The 540b circuit was “borrowed” from Don Lancaster’s video cookbook... it works. The 630 board doesn't do colour composite as far as i can see, it only incorporates the invert feature.
My 600d Colour board will not do composite. I wanted something that would provide RGB as the highest quality source, which could be converted in many ways. You can upconvert it to hdmi, or feed it directly to scart, or convert to s-video and composite... whatever you like. I will try to document the different solutions. I could make a little adapter board for composite if there is demand.