G5 screen acting weird

I recently got this iMac from a friend. It's been having these screen issues:http://www.youtube.com/watch?v=Dlc-UDIukP8

I replaced all of the leaky capacitors and any of them that were bulging, but it's still acting funny. I've also applied pressure to the GPU, but that didn't work either. This is the 3rd iMac G5 that I've gone through, and I'm wondering what other people think I should do? I'd like to repair it if at all possible.
Any help would be appreciated,
Thanks.