We delve a little deeper into the NES and have a look at that rather unusual cartridge connector. It’s certainly an interesting arrangement compared with the cartridge slots found in most other consoles! After removing the loading mechanism, I can finally get at the contacts properly and give everything a good clean.

Dirty connections are one possible reason for the familiar flashing red light or blank screen when trying to play a game. It’s happened to me before, so I thought I’d start by cleaning the contacts on both the motherboard and the cartridge connector. While the machine is apart, I also want to have a look at the electrolytic capacitors.

This particular Mattel NES has a CPU-11 mainboard, with quite a few ceramic capacitors and only four electrolytics that I could identify. Three of the smaller ones were marked 100 uF at 6.3 V, 2.2 uF at 50 V and 1 uF at 50 V. There’s also a much larger capacitor in the power and RF section.

I’ve been looking through my spare capacitors for possible replacements. I found a 100 uF 16 V Panasonic, a 1 uF 50 V and a 3.3 uF 50 V that I was considering for the 2.2 uF position. The voltage rating can be higher than the original, although changing the capacitance is something to check against the circuit before fitting anything.

For the cleaning, I’m using an ordinary eraser, some isopropyl alcohol and a plastic card with cleaning material wrapped around it. The alcohol I’ve got here is 99.8%, which evaporates quickly and is handy for this sort of work.

I started with the exposed contacts on the motherboard. They didn’t look particularly filthy at first, but the amount of grime coming off with the eraser was quite impressive! I kept the board supported on a flat surface to avoid flexing it, then used a little isopropyl alcohol to remove the remaining residue.

The cartridge connector needs a slightly different approach. I wrapped some cleaning material around the edge of a card, dampened it with isopropyl alcohol and carefully slid it in and out of the connector. After a few passes, dirt started appearing on the cleaning material, particularly on the side where the game cartridges make contact.

It’s worth repeating the process until the material stops collecting grime. Remember to clean your game cartridges too, otherwise you’re only going to put some of that dirt straight back into the connector. With how much trouble these machines can be to open, I’d rather not have to do it again next week.

Replacement cartridge connectors were available for around $10 delivered on eBay at the time, although the example I handled didn’t feel quite as sturdy as Nintendo’s original. Its outer metal casing came away rather more easily than I’d have liked, so cleaning the original connector seems worth attempting before replacing it. If I somehow managed to set the thing on fire, at least a replacement wouldn’t break the bank!

With the contacts cleaned, I’m ready to move on to the capacitors. I’ll get the soldering iron out for the next part, then we can put everything back together and see how the machine behaves.

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