PowerBook 17" problem

Hi,

I have a problem with a PowerBook G4 17" 1.67Ghz A1107. Was working fine apart some graphic problems sometime when opening the screen after sleep, would show all distorded screen with mixed up pixels blinking…
Closing , then re-opening the lid would solve the problem.
It did that the other day, but this time the trick of closing-opening the lid did not worked. Screen stayed black. Even after force reboot, the screen stayed black , even tho I had the chime and distinct noises from the HD and stuff that the machine was booting.
So I though it could be bad contacts on the screen connectors to the board. I elected to swap the screen with a 17" wreck, a HR A1139. Had tried that before and it was working, didn't kept the HR screen cause it had a yellowish tint… Anyway I thought it would work.
But , did the swap , and now the machine won't boot. Only the fans runs, nothing else.
Tried reset PMU, zap PRAM, swapping RAM places… no joy...
Do you think a dead video chip could cause that ?