FIXED:I found that the capacitor at CC702 looked a little charred. I replaced it and the screen instantly appears and the brightness works perfect.Thanks for the help.
And after all this, my son trips over the power cord (1 minute into testing the fix) and snaps off the center pin of the DC power jack inside the machine.Luckily it's an easy/cheap fix, but GRRRRRR! It still works with batteries though.