That board has no corrosion at all (from the picture).

I'd reseat all the ICs that are mounted in sockets. Be VERY careful doing this, and do not touch the 5101 (U8) with anything metal or your hands. It is prone to static. Obviously do this with the machine off. Gently prize each chip from one side and the other. Don't try to remove the chip from one side. Prize a little at a time until it is out then carefully push the ICs back in without bending the legs. See it the game boots after that !