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Electrolytic Capacitors

Discussion in 'General Electronics Discussion' started by Sanjaya, Dec 13, 2011.

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  1. Sanjaya

    Sanjaya

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    Dec 13, 2011
    I have an LG CRT monitor. There are 10uf 50v Several electrolytic capacitors in it. There is also a one very big 10uf 50v electrolytic capacitor near the flyback transformer. I want to replace that big capacitor as it is bad. But there are no such big capacitors in the market. They have only small capacitors with that capacitance value. So how should I replace it? Please help me.
     
  2. alfa88

    alfa88

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    Dec 1, 2010
    If it's the same spec.s who cares if it's smaller. I've seen a dramatic decrease in the size of electrolytics over the years. What you might want to do is select caps with a higher Voltage rating and a greater temperature range especially since you're using them in a high temperature environment.
     
  3. Sanjaya

    Sanjaya

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    Dec 13, 2011
    Thank you for your reply. I wonder why the same circuit contains one huge capacitor and several small ones for the same specifications. Is there any watt value related to capacitors? Is it ok to replace the bigger one with a smaller one available in the market?
     
  4. duke37

    duke37

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    769
    Jan 9, 2011
    Perhaps there is a high ripple current at this point and you need a capacitor with a low series resistance.
     
  5. Sanjaya

    Sanjaya

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    Dec 13, 2011
    Thank you for your reply. How to ask it from the sales person?
     
  6. davenn

    davenn Moderator

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    1,892
    Sep 5, 2009
    just ask for a 10uF (uF = micro Farad) 50V electrolytic capacitor. You will be able to get either 85deg C or 105deg C. the cap should also have that marked on it if not 105dec C is preferable, it will last longer.

    a 10uF 50V capacitor is pretty small... 5mm diameter and ~ 10mm long

    just make sure its a 50V and not a 450V cap... it's in the Hi Voltage section

    Dave
     
  7. jackorocko

    jackorocko

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    Apr 4, 2010
    if duke is right then you need a cap with good ripple rejection, I think that is what you want to ask the sales rep. I may be completely wrong though...
     
  8. duke37

    duke37

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    769
    Jan 9, 2011
    Since the capacitor is near the flyback transformer, perhaps it has to deal with high current pulses. Try to get the specification of the old capacitor and then find a better one if possible.

    Voltage
    Capacity
    Temperature
    Ripple current
    ESR
     
  9. TedA

    TedA

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    16
    Sep 26, 2011
    Sanjaya,

    I believe that many CRT monitor / TV sweep circuits use an electrolytic capacitor that is worked very hard. The factory part often fails, even though it is a special type. If the capacitor you must replace is larger than others with similar capacitance and voltage ratings, then odds are, it is one of those. A regular electrolytic may fail very quickly if you use it as a replacement.

    The larger cap really can dissipate more power ( watts ), but the ratings you will see are for ripple current and ESR.

    What information do you have about the original? Was there anything printed on it that could lead to identification of the manufacturer, and series or type?

    If you cannot find a special duty sweep circuit rated replacement, you might try using a part with high ripple current, low ESR, and high temperature ratings. Such parts are used mostly in switch-mode power supplies.

    Also, going to a higher voltage rating gains a larger case size and better heat dissipation.

    In the US, most major industrial electronics distributors carry such parts.

    If you cannot find such an electrolytic, you might use a film dielectric capacitor, if there is room for it. Metalized polypropylene might be good.

    Ted
     
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