Capacitor questions

DAJE

Well-known member
(1) I bought 20 x 100uF electrolytic caps, and every single one of them reads 86-87uF in my component tester (which is pretty accurate for most things). They're Rubycons, and from a reputable seller so I'm sure they're not rejects, and it says right there in the datasheet ±20% tolerance, and 86 is within that range.

So, reassure me; I can use them for pedals that call for 100uF caps and they'll be OK, right? I don't need to worry about a measly 13-14% below spec?

(2) I also bought some tantalum caps ranging from 1uF to 10uF. No problems there, all is well.

I also noted that there are tanty caps available in lower ratings, from 100nF to 1uF. I've seen that some people use them in their builds in place of film box caps. I hear that this is OK as long as you orient them so that the + is in the direction of the signal flow. Understood.

So, my question: if the direction is not obvious to me, I expect I'd guess right about 50% of the time. Is there some cool trick for figuring out which direction to use or am I just expected to screw everything up and post clueless requests in the Troubleshooting Forum? Because I'd rather just use film caps if that's the case, I can't guess wrong if polarity isn't a thing.

(I know the pic is a 1000uF cap, it's the closest I could find and otherwise identical, except my 100uFs are 50V. )
 

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DAJE . . . . .

1) Yes. Those 100µF electrolytic that measure 86 are fine for 100µF usage.

2) Tantalum caps are polarized, so I'd NOT use them in place of box films, which are NOT polarized. In fact, where very small valued tants (1µF and less) are used in signal paths, I rarely use them and instead apply box films without issue.
 
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