1990 Fender Red Knob Twin Intermittent Siren Like Sound And Crackling

Discussion in 'The Workbench' started by jalexquijano, Jan 23, 2018.

  1. jalexquijano

    jalexquijano Member

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    My 1990 red knob twin produces a 5 seconds siren like sound with some crackle when the amp is warming up during the initial 45 minutes of playing. Its intermittent and its produced even without a guitar cable plugged in. Could this be a preamp tuve in v7 or v1?
     
  2. Len

    Len Well-Known Member

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    Crackling usually means a bad tube, dirty tube socket or cold solder joint at a tube socket.
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    A bad preamp tube is a possibility but,
    Sometimes w/ this amp
    broken or cracked controls or connections, oxidized jacks.
    The last one I worked on had a broken control....and it squealed (like a siren) intermittently.
    For some reason this amp had a problem with the controls breaking....and the controls were discontinued. But there is some substitutes around that you can install.
     
  4. jalexquijano

    jalexquijano Member

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    well i changed V7 preamp tube which is the first stage preamp. i will buy a magnifying glass and check all connections once again.
     
  5. jalexquijano

    jalexquijano Member

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    would you recommend JJ 12ax7 or sovtek 12ax7b for this high gain combo amp?
     

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