I am recapping a vintage power supply and I've done similar before but I'm a hobbyist non-expert. My understanding has always been that using a non-polarized cap is acceptable where an polarized capacitor is specified but that, essentially, that's uncommon because the NP/BP cap will be substantially larger and more expensive anyway.
I'm hoping someone can help me understand why it would be that the 250uF/100V part I'm trying to replace is available very inexpensively (and in a reasonable package size) as a non polar electrolytic apparently intended for speaker crossovers ($3.50 currently) but Mouser has nothing at all in that spec for less than like $12 a piece.
This suggests to me that something else is going on here and I'm wary of using the cheaper "spec-compliant" non polar part because I assume I'm missing something. Are caps in speaker crossovers different or special (or worse or unreliable thus cheaper)?
Thanks for any insight. I have framed this as this specific question but if you think this bears as a jumping off point to link to or gently explain other characteristics of capacitors that I'm apparently unaware of, I'm all ears!
Best Answer
It's actually the polarity that you have to worry about more, non polarized caps can be used wherever polarized caps are used. But, there are other properties (such as max voltage, and ESR) of capacitors that need to be considered and what the application of the capacitor is.
In general if it's a power bypass capacitor, you need a higher voltage rating than the application (or existing capacitor) and a lower ESR (equivalent series resistance).
If the capacitor is for a filter, then if you don't want to calculate how it will alter the filter frequencies, then you will need to match the specs of the cap as close as possible.
I didn't look at the links, but as far as I know all electrolytic caps are polarized. (you can put them back to back, positive to positive, to make them unpolarized)