Marshall Valvestate Vs100h Sounds Octaved

Discussion in 'The Workbench' started by Oscar Pauly, Apr 25, 2018.

  1. Oscar Pauly

    Oscar Pauly New Member

    Jan 9, 2018
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    Hello! My Valvestate VS100H sounds like it has an octave down along with the original signal. The preamp tube is OK. Any hint? Thanks!
  2. ampmadscientist

    ampmadscientist Well-Known Member

    Jun 26, 2014
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    Bio-Isolation Lock Down
    Use another amp to decide if the line out signal of the VS preamp still has the octave problem.
    Try inserting a guitar signal into effects return. Is the problem still there?
    Bypass the effects loop with a cable from send to return, is the problem still there?

    This may help narrow down preamp, power supply, power amp..where "is" the problem, or is it everywhere?

    Test the plus and minus 15 volt DC supplies to see if you are getting anything usable.
    You can measure DC supply from the pins of the op amps...each audio IC op amp basically has + and - DC on the pins.
    (it's easy to look up the pin out of an op amp)
    So you check to see if your 2X (plus minus) 15 volts supplies is functional.

    Being an old amp there is age issues w/ components particularly electrolytic capacitors.
    The connections to chassis, the connectors between boards, jacks pots should be throughly cleaned, oxide is all over that amp.

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