A component cable is missing the 4th line you will need for sync to get an RGB signal working

Nice, I've recently had a go at making my own VGA to SCART cable with sync circuit. I purchased an eBay Wii SCART cable and my issue is the sound has a buzz or hum that cuts in and out. I think it's grounding does that outer shield have a connection to anything? I've only fired up the Wii home scree...