s-video.  I've just about traced out the circuit Micomsoft used.  With their application, composite video output is used for Y output, and C isn't fed back into the CXA1145P:
http://gamesx.com/wiki/doku.php?id=av:micomsoft_xmd-3