If your NES is showing a corrupted screen, a gray screen, or blinking blue, you may need a new 72 pin connector. The 72 pin connector is what the game cartridge connects to and over time the pins can become dirty, bent out of shape, or depressed too much to be able to read the game properly.
Ready to replace or repair? Follow these ten steps.
Turn the NES over. Remove the six screws from the case and lift off.
Remove the six/seven screws from the RF shield.
Remove the six screws from the cartridge tray. The two gold screws will be slightly longer and will need to go back in the same location.
Nearly forgot! There are two more to go. Remove the two screws from the bottom left corner that are holding the motherboard down.
Slide the cartridge tray towards the top and lift off.
Pull up gently on the motherboard while tugging off the 72 pin connector.
Place the new 72 pin connector on.
Slide the cartridge tray back on.
!Important! If you look at the cartridge tray from the side, you will see a section of plastic on the bottom. This will need to slide beneath the motherboard. If it is not beneath the motherboard and you replace the screws, the bay will not depress and click, and the cover will take effort to replace the screws.
Guides that tell you not to screw the screws for the cartridge tray in all the way have not replaced the cartridge tray properly.
It can be helpful to depress the cartridge tray before putting it back on to ensure this happens.
Reverse the order the screws were removed in by repeating steps #4 to #1.