I think that your problem is most likely sync related.
I've never really liked that wiring diagram - pretty as it is.
The problem with that diagram is that sync ground (VGA 10) is not connected to anything. What is your VGA 10 connected to? Can you get connectivity between VGA 10 & your SCART ground? VGA 5 (another ground, H-sync I believe) is similarly not connected to anything. So maybe you should start again?
From the top:
- connect RGB (VGA 1,2,3 to SCART 15, 11, 7)
- connect H+V sync (VGA 13+14 to SCART 20)
- connect Switching signal to SCART 16 (5v from VGA 9 or MOLEX +100ohm gives 2v, or bridge SCART 20 -> 16)
After that:
- cut off any wires from VGA 4, 11, 12, 15. These are monitor ID, worse than useless to us. Don't get them mixed up with your grounds.
- cut off wire from VGA 9 (5v) if it is present and you haven't used it.
- gather whatever is left, they are the grounds (VGA 5, 6, 7, 8, 10). Twist them together and connect them to a suitable SCART ground pin (e.g. I prefer SCART 17, but any should do)
- Connect VGA shield ground to SCART shield ground (SCART 21)
PS, I always refer to these pinouts with my pin numbering format:
SCART pinout:
http://pinouts.ru/Home/Scart_pinout.shtmlVGA pinout:
http://pinouts.ru/Video/VGA15_pinout.shtml