The Nintendo NES system is equal parts old school and awesome. Unfortunately, it's easy to wear down your game cartridges after years of cramming them into the game slot. Follow Ben as he builds a device that automatically loads your game cartridges for many years of Super Mario Bros. to come. How to Build a Slot Loading Nintendo Game System: Part 1 of 3. Modding the Circuit Board. Ben takes apart a NES and gets to work modding the circuitry and building a new cartridge connector. Watch the rest of this project in this handy playlist:.