Boots from battery, but not from adapter

Replaced the DC-in board. As soon as I plug in the adapter, the menu bar says "Not charging". It is not an adapter problem - I use the same as the one for my same unit. Logic board?? That would be a shame, since everything else works.

Something did change when I replaced the DC-in: when I press the power button I hear some sort of sound for maybe 2 seconds, as if it were trying to boot, but the sound dies, and pressing the button again does not repeat the sound, until I unplug the adapter, re-plug it, the sound returns on the first press. So it looks like it is getting power from the new DC-in board?

Then I had this thought: Can I do some soldering and make the computer think the adapter is the battery?

Don't know how I can add to my answer to my own post? When I submit without typing anything here, I'm told that this field is required and won't let me submit. When I submit with this field filled in, I'm told that I can't answer my own question??