Internal speakers don't work

Question

My husband uses the dual USB late 2001 iBook more than I do, mainly with Toast and a Griffin iMic to copy our old vinyl records to CDs, and to run VirtualPC for his PC model railroad design app. He does all this in OS 9.2.2.
I used the iBook yesterday, and discovered that the internal speakers aren't working at all. (He hadn't noticed!) No startup chime, no alert beeps, nothing. The sound settings are not set to "mute". I rebooted in OS X (version 10.1, the original, which we've never upgraded), and it didn't make any difference. Still no sound.
If we plug in a set of headphones or external speakers, they will work, playing the startup chime and all other sounds.
It's never been taken apart, so it's unlikely that the speaker cables have been accidentally disconnected.
So far, I've tried the following, none of which helped: trashing the Sound prefs in OS 9 and restarting; resetting the PRAM; starting in OS X and then restarting in Open Firmware, resetting the NVRAM and then resetting the PRAM again. I also tried the hint in This Post - restarting with the headphones connected and then disconnecting them. And I tried plugging the iMic into a USB port, and the headphones into the iMic, and restarting and then disconnecting. No use! The iBook Audio Update was already installed, so that's not it.
We've compared the iBook's OS 9.2.2 Sound control panel with the one on a 7300 also running 9.2.2, and notice one interesting thing. When the iBook is freshly rebooted, the Sound > Speakers tab has the headphone icon present and highlighted, even when the headphones aren't connected. One can plug in the external speakers, and select the speakers icon, and they'll work. But it always defaults back to a highlighted headphone icon upon restart - even when the speakers are plugged in. The 7300's Speakers tab does not show any headphone icon at all, unless the headphones are actually connected. But this is only in OS 9. I don't see a comparable setting in the OS X System Prefs, where I can check on the speaker settings.
It's as if the iBook's sound port thinks the headphones are connected, even when they're not. Could this be a hardware problem with the port, or some kind of logic board problem?
My next step will probably be a reinstall of both OS's.
Dorothy

Answer 1

Ronda and Dave2,
Thanks for responding.
I'm beginning to think it has to be a hardware problem. It happens in both OS's, and when booting from the OS 9 install CD that came with the iBook - no startup chime at all. But the chime is there when either headphones or external speakers are hooked up.
I did restart with Command-Option-O-F, got into Open Firmware, and followed the instructions for resetting the NVRAM.
The OS X Sound preference pane has only two tabs: Alert and Output. Output shows only "Built-in audio controller", no matter what's plugged into the output port. (In OS 9, the Sound control panel has 4 tabs: Alert, Input, Output and Speakers.) So, in X there's no way to know what speakers the iBook thinks it's using.
I haven't tried resetting the PMU; it didn't seem from the KB article on PMU reset that doing that would help this problem. (I'm cautious about fiddling with the PMU.) But, the battery is old, doesn't hold a charge very long, and we need to get a new one. We normally use the power adapter, anyway. So maybe a PMU reset would do something.
I did ask my husband - an experimental physicist - if the speakers could have been damaged by too loud a sound when he was working with Toast, and he said the the sound circuitry should prevent that, unless there were a design flaw.
On further thought, I probably won't bother reinstalling the systems - just wait until I get back to civilization next week and take it to an Apple Store. (The only authorized service center within 100 miles of this house is one CompUSA 50 miles away.)
Dorothy