It’s very easy to take apart the original toaster style Nintendo NES. You only need a standard Phillips screw driver and optionally a dental pick tool.
- Flip the NES on it’s top and remove the 6 screws from the bottom of the NES
- Remove the top of the NES and set the NES on it’s bottom like normal
- Remove the 6 screws holding on the metal shielding
Nintendo NES top cover removed exposing metal cover - Remove the cartridge caddy by removing the 6 screws that hold it in place. Take note that the 2 silver screws are longer and remember to put them back in the same spot.
Nintendo NES with top cover removed 
Nintendo NES view of game cartridge caddy 
NES Repair remove game cartridge caddy step: a 
Nintendo NES remove game cartridge caddy step: b 
Nintendo NES View of Motherboard and 72 pin connector. Game cartridge caddy removed. - Remove the last 2 screws that are located near where the power supply and component cables plug in.
- Now you can remove the motherboard from the NES.
Nintendo NES Motherboard with 72 pin connector removed 
Nintendo NES Motherboard Removed
