Have this 820-3209. Corrosion around lp8550, pretty bad. Removed LP8550, cleaned corrosion, noticed all pads looked fine but pin 13 was badly corroded and became shitstain. Used boardview to check where it's connected, no net. It doesn't seem to be connected to anything but has designation tp_bkl_fault. Put on the new bga chip anyway, no display, but bcklt does work. (Previously did not, also no display).