I have a 12" 1GHz PowerBook that's a couple years old (very light usage). All of a sudden a couple weeks back it wouldn't get more than 10-15 seconds into boot without kernel panicking in various ways. Same story booting off CD or FireWire, without extra RAM or AirportCard. So. Took it to Apple Store, guy says "whoa, needs a new logic board. Apple will fix this for $1300." [computer worth maybe $600 in top shape on eBay].
So I figure I can replace the logic board myself, at the cost of only a new logic board.(~$300, from a reputable local seller). Followed detailed dismantling instructions from ifixit.com. Replaced logic board and reassembled computer. Logic board is the correct type (1GHz G4)-- no funny business with upgrades, I just want my laptop working again. I was anti-static wrist-banded the whole time.
Close it all up, hit the power and... nada. Well, something. It does turn "on" as evidenced by the Caps Lock light toggling after hitting power. Holding down power for 5 seconds turns it "off". I did this later with the top casing off and observed that at the time it turns "on," the fan spins for less than a second, and then stops. No other action happens-- no hard drive spin, no audio, no video. I've checked all the connections, but to no avail. Same story. The fact the the fan and keyboard are getting power implies that the basic assembly went OK.
Is the new logic board worse than the old one, or does the behavior suggest a particular problem? I don't want to throw good money after bad, so if this project doesn't work, I'll have to throw it all away and get a MacBook Pro, but I'd really like not to...
Recently my powerbook started to work so slow that I couldn't do anything on it. Tired of watching the spinning wheel, I did some research on the internet. Everything was pointing to a broken hard drive. So I bought a hard drive, replaced the old one and got the same problem described in the post.
After pressing the power button, I have no video, the sound of the hard drive (or the fan)working, DVD (left in the optical drive) starts to spin and after a while there is a silence. Caps lock lights, I can turn the laptop off by holding power for several seconds. And I noticed that Num lock lights somehow when I press F5.
Brought powerbook to the Apple service center, but all they could say to me that my laptop had a bad logic board, need to be replaced and would cost me around 700$US.
I really like my powerbook, but now I'm thinking about buying a MacBook, instead of fixing an obsolete hardware.
And still I have some hope that this could be repaired.
First off, given the story you describe (that your system worked, albeit slowly, until you personally replaced the hard drive), the first thing you might try is just disconnecting the reed switch from the DC-DC board and seeing if it boots correctly with that disconnected. A reed switch is easy to break, and it controls the sleep/standby behavior, which could cause symptoms like yours if it's busted. The system should boot fine without it under normal circumstances (though not be able to sleep on latch-close of course). Since it sounds like you're already familiar with cracking the case for the hard drive, check out the take-apart guide on ifixit.com and see how to open it up and disconnect the reed switch. It's easy to check and that part is way cheaper than a replacement logic board if that's the problem.
I didn't follow up on this previously, but I actually fixed my own PowerBook by buying a used logic board from eBay (!) for $300 and installing it myself. Our symptoms were a little bit different, but if it really is your logic board at fault, then it's certainly possible to have a go at it. It requires a lot of patience, deep breaths, and static protection, knowing that you could really break something for good if you're not careful, and then you're even further in the hole having bought the logic board. It's your call whether it's worth trying it versus getting the MacBook.
If you go down the route, check out eBay auctions by "falconprince" for the part you need-- I had a very good experience with them (the first logic board they sold me was actually faulty, per my post above, but they replaced it instantly when I called them on the no-DOA warranty).
There are powerbook take-apart guides with convenient printable screw guides available for free download from ifixit.com (which also sells parts like logic boards, although typically for a premium over what you'd pay on ebay since they're a "real business"). The take-apart and reassembly was a little harrowing for me-- I'd never done laptop repair before-- but so far my system is healthy after the operation.