I have watched your video on this topic, but it seems my problem is different. My Powerbook G4 will try to boot with the charging cabling inside and also when I disconnect the charge cable, it will try to boot. When I say 'try to boot' I mean it will try and make noise for about 5 seconds and then die.
I have tried taking out the ram and putting it in the bottom slot (it was in the upper slot). This did not help.
Do you have any suggestion on what I could try next?