My 5 year old ibook would only boot up and stay on on for a couple of minutes, and then automatically turn itself off.
I took it to a commercial computer store with a Mac service dept and they wanted a $55 "bench charge" to determine whether the problem was the power board or the logic board, saying it would be $95 for a new powerboard, and several hundred if it was the logic board.
They recommended I just junk my old "obsolete" ibook, and get a new one, of course...but that is not presently an option for me.
Rather than spend $55 just to find out what was wrong, and then another $95 plus to fix it, if I was lucky, I decided to follow up on a comment I saw in a chat thread about "computer problems" and searched up ifixit online on the public access computer at the local library.
A little study there convinced me it was probably the power board, and I discovered that it would cost me less than $50 for a replacement part and a couple of tools...and the instructions looked simple enough to try doing it myself.
This seemed like a better gamble, heh, so I sprung for the parts and tools from ifixit.
Got the parts and tools from ifixit in just 2-3 days via first class mail, and followed the illustrated tutorial I had printed out at the library for the installation, and was back online in no time at all.
It was a little tricky getting the cover off, to expose the guts and get at the power board, but I managed to do it without breaking anything.
After that, it was nothing to replace the power board and put the whole thing back together...and now it's all good.
Took less than an hour, from start to finish.
Needless to say, I'm very pleased.
The tutorial (and tips and encouragement from the ifixit staff over the phone) were excellent, especially on the trickier aspect of removing the back cover without breaking the little plastic tabs that hold it together.
It turned out to be pretty easy though, especially with that handy little spudger goodie.
I had looked around some on ifixit, but could not find any information on actually testing or diagnosing, for sure, in advance, whether the initial problem was really the power board, or the logic board.
That was the only sketchy part of the operation, really.
I would have felt a little more comfortable about ordering the part, if I had known for sure...but since it would have cost me more to get that diagnosis from the shop than to just go ahead and actually replace the power board, I took a chance, since the problem did seem pretty consistent (if not identical) with other peoples' descriptions on ifixit, of the various symptoms of a bad power board.
Perhaps I could have gotten some tips on this over the phone, but I didn't pursue that, so, oh well...
If there is some means of more precisely diagnosing whether it's really the power board or the logic board that is faulty, for sure, that should probably be more prominently featured, I think.