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Discussion in 'Datasheets, Manuals and Component Identification' started by HellasTechn, Oct 25, 2016.

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  1. Oct 25, 2016 #1
    HellasTechn

    HellasTechn

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    Hello friends !

    I would like to ask about this capacitor. I have seen such in old telephone sets and in switching PSU's. What kind of caps are they and what are they mainly used for (audio applications?) ? Also how can we read it's value ? Is it the same way we read ceramics ?

    Thank you !
     

    Attached Files:

  2. Oct 25, 2016 #2
    HellasTechn

    HellasTechn

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  3. Oct 25, 2016 #3
    davenn

    davenn Moderator

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    the basics of that is answered in the link you gave .... keep reading :)

    Dave
     
  4. Oct 25, 2016 #4
    HellasTechn

    HellasTechn

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    So 1 cap lead to the Mains ac socket (line) and the other lead to say red probe of DMM and then the black of the DMM to neutral of the Mains socket ? and then reverse the cap and read again ?
     
    Last edited by a moderator: Oct 25, 2016
  5. Oct 25, 2016 #5
    HellasTechn

    HellasTechn

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    I have. For theese specific caps they say this
    "These are also very popular for high-frequency circuits,"

    so ? what are they good for ? Serving as HF filters ?
     
  6. Oct 25, 2016 #6
    davenn

    davenn Moderator

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    for those "greencaps" their common nickname for obvious reasons, audio use, definitely wouldn't use them for RF
     
  7. Oct 25, 2016 #7
    davenn

    davenn Moderator

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    NO, NO, NOOOOOOOOOO

    Edd did say gnd socket ................... but still very dangerous advice, I have deleted his post and edit it out of your post
    don't ever go near trying
     
  8. Oct 27, 2016 #8
    HellasTechn

    HellasTechn

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    Please go ahead and delete my post #4 and this one. Better be on the safe side.
     
  9. Oct 27, 2016 #9
    HellasTechn

    HellasTechn

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    See ?
    This is what i am talking about, while this site states they are popular at high freq circuits, you say not for RF.

    While i have very limited gnowledge on electronics it is not easy for me to understand what they are best used for.
    And then i ask is there something like a guide thet someone like me can look and quickly figure out what kind of cap to use in some circuit ?

    For example i know that for smoothing we use electrolytics.
     
  10. Oct 27, 2016 #10
    HellasTechn

    HellasTechn

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    Is "Greencap" their nickname ? i dont know how that relates to audio but please, please don't take me wrong it may very well be my poor skill in english (some idiom i am not aware of).
     
  11. Oct 27, 2016 #11
    Arouse1973

    Arouse1973 Adam

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    It looks like a Mylar film cap to me, might be wrong. If it is then they are classed as general purpose caps normally for DC and can be made to withstand very high voltages. They can have large losses in AC circuits at high temperatures.
    Thanks
    Adam
     
  12. Oct 27, 2016 #12
    davenn

    davenn Moderator

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    I wouldn't use them (and you will never see them in signal paths of HF (high freq and up) circuits) in RF circuits over a MHz or two, they are not stable enough


    yes and also commonly used in audio circuits as interstage coupling of the signal ... between inputs and preamps, then between preamp and power amp stages




    That was sorta answered in that link.....

    capacitors are marked in 5 common ways

    1) the direct uF value 100uF, 1uF, 0.1 uF etc

    2) indirect uF way, by showing a decimal value, .1, .001 etc ( the leading zero is commonly dropped to save space
    if you see a cap with .1 on it, IT WILL be 0.1 uF

    3) the 3 digit code, saves lots of space, 106, 104, 103, 102, 683 etc = 10uF, 0.1uF, 0.01uF, 0.001uF, 0.068uF = (68nF / 68000pF)

    4) any ceramic, mylar, polyprop, polyester cap marked in whole numbers eg 10, 1000, 2200 is a pF value eg 2200 = 2200pF

    5) not really seen any more but really old tubular caps and some very small caps during 70's and '80's used colour banding like resistors

    an example was in another thread over the last couple of days .....

    upload_2016-10-28_8-25-13.png

    you can see the lower one has spewed its guts and let out the "magic smoke"


    Dave
     
    bushtech likes this.
  13. Oct 27, 2016 #13
    davenn

    davenn Moderator

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    a nice chart I just found

    [​IMG]


    Dave
     
    Arouse1973 likes this.
  14. Oct 27, 2016 #14
    davenn

    davenn Moderator

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    you would do well to read the section in the wiki entry, about 1/2 way down the page

    https://en.wikipedia.org/wiki/Capacitor_types

    Comparison of types an extensive table of types, their make up, uses and disadvantages
     
  15. Oct 27, 2016 #15
    davenn

    davenn Moderator

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    no, greencaps are definitely polyester :)
     
  16. Oct 28, 2016 #16
    Arouse1973

    Arouse1973 Adam

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    So are Mylar film and Mylar polyester :)
    Adam
     
  17. Oct 28, 2016 #17
    Arouse1973

    Arouse1973 Adam

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    Further investigation reveals that Mylar is a trade name and is in fact PET a form of polyester, but there are more than one type of polyester :)
    Adam
     
    Crystal-JU-206 likes this.
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