PowerMac G4 (PCI): Microphone port broken?


Anyone who can possibly give me a hint as to where to start backtracking this problem? It's simple, sort of: my PowerMac G4 (PCI, 10.4.2) doesn't recognize any audio input. I've messed a bit in the "Speech" preferences (but been careful enough not to change anything unknown for me), by selecting between 'Sound input' and 'External micrphone'. Same result.

The microphone is brand new, and works great on other computers. However, I've only tried it on a few PC's, and given the fact that I dont know OS X by heart, I'd ask you folks what to do.

Any setting I've missed, anything? Something Mac users takes for granted that a mac user will be doing (and that I haven't done, obviously)?

Anything. I'd love to use Skype like I did in the pre-Switcher days ;-).

If needed, I can upload a screenshot of the 'Speech recognition' part of System Preferences, if that might help.
Your Mac requires an Apple Plaintalk microphone. Good luck finding one of those. Normal mic's that work on PC's will not work on this Mac. Years ago, Apple foolishly used a proprietary connector for it's audio-in called Plaintalk.