iBook won't run from AC/Charge battery. Not DC board or adaptor.

Bought a used, supposedly "refurbed" iBook recently. Everything checked out upon delivery, computer ran well for several months. Then, with no incidents, drops, or damage, battery stopped charging and the computer will not run from power cord. When plugging it in, adaptor's light ring does not come one, and there is a distinct "click" noise. I have tried other power adaptors, no luck. Also ordered a new DC board and replaced it. Still nothing.

If I wiggle the cord a lot, it will make several clicking and crackling noises, and occasionally the green ring will flash, but not stay. At one point I was able to hold it at the perfect angle to maintain the light, but even then it would not power on without the battery. I've tried resetting the PMU (followed directions on Apple site, but didn't get any confirmation, how would I know it worked?) At this point, I'm afraid it's the logic board, but would be thrilled to hear any other suggestions. Thanks!