How To Extract Signals from NTSC SNES SCART Cables?

How do you extract audio/video signals from a fully wired NTSC RGB SCART cable? I want t use my SCART cable with my N64 and my GameCube but they don't support RGB (yet). When I hook up the cable, it automatically swaps to RGB mode and I can't get a picture on screen. So until I can afford the N64RGB board and the parts for the GCVideo DVI mod, I want to use S-Video but all of the cheap cables I see for sale are not good and some of them are just composite sent over the S-Video cable. Seeing my cable is fully wired for composite, S-Video, and RGB, how do you extract S-Video from the cable or disable RGB mode? How do you wire it for Sync on Luma when in RGB mode? My SCART to HDMI converter supports S-Video over SCART.

 

The RGB switching signal is on pin 16 of the SCART plug - so if you just disconnect that it should switch back to S-Video or composite.

Assuming the Y/C pins are connected, you should just have to select S-Video mode and it should work.

As far as sync is concerned, there are 3 places you can get it from (at least on the NTSC Nintendo consoles) - the first is (Multi-AV) pin 3, which is purely a sync signal, the second is pin 9, which is composite video, which includes sync and the last is pin 7, which is the Y component of the Y/C output.

 

Ok, so should I wire a SPST switch in between the RGB switching signal wire and pin 16? I would still like RGB on my SNES. How can I swap it to S-Video mode? I've read online that 0V means that it is in S-Video mode.

So I should just disconnect the Y wire and solder separate wires to the Y wire and then send one wire to the Sync Pin and other to the Y pin on the SCART plug? The cable is already wired for C-Sync.

[UPDATE]

So I opened up the SCART plug's housing and saw there was a resistor(?) connected to Pin 16. I de-soldered it and put the cable back together. The converter defaulted to Composite video mode instead of S-Video and the GameCube and the N64 worked fine with the cable. For giggles, I plugged it back into the SNES and the game plugged in was Mario no Super Picross (Mario's Super Picross) for the Super Famicom (tabs have been removed for SFC games), something I have only seen in RGB mode and it looked awful, even with my converter. So how do I get it to display in S-Video mode? Is S-Video even wired up or is it just wired for composite and RGB? I tried asking the seller who sold me the cable but eBay wouldn't let me send the message.

EDIT: I just sent an email to the seller asking if it is wired for S-Video and I'll post here when I hear back.

 

S-Video mode was rarely used in SCART. You had to have a SCART socket wired for s-video on your television, which many weren't.... especially older televisions, as it was a bit of an afterthought.

I assume you don't have a SCART TV in America, anyway. If s-video is wired up, just make an adapter with a SCART line socket to an s-video DIN plug. Then you don't need to worry about switching anything.

 

My converter supports it even though the manual doesn't say it. It had a mishap where it was cycling through all of its modes trying to detect what the weak signal was. It showed 3 modes: SCART AV, SCART S AV (I assume that is S-Video mode), and SCART RGB. SCART TVs are extremely rare here in the US. If you find one, the port is labelled as an "EIA Multiport - Stereo" and usually its an old CRT RCA Dimensia. I'm not sure if any HDTVs here have a SCART port. I thought about importing a PAL CRT with RGB SCART input and NTSC support for light gun games but I don't know where to look and can't seem to find one. A PVM might be a better option for that.

As for the adapter, I thought about making one but I can't find the parts, mainly the SCART plug. I've seen adapters like that for sale online. What I was hoping I could do was take a SCART coupler, open it up, add a SPST switch to Pin 16, and mount it somewhere on the coupler so I can plug in the SNES SCART cable and swap between RGB for the SNES and S-Video for the N64 and GameCube. The ultimate goal is to get S-Video over SCART as my TV lacks an S-Video input. I just wish I could get an S-Video cable (that doesn't suck) or an S-Video SCART cable for my N64 and GameCube to hold me over until I get the N64RGB Board and the GCVideo DVI.

 

As retro said, it's an uncommon thing to find in a SCART socket - if you have something that does support it then the most common wiring is that Y goes to pin 20 (I.E. the pin that normally carries composite video) and the C goes to pin 15 (which is normally the red input). Note that you don't need an extra sync line - Y/C conventionally carries the sync with the Y component.

It does mean that you will need to switch over both the switch line and the red signal if you want to make the cable selectable between RGB and Y/C

 

So how can I open up the SNES end of the cable to get to the pins on the SNES side while still being able to put it back together? I'm thinking that since the converter swapped to composite mode after desoldering the resistor, either the cable isn't wired for S-Video or it didn't output S-Video because of the capacitor on the Red wire. Should I remove it and see what happens?