G3 dual only runs off battery

Nor will it charge a battery. Nor will it boot when the ac adapter is plugged in (regardless of whether there is a battery present).

If the computer is running off the battery, plugging in the ac adapter will cause the computer to instantly snap off.

I've swapped out the dc in board and cable but it did not change the situation.

At this point I'm taking any and all help, including wild a** guesses.

Thanks!