Microphonic Power Transformer? Fender Blues Jr

Discussion in 'Amp Tech Center' started by soma89, Jul 29, 2020.

  1. soma89

    soma89 Tele-Meister

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    Hey there,
    So I opened up my blues jr for the first time to install a new cannibis rex speaker in it...
    I noticed when I started it up again I was getting a high pitched ringing/pinging sound ACOUSTICALLY from the power transformer. This hum does not come through the speaker. It is not loud but loud enough to be heard when playing at low volumes. Starts as soon as I turn on the amp and stops when i turn the amp off.

    I have fixed the hum with some thick black gaffers tape and a sliver of wood. I taped the wood over the largest surface area of the transformer..It no longer causes this ringing noise.

    I guess when I removed the chassis to install the speaker, I loosened up some laminations or something..screws are as tight as possible.

    I was told by someone to just open the transformer up and fill it with Form-A-Gasket.

    Any other ideas as to how to fix this in a neater way?
    Should I just buy a new transformer and cut the bs?

    I can live with it as is but it's just bugging me that the transformer is covered in a clump of gaffers tape, even though I cant see it. Its more of a mental thing i guess.
     
  2. Jon Snell

    Jon Snell Tele-Meister

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    If you loosen the mounting bolts and move it slightly whilst re tightening, that should stop it ringing.
    The ringing is caused by stray magnetics making the lamination/s or cover ring.
    In extreme cases filling with epoxy resin will stop it but not usually necessary.
     
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  3. soma89

    soma89 Tele-Meister

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    Sadly nothing i do with the screws has any effect on it. It only stops if i hold the transformer with a baseball grip.
     
    Last edited: Jul 29, 2020
  4. Jon Snell

    Jon Snell Tele-Meister

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    soma89 likes this.
  5. schmee

    schmee Doctor of Teleocity Silver Supporter

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    How do you know it's the tranny?
     
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