What is that dust? Not to be nosey but where do you live? Since dust is different all over the world, certain kinds of dust can be corrosive. Others can be conductive. Somewhere I had a chart of dust composition and properties but right no I can't find it. Here in NYC, the dust is heavy in iron/rust, and it can be conductive if enough lands on a circuit. At best wash the board!

A IIvx is old enough to require a recapping.