NES Slotmaster Is an Open Source Solution to the Original NES' Flawed Cartridge Connector
A custom but open PCB and 3D-printed bracket replace the troubled NES front loader connector with an off-the-shelf 72-pin option.
The Nintendo Entertainment System, or NES, has a distinctive industrial design. Even those who did not grow up with it feel compelled to insert a cartridge, press down to lock it, and then hit power. However, the connector responsible for that nostalgic insertion fails over time, resulting in a blinking red light and flashing screen. (And no, blowing on the cart does not fix this issue!) Merlin Shaw of Geek Island Gaming has designed and open sourced the NES Slotmaster, a drop-in NES front loader replacement connector.
The original NES cartridge connector's contacts become worn over time. Eventually, they lose tension and no longer grip the cartridge's edge fingers. The most common fault is that the console and cartridge's authentication chips fail to communicate, resulting in an endless reset cycle. This reset cycle is why the NES blinks its power light and flashes the television screen.
Over the years, several solutions have come to market. For example, you can buy replacement NES connectors that retain the pop-up design. However, these are likely to wear out eventually, as well. Another example from several years ago was a Kickstarter project called Blinking Light Win (BLW.) [Author note: I backed this project and was happy with the solution!] This kit replaced the entire slot-loading mechanism. However, it is no longer available.
The NES Slotmaster's design is similar to BLW's but does not rely on proprietary parts. You need to fabricate a custom-printed circuit board (PCB) and 3D print a bracket, but both designs are freely available. The 72-pin electrical connector is a modern part that is readily available. An NES Slotmaster swap requires no mechanical or electrical modification on the console!
Shaw mentions an alternative design in the works that uses a flexible printed circuit (FPC) cable. That design trades off solder points but may be less accessible for modders with beginner soldering skills. Again, the existing through-hole solution that is available now does not require soldering inside the NES console.
You can download the PCB Gerbers and STL file from the NES Slotmaster GitHub repository. There is a bill of materials available (which should be under $20) and instructions on assembling the unit.