I've now reseated all of the ICs and the CPU. It looks like none of the ICs on the daughterboard are socketed, so I didn't remove it.
I also tested the voltages from the power supply and compared to those listed in the "A1000 Assembly Level Repair" document. Voltages were as expected (well, I did read ~12.1v and ~5.2v, but I assume this is within tolerances)
Same behavior. :-(