It's one of the two  AT&T components on the main logic board (107-0134/152-0012) that is maybe faulty, but it's operating normally for now. One of them has an "electric" smell. The caps are all in that corner too.

Does anyone know if the capacitors on a Duo 250 are all on the logic board? I don't see any on the screen's inverter board, but I am getting very dark corners as it runs for a while. Powering it down and waiting seems to resolve it.