I had a similar problem. After cleaning off all the residue from both sides of the motherboard, the X502C booted to the BIOS window, but would go no further. I then discovered that the disk was not running. I checked the disk with a microscope and found that a track had dissolved leading to the motor drive chip. I carefully soldered a wire to bridge the gap and rechecked with the microscope. The disk now ran, so I reassembled the laptop and all was working again.