Mac OS 9 Lives
Mac OS 9 Discussion => Hardware => Topic started by: viksn0w on October 17, 2026, 04:54:23 AM
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Hi, as of the title I've bought an iBook G3 Dual USB 2001 500MHz, when bought I used for a couple of days and sound worked, then it stopped entirely from the speakers and only via the AV Jack. I've ripped it open and occasionally when flexing the board it came back to life, I want a proper fix. I've found a P72/P73 logic board scheme where I could trace the problem and probably is the Q82 transistor that manages the mute function of the amplifier ( U25 LM4863M 16 pins) where it is on PIN 16 HP-IN.
If I short HP-IN and GND, audio from the speakers comes back. When HP-IN is 5v, it tells the amp to switch from speaker to headphone mode. From the schematics I've checked and the PIN 16 is connected to a Q82 - 2N7002 transistor but I cannot point where the Q82 is. I've found the R399 which is also connected to the Q82, but I can't see it.
If someone of you knows where I can find it or can send me a photo of it (it would be preferable), thanks!
Link of the P72/P73 scheme: https://www.informaticanapoli.it/download/SCHEMIELETTRICI/APPLE/Apple-MLB-Block-Diagram-for-P72-051-6130-C.pdf (https://www.informaticanapoli.it/download/SCHEMIELETTRICI/APPLE/Apple-MLB-Block-Diagram-for-P72-051-6130-C.pdf)
Link of the U25 LM4863M 16 pins:
https://www.ti.com/lit/ds/symlink/lm4863.pdf (https://www.ti.com/lit/ds/symlink/lm4863.pdf)
Note:
I know that the P72/P73 is probably for the iBook G3 2002, but I've checked for other components and also the labels are matching, so it is pretty reliable for my 2001 model.
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Updated, found it on the other side along other resistors (near the AV port), everything seems fine I guess, so the problem is either the chipset with a cold solder point or is more downstream but couldn't figure it out yet