4.7uf polyster capacitor replacement

Discussion in 'The Projects Forum' started by Bigbizkit, Nov 11, 2015.

  1. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
    1
    Replacement for 4.7uf polyster Capacitor.
    Hi guys, i am working on a bass preamp by ESP. And it requires one 4.7uf polyster cap.
    Now, I am having problem finding a 4.7uf polyster cap, i cant find it in our local electronic store.
    The ESP Site said its possible to replace the 4.7uf with five 1uf polyster. But i only hav 4 of them caps.
    But i was able to get this different capacitor, (i cant tell the cap type but the marking says 3900 100- WIMA 2n 10%)i assume that is 3.9uf.
    (the pix is shown below. The blue cap that is..) so lazy to get good cam.
    So my point is, can i use two caps in parallel? the blue one wich i assume is 3.9uf and the maroon cap with marking 105?
     
  2. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,147
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    No pix uploaded. Knowing aproximately (Country) where you are in the world helps with a source.

    Polypro is probably better: Source for 3.9 uF: http://www.parts-express.com/cat/metalized-polypropylene-crossover-capacitors/294

    Capacitors in parallel (||) add Ct = C1+C2+...Cn
    The issue is 3.9 +-10% || 1 uf 10% = 4.9 uF +-20%
    Intuitively, Ct will be smaller than the largest cap. Also intuitively, 8 uf || 8 uf is 4 uF. Sol two like values half.

    Capacitors in series follow the resistor in parallel rule 1/Ct=1/C1+1/C2...1/Cn
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,834
    Put your 4 x 1uF caps in parallel and you will be fine. Caps are generally +/- 20%. Not a very precise component. The only effect can be that some filtering if base tones will occur. This is unlikely to be noticeable since the filtering is done in a tone control circuit. Also, the equation of filtering is logarithmic, not linear. You will not notice 20% less bass. Much less and not likely noticeable.

    Finally, if a cap is labelled 3900, it is likely 3900 pico farads. Or, 0.0039 uF. Not nearly enough and you will notice significant loss in gain overall, and more in the bass notes.
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,659
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    Fine point: The tolerance is still 10%.
     
  5. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
    1
    Im kinda lost here... Is the 3900 cap =3.9uf or .0039uf like gopher said... Hmmmm..
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,834
    Measure it or take a picture and post it. Or try it in the circuit.
     
  7. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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  8. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
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    Here are the caps,
    The maroon cap marking says 105, and this is the blue cap i was talking bout.... 3900....
    I connected these two caps in parallel.
    And Oh! by the way guys, wud u be so kind enough to tell me what type of capacitor is the blue one?
    Thank you so much...
     
  9. #12

    Expert

    Nov 30, 2010
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  10. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    4.7uF is a common value in MLCC and they're tiny with exceptionally good ESR.

    There are plenty of better (more expensive) foil types than polyester that will be approximately the same size.

    If its stereo - any change of component material should be duplicated on both channels.
     
  11. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    Well, I linked to the datasheet. and it basically says "Metalized Film Polyester"
     
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