I did that/ That was actually the first thing I tried, before a PMU and PRAM reset. I hooked it up to my VGA Apple Studio Display 15" LCD. I also tried the parts donor, same thing. They both do get video if I put in the stock processor cards.
This does not make any sense. If it were a bad card, I would not get anything, not even a chime.
I don't even know if this thing is still under support. Fortunately, I still have the box for it.