My A button was requiring a harder press for the input to be registered than normal, so I opened up my GBC and noticed this transfer on the PCB. I guess years as a child hard holding A to improve pokemon catch rates had caught up. What's the best way to remove this? Isopropyl alcohol and cotton bud?
The buttons use a carbon based compound to make contact. I think you'll likely need to source a new button replacement. That is likely the carbon layer.
In general, rubbing alcohol is the goto for cleaning on a PCB. I use an old ultrasonic toothbrush or regular old toothbrush if I can't submerge whole boards in an ultrasonic cleaning bath.
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