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Cap can with leakage - how much is okay?

Discussion in 'Shock Brother's DIY Amps' started by itsGiusto, Jan 19, 2021.

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  1. Jan 19, 2021 #1
    itsGiusto

    itsGiusto Tele-Holic

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    I bought a 20-20-20-20 cap can last year to replace the old one on my 1972 princeton reverb. I was doing some maintenance on my amp today, and I removed the cap fully from the amp, so I decided to see if it's working correctly. All 4 lugs measure the correct capacitance. However, when I test the resistance from each lug to ground, 3 of the lugs have some leakage. I don't know if it's enough to replace it, however.

    One lug measures infinite resistance to ground. Another one measures ~50M, another measures ~30M, and another measures ~60M.

    What do you all think? Should I replace the cap?
     
  2. Jan 19, 2021 #2
    tubeswell

    tubeswell Friend of Leo's

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    If the High-Tension voltages at all the nodes are okay/ballpark, the cap will be fine. '30M', '50M', '60M' and 'infinite resistance' amount to pretty much the same thing in an e-cap. YMMV
     
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  3. Jan 19, 2021 #3
    galaxiex

    galaxiex Tele-Afflicted

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    To really test for leakage you need to test at high voltage with something like this...

    100_2345.jpg

    Notice this can test at up to 450 Volts.

    If a HV cap is gonna leak, that's where it happens.
     
  4. Jan 20, 2021 #4
    dogmeat

    dogmeat Friend of Leo's

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    ahhh yes... the 'ol Spenard lie detector
     
  5. Jan 20, 2021 #5
    itsGiusto

    itsGiusto Tele-Holic

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    Okay, put the can back in, and the voltages were great, very very close to spec. so I guess there's no worry. I had thought that leaky caps caused more problems than just voltage changes, but maybe that's only for coupling caps, not filter caps.
     
  6. Jan 20, 2021 #6
    FenderLover

    FenderLover Poster Extraordinaire

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    I don't know what meter you were using to measure 30/50/60M ohms but measurement accuracy come into play with those high readings. I'm not surprised that it works well in-circuit.
     
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