I use my 15Al a lot, and, among other things, the small DC power connector (not the larger three-pronged one) does not fit consistently into the Powerbook. I first thought that the LED was malfunctioning, or that the white power supply block was going, until I heard a tiny fizzing by the side of the computer and realized that there was a spark jumping.
Not good.
I took it to an Apple Store and the Genius said the plug was physically deformed. I took a look; it was. He suggested I buy a new power adapter.
I took the thing home and looked again. The outer shell, which should be cylindrical, was an oval shape about 2 mm longer in one direction than the other. I took a pair of small pliers and repeatedly bent the shell back into a cylinder.
There! A quick fix addressing several threads I've read here.