Higher value capacitors in P/S

Discussion in 'General Electronics Chat' started by redrooster01, Jul 24, 2015.

  1. redrooster01

    Thread Starter Member

    Jul 15, 2014
    84
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    Would it be safe to use 4700uf instead of 3300uf capacitors in a tapedeck power supply? Ive marked the ones I want to change,C336 has a ''star'' above it that just means it has a part number.I live in a fairly remote area and it takes weeks to order anything through the post but I can get the 4700uf caps here OK. Ive spent about an hour looking for a previously answered question on this subject without success.Any help would be appreciated.
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    If it will fit physically (diameter, height, lead spacing), I don't see any problem. 35 V is a minimum for this application.

    ak
     
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  3. redrooster01

    Thread Starter Member

    Jul 15, 2014
    84
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    Thats good to hear! Im being careful because the tapedeck is a vintage high end Pioneer CT-W910R that Im rebuilding.Thankyou for taking the time to help me with this AnalogKid and the quicker than quick response.lol
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As mentioned in a recent similar thread Electrolytics have typically wide tolerance value of -0% to +100% by many manuf specs.
    Max.
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    Wow, "-0% to +100%", could you link any one to see?
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    What's reason to make you have this thought : use 4700uf instead of 3300uf capacitors?
    And what kinds of load are you always used?
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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  8. PackratKing

    Well-Known Member

    Jul 13, 2008
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    [ I will likely catch hell for this] It seems to me, that when the given capacitor is still in production, it could / should be measured for its actual individual capacity, and then labelled accordingly...
    Yeah... I know... I've heard it all before... That would " Kawst teww Muuuch "
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
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    Your right, that's a terrible idea. Capacitors, like resistors, have "standard" values with tolerances. Values for caps used as power supply filters are not critical and good designs take typical electrolytic tolerances (of -20% to +80%) into consideration.

    The tolerance figure I used is from what I've seen marked on components and/or documented in datasheets. For the questioning types, here are two online references that you can choose to believe (or not): electronics-tutorials.ws and radio-electronics.com
     
    Last edited: Jul 25, 2015
  10. dl324

    Distinguished Member

    Mar 30, 2015
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    Out of curiosity, I searched; P tolerance is -0% to +100%:
    EIA cap tolerance codes.
     
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  11. ScottWang

    Moderator

    Aug 23, 2012
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    What I can accept is quite normal that is from -20%~+20%, too much tolerance will make designs become more difficult.
     
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  12. RichardO

    Well-Known Member

    May 4, 2013
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    The only downside to using a larger capacitor value is that the lower ripple voltage can increase power dissipation in the pass transistor of the voltage regulator. This assumes that the cap is the same or better than the one it is replacing in all other ways.

    edit: I just thought of another potential problem caused by a larger capacitance value. The surge current charging the cap will be larger. This could strain the rectifier diodes.
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It also increases the VA required value of the transformer if used at the maximum current rating.
    Max.
     
  14. ScottWang

    Moderator

    Aug 23, 2012
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    Have you even really use the tolerance equal or over +50%?
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Have you ever measured some of the larger capacitors for value?
    In most applications I have used it is not a problem, it may even be an advantage!
    Max.
     
  16. ScottWang

    Moderator

    Aug 23, 2012
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    When I measured the big capacitors as 2200 uF and 3300 uF or 4700 uF, they are all in +0~20%.
     
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