You need a normal Philips screwdriver, some patience, a small screwdriver, some patience and last, but not least a new 72 Pin Connector.
This is my NES, “artistic angle style”.
Turn the NES upside down, you’ll have to unscrew the top.
Next you’ll have to unscrew the uppermost metal plate and remove it, you’ll see which screws I mean. If unsure, watch the Youtube video.
Next remove the screws holding the cartridge slot, make sure to remember where the longer screws are supposed to be and gently jerk it out from the Pin Connector (the place where the cartridge connects).
You’ll be left with the motherboard in front of you. Now you’ll have to turn the board upside down to access the other side of it. To do that you’ll have to unscrew…
…the screws around the upper right corner. Screw them. Off.
And now you can turn the board around where you have yet another metal plate, but to lift off this plate you’ll have to…
…firmly pull out the controller and power ports and make sure to mark which one that’s the cable for Controller 1 and which one is for Controller 2.
And now you can simply lift it off with very little effort to see this marvellous image: the true innards of the system. I know, I’m such a geek. Can you spot the Lockout Chip?
It’s this one, at the lower right of the board. It’s labelled 3195A.
Now gently pull out the 4th pin from the left, like I’ve done in this picture. I used a small screwdriver but honestly it was easier to use a Wine Bottle opener as when I fixed my brother’s NES. I kind of twisted it around and twisted the pin cleanly off. Anyhow, now you can connect back the power cords and stuff and test if you’re getting a blinking red light. If not, you’ve succeeded.
... and a last optional, but strongly recommended part of this tutorial. Remember when Nintendo said that blowing the cartridges didn’t work? Well, they were right. While it might initially remove dust from the connectors it will oxidize them at the same time, making them less able to connect properly for a good reading of the cartridge. Just pull it out…
…and you’re seeing this picture. Now just insert your brand new 3rd party connector…
… and you’re done. You’ve region unlocked your NES and added a new pin connector.
And here’s the Youtube Tutorial: