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Would you change this cap ?

Discussion in 'Electronic Repair' started by Bill, Dec 6, 2003.

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  1. Bill

    Bill Guest

    Hi folks- If an electrolytic measures slightly over it's rated value
    with a trusted meter, would you consider this cap bad thus replace it
    ? For example, if a 100uf measures 107uf, does that mean the cap is
    drying out and must be replaced ? Thanks

    Bill
     
  2. Not at all. Most electrolytics have a tolerance of at least 20%.
    This means that 107uf is well within spec for a 100uf cap.

    In any case, the electrolyte drying out would have the opposite
    effect from what you're describing: Capacitance would, in that event,
    decrease.


    --
    Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
    (Known to some as Bruce Lane, KC7GR)
    kyrrin a/t bluefeathertech d-o=t c&o&m
    Motorola Radio Programming & Service Available -
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  3. If you suspect the cap may be bad and you don't have the equipment to test
    it for ESR, DA, and leakage, or if there is any evidence of electrolyte
    leakage, change it. 100uF caps are pretty cheap and easy to find.

    The capacitance is well within tolerance, but there are other
    characteristics that could be off.

    Try http://my.execpc.com/~endlr/index.html for some good info on capacitors.

    Leonard Caillouet
     
  4. Clint Sharp

    Clint Sharp Guest

    Unless the cap is something really special I wouldn't suspect it of
    being faulty for being more than its marked value, the tolerance on
    electrolytics is usually greater than 10% anyway. On the other hand, if
    the cap has been removed and is a standard part, I'd replace it anyway
    if I had one in the parts drawer, purely because the action of heating
    up the leads twice (once out, once in) is not wonderful for the part,
    it's a dirt cheap part at that.
     
  5. Bob Parker

    Bob Parker Guest


    A lot of electrolytics have a tolerance of +50/-20%, as far as I know.
    So +7% is entirely within that range.

    Bob
     
  6. Guest


    Plus, most cheap multimeters or only about %10 tolerance on their
    measurements.
     
  7. RonKZ650

    RonKZ650 Guest

    Use an ESR meter. Even a fantastic quality mutimeter will regularly check caps
    as good when in fact they are bad.
    Ron
     
  8. Jerry G.

    Jerry G. Guest

    Standard electrolytic caps, unless specified as precision, have a tolerance
    of about -10% to about +20% of their nominal cap value. If you are using a
    low cost cap meter, there may also be a 10% error to start with. The ESR
    rating of the cap is also very important. As the cap ages, the ESR will go
    up, and the cap value may decrease. In some cases the cap may start to go
    resistive, or shorted.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    Hi folks- If an electrolytic measures slightly over it's rated value
    with a trusted meter, would you consider this cap bad thus replace it
    ? For example, if a 100uf measures 107uf, does that mean the cap is
    drying out and must be replaced ? Thanks

    Bill
     
  9. Asimov

    Asimov Guest

    "Jerry G." bravely wrote to "All" (07 Dec 03 01:19:04)
    --- on the heady topic of "Re: Would you change this cap ?"

    +20%?!?! You mean more like +100%!!! -10/+20% is more like a precision
    electro... ;-)

    JG> From: "Jerry G." <>

    JG> Standard electrolytic caps, unless specified as precision, have a
    JG> tolerance of about -10% to about +20% of their nominal cap value. If
    JG> you are using a low cost cap meter, there may also be a 10% error to
    JG> start with. The ESR rating of the cap is also very important. As the
    JG> cap ages, the ESR will go up, and the cap value may decrease. In some
    JG> cases the cap may start to go resistive, or shorted.

    JG> --

    JG> Greetings,

    JG> Jerry Greenberg GLG Technologies GLG
    JG> =========================================
    JG> WebPage http://www.zoom-one.com
    JG> Electronics http://www.zoom-one.com/electron.htm
    JG> =========================================


    JG> JG> Hi folks- If an electrolytic measures slightly over it's rated value
    JG> with a trusted meter, would you consider this cap bad thus replace it
    JG> ? For example, if a 100uf measures 107uf, does that mean the cap is
    JG> drying out and must be replaced ? Thanks

    JG> Bill

    .... Is reactance then illusory? No, it just appears that way...
     
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