iBook G4 freezes up tight

[Silencio]

Pulling my hair out trying to figure out this problem with a 1.2GHz 14" IBook G4 a friend inherited. After running with any kind of load on the CPU for 8-10 minutes, the machine freezes hard. No KP message, nothing I can really see in the system logs. Just freezes up tight.

Booting off a Apple Hardware Test and running multiple extended tests yields a clean bill of health (and no freezes).

Done an erase install of the OS (booting off the DVD and running the installer seems to not place enough load on the machine to freeze it up). Tried different RAM. Reset PMU and PRAM. My best guess is the thing is simply overheating under load. Next step is to install and run Temperature Monitor and see if it locks up when it reaches a high number. Curious if anyone out there has dealt with anything of this and what procedures are good to try in order to fix it, or what parts to replace to help out (say, reseating the heatsink and replacing the thermal pads inside the machine).

[SteveO]

Might try the routine stuff like onyx or applejack, etc. Sorry don't have much else to offer. Never heard of a problem like this.

[Silencio]

Okay, got it to freeze while running Temperature Monitor. Graphics processor die at 47.5°C, processor bottomside at 47.8°C.

[C(-)ris]

Seems normal. Does the temp rise and then crash at a certain spot? Or does it sit there for a long time?

[volcs0]

Google around - there are known problems with iBook G4 logic boards.

I have a lemon myself - will freeze up randomly after some period of use.

There are some homebrew fixes on the web - look around.

[anonymouse1]

Does it freeze with an external HD?

Have you tried running it with JUST the original HD?

Do the fans work? Have you tried vacuuming it out?

[Silencio]

Anonymouse: yes, it does freeze when booted off an external HD just the same.

I did ponder the question of the fan working, but it's not so easy to hear it over the ambient noise level of my office. May need to try it in a quieter place to see if I can detect it spinning. And yeah, trying to unclog the vents is probably a good idea, too.