I used to blow the dust out of the cartridges but I heard that can actually damage the cartridge or the system itself.
I am looking for the proper way to clean old Nintendo game cartridges (such as NES and SNES).
Is cleaning the edge contacts sufficient or is it necessary to open the cartridge and do anything inside?
Cotton swabs and isopropyl (rubbing) alcohol should do the trick. Try to keep the alcohol from the plastics; use it sparingly.
There is also fancy contact cleaner used in the electronics industry that works quite nice and is very stable. For example, "CRC QD Contact Cleaner". Make sure you don't get the type used for lubricating potentiometers. We want the quick drying, stable variety that doesn't leave a residue. This stuff is made for cleaning sensitive electronics and metal connectors. When in doubt, read the datasheet for the product. It'll say things like:
Ideal for telephones, PCs, relays, edge connectors, tape heads, buss bars, circuits, contacts, printed circuit boards, switches and circuit breakers
(Emphasis mine)
This solution is also good for cleaning out really crufty carts, where the circuit board may be dirty enough to cause an electrical problem. In this case, you can either disassemble the cartridge and clean it gently with rubbing alcohol, or (if the cart is hard to split without breaking it) you can use the contact cleaner to spray inside the cart, letting the liquid run and "boil" (it has a very low boiling point, which is why it works as it does) clear out the cracks in the cart.
Bonus: Good for cleaning keyboards, too. Especially older chiclet style keyboards.
It should be ok for paper labels, etc. to be wetted with contact cleaner, but try not to soak it.
However, unless you really have to, you probably don't need to clean out the inside of the carts. Maybe if they have been moldering in basement for years and you want to get rid of unsightly splotches or visible dirt. Electrically, everything inside the cart has a good connection (or did at the factory) and cleaning will not help improve that. But, as I say earlier, if cruft is causing what might be an electrical short, causing dodgy behaviour, cleaning the circuit board carefully with the right stuff is fine.
The outsides of the cartridges should be treated the same way they told you in the original packaging material: at most use a damp cloth with regular water (and maybe a little vinegar if you want to freshen them up) and allow to dry.
Don't use a rubber eraser. This eventually removes the gold or copper cladding on the contact fingers. In a shop I worked at, you'd be read the riot act if you rubbed contacts with anything. And I'll have to disagree with anyone who suggests that paste metal cleaners from the store are useful for anything but the grungiest, filthiest carts, and even then I wouldn't recommend it. These compounds often have gritty lapping material in them, which is all sorts of bad.
I've also seen people recommend sandpaper for stubborn oxide. This would be a mistake, and should not even be considered a last resort. Under few circumstances would oxide be so crufty that it needs grit to remove (and grit causes scratches, which encourages and promotes further harder to handle oxide). If your carts are this fouled, you are already into Retrounaut Archeology, in which case you are sort of on your own. The rest of us should stick with non-destructive or minimally destructive techniques.
And, yes: moist air from your mouth is not great for metals. I understand that blowing into the cart is part of our learned wisdom for getting these things to work, but it's really selection bias at work.
I used to use a clean rubber eraser to clean golden contacts in general, not only cartridges but that can also leave residues if you don't clean it properly after.
There is a comprehensive article on Arstechnica website that recommends using Q-Tips, Brass polish, high-concentrated alcohol, and lint-free cloths. Based on the instructions and the companion video, it seems very effective. It demands you to open the cartridge though.
See here for detailed instructions: http://arstechnica.com/gaming/2013/08/the-cheap-easy-way-to-make-those-old-game-cartridges-as-good-as-new/
Some game cartridges such as the NES and SNES Zelda included a way to save your game. This was typically done using a lithium button cell to power memory chips inside the cartridge.
The battery has a lifespan of about five years, but the battery can also leak which has the potential to spread down the battery leads and into the circuit board, eating away at the metal and destroying them.
So for these kinds of cartridges you need to be opening them up and replacing the battery, or you won't be able to save the games. It will look like everything is working and saving correctly, right up to the moment the system powers off, and then poof, the data is gone.
The battery is most likely soldered onto the cartridge. To replace these kinds of cells you need to buy replacement batteries that have solder tabs already attached. Do not attempt to solder wires onto normal batteries. The heat of the solder gun directly touching the metal case will most likely damage or destroy the battery.
Do a web search for "button cell with solder tabs" and find the same voltage of cell. These are not expensive. If you can't find the same exact type or the cell in the cartridge is not labeled clearly, do a web search on your system type and the game name, and you will likely find the battery that you need. The 3 volt CR2032 is very common for battery backups.
To remove the dead cell, buy some desoldering wick to pull the solder off the board around the battery terminal with a cheap hobbyist soldering iron.
When the iron is hot, wipe the tip on a wet sponge to quickly clean the crud off of it before using it to heat the circuit board. Try to minimize the amount of time it touches the board, as too much heat can damage nearby components. Be careful, the tip of the iron will give you severe 3rd degree skin burns instantly on contact. Don't let it fall off the table on the floor, or it'll burn a hole in carpet or vinyl flooring before you can even reach down to pick it up.
You may need to use a pliers to flatten the battery tab after removing solder with the wick. After removing the cell, use more desoldering wick until the hole in the board is clean.
When attaching the new cell, make sure the polarity is oriented the same way. A reversed polarity cell could possibly damage the circuitry.
To reattach the new cell, use rosin-core solder. The smaller the diameter of the solder, the easier this process will be. Slightly bending the tips of the new battery terminals will keep the battery from falling off the board while you solder.
If you couldn't find an exact size/type replacement, just remember that the substitute cell should not touch the board anywhere except at the terminal points of the old cell, and the replacement should be near the same height as the original, or it may not fit inside when the cartridge is screwed closed.
