NES Controller Repair Tip?

[HyruleHero]

seems latley ive had alot of NES controllers crap out on me lately. Besides the fact they are all about 20-30 years old what may be causing them to crap out. ive opened them, cleaned everthing with some rubbing alcohol , nothing seems to get them to work. i researched online and one site says to clean the contacts with sandpiper. i tried this on one controller, it ssemed to clean them up and brighten them but nothing works. i tried the same controllers on different NES and i confirmed it was the controllers. what gives? just old age or is there something more to this?

[Niku-Sama]

Might be the black dots in the rubber parts not working. When they get glazed over they don't make very good contact. Some times a pencil eraser fixes it but it's probably better to replace them.

http://pages.ebay.com/link/?nav=item.view&id=171548325558&alt=web

[Tanooki]

I'd have to agree with dirty connector pads. I will rub those well with alcohol on a paper towel when something gets picky and I'll find usually a good but of black and gray junk wipes off and it improves.