I didn't have the foresight to take pictures of the incident beforehand so I'll have to make do with a verbose description of the problem.
Symptom: the iBook just doesn't seem to handle power very well. "Jiggling" the connector around helps. But if it doesn't get jiggled right - and further jiggling added to the problem - the laptop won't charge fully or .. well, stay on.
It also can't be good for the power electronics to be given bursts of a couple amps of power every few seconds or so if I'm not paying attention.
So, after much anger, and Yet Another CD Not Ejecting Properly From The DVD Drive, I decided to strip the iBook down (again!) to take a look.
It takes quite a bit of disassembly to be able to reach the CD drive to replace it. It doesn't take all that much to get to the power input daughterboard. Then, removal of the daughterboard showed a couple of interesting issues. Firstly, there's some cracked/dry joints rocking hard around the power connector. Secondly, those now dry joints are black with what I'm guessing is a whole lot of DC electrical arc'ing going on.
A little bit of hot soldering iron action later and the damage was reversed. The power feed seems much more stable now. Thank god! I can stave off replacing the G4 iBook for another day.
This leads me to the subject of this post. Yes, the magnetic DC power connector Apple introduced into their laptop range is very nifty but it does make sense. Even just the normal insert/remove cycle of these power connectors could cause joints to crack and this sort of damage to occur. But there's a flipside - I've seen at least one magnetic connector blackened with DC arcing after something unknown to me had occured. So there's still apparently a slight chance of DC arc'ing happening - but my pet cat won't be destroying anything by dashing across the room and taking the laptop with it.