Flip the cartridge face-down on your table.

Use a 3.8 mm gamebit screwdriver to undo the 3 screws on the rear of the cartridge, and set them aside.

Gently lift up the half of the cartridge facing up, and set it aside.

Gently lift out the PCB, and clean the pins with isopropyl alcohol and a cotton swab. if the pins still remain dirty, carefully sand the pins with a very fine-grit sandpaper.