BF Vibro Champ issues

Discussion in 'Glowing Bottle Tube Amp Forum' started by Stan Martin, Sep 24, 2019.

  1. peteb

    peteb Friend of Leo's

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    the OT primary should measure about 270 DCR. You do not need to pull the tubes to measure this.


    the OT secondary should measure about a half an ohm DCR. Measure with the speaker unplugged.
     
  2. Stan Martin

    Stan Martin Tele-Afflicted

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    Hi Pete,

    With the tubes in I am reading 23 ohms between the primary and 2.1 ohms between the secondary. I would assume the OT is on the way out,hence the low volume, eg. no volume between 2-4 and on 10 it aounds like it should at the halfway point.

    Stan
     
  3. monkeybanana

    monkeybanana Tele-Meister

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    mmhmm
    Hope you found your problem there.

    Just wanted to add, I brought back to two BF Champs back to to life with the help of some of the same fine folks in this thread. I also experimented with bias (one of the 470s was cooked) and they do need to run hot to sound good. Too cold and they treble sounds bad.
     
  4. peteb

    peteb Friend of Leo's

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    I agree, the OT looks to be a problem.



    there must be some shorted windings



    EDIT:


    I think there is one more check that should be done before the OT is considered bad. Disconnnect the OT from the plate, and then measure the resistance of the primary. There is an outside chance that the tube socket is shorting to ground and giving a bad measurement.
     
    Last edited: Sep 26, 2019
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