Capacitor - where can I get this one?

Discussion in 'General Electronics Chat' started by Tbert, Oct 4, 2014.

  1. Tbert

    Thread Starter New Member

    Oct 4, 2014
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    hi folks, I'm a complete newbie here, i've searched the Internet for these answers and my inquiries have led me here. I have a welder Manufactured in 1990, and I discovered this fried capacitor the other day.What is it and where can I get a couple? Thank you so much... image.jpg
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    It is a .05 uFD(microfarad) 500V Ceramic disc capacitor. The tolerance is -20%/+30% and the temperature characteristic is Z5U (pretty sloppy).
    I would start with Digi-Key.
    Any idea why the problem occurred?
     
  3. #12

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    Nov 30, 2010
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    Last edited: Oct 4, 2014
  4. Tbert

    Thread Starter New Member

    Oct 4, 2014
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    If you please, guys... Here is a link to the Owner's Manual to my welder. It contains wiring schematics for it, which are Greek to me...Maybe they help you to make sense of the Capacitor's placement and importance in the circuitry? My machine's Serial# is KA755791

    http://www.millerwelds.com/om/o353b_mil.pdf

    Thank you so much. Already within a few minutes, you have been light-years more helpful than the Miller folks have been in 24hours. Nothing against them, but i'm sure you have a better grasp on these finer points!!
     
  5. Tbert

    Thread Starter New Member

    Oct 4, 2014
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    image.jpg

    Here you can see the capacitor's location a little below right center...it is attached to the bottom of the Polarity-Changing switch
     
  6. #12

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    Last edited: Oct 4, 2014
  7. takao21203

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    maybe a foil cap would work too? For contact arc extinguishing maybe.
     
  8. #12

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    Nov 30, 2010
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    Foil? Like Mylar or poly? Yes. Self healing aspects are good but the price is higher.

    Still running into the, "not in stock" problem.
     
  9. takao21203

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    Apr 28, 2012
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    Depends. I have some here actually, for higher voltages.
     
  10. ISB123

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    May 21, 2014
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  11. #12

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    Nov 30, 2010
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    It's bigger than it looks in the picture, .63 inches in diameter.
     
  12. alfacliff

    Well-Known Member

    Dec 13, 2013
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    c14.
     
  13. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I think it is either C15 or C16???
     
  14. #12

    Expert

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    I don't think whether it is C14 or C25 or C273 is important. It exploded, the label is legible, replace it.
     
    GopherT likes this.
  15. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    So, you are arguing that common sense is the way to go? If all of your friends would be using common sense, you would just follow along and use common sense too?
     
  16. #12

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    Nov 30, 2010
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    Guilty :oops:

    I'm a pragmatist. Sometimes this gets in the way of deep, intellectual conversations about minutia, but it's a burden I have learned to cope with.
     
    Last edited: Oct 4, 2014
  17. takao21203

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    Apr 28, 2012
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    I have disassembled quite a few commerical appliances, and often parts of the PCBs are left out or it is patched. That's how it goes and it DOESNT matter and if you dont meet quota on the assembly line in fareast the manager yells uncomprehensible F-words at you.

    Chances are that is why the part exploded after some time.

    I've heard stories at place of assembly they did not have a schematic or even, a schematic doesnt exist at all. Or a coil goes nowhere, I like that one, and yes there is really such a schematic (but it is just unused tap so maybe doesnt matter).

    I think at an assembly line in fareast you have to grasp quick even without a schematic or you are out in no matter of time...OK these days it's all pick'n'place? To some degree, yes...
     
  18. Tbert

    Thread Starter New Member

    Oct 4, 2014
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    Boy, you guys are good! Thanks a bunch!

    So, if i understand thus far...this capacitor is in this location for spark suppression? That makes sense to me, i never had a clue what purpose these things typically serve. If that is typically their use, that would also make sense...maybe it blew because someone flipped this Selector Switch while welding - a BIG no-no - so it was under load at the time?? I'm just guessing.

    So, i can buy the one located in Post#10? That is a suitable replacement?

    You guys are awesome!!

    Is there anything tricky about replacing them? I can just unbolt it, or maybe even cut the leads a little long from the old one and re-solder the new one in, if necessary??

    (Fyi - I'm not a Smart phone carrier, nor work near a computer ... so I apologize if my responses are sometimes delayed!)

    Thanks!!!
     
  19. takao21203

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    Apr 28, 2012
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    I am not sure if a small ceramic capacitor could take the surges from these contacts.

    Maybe it's just some kind of grounding or to get rid of some unwanted waveforms.
    Or was just built in to see if someone switched the polarity while welding.

    Its pretty hot in there not enough to melt solder but time and electrical stress do their job.

    I wouldnt solder it if possible, and possibly install a 2000v large metal film capacitor, more suited, and less likely to fail again.

    I used electrolytics on large relays (switching upto 200 Amps), and that almost got rid of any arcing. Without it was just horrible they would stick together in no matter of time. 50nF? Not sure if this value could take much charge if you consider these contacts are large.

    But they arent supposed to be switched when the unit is on? So rather there is some parasitary waveform they want to get rid of, or otherwise the line has just no ground reference.

    The schematics are a bit coarse to dig into, to be honest, without able to see it in real life.
     
  20. #12

    Expert

    Nov 30, 2010
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    Yes, the capacitor in post 10 is the right value and twice the voltage rating.
    If a 1000 volt capacitor can't survive in a 500 volt position, we can find 2000 volt capacitors. ;)
    Solder that sucker in there. All you have to lose is 49 cents plus shipping. :D
     
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