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Fluorescent Shop Light Ballast Caps
It never ceases to amaze me that these capacitors appear in the AC power line circuits inside old-school fluorescent shop lights:

Shop light ballast cap It really is a capacitor:

Shop light ballast cap A – test Its sibling from the other end of the fixture had more ESR:

Shop light ballast cap B – test Both were likely within spec, whatever that means.
I have no idea what’s lurking inside the tidy LED tubes now living in that same fixture, of course.