Originally Posted by sparkyuiop

Hello all I have been having the same problem and I think I found the answer. I have a customers G4 ibook to repair and the fan runs at full speed and there is no chime or display.
I took the thing apart and inspected it but it looked fine. I tried removing the ram and trying all the reset combo's but nothing. I don't actually think the computer was in a position to accept commands.
I was about to give up when I plugged the keyboard in for one last shot while it was in bits and it booted. I then assumed it was either an intermittant fault or a dry joint.
I then reassembled it, booting it after I added each part and it worked untill I replaced the bottom armour protection foil.
I didn't take it apart again but when it was all together I tried putting pressure on it in different places to see what happended and hey presto!
I found that if you hold it in your left hand with your thumb next to the trackpad and your four fingers exerting pressure on the base of the laptop by means of its own weight while tilting it backwards it works every time. If you release the pressure it will die instantly.
So I assume this is indeed a dry joint, however I am yet to find it as the logic / motherboard has very tiny components on it and if it is one of those, a soldering iron would probably kill it for good.
This does seem to be quite a common fault on the G4 ibook and if I were to hazzard a guess on what causes it I'd say it was the casing. It is very flimsy plastic and if you were to continually pick it up by the way I got it to work, it could possibly cause the problem.
Anyway if anyone else try's this and it works for them please let me know. If I find the dry joint I will post a new comment to say where it is. Take care all.