know what's wrong with this machine.
To recap, I got an AIO from a local school. It had stopped working and had been stripped for parts. I put in a hard drive, CD drive, RAM, etc., and couldn't get it to boot. Turned out the analog board had died. Also, the front panel control board had been removed to be repaired. One of the headphone jacks had been removed, the other was resoldered in an attempt to repair students' damage.
So another g-lister sold me the good analog board and video board out of his dead AIO (less than $15, shipped, from Minnesota). I installed them, and the machine booted and ran just fine. With one exception: no sound from the internal speakers, or from the rear I/O card jack. But I did get sound from the single front headphone jack. So thinking the board was bad, I bought the g-lister's front control panel board (less than $7.50, shipped), which had suffered almost the same fate as mine, but which had one original jack that was unsullied. The other had been desoldered and removed. The lister claimed
his AIO had sound from the internal speakers after he removed the bad jack.
Got the board installed, and ... no internal speaker sound, and no sound from the rear I/O card jack, but I could get system sounds as well as CD sound from the front panel headphone jack.
Did a complete teardown of the machine. Ran continuity tests on all cables and wires related to the sound system: everything checked out perfectly. Patched the speakers to a G3 desktop and found they worked perfectly. Swapped out the motherboard, I/O card, and processor for known good ones, did a logic board reset, cuda reset, clean install of OS 8.5, 8.6, 9.0, 9.1 and ... no speaker sound, no sound from rear headphone jack, just sound from the front headphone jack.
The only thing I didn't/couldn't check was the two grey and dark blue wires that go from the control panel board to a multi-wire connector that attaches to the power supply board. The wires have continuity from one end to the other, but I don't know if there's a bad diode or something on the power supply board that defeats internal sound somehow.
I've looked at the G3 AIO developer information at the Apple web site, and it says nothing about the power supply board's role in the sound system. I suspect it's just a power feed to the speakers, though the wires are tiny.
The main ribbon cable that goes from the front panel to the I/O board checked out perfectly for continuity at all 40 female pin slots, so it's not that cable.
The only thing left is the front panel control board, or the abovementioned power supply board connector, which I doubt as there are no other issues with the machine or the power supply. That's why I'm looking for a pristine board, at a reasonable price. Or, if you've got an idea of what's wrong, I'd like to hear it.
Thanks for your interest, Jim Scott
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