**update**
Well, still not going great over here. Combining or disconnecting the H or V sync didn't do anything (which makes sense to me), and as for uninstalling the video drivers - I've been doing that from the beginning (several times now). I have been able to stabilize the picture, but it still looks like crap and can't be read and the color is very inconsistent. (I think manually degaussing might help with this.)
...But there is still a problem getting the image to extend to the vertical limits of the screen.
Does anyone know what causes this, or what a fix is? Getting this thing going is a real pain in the neck.
PS- anyone out there with a Pentranic - is it normal for the screen to be illegible at 640x480?