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  • Vintage cap voltage rating question

    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.
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    Last edited by DrGonz78; 09-10-2019, 11:46 AM.
    When the going gets weird... The weird turn pro!

  • #2
    That seems like an odd way to indicate voltage rating.?. AC/DC maybe?
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #3
      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.
      - Own Opinions Only -

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      • #4
        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.
        Juan Manuel Fahey

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        • #5
          Also helpful for those times you are testing an amp without tubes installed, no?

          Justin
          "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
          "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
          "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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          • #6
            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
            Juan Manuel Fahey

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            • #7
              Originally posted by J M Fahey View Post
              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.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "If you're not interested in opinions and the experience of others, why even start a thread?
              You can't just expect consent." Helmholtz

              Comment


              • #8
                Originally posted by Chuck H View Post
                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
                soldering stuff that's broken, breaking stuff that works, Yeah!

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                • #9
                  Thanks for the responses!! All of the small eletros had spewed their guts out all over the place.
                  When the going gets weird... The weird turn pro!

                  Comment


                  • #10
                    Originally posted by DrGonz78 View Post
                    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
                    Juan Manuel Fahey

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                    • #11
                      Originally posted by J M Fahey View Post
                      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.
                      "Take two placebos, works twice as well." Enzo

                      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                      "If you're not interested in opinions and the experience of others, why even start a thread?
                      You can't just expect consent." Helmholtz

                      Comment


                      • #12
                        Originally posted by DrGonz78 View Post
                        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.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment


                        • #13
                          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.
                          "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                          • #14
                            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.
                            Education is what you're left with after you have forgotten what you have learned.

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                            • #15
                              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.
                              When the going gets weird... The weird turn pro!

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