Re: No quite wizadry but.../ Percussive Maintenance
When our IBM XT PCs played up, the standard first-line support "fix" was to turn them off (I miss the "Big Red Switch") lift them about 2cm off the desk, make sure they were level and then allow them to drop. It often worked, the theory was that it would reseat the chips and cards.
It worked on IBM ATs too, but often didn't work on "lesser" machines. We speculated that they did not have the necessary gravitas.