IBook G4 doesn't boot

Question

Hi,
I just bought a broken iBook G4 on eBay thinking I would be able to fix it without replacing the logic board. The iBook doesn't boot properly. When I press the power button, I can hear the SuperDrive start up, then the screen with the gray Apple shows up and the OS starts to load normally. But when that screen goes away and the blue background comes up, it just stops there... no "Loading Mac OS X" window with the progress bar. I figured that this may have been a deviation of the iBook G4 logic board problem where people used clamps to pin down the left side of the iBook and hold the faulty chip to the logic board, allowing the iBook to boot. I gave it a shot, but instead of using clamps I tried putting a small rubber shim on top of the faulty chip inside of the case to see if it would work. The first time I booted it up after I placed the shim, it worked fantastically. No hanging at the loading screen, no sluggish performance.
That was the way it worked for a couple of days. However, the booting problem soon returned. I tried booting from a Tiger reinstall disk to verify/repair the disk/permissions, but the iBook hung at the same blue screen. I didn't have the original install discs that came with the iBook, so I couldn't run a hardware test on it. I also tried booting from a Leopard install disk to no avail. Resetting the PRAM, NVRAM, and PMU did nothing as well. I even went so far as to replace the RAM in the expansion slot with RAM that I knew was working, but the iBook remained broken.
The strangest part of this was that the iBook worked perfectly on another computer when put into TDM. I was able to verify/repair both permissions and the disk from my Power Mac G5. Even though the iBook's screen becomes scrambled with random colors and lines after a few minutes in TDM, it functions just fine on another computer. I was even able to successfully boot my Power Mac and iMac from the iBook in TDM. Seeing as this was possible, I tried reinstalling Tiger on the iBook (in TDM) remotely from my Power Mac. It worked like a charm. Following that reinstall, I downloaded and installed all of the software updates. Then I tried to boot the iBook natively again, but to no avail. It still hung at that same blue screen.
At this point, I suspect that there is something wrong with the logic board that I am unable to fix without completely replacing the logic board itself. That's sort of disappointing, but I guess that's just the way it is. If anyone has any input to this, feel free to respond. Here are the iBook's specs:
CPU: 1Ghz (1064Mhz)
RAM: 256MB soldered, 1 expansion slot open
HDD: 30GB 4200 rpm
Screen Size: 12 inches
Optical Drive: Combo Drive
For the complete list of specs, see this page: http://support.apple.com/specs/iBook/iBookG4_Early2004.html
Thanks,
-Trevor

Answer 1

Trevor,
I just took the heatsink off and I see the GPU. However, there are multiple parts to it.
So that would be called a daughter card. The problem with a daughter card is that the possibility of a reballing/reflowing failure is increased.
Should I place a shim over the whole chip or just one part of it?
It's that whole daughter card that has the problem. I've got a post around here somewhere. Here's the thread:
http://discussions.apple.com/thread.jspa?messageID=6051715&#6051715
The picture is here:
http://tinyurl.com/3835w2
Also, what material should I use for a shim here?
Probably the most elegant solution would be to use thermal pads like the ones that are already there. Don't build them up too much.
What about from underneath?
My fear is that a metal shim will short the GPU and damage the logic board permanently. But I also fear that an insulating shim will not conduct heat as it is supposed to and cause the GPU to overheat.
Dale at Superior says that chip doesn't put out much heat but better to be overly cautious. I wouldn't use metal since there's no give to it. What's directly under that 9200 daughter card? One of my thoughts was to shim from both sides.
Where did you put that first shim?
Richard