PowerMac G4 Has No Display/Video Output

Ok So I searched and didn't find this on the forums.

I just bought another Powermac G4, it's I think 400mhz. I had problems getting it to work at first, turned out it was a bad hard drive, at least that's what I came up with.

But now the thing just died.

It started not responding when the screen saver came on. I had to restart the machine but pressing the restart button to get it to come back on.

And now after doing that a few times the thing just doesn't work. I hear the chime, the lights come on, the fans go, the HD spins, but there's NO display!

I tried replacing the video card with one from one of my other G4s but no luck. The video card the the "bad" machine works in my other G4.

Whats wrong? Logic board?

I'm thinking the logic board but I'm not 100% sure. Let me know if theres anything else I can test/try.

Thank you.