vintage electrolytic cap voltage

Hello all

I found many electrolytic capaciutors in my vintage amp which degraded and need to be replaced. but many of them labeled strange voltage rating as "1000uf 40/48V"
.

So, what is the meaning of "/" at the voltage rating of the cap?


Thank you
 
I have never seen low voltage ones rated like that.
They used to have a surge rating like that when fitted to tube/valve radios that had directly heated rectifiers where HT came up before the remaining tubes warmed up and put the load on.
 
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Just an FYI: A surge rating is still (technically) a thing even on modern electrolytics - just not prevalent on data sheets. You can find it mentioned in some manufacturer's design notes or other technical documents but the only standard datasheets that tend to give a value for it are ones for the larger screw terminal can capacitors. It is typically 10-20% larger than the rated voltage and is usually the forming voltage used during the manufacture of the capacitors. I would guess that the reason you just don't see it given obviously any more is for liability reasons - too many half-a$$ed designers that don't understand that there are very strict limitations on the frequency and duration of the over voltage events - they see xxV surge and think it can handle that several times a minute - and them blame/sue the manufacturer for "defective parts" when is doesn't.

Hal
 
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