Bart on Twitter: "Did anyone already build an RGB scart cable for the Ultimate 64? I found the following pinout, but it's not clear where to connect the composite sync to on
Video cable schematics
Scart 2 RGB : Pinout cable and connector diagrams-usb, serial rs232,rj45 ethernet, vga, parallel, atx, dvi...
Scart to RCA and S-Video adapter pinout diagram @ pinouts.ru