Mystery capacitor?

Discussion in 'General Electronics Chat' started by tam22, Jan 14, 2013.

  1. tam22

    Thread Starter New Member

    Jan 14, 2013
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    Hi all

    Can anyone help identify this capacitor please. It's from a sewing machine if that helps in any way... Hope the photos are clear enough.
     
  2. praondevou

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    Last edited: Jan 14, 2013
  3. tam22

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    Jan 14, 2013
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    Hi Thanks for that - I guess the value burned off the top as the capacitor expired. Is there anyway of working out a suitable replacement from the remaining visible codes?
     
  4. thatoneguy

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    Feb 19, 2009
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    It's a line protection capacitor, required by UL and CE regulations.

    They are typically 0.47uF to 0.68uF X2 Rated (meaning it is designed to go from hot to neutral on your mains) 450V polyester film. I replace a lot of them in sewing machine controllers I work on, if you don't (and there's leakage, it's no longer UL Listed, and guess who is responsible if a fire breaks out?

    Digikey and mouser have them, but the new ones are in a nice grey plastic box rather than wrapped in kapton like the one you are showing. The only hard part will be finding one with the same pin spacing so it is a drop in replacement.
     
  5. tam22

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    Jan 14, 2013
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    Thanks very much; can I just clarify; do you mean a min of 0.47uF to 0.68uF or .047 to .068uf? - I can only find the latter.
     
    Last edited: Jan 14, 2013
  6. thatoneguy

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    Sorry, 0.068uF

    Usually 0.47μF. If in US, i'd suggest 250V or higher.

    If there is another one, replace it as well, as the markings should be readable.
     
  7. tam22

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    Jan 14, 2013
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  8. thatoneguy

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    When it comes to safety items, such as this application, I only use prime parts.

    Kemet has a wide selection, affordable at Digi-Key

    Only use eBay for hobby applications, never for repairing something that will be connected to mains supply. Parts are very hit and miss, in a hobby, not a big deal.

    In an application, lack of fire and maintaining certification is preferable by far to saving a dollar or two on shipping. You don't want to learn the hard way by waking up to a flaming house, or worse, a customers house going up in flames due to a $0.75 eBay part.
     
  9. tam22

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    Jan 14, 2013
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    Thanks for the heads up. A good point well made, however I was really asking if the value would be suitable rather than the item itself.
     
  10. thatoneguy

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    It depends on the value of the other one in the circuit. There's usually a 0.068μF for high frequency EMI reduction from the switched supply, and a 0.47μF for safety and some swtiching noise reduction as well. Wiki Link for a bit of info on why they exist

    There should be one of each on the board, in addition to an inductor/coil of wire somewhere.

    Are you in the US or a different area of Earth?
     
  11. tam22

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    Jan 14, 2013
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    I'm in the UK. It's on the switched supply but there's nothing else there at all - it then just feeds dirctly to the motor.
     
  12. thatoneguy

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    The purpose is to minimize noise spikes from the motor control making it back "out" to the power supply line, causing a non-sinewave voltage on that circuit. You should look for a higher voltage rated one if on 220V, rapidonline should stock them, same style, by Kemet in the grey boxes.

    The wrapped ones are the "old style", and use of the new ones is strongly suggested when changing them out.
     
  13. tam22

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    Jan 14, 2013
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    So just to confirm I'm looking for a 0.068μF and 400V and thanks for you help!
     
    Last edited: Jan 15, 2013
  14. thatoneguy

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    Yes, if there is another 0.47uF on the board that is the wrapped kind, replace it with the newer box style as well. Capacitors are one of the things in electronics that do go bad after a period of time, mostly because technology has improved.

    Better performance and safety on new replacements are the reasons to replace all of the X2 caps on your board you have while it is apart. With other circuits having electrolytics, the older electrolytics just plain stop working and have even worse characteristics to start with in a lot of cases.
     
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