Here's a Quick Tutorial to Fix a Stuck Nintendo 64 Reset Button
Remove the six screws on the bottom of the Nintendo 64 console.
Open the console and located the reset button, then squeeze the tabs holding the reset button and push upward so the button pops out.
Clean inside the hole where the reset button is with a cut-tip or a toothbrush dipped in rubbing alcohol. Repeat this step and clean around the reset button itself. Then wipe dry with a standard paper towel.
Place the reset button back in its home, and push up and down, making sure the button is no longer stuck or jammed. Now place the top of the lid on top of the console, again making sure the reset button functions, as it should.
Just before you re-assemble the console, clean out the cartridge slot with some 220 grit sand-paper. Place the sandpaper inside the cartridge slot and rub gently back and forth.
Re-assemble the console and get back to gaming.
How to Video:
Here is a How to fix a Stuck Nintendo 64 Button on YouTube we Created for this Article
Why is the cleaning of the cartridge port necessary? Or are you saying just do it since you have it opened?
I just did it, since I have the console open, I use a little fine grit sandpaper to clean it. Or you dip an old toothbrush in some rubbing alcohol and rub that back and forth on the pins.
It's absolutely horrible advice to clean out the cartridge slot with sand paper. It's one of the worst things you can do to a console long term because it will wear out the pins. It's pretty insane that the author recommends using sand paper when rubbing alcohol will do the job of cleaning the cartridge slot without doing any damage to the console, a material that he already has as a part of this tutorial.
Blah Blah Blah - Everyone is an Expert Nowadays! Cleaning the cartridge slot with sand paper ONCE, is not going to harm or do any damage at all!