Nice ghetto fix there and really cool to see one of these brought back to life!

Also, I think you may eventually get Galvanic corrosion due to dissimilarity of properties between Aluminum and Gold (gold plating.) But indeed for a quick go/no-go test, this was a brilliant fix.
Graphite, drawn on a thin layer like that, will have a pretty high impedance over the length of the entire trace, so even if it did make contact, there's still a chance it may not be able to carry enough signal current between the cartridge and the board for the two to communicate. So that's probably why it didn't work. Otherwise, imagine if you could just draw traces with a pencil - you could create prototype circuits board right on paper!

Cool point-to-point wiring job. The small SMD resistors on the leads of the transistors is a nice touch too.

Interesting. I wonder what would cause that.
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