ok, I connected the blanikng and got the picture. thanks
btw, I found this interesting link:
http://mts.speccy.cz/doc/128_rgb.pdf
its used for connecting ZX spectrum+3 to RGB scart, so it has interesting technical details.
i also so a solution for amstradCPC that connects SYNC to BLANKING to switch to RGB; what do you think about that? (unfotunately amstrad connector has neither +5 nor +12V; bit offtopic.. sorry..)
oh, and last question; can I connect R(G)(B) ground to blanking ground? (don't have enough wires..)