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capacitor testing question

Discussion in 'Electronic Basics' started by RichK, Jan 18, 2005.

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  1. RichK

    RichK Guest

    I have a broken small appliance (food processor) where I think the problem
    may be with the motor start capacitors. When I try to use the unit, there
    is a buzz, but the motor doesn't run. There are 2 capacitors labeled "motor
    start". Both are rated for 170 VIC. One is 100 mF; the other is 130 mF.
    All I have for testing is a digital multi-meter. When I test both of the
    capacitors on a high-resistance scale, they seem to pass current for about
    15 seconds. (On the 200k ohm scale, the resistance slowly rises until it
    shows "open".) Does this mean that they are bad? Is there any other thing
    I can test without a capacitor meter?
     
  2. RichK

    RichK Guest

    Sorry. The item "170 VIC" should read "170 VAC". My spell-checker "fixed"
    it thinking that I had spelled Vic's name wrong.
     
  3. Andrew Holme

    Andrew Holme Guest

    No, on the contrary: it's normal. You're charging the capacitor up.
    Current slows and finally stops as the voltage on the capacitor approaches
    that of your multimeter. Try measuring the voltage across the capacitor
    afterwards: you'll see it discharge through the meter.
     
  4. RichK

    RichK Guest

    thanks
     
  5. Jerry G.

    Jerry G. Guest

    To know if the cap is on value, you need a capacitor testing meter, or such
    a scale on your volt meter. To see if the cap is functioning properly under
    working conditions, a capacitor ESR meter is required. The only other
    reliable way to test them, is to change them.

    It is also possible that the motor is defective. I have seen defective
    motors in appliances from time to time.

    --

    Jerry G.
    ======


    I have a broken small appliance (food processor) where I think the problem
    may be with the motor start capacitors. When I try to use the unit, there
    is a buzz, but the motor doesn't run. There are 2 capacitors labeled "motor
    start". Both are rated for 170 VIC. One is 100 mF; the other is 130 mF.
    All I have for testing is a digital multi-meter. When I test both of the
    capacitors on a high-resistance scale, they seem to pass current for about
    15 seconds. (On the 200k ohm scale, the resistance slowly rises until it
    shows "open".) Does this mean that they are bad? Is there any other thing
    I can test without a capacitor meter?
     
  6. Miles Harris

    Miles Harris Guest

    I doubt it. Have a better look; you should replace them (if necessary)
    with the correct values.
     
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