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Originally Posted by Al Skierkiewicz
Were the cases damaged? i.e. blown off or burned. Simple electrical failure of some of the FETs without case damage, may indicate a static problem. Were the same FETs involved in all cases with the same motor? That might be an indication of a bad brush assy. or a bad drive part in one direction.
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No case damage at all. All damage was limited to the FETs alone. The underlying substrate was unaffected.
It almost always involved different motors/speed controllers each time it happened (globe, drill, CIM). We never had a problem with a rebuilt Victor, and we didn't replace any of the motors this year. By Nationals all Victor problems had gone away, but we'd replaced/rebuilt a half dozen by then.
Static is a possibility.
Any ideas on tests we can run in the off-season? I'd like to make it into a research project for the students, but I don't want to risk expensive mistakes.