The reason why the front loading NES blinks on and off is because the lockout chip is causing the system to continually reset itself. The lockout chip can control the reset line and will activate it repeatedly it unless it is in constant communication with an identical chip inside a cartridge. In order for the cartridge's lockout chip to communicate properly with the system's lockout chip, it needs a good connection from the pin connector. Too often, the NES pin connector cannot provide it.
The lockout chip has 4 pins dedicated to it. Even if the lockout chip has a proper connection, the pins that connect to the CPU and PPU bus may not. The NES 72-pin connector has 56 other pins that may also be in use by a cartridge at any particular time. If the connector or the cartridge pins are corroded or dirty, reliable contact between the console and cartridge will not be made, leading to solid color screens on powerup, in-game crashes and glitchy graphics. Again, the NES's pin connector too often does not have solid contact with the corresponding cartridge pins.
So, what is the problem? The problem is the way the cartridge pins are supposed to make contact with the console connector pins. Inserting any type of PCB contacts into a slot is OK so long as the PCB is supported, whether horizontally or vertically. If Nintendo had designed the cartridge slot so that all you needed to do was to simply insert the cartridge into the slot, I seriously doubt the front loader would acquired such a reputation for unreliability. However, Nintendo went one step further and decided it would be a good idea to require the user to have to push the cartridge down until a latch caught the spring-loaded tray for both sides of the contacts to make a connection.
This is the point where unnecessary wear occurs on the console connector. A cartridge connector's pins get pushed back normally when a cartridge is inserted, this is built into the design. But for a NES, the bottom row of cartridge pins get pushed twice, one when you insert the cartridge, a second time when you push the cartridge down. This has the unfortunately effect of putting way more extra strain on the pins then they should have. The consoles pins can be bent to the extent they are unable to make contact with the cartridge pins or in extreme cases knocked completely out of alignment. A crude visual representation of the manner in which the console connector makes contact with the cartridge pins is here :
Nintendo's brilliant design was intended to mimic the function of VHS players of the time. In the mid-80s, when VHS players were gaining their way into households at a fast rate, they typically used tray loading mechanisms similar to compact cassettes, just oriented vertically instead of horizontally. In an old-style VHS player, when you hit the open button, a trap would pop up in the top and you would place your video tape into it and push it down until it closed. As is well-known, Nintendo wanted to distance itself from the previous home video game systems that had given themselves a poor reputation for quality and value. So Nintendo designed its NES into a boxy two-toned gray shape to fit in with VHS players, cassette decks, TVs and home stereo systems of the time. It even came with A/V outputs, something never seen before in a video game system. The NES stood for the Nintendo Entertainment System, the games were officially called "Game Paks", not "Cartridges" and these Game Paks were long and thin and loaded like VHS tapes.
At first, a console would play fine. After a while, however, the blinking light and/or solid color screen would appear. At this point, players would typically blow into their cartridges and consoles. This worked OK in the short term to clear dust and improve conductivity with saliva deposits, but over time the corrosive nature of saliva would do damage to both connectors. Nintendo's cartridges did not have gold plated contacts, which are more resistant to corrosion. Another thing players would do is to insert a second cartridge into the console above the first, pushing down the game even further and perhaps improving the contact.
Nintendo became aware of the problem and offered certain solutions. It released a cleaning kit containing a cartridge with an edge covered in cloth and cleaning wands for cartridges. Nintendo instructed the user to use water and wait for an hour after cleaning for drying off. Howard Phillips of Nintendo of America later explained that it did not instruct users to use isoprophyl alcohol, a superior cleaning agent, because they were worried that kids would set themselves on fire! Nintendo also set up service centers that could replace the pin connector, although there was a fee that could be incurred if the console was out of warranty. Finally, in 1993, Nintendo released a new design of the NES at a budget price, the Top Loader. The top loader's connector was much more reliable, but the console looked radically different from the front loader, did not have A/V inputs and its video output looked washed out and had noticeable jailbars by comparison.
One other unofficial but popular solution was to use a Galoob Game Genie. The Game Genie was a cheat device that fit in between the console and the cartridge. Because it added an extra two inches to cartridge, it could not be pushed down and aesthetically looks unpleasing because the cartridge sticks out of the NES. The Game Genie's PCB is substantially thicker than a NES game cartridge's, allowing it to make contact with both sets of pins inside the console connector without needing to be pushed down. Unfortunately, this made it very, very difficult to use a Game Genie with a Top Loader, and Galoob released a now-rare adapter for top loader owners. Even if you used no codes, the Game Genie is incompatible with games that manipulate the mirroring on the cartridge like Castlevania 3 and Gauntlet and the other usual suspects that fail to work in cheap NES clones.
After the NES was retired, third party companies came in with unlicensed replacement console pin connectors. The NES was built so the console connector was easily replaceable. However, these connectors developed a reputation for having a grip of death on the cartridges, making it very difficult to remove the cartridge from the system. They also had a reputation of wearing out very quickly and becoming worse than the original they were intended to replace. At least with a genuine Nintendo cartridge connector, the cartridges were always easy to insert and remove.
The Blinking Light Win
In December of 2014, a company called ArcadeWorks launched a kickstarter campaign to build a reliable replacement NES connector. They called this product the Blinking Light Win (BLW) and the kickstarter campaign was very successful. They sought to raise $15,000 and actually raised $44,080. Instead of trying to clone Nintendo's part, they designed a connector where the cartridge would simply plug in and play without having to push down. They also designed a replacement plastic tray piece to replace the original spring/latch mechanism. This replacement piece keeps the cartridge in place, its pin connector from shifting and people from breaking the pin connector by preventing them from pushing down. The creators of the BLW intended to make a quality product where they pins would not wear out over time.
In late June of 2014, backers finally began receiving their kits. One of the reasons for the delay is because ArcadeWorks added a lockout chip clone to every BLW connector (kickstarter stretch goal), ensuring that the lockout chip in the console would make a reliable connection with something it could recognize. Also, unlike the official Nintendo chips, this lockout chip clone (NTSC/PAL-A/PAL-B/Asia) is region selectable by power cycling the system. The default setting is NTSC. There is no need to snip pin 4 on a front loader NES with BLW. This makes it useable with consoles from any region, but it won't make games designed for PAL timings like Elite or Aladdin work in an NTSC console.
In the kit comes the cartridge connector, the replacement tray, a pair of stickers and an instruction sheet. The only tool you need to install it is a standard #2 phillips head screwdriver. The screwdriver cannot be too short, otherwise you won't be able to reach the screws in the recessed holes on the bottom half of the NES case. In the past, some people have done intensive mods like removing a Game Genie connector from a Game Genie and soldering it to the edge connector of the NES PCB, but the BLW was designed to make the mod as easy as possible. No wires, no soldering here, no complexity here. All you have to do is to unscrew the case, unscrew and remove the RF shield and original tray loading mechanism, pull off the original connector, push on the BLW connector, align the replacement tray and screw it in, screw back in the RF shield and the top half of the cover. This kit is ingenuous. Note that the replacement tray does not have a metal bar across the top, unlike those seen in the preview pictures like these :
One of the two stickers the kit comes with says "KEEP CALM AND DON'T PUSH DOWN" and the other one has a BLW graphical logo. Not only are they a nice touch and reportedly of high quality, but they also remind people, if placed on the system, that the system has been modded and they should not push down. This is important because considering the millions of NES front loaders made, there is no reason to assume that any particular NES would have one of these installed unless you knew what to look for. The longer KEEP CALM AND DON'T PUSH DOWN fits very nicely on the lip of the front loader in front of the tray mechanism. The font is Nintendo appropriate.
Most of the reviews I have seen online have remarked on the good build quality of the product. However, most have also noted that the cartridges are much more difficult to remove than a true Nintendo connector. While ArcadeWorks indicated in its Kickstarter that's product would not have a death grip. On the installation instructions paper that comes with the kit, the company explained that it made a compromise between the ease of removal and getting a good connection between the connector and the cartridge every time.
It is important to remember that this kit has to work with cartridges have have been around for twenty to thirty years already and have been used and abused. It also has to work with unlicensed cartridges which did not use facilities up to Nintendo's manufacturing standards. One reviewer commented that the grip strength of the BLW is similar to the cartridge connector in the NES top loader. However, the top loader has the advantage of allowing the user a lot more room on the cartridge to grab it when they want to remove it.
While the kickstarter campaign ended in January, the BLW is also available from the ArcadeWorks website for $24.99 : https://www.arcadeworks.net/blw Some kickstarter backers have complained that people have been obtaining these kits from the site earlier than they have received them. This device will be in high demand because it does what it claims to do, is reasonably priced, easy to install and the reviews have been very positive. ArcadeWorks states that current orders will be shipping at the end of July due to high demand. I suspect that used video game stores and ebay resellers are probably buying these in large quantities so they can sell the piles of front loaders they have lying around.
Regarding the lockout chip, this is a useful feature when you are using unlicensed cartridges. While Tengen cloned Nintendo's lockout chip, other companies like Camerica, AVE and Color Dreams used discrete circuitry to defeat the lockout chip by stunning it with negative voltages. Nintendo got wise to these efforts and released its last front loader PCB revision, NES-CPU-11, with extra resistors to nullify these efforts. If you have one of these PCBs, you may find that unlicensed cartridges will not work on it unless you disable the lockout chip or installing a BLW.
So why do I not have one yet? The chief reason why is because my front loader's original pin connector works very well. I mainly use it with an NES PowerPak these days, which I have owned since 2007. I no longer blow into cartridges and use 99% isoprophyl alcohol to clean my cartridges. 99% is available at electronics stores, but 91% can be found in drug stores. Even if you own a BLW, you need to keep your cartridges clean. Keep scrubbing them with alcohol and Q-tips until you no longer see black on the Q-tip. Make sure to use both wet and dry applications of a Q-tip. Alcohol evaporates much more quickly than water, so you can try your cartridges instantly. Cartridge contacts in very poor condition may require electric contact cleaner or pink erasers.
Finally, I note that the front screws holding down the original tray do not rest completely on the case and come loose, preventing good connection with the pin. The solution is to tighten the screws, but not to tighten them too tightly, otherwise the spring latch will not click into place. Of course, things can change and my pin connector may go bad. I won't be doing crazy things like boiling them, which has a surprisingly good success rate. I probably will buy a BLW by the end of the year just in case.