Marshall Valvestate Bi-chorus Effects Loop Popping

Discussion in 'The Workbench' started by Oscar Pauly, Jan 9, 2018.

  1. Oscar Pauly

    Oscar Pauly New Member

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    Hello!
    My old Bi-Chorus 200 is having some weird popping noises when I slightly knock on the case. I checked the tube with a tube tester and it is OK. When I bypass the effects loop, the pop goes away. I checked the Reverb PCB and it does not seem to be any fried component.

    Any ideas? Thanks!
     
  2. Edokter

    Edokter Member

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    Could be a loose connection anywhere in the reverb circuit. Just keep hunting.
     
  3. tschrama

    tschrama Well-Known Member

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    IIRC there a quite a few ribbon cables inside with plugs and sockets. Atleast the old ones did. Mine allways had intermittent connects on these cables untill I soldered them securely.
     
  4. Oscar Pauly

    Oscar Pauly New Member

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    You are right, I will keep looking. I thought probably on replacing all effects loop jacks.
     
  5. Oscar Pauly

    Oscar Pauly New Member

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    Good hint! Those plugs are kind of loose, I will solder them to the PCB and see if that helps. Thanks!
     
  6. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    "When I bypass the effects loop, the pop goes away."

    Replace send or return jacks of effects loop.
    Switch contacts in jack are corroded, and signal path is intermittent. (the switch contact in the jack "is" the signal path).
    When this contact corrodes, the signal path is corrupted.

    Cleaning the switch contacts is temporary, the problem always comes back later, therefore install new jack(s).

    FAKE CLIFF JACK ALERT:
    if the jack does not say "CLIFF UK," it's a knockoff. The knockoff does not say "UK." Be careful when you purchase cliff jacks.
    The knock-off is inferior, and will fail very quickly.
     
  7. Oscar Pauly

    Oscar Pauly New Member

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    Thanks to everyone for the hints! I finally fixed it after changing the speaker jacks and re-soldering all reverb board connections. YYYEEESSSS!!
     
    tschrama likes this.

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