Im looking to make a psudo custom cable for my snes/N64 but it requires sync on green. From what I understand it’s a composite sync on the green line not a normal c-sync. I’m assuming taking BNC breakouts and combining the sync and green line wouldn’t work because that’s not the right sync.
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Hey Cooper, welcome to the site.
I think bouncing sync over to the green line is possible, but probably not easy.
I know the PS1 and PS2 have sync on green output, and some monitors require processing that to csync, but I haven’t come across anything going the other way round.
The type of sync is usually a factor with the display you’re using.
If you could give us an idea of what your end goal is, maybe some other, more tech savvy, users can speak to those particular aims.
The Retro Setup thread will attest to the various gear problems overcome by various members.
I think a few VGA monitors accept RGsB, but should also accept RGBHV, which is probably easier to achieve.
I’ve never made any cables, and most of what I learnt about sync comes from a few online resources.
https://www.retrorgb.com/sync.html
Hope that helps. 
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I agree. @cooper let us know the bigger picture and your ultimate goals and we’ll do our best to find you a solution.
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The end goal is just RGB over RCA’s from either the N64, Snes, or Genesis 3 into my ossc’s component input which accepts ypbpr and rgsb. I could just get a hdretrovision cable but that $60 and out of stock and bordies N64 board, which can output ypbpr and rgsb, is more expensive and I’d still need my own cable for that.
If your end goal is component into the OSSC:
You could use SCART output on a bunch of consoles with a simple SCART cable going into a Component converter like the Shinybow SB-2840. The Genesis supports this natively.
For consoles that don’t support SCART like the NES, SNES, or N64, you’d have to mod them, or go with a direct to component solution like HD Retrovision’s cables.
Most other consoles will support SCART RGB output.
Of course, that puts you down the rabbit hole of SCART, SCART switches, and modding consoles, which is not an inexpensive endeavor.
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Honestly, in my experience SCART is the way to go. For me it has been easiest to convert SCART cables into whatever crazy configuration I need. I think the SCART to a Component converter is good advice.
Oh I’ve been modding but scart is hell and expensive and I’d rather not have bulky switches so I think occupying all of the inputs I can on my ossc and retrotink would be the most painless for cabling and switching.
As for the direct question about making a custom cable:
YPbPr is natively sync on green. The green plug (Y) carries sync, and luma. The trouble is that the N64 and SNES do not output YPbPr, so you need to build a conversion into the cable from the RGB at the multi-out. That’s why the retrovision cables are expensive, as they cost a bunch of research and development to make.
Edit: There is actually a little chip in the cable that does the conversion.
Sync on green and the native format of compenent’s YPbPr are different. The sync is sent along the luminance line and different color space is used to deduct the one missing color from the other 2 and the luminance. Sync on green is an RGB format with sync sent along the green line and no decoder needed
Ah I see. I guess I just don’t really see the lure of making a custom solution for going with RGsB when the SNES outputs RGB natively. The SNES output for sync is CSYNC, so you’d have to try and find a way to strip it first, only to combine it back into RGsB. Why not just buy a SCART cable and plug it in?
As for the N64, you can mod the console to output RGB for about five bucks.
I don’t want to have a scart switch. Scart is bulky and redundant with 21 pins. And no need for a sync stripper if I don’t start with c sync anyways
I’m not sure how you’d get raw horizonal and vertical sync out of the SNES. Perhaps you could run the normal RGB output into a D-SUB15 VGA cable and use the VGA input instead of the component RGsB input?
it’s not just a h+v on green it’s composite sync
Ah, then you just need to combine green and sync and that’s it.
Would this help?
thats what i was looking for. i wasnt sure if it needed to have a cap on the line before it goes into green or if the combined signals needed a filtering cap 
would it be best to do this from a cable standpoint or from the console itself
Would be tougher to fit it in a cable unless you did a big hunk of heat shrink or something to hide it, maybe a little custom 3d printed enclosure?
At least you’re not modifying the console, so it would still have CSYNC at the pinout in case you need it at a later date.
couldnt i leave csync intact and use an empty pin and just pop open the cable i have and rewire it
edit:can leave the whole thing intact and move composite video in the cable to green
Yeah that should work.
On that maxim chip there is a low pass filter on the amplifiers. I wonder if that would lead to a softer image (probably), and if it can be disabled somehow.
Makes me wonder if you should use either the THS7374 or the THS7316. The THS7374 can have the LPF disabled completely, and the THS7316 is known to have a really minor LPF that’s not really noticable.
Honestly it’d probably be easier on my Genesis 3 than my snes. I’ll probably get a snes Jr soon anyways