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trying to find a part..

Discussion in 'The Workbench' started by datavomit, Aug 25, 2021.

  1. datavomit

    datavomit Active Member

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    so Im on mouser getting some components and for the life of me i cant find the a 47nF Class X capacitor to replace C15 on my JCM900 MKIII PWR Amp PCB.. can anyone help me out with a possible voltage i should be looking for?? TIA
     
  2. Dogs of Doom

    Dogs of Doom >>> Moderator <<< Staff Member

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    like this?

    https://www.tubeampdoctor.com/en/suppression-capacitor-47nf-class-x2-305ac

    just a fyi: it's always best to not be so cryptic in a thread title. We get people who do not cough up very much info on their postings, & then people end up having to beg them to give the proper information about their problem.

    Instead of solving their problem in a handful of posts, it ends up going on for pages & people still don't even know what the issue, or question is.

    This turns people off, when they are trying to help people, in good faith, when it appears that people aren't asking for help, in the same good faith.

    So, in other words, having such a vague title, will probably get you less helpful people to actually help. You might get the lookie loos, who can't really help anyways, but, the ones who can & will help have seen this play out all too often, & have felt that they've been burned, simply for wanting to help...
     
    Last edited: Aug 25, 2021
  3. datavomit

    datavomit Active Member

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    i will have to remember that for next time.. thank you for your 2 cents..
     
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  4. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Presumably this is the line voltage safety capacitor, so 250 volt rated should be adequate.

    Do use the X2 type if that's called out. X2 caps are designed to become open circuits if they fail. Much better than shorting and making the chassis hot.
     
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  5. mickeydg5

    mickeydg5 Well-Known Member

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    The first one dude.
    0.047 uF Film Capacitors – Mouser
    Series catalog (mouser.com)
     
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  6. datavomit

    datavomit Active Member

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  7. pedecamp

    pedecamp Well-Known Member

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    Tough crowd here....:scratch:
     
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  8. MarshallDog

    MarshallDog Well-Known Member

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    :funny::lol::lol::lol:
     
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  9. mickeydg5

    mickeydg5 Well-Known Member

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    He dont know me very well, do he?
     
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  10. mickeydg5

    mickeydg5 Well-Known Member

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    Now I know your cognizance is above average for around here. Well, maybe.

    :thumbs:
     
    Last edited: Aug 26, 2021
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  11. datavomit

    datavomit Active Member

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    I do repair electronics for a living.. well not so much anymore but at the start that’s all I did.. all i do now is for hobby purposes.. I’ve just never messed with class x capacitors and the schematic didn’t say anything for a voltage.. additionally I was ordering parts just based of schematic values and a picture of the board and didn’t have a pic of the side of the safety cap(I was at work fucking off instead of doing work)
     
    Last edited: Aug 26, 2021
  12. mickeydg5

    mickeydg5 Well-Known Member

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    The Marshalls started at 250V but ended up at 630V in that amplifier design/application.
    To be honest, a Class-X is not even required there. :shrug:
     
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  13. datavomit

    datavomit Active Member

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    interesting.. always good to learn new things. Thanks for your help!
     
  14. mickeydg5

    mickeydg5 Well-Known Member

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    Think about it.
    The capacitor is coming off of the HT supply with like 325-345VAC. Capacitors are generally rated for DC and AC applications are much harder on capacitors.
    I would have placed a 630V rating or more there to begin with.
    I think they, Marshall, thought a Class-X would cover any pulse voltages but as I said above this really is not a job for Class-X situation. This capacitor is in line and is absorbing inductor build ups as well and that is not a pulse.
     
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  15. Micky

    Micky Well-Known Member VIP Member

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    Ouch.
     
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  16. Matthews Guitars

    Matthews Guitars Well-Known Member

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    An X class capacitor is designed to be strapped across line voltage and fails OPEN rather than short so as not to make the chassis hot if the capacitor should fail.

    You would properly replace a "Death cap" with an X class capacitor.
     
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  17. mickeydg5

    mickeydg5 Well-Known Member

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    You do understand it is intentional to give that impression, right?

    :noplease:
     
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  18. mickeydg5

    mickeydg5 Well-Known Member

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    Nope it shorts, more precisely it shorts the AC supply.
    There is supposed to be a safety device in the AC supply circuit like fuse or circuit breaker that would then trip removing voltage entirely from the device.
     
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  19. neikeel

    neikeel Well-Known Member

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  20. Matthews Guitars

    Matthews Guitars Well-Known Member

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