Master System game not booting? I open an Olympic Gold cartridge with a 4.5mm Gamebit and clean both sides of the contacts with isopropyl alcohol.
Black, tarnished contacts on a Sonic the Hedgehog Master System cartridge cleaned up with Brasso and kitchen towel, with the pros and cons of using it.
A quick how-to: open a Sega Game Gear cartridge with a 3.8mm Gamebit and clean its dirty contacts with isopropyl alcohol.
A five pound set of 3.8mm and 4.5mm game bit screwdrivers for opening Nintendo and Sega cartridges: why handles beat loose bits, and how they held up.