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DSE ESR meter.

Discussion in 'Hobby Electronics' started by ian field, Feb 6, 2008.

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  1. ian field

    ian field Guest

    Since getting hold of one of these kits and putting it to use, I've been
    getting the impression that modern electrolytics are manufactured with much
    lower ESR than was anticipated when the meter was designed and now I suspect
    that electrolytics with ESR values approaching the values in the table
    printed on the front panel might cause problems in modern fast switching
    PSUs.

    Is there a revised table I can print out and stick over the old one?

    TIA.
     
  2. Bob Parker

    Bob Parker Guest


    The charts on the front of the Mk1 and Mk2 ESR meters were only ever
    meant as a rough guide to what to expect until the user gets familiar
    with using the meters in real-world repairs.
    The Mk1 meter's chart was derived from an old capacitor catalogue,
    and the Mk2 meter's chart was the end result of me measuring a big pile
    of unused electrolytic caps and averaging out the values as best I
    could. The figures were all over the place.
    The Mk2 meter chart in text form is at
    http://members.ozemail.com.au/~bobpar/2003esrchart.txt
    Except in very rare cases, the ESR of an electrolytic cap which is
    causing problems will be found to be >10 times what the charts say, more
    often >30 times or above 99 ohms (the meter's maximum reading).
    There's only one repair situation I know of where ESR is critical -
    in one capacitor in one type of switching power supply which is
    sometimes found in older Sanyo, Teac and a few other TVs. An
    electrolytic cap which is usually about 47uF/25V connects from the base
    of the switching transistor to the collector of a control transistor,
    allowing the control transistor to progressively short out the switching
    transistor's base drive and control the output voltage.
    When that cap develops an ESR of maybe 10 ohms or more, the power
    supply loses regulation and the main B+ rail goes higher and higher,
    taking out a lot of circuitry and sending the EHT very high. It's a
    really stupid fail-UNsafe design.
    I hope this might have clarified things a little bit.

    BTW ... has anyone here bought one of the Altronics ESR meter kits
    yet? If so, I'd like some constructor comments because I've never seen
    one. :(



    Cheers
    Bob
     
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