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1200 sunn head crackling when turned on

Discussion in 'Amps and Cabs [BG]' started by dominicRHIN, Aug 12, 2016.

  1. dominicRHIN


    Dec 18, 2014
    When turning on i hear can crackling. it goes away quickly, if i turn on and off I will not hear it but if it sits for maybe more than a hour i will hear the crackling when i turn it on.....I noticed some flashes of light from the tube on the far light....is that the pre amp tube? do they or one of them need to be replaced.....video attached

  2. Is the noise coming from the amp only, or do you hear it coming from the speakers?
  3. dominicRHIN


    Dec 18, 2014
    i have tried on two different cabs with the same head, noise comes out of speakers as i turn on
  4. SunnBass

    SunnBass All these blankets saved my life.

    Aug 31, 2010
    Columbia, Mo
    My guess is leaky capacitors, and a tube preparing to fail.
    Last edited: Aug 13, 2016
    Old Garage-Bander likes this.
  5. I am assuming that this amp has never had anything done to it.
    Based on that;
    replace filter caps
    retension tube sockets
    clean pots
    then get back to us.

    If that dosen't cure the noise, it is still not a waste,
    as it should have been done by now, anyway.
    bassmeknik and dominicRHIN like this.
  6. I miss having one of these, crackles and all.
  7. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    This is the solid state rackmount job, not the old valve power section one. They are notorious for failed solder joints on the pcb that is a giant nutpain to fix, they do this when they have it.
    TMARK likes this.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This is a fairly complicated amp, the output stage is not simple class AB. You may want to find an experienced tech who has a track record with this particular product, or its Fender equivalent. Disregard all the guesses that are trying to be helpful, this is not an amp to attempt fixing based on well intentioned guesses.

    Where are you located? Often, an older tech at a Fender Electronics service center can end up being your best bet, otherwise a hack tech could easily turn this amp into a smoldering piece of scrap.
    99Z3 likes this.
  9. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

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