Have you tried it on a known-good power adapter? My 12" PowerBook would not charge for a while because the plug (actually the wiring to the plug where it bends before entering the plug housing) had deteriorated. I had to take it apart and do some resoldering.
Looks ugly now but it works perfectly.

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I only have one power supply, but that's on my list of things to check to see if I can get it working again. There's a couple of inexpensive parts I want to try replacing, too, before I do a logic board replacement. I believe the battery itself has some charge cycles left in it because the voltage reading and maximum charge the battery can hold are still in tolerances for a good battery. It won't take a full charge like a new battery, naturally, but still would take about 2/3 of a full charge if the numbers I'm seeing are any indication.