OK so I managed to get an Apple 16" Color Monitor from 1993, it did work they guy showed me, however when I hooked it up to my IIsi I get nothing just a black screen.  Does it need a special Monitor type or is something broken on the IIsi?  The computer does post (play little sound) and then the hard disk spins for a while so I think it booted but no video.

Any ideas, thanks