I just use a Gemini cleaning kit to clean the connectors on every system I get, so far I haven't disassembled any consoles just to clean or refurbish the connectors. With the connectors cleaned and the games cleaned, most games I have start up on the first time(not all of them but some games are worn). This goes for multiple NES consoles, they usually work fine. I'm a bit surprised so few people seem to use cleaning kits, people clean the games but don't bother cleaning the console. Besides jumping to boiling connectors or bending pins. I also clean SNES, Genesis, SMS, and Gameboy systems whenever I get them.