On Friday, May 6, 2016 at 8:30:29 PM UTC-4, wrote:

When it has that plastic sheath over it, the bulging top does NOT indicate it is bad.

Ummmm..... Not on my watch! I do keep an ESR meter, and I also keep a cap-tester that can test at actual operating voltages and in AC or DC. ANY physical indications of ANY nature other than friction or impact will get a cap changed. And every electrolytic in an item that affects the perceived problem will get tested with that ESR meter. When in doubt, change it out.

The problem with swelling is that it may not be affecting the cap *today*. And the actual stresses on the cap may be well below its rating. But when (not if) it fails, it will be at the most awkward possible moment and take much with it. Murphy's Law. Caps, even very good ones, are much cheaper than the time it takes to replace them. Just keep that in mind.

Peter Wieck
Melrose Park, PA