Those sticks are a real surprise the first time you open them huh? That spring jumps and it's like a puzzle putting it all back together.
The replacement sticks that are all over eBay aren't that great. The OEM N64 sticks use 2 optical sensors for x/y motion - those little black brackets you saw have slotted wheels at their ends. Moving the stick passes the wheel through the sensor and you have a rotary encoder. Very accurate.
The eBay sticks are modern analog sticks. They use 2 potentiometers for x/y motion, which are easier to implement than the N64's rotary system. The resistance changes linearly with stick movement.
The problem is that the N64 expects to see rotary motion encoded in quadrature from the stick - angular velocity and acceleration. The modern sticks do linear motion. So those replacement sticks have an encoder chip in them to convert from linear to angular data, and for whatever reason (poor coding in chip/slow chip/crappy pots), they don't do fast motion or precise movements well (i.e., edge cases of acceleration). Smash Bros with them is hard to pull off smash attacks and James Bond has the occasional bout of Parkinson's when you use those sticks.
Ironically, the N64 sticks are actually more reliable as designed. The optical sensors won't wear out mechanically the same way the wiper pots do in modern sticks. As we learned as kids, though, the damn plastic Nintendo used in the actual stick was the problem. The white dust you see in the sticks is a symptom, not the cause. You can put tape on the stem of the stick (see Youtube) to eliminate excess free play in the stick. If you have steady hands, you can wrap a small layer of epoxy/JB Weld around the stem instead. Lasts longer than tape. Use silicone grease from an auto parts store and don't use any liquid lubes, they can interfere with the optical sensors.
There. Now you have the totality of my N64 repair knowledge. I await Raban's nuanced critique.
