I made something similar at one point to use with European Mega Drive 1 SCART cables, and it worked great for getting RGB out of the Genesis 1. It should work with a few systems, but there'll be exceptions. For instance, the European Sega Saturn SCART cables expect +5V on a different pin on the Saturn, as discussed here: http://nfggames.com/forum2/index.php?topic=4236.0shateredsoul wrote:hmm, so what do you guys think about the pvm to scart converter? Found one on ebay, specifically made to connect european or japanese scarts to a 25 pin sony pvm rgb. Does the converter preserve the RGB signal?
If you use Japanese "SCART" (21 pin) then all should be fine there. But the Japanese and European standards are wired differently, so you wouldn't be able to use a European SCART to PVM adapter with a Japanese cable, you'd need a pass-through to rearrange the pins. However it looks like the seller on eBay with the SCART to PVM adapter also has a Japanese to European SCART adapter, so you probably already knew you were covered there.
There's also things like the SNES where your cable construction should be different based on the region of the console: http://www.gamesx.com/wiki/doku.php?id= ... ndomultiav
Fortunately eBay is full of SNES SCART cables intended to be used with a US system, so you should be good to go there.