Testing a filter choke or finding a replacement?

Discussion in 'Shock Brother's DIY Amps' started by Robster, Apr 24, 2019.

  1. Robster

    Robster Tele-Holic

    Feb 14, 2009
    Marietta, GA
    I picked up this 1966 Gibson Minuteman GA20RVT amp.
    Looks like someone disconnected one wire from the filter choke, then looks like the added in more capacitance with a large 470uf cap instead. Normally the power supply caps are only 20uf...
    Can I test this filter choke or find a replacement? I want to get the amp back to stock condition.
    magic smoke likes this.
  2. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    You can check the integrity of the coil with a multimeter. Measure resistance from one lead to the other and from one lead to the frame of the choke. Lead to frame should read open, and lead to lead shouldn't be open or unusually low. Somewhere in the 50 ohm range is a reasonable number, but that will depend on how the choke was designed.

    To actually test the inductance requires more specialized gear like an LCR meter, though.

    Sent from my Pixel 2 using Tapatalk
  3. Nickfl

    Nickfl Tele-Afflicted

    May 24, 2016
    There's a method for estimating the inductance of a choke here: http://www.diytube.com/phpBB2/viewtopic.php?t=3334

    I used it to measure a choke pulled from an old radio a while back and it seemed to work.

    It's the post about halfway down that mentions a 3.75k resistor.
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