Childhood toys: 40 years on 2-XL works just fine
blog.jgc.org
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If you don't have re-circulation / ventilation fans, it really shouldn't get that messy if the exterior case is moderately tight. My image of "old electronics" is mainly from old mainframes / desktops, and those have copious fans to really suck in all the dust and pet hair.
I had almost worked out myself how it worked by playing those special tape in a normal recorder.