noisy transformer? What the ....

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by OlAndrew, Mar 12, 2008.

  1. OlAndrew

    OlAndrew Member

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    The power transformer in my vintage Gibson amp has gotten noisy...the transformer itself hums loud enough to be annoying. Its running cool, voltages are OK everywhere but there's this noise. Guess I'll change it out on general principles.
    Can't think of a way to fix that otherwise, any ideas?
     
  2. donnyjaguar

    donnyjaguar Member

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    Paint it & tighten the screws.
     
  3. pgissi

    pgissi Member

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    Its most probably on its way out, especially on a "vintage" amp.

    It was designed for 110vac an is now eating 120 to 125vac, its a matter of time
     
  4. Trout

    Trout Member

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    Electro-mechanical Vibration and hum are not necessarily signs of a failing transformer nor are they the same thing. I have seen plenty of brand new production units doing exactly the same thing. They vibrate and can give off a very audible hum type sound.

    If the transformer is actually generating a hum mechanically there might be a few solutions, Isolate the mounting, isolate the chassis to prevent the cab from resonating/amplifiying the vibration.

    If the transformer is suddenly generating a BUZZ that is audible through the speaker, Now we are talking other potential issues, Some transformers inherently do this, Hammond comes to mind in some models.

    The hum might actually be increasing due to something in the circuit loading it more, Bad Tube, Bad caps and so on.

    There is no real blanket statement that covers this.

    Generally speaking, its rare for a power transformer to die slowly, usually it is a brief harsh buzz or pop, a bit of magic smoke rises from the amp, and is proceeded by silence.
     
  5. plexi67

    plexi67 Member

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    Some of the old Gibson amps are hard to find a same size tranny that fits,when looking for a replacement. sometimes its easier to just have it rewound,and built a little better or beefed up.
     
  6. phsyconoodler

    phsyconoodler Member

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    Hit it with a hammer.Don't laugh,I saw an old tech do just that and the hum stopped.The laminates may be coming apart,but it may be a bad filter cap.
     
  7. Wakarusa

    Wakarusa Member

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    Agreed. The mechanical hum is the core laminations vibrating against each other. Why they vibrate is a longer story than I feel like typing this evening. The advice to tighten the screws and paint it was actually pretty much spot on :). I imagine shellac (or whatever the original stuff they coat the laminations with is) would be better, but don't see why paint wouldn't work in a pinch. Just make sure it's Pre-CBS paint so it doesn't ruin your tone...
     

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