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Randell amp

Discussion in 'Electronic Repair' started by lurk, Apr 23, 2007.

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  1. lurk

    lurk Guest

    I'm working on a Randell amp...I changed the 2 electrolitic caps in the
    power supply..but it still has a hum when the volume is turned up
    alittle...I esr'ed the other caps in circuit and they look
    ....... any suggestions ? thanks
  2. Guest

    Are you able to point to a schematic? I am thinking hum-loop, dirty
    controls or a leaking bypass cap. As to the two electrolytics you did
    replace, make sure that you followed the schematic exactly. In some
    cases these caps are part of a voltage-doubler circuit, so (at least)
    one will be above ground on both ends. Similarly for an LC circuit.

    Peter Wieck
    Wyncote, PA
  3. lurk

    lurk Guest

    Peter...thanks for your answer....I got this unit to repair and
    whoever ...... replaced the 2 large caps in the pwr supply... but
    they had them reversed....and it kept kicking the breaker out...I
    rewired them and it don't kick the breaker now but the hum is
    there..I checked the caps with an ESR meter and they look ok...but I
    wonder if wiring them backwards ruined the caps....what other test can I
    do on them.....thanks
  4. Guest

    It is quite likely that the caps are ruined. In any case, I would not
    trust them given the (relatively) low cost of replacements. Additional
    tests that I perform even on new caps right out of the box/bag is a
    full-voltage test on a cap checker, as well as a simple confirmation
    of basic capacitance.

    Good luck with it.

    Peter Wieck
    Wyncote, PA
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