It looks to me like the previous owner must have been Driving the Portrait from the MoBo video. The card you've got looks to be the Rev.1 High Resolution Display Video Card. Even my Rev. 2 ©1988/89 Card is incompatible with the Portrait Display:

http://home.earthlink.net/~gamba2/vid-mon-matrix.html

Give the VidCard a try with a supported Monitor from that list. A good MultiSync CRT or a REALLY good MultiSync LCD with a VGA adapter will do as well. I cannot stress enough how important it is to have at least one high quality MultiSync CRT in a 68k or Rainbow PPC toolkit. That's a much better setup for your situation.

I've picked up at least a half dozen Mac II era VidCards from lots I've snagged over the years. All have tested good at some point over the last couple of years. Yours may need caps to function at all or not, but it will need a recap at some point. I've got to start doing those, I've been procrastinating. :

.