Success with autoswitching to SCART

[Serpent]

I've tested one of the cables that remained unplugged in the scart connector and I've found out it corresponded to pin 10 on the vga connector. I've soldered this cable to pin 8 on the scart and cut it off from the vga connector. I've joint this cable to another cable. I've also soldered another cable to the vga shield, for the ground. I've taken both cables out through one of the holes for the screws.  I've plugged these two cables to one of the cpu power connectors, the ground to the black (I think it has to be the one which is not by the yellow, but the third one) and the other one to the yellow. Thus, I get 12v that travel through the VGA-SCART cable to the SCART connector. It works as I expected. See picture: http://www.jayma.org/autoswitch.jpg

PD: tomorrow I'll test if this works without the ground, as Andy says.

[Serpent]

Yes, as suggested by Andy, there's no need for ground, so it works with just one cable from the yellow connector.