Anyone who’s ever owned an original Nintendo NES “front loader” has had to deal with the infamous blinking red light problem.  You pop-in your copy of Contra ready to show off with the 99 lives cheat code, power on your NES, and… (cue sad trumpet music) nothing. Just a gray screen and flashing red power light to mock you. Overtime, you develop all kinds of techniques and methods to get your game to work; you blow in the cartridge, jiggle the game back and forth while in the slot, shake your fist in the air and mumble obscenities, or maybe you’re the kid in the neighborhood with the magic touch that can push the game in just oh so slightly enough and slowly push it down until it clicks. Bam! Sometimes it worked, sometimes it didn’t.

But why Nintendo? why?! Well, the cause is two-fold: dirt and design. 

Let’s dive into the NES internals and take a look at what is actually going on and maybe in the end we can get your old console playing games like new, or at least a bit more reliably.

Blinking Light Causes

The reason for the red blinking power light is quite simple: it’s just the NES’s way of saying it can’t read the signal from the cartridge. So somewhere between the game and code on one the NES chips, a failure is occurring.

Tracking down the cause might not be as simple as the explanation but there are a few prime suspects that we’ll take a look at: The 72-pin Connector, the Game Cartridge themselves, and the Lockout Chip.

72-pin ZIF Connector

The 72-pin connector (this is what your game plugs in to) was as much marketing as it was clever engineering. After the video game market crash of 1982, Nintendo had some trepidation for how American consumers would welcome a new Video Game Console into their homes. You probably noticed (or remember, if you’re old enough), Nintendo never referred to the NES as a game console, it was an Entertainment System. To further separate itself from the game consoles of the previous generation, it used a front-loading cartridge slot which was similar in style to many of the early Video Cassette Records of the time. This is unlike most (if not all?) previous game consoles where a top-loading mechanism used for loading its cartridges. 

Pause for dramatic effect.

In comes the Zero-Insertion Force (ZIF) cartridge socket, a.k.a., the 72-pin connector.

The ZIF design made it so the game cartridge would slide into the connector with ease. Almost effortlessly, with just a slight push you were ready to game-on. Compare that to some of the Atari consoles of the day where it sometimes felt like an arm wrestling match to get it to accept your game. But with this great convenience that ZIF brought us came an unintended consequence. The design itself allowed for a build up of dirt and grime over time. With the more traditional cartridge slot designs, the friction between the cartridge and connector pins was great enough to gently scrape away dirt and dust each time a game was inserted. But with ZIF, the friction as intended, is minimal, leaving the dust and grime to build up over time.

A Note on Blowing in your Game Cartridges

Remember blowing in your Magnavox Odyssey or Atari 2600 games to get them to work? Of course not, you didn’t need to! But with NES games, we did – and for the most part, it seemed to have worked! For at least a little why. Convinced we were simply blowing the dust off the contacts, the more likely reason blowing in your game cartridges worked is that it created a layer of conductive moisture (spit, if you will) which was often enough to create a connection between the game and the connector pins while breaking down some of the fatty gunk that had built up. Over time this technique actually made the problem worsen as introducing moisture would eventually lead to tarnishing of the pins.

Dirty Game Cartridges

Just like the 72-pin connector, the contacts on your game cartridge get just as dirty and in the same way prevent a solid connection between the game and the console. It’s also possible, though probably less likely, that the traces leading from the contact to their destination (or even the contacts themselves) have some sort of damage or wear from use. 

Faulty “Lockout” Chip

Nintendo had a fairly esoteric view of its market. Games were to be licensed or manufactured by Nintendo and by Nintendo alone. But what should they do with all the third-party game developers that were making unauthorized games for their NES? The solution was to design a “lockout” chip that would prevent these unauthorized cartridges (including those from other regions, such as Europe’s PAL) from working on any Nintendo consoles.

Sometimes called the “CIC Chip ” or “10NES Chip”, the lockout chip worked to prevent unlicensed games by looking for a companion chip on the game cartridge itself. If there was a match and the chips could communicate, your game would play. If not, your game would be stuck in an endless reset loop indicated by the flashing red power light. 

This didn’t fully prevent unlicensed games on the NES as manufacturers and developers eventually found all sorts of way to get around it, including reverse engineering and creating a clone of the chip, as was the case with Tengen (an Atari subsidiary) and my personal favorite, cartridges that would strategically send a voltage spike to knock the chip offline, rendering it useless! 

Nintendo “Lockout” Chip

As for our purposes, these lockout chips could, and often did, become faulty and “lockout” your perfectly licensed game on an otherwise working NES.


In the next section, we’re going to strip down the NES and get a good look at the guts. Grab your phillips screwdriver and ready!