Quote:
Originally Posted by wd40addict
so must be able to tolerate (200*1.4) + 185 = 465vdc. Which is the worst case during a negative AC cycle.
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I replaced the one in my set with a 0.68uF 1kV rated polypropylene type. I think any capacitor that gets mains AC voltages, or close, on it should be 1kV rated, to ensure safety. The reason is that voltage spikes come along at times riding on the mains wave and they are generally sourced from a low impedance, so the effects can be very destructive, if the insulation in the capacitor fails. I also have seen failures in 600V & 630v rated poly caps with mains applied, where you would think they should be just fine and also the common X2 rated caps that are generally not reliable either and I no longer use them. Repeated voltages spikes break down the metalized paper and the capacitance falls with time, that is if they don't smoke first. Probably a DC 800V rated cap would be fine for applied mains AC voltages but its an odd rating and 1kV is more common.
Luckily modern capacitors are smaller than their vintage counterparts so the size often matches.