Assuming we are talking true S-Video (Super VHS), you should have a small din connection on the back of the tv, sort of looks like a "PS2 Mouse connection"
This connector has one pin for the video information- without any color/chroma information with an associated ground. then there is a pin for Color/chroma information and it's ground.
When you make your connections and have only black and white, the color/chroma connection is bad ( the Akai). When you made the connections with poor image (Mitsubishi)- the video connection is bad.
I do not know the connecting cable or the video card, but it appears that the TV's are likely fine,the cable or the way you are connecting is wrong??
Alot of cards use 2 phono connectors for the out put the cable is such that 2 phono cables merge to 1 din connector, if this is so, you may just need to reverse the connections on the phono connect to the card.
Hope this helps??
Rick Nieman
Nieman Video Displays
Rick@Niemandisplays.com