Which Scart cable to get for a US Snes

You're welcome. I know that you can kill an input on a JAP21 device (like an XRGB3) by plugging in a Euro Scart cable so the opposite is probably true as well.

 

Well its not mine and plus I would never do that without research.

Now I have this damn scart cable I need to send back or sell it off.

 

Technically you need the same SCART cable as a PAL SNES (with transistors inside). Basically every unofficial SCART is "wrong", the signal from the multi-out has high output impedance and can't drive a normal TV properly (RGB was provided for reserved use, if it was meant to directly drive a TV they would have included the necessary amplifier in the console).

 

That sounds far fetched. Do you own both an NTSC and PAL console to compare their signal levels?

 

I actually do own both consoles but the signal levels/amplitude (which should be for all intents and purposes identical) has nothing to do with the matter. Every SFC/SNES has high impedance signals at the multi-out, this is evident from the schematics. The transistors between the PPU2 to the multi-out are only to bias (change the DC level of) the signal for the RGB encoder/multi-out; there isn't a final buffer/driver stage to provide a consistent, low output impedance. The official SCART cable's transistors are the final driver stage, giving it an approximate 75 ohm output, allowing it to adequately drive a standard 75 ohm TV.

If you just wire the multi-out to the TV (through ac coupling cap or not), the signal at the TV will be attenuated *and* distorted. This is because the last transistor stage before the multi-out relies on a pull-up to source current--it does not actively source current. This fine to drive a subsequent 10k+ ohm amplifier stage, or maybe even a 1k ohm monitor, but it cannot drive a 75 ohm TV.

 

Uh, OK. Then what's with the popular belief that NTSC and PAL consoles should use different cables?

 

Well they do have different output circuitry (and multiple revisions apparently) so they should have different cables to suit.

My point is that the official SHVC-010-style NTSC cable must be meant to drive old high-impedance Japanese 15 kHz computer monitors, not actual TVs (where the "JP21" input is rare). The official SCART cable is however meant to drive a TV, hence the driver stage.

It looks possible to use an official PAL SCART cable with a NTSC system (on a SCART TV), but I don't have the precise schematics to know 100%. Theoretically the DC offset could be harmful to the TV's termination resistor.

This cable hell exists because manufacturers are cheap (especially 3rd party factories who do very little R&D), there aren't many game collector-RGB enthusiast-electrical engineers that have this stuff to pull apart and examine, and because when a "bad" cable works for a group of people, the burden then retroactively falls on displays to work with bad signals stemming from interconnect problems (instead of blaming the output circuitry or cable design).

If Nintendo wanted people to have the choice of RGB, they would have included an actual amplifier in the console as Sega and SNK did. Today it's probably best to just add a video amp right into the console, or get an XRGB which can tolerate high impedance output signals unlike traditional TVs.

 

Amp in the console sounds interesting. Realistically, I doubt people will mass produce new cables for that. It's considered tolerable enough on too many TVs.

 

Is It possible to make a internal rgb cable and could you solder to the av pins on the board?