Vintage cap voltage rating question

[DrGonz78]

So I ordered a 25uf 50v cap as that's what I read on it before pulling it out. Pulled it out and it actually reads 25uf 50/60v. So my guess is that it's a 50v rated working voltage cap with a 60v peak rating. Does that seem correct? Not too worried about really, just curious for educational reasons. The cap was found in an old Fender Taurus solid state amp.

[Chuck H]

That seems like an odd way to indicate voltage rating.?. AC/DC maybe?

[Helmholtz]

So my guess is that it's a 50v rated working voltage cap with a 60v peak rating. Does that seem correct?

That is correct.

[J M Fahey]

Yes.
The higher value is called "surge" voltage, whatever it can stand for a few minutes.

Significative in Tube amps, since until filaments heat up supply voltages peak/surge significantly higher, irrelevant in SS amps, so it was dropped.

[Justin Thomas]

Also helpful for those times you are testing an amp without tubes installed, no?

Justin

[J M Fahey]

Yes, same thing.

But in general mopern caps do not even show it, although I guess it´s still in the datasheets.

Now WHO reads a capacitor datasheet is another problem

[Chuck H]

Now WHO reads a capacitor datasheet is another problem

Well "I" do because I don't just build, I design. So things like surge voltage matter to me. Guys that build often use caps that some reputable source has already determined the suitability of for tube amps in general. The number of amps getting built with over 550V of unloaded voltage is pretty small I think. It comes up here with certain models that are sort of known by this community to have special needs. Otherwise, not so much. But I think you might be heartened by the number of members here that actually DO check out spec sheets when it seems appropriate.

[nosaj]

Well "I" do because I don't just build, I design. So things like surge voltage matter to me. Guys that build often use caps that some reputable source has already determined the suitability of for tube amps in general. The number of amps getting built with over 550V of unloaded voltage is pretty small I think. It comes up here with certain models that are sort of known by this community to have special needs. Otherwise, not so much. But I think you might be heartened by the number of members here that actually DO check out spec sheets when it seems appropriate.

I bet chuck reads datasheets while eating his Rice Crispies
nosaj

[DrGonz78]

Thanks for the responses!! All of the small eletros had spewed their guts out all over the place.

[J M Fahey]

Thanks for the responses!! All of the small eletros had spewed their guts out all over the place.

Can you spell m-e-s-s-y ?

Well "I" do because I don't just build, I design.

I know, I know

I think you might be heartened by the number of members here that actually DO check out spec sheets when it seems appropriate.

Here? sure!!!!

But this is an above average Forum ... and that is an understatement

[Chuck H]

But this is an above average Forum ... and that is an understatement

I do have horse blinders on, I suppose, because I'm not an active member of any other forums. In my head this place represents "the rest" of the demographic in this amp genre that isn't me. I'm familiar enough with the gear forums that I have perused. Specialized forums for Marshall owners or Les Paul owners. I always take those forums to be more "gear head" rather than gear build places. So I don't expect much going in. And I've read enough good tech at places like the Amp Garage and the old AX87 site that I just figured it was all like it is here, though I knew this was the best of them. Still... It's hard to imagine the number of shade tree techs that are still operating low tech on mojo based lore while this forum exists. But I do know it's still happening.

[Chuck H]

Thanks for the responses!! All of the small eletros had spewed their guts out all over the place.

Eewww! I've only had to clean up after that sort of thing twice. Such a smelly mess. And you will never think you got it clean enough Still beats having them go off like little fire crackers or dead shorting and taking out more expensive components I suppose.

[The Dude]

Smell is actually a good troubleshooting tool. If you've done this for long enough, you can distinguish between leaky caps, burnt transformers, carbon resistors, solid state devices, etc.

It's still never a good sign when a bad smell is emanating from an electronic device.

Edit: I forgot selenium rectifier on my list of smells.

[Enzo]

Oh, AMEN.

NOTHING smells like burnt selenium rectifier. And even after 50 years, I would recognize it instantly.

Burnt resistors smell different from burnt plastic transistors. Caps smell different. Transformers have their own smell. Burnt circuit board smells different too. Yes, by experience, you usually know what burnt up by the aroma.

[DrGonz78]

You know what the amp didn't actually smell bad. The amp had that 60's Fender tube amp smell to it, even though it is a solid state amp. I think they could package that scent and a bunch of vintage amp loving techs would buy it off the shelves.