So this post is specific to Game Boy games, but is applicable to your NES, SNES cartridge as well. Over time, the gold contacts on game cartridges get dirty so a good clean is needed. The old trick we remember as kids in blowing into the cartridge is only a temporary fix, and is usually more harm than good in the long run as the moisture from our breath can cause oxidation (Hence why we then decided to blow on the cartridges through a t-shirt 🙂 ). For a lot of the older loose games that i get, i do a few things to make sure they run the best when i decide to play them.
Tip 1 – Use Melamine Sponges to clean off any permanent marker stain on the cartridge
Kids like to tag their possessions with permanent markers. Unfortunately collectors don’t like that. Easy to fix, just put some water on melamine sponges and rub against the permanent marker to remove. You can pick these up at Daiso or other $2 stores.
 
Before and After
Tip 2 – Clean the connector with an eraser
Sounds strange, but a standard eraser does wonders against the dirt on the connectors. Basically helps to get it back to the sparkling gold colour that it was designed to be.
Another Before and After
Tip 3 – Isopropyl alcohol and Q-Tips to give it the final touch
Finally use a bit of isopropyl alcohol and a clean q-tip and give the connectors a good brush over. Dry off the alcohol with the dry side of the q-tip.
Seeing black smudges on the Q-tip is a good thing!
Let the cartridge dry for a bit before loading it in. And there you go, good as new 🙂
That battery needs serious attention too, looks like it has already started destroying the board. Replace it asap.