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  1. #1
    Evening Chaps,

    I wondered if anyone could help me with the correct size capacitor for my PSU. The calculations come out to 11,764 uF and the voltage is 68V (allowing an additional 20% as per Gecko guide =88v) I've found a 10,000uF 100v capacitor on eBay, is this close enough or should I use three 4,700uF 100v and wire in parallel?

    Many thanks

    Mike
    Last edited by RocketBoy; 23-06-2016 at 09:36 PM. Reason: cannot add up :-)

  2. #2
    Personally I would use three as you say because they are generally cheaper. Something like this :https://www.rapidonline.com/samwha-h...acitor-11-3121
    ..Clive
    The more you know, The better you know, How little you know

  3. #3
    A piece of advice about capacitors:

    Don't buy a capacitor from non reputable seller, especially ebay.
    Too many reasons to explain here but in short : China, not genuine, quality, NOS etc.


    Buy from Mouser or RS online, i don't know about Rapid online, but i assume as Clive pointed you there it should be good. Buy a brand capacitor- Panasonic,etc. Look for rating 85C or even better 105C rated


    Plus i wouldn't save a dollar from a capacitor. A good normal one 85C is rated 2000-3000h at the temperature rating. A better one exact value, not a stack of cheaper smaller ones, that is meant especially for computer and other power supplies could be rated 105C and 20 000h . So its up to you if you will save a $ or 2 from your power supply. Questions to ask yourself: how many hours per day the machine will work, how many years you expect it to last, do you have time later to stop production and investigate eventual problems.

    If it was me i would buy a single screw terminal can type capacitor, meant to be there, less space, easy to exchange.
    Last edited by Boyan Silyavski; 24-06-2016 at 09:22 AM.
    project 1 , 2, Dust Shoe ...

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  5. #4
    Don't get paranoid with Cap quality or go OTT it's not that critial.
    Go with 3 x 4700Uf. They are cheaper and easier to find and provide less ripple than one large Cap. Even the cheap Ebay ones are ok provided you size them correctly. Give them plenty of overhead on voltage and you won't have problem.
    I've built probably 100 + and just about every one used 3 x 4700 and never had any issues, Zero failure (Unless I cock up polarity.!!) The PSU running my Own machine is nearly 10yrs old and used Cheap Ebay caps, It's still going strong and as runs for 10hrs day most days.

    I buy mine from Farnell.
    Last edited by JAZZCNC; 24-06-2016 at 11:10 PM.

  6. #5
    You can buy cheap Chinese capacitors from China, or you can buy expensive Chinese capacitors from RS or Farnell. It is your choice depending on your perception of quality and service.
    Albert Einstein may have been a genius, but his brother Frank, was a monster

    Sent from my clunky old Windows 7 Machine

  7. #6
    One large cap just means there is just one large component which, when it fails, will render your PSU broken.
    Provided the conductor area of the connecting bus is large and it's length is short there is no reason not to use several smaller caps in parallel, but buy branded quality from a reputable supplier,

    - Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  8. #7
    I am partly retracting my former statement in the light of this article http://www.hardwaresecrets.com/how-t...ic-capacitors/

    Rob
    Albert Einstein may have been a genius, but his brother Frank, was a monster

    Sent from my clunky old Windows 7 Machine

  9. The Following User Says Thank You to cropwell For This Useful Post:


  10. #8
    Rob at our time of life if they last 10 years it's a bonus
    ..Clive
    The more you know, The better you know, How little you know

  11. #9
    Quote Originally Posted by Clive S View Post
    Rob at our time of life if they last 10 years it's a bonus
    Ten more yrs.!!! . . . . Now't like being optimistic.

  12. #10
    Quote Originally Posted by cropwell View Post
    You can buy cheap Chinese capacitors from China, or you can buy expensive Chinese capacitors from RS or Farnell. It is your choice depending on your perception of quality and service.
    Its absolutely not like you present it.
    project 1 , 2, Dust Shoe ...

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