Anyone with a working Valvestate 8080? Is the clean channel low?

Discussion in 'Marshall Amps' started by Rickybocker, Oct 10, 2021.

  1. Rickybocker

    Rickybocker New Member

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    I just bought a fixer Valvestate 8080. It had dirty pots/switches and was farty on the clean.

    I've repaired everything in the clean channel circuit and it sounds good, but its very quiet compared to the channel 2. THe channel 2 volume is extremely loud. but the clean is just not able to get anywhere close to the same level.

    I'm still researching to see if theres anything I'm missing but I just wanted to know If this is how its supposed to sound.
     
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  2. SkyMonkey

    SkyMonkey Well-Known Member

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    I had an 8080 back in the 90's and don't remember any of that happening.
    The amp sounds like it still needs some 'Fixing'.
     
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  3. Rickybocker

    Rickybocker New Member

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    Thanks. I'm stumped. I fixed a dsl100 a few months back. Seemed like this amp would be simple compared to that one. I have a another post going in the workbench, but I just wanted some confirmation on how it should sound.
     
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  4. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Do you have an oscilloscope? If so, measure signal levels stage by stage. Use an audio generator, which can be even an app on a tablet, phone, or computer.

    I'm going to bet that there's an op amp in the clean channel that's blown up. You'll know it when you find one where the output of it is lower than its input signal level.
     
  5. GabrielEngel

    GabrielEngel New Member

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    My 8080 does not exhibit that. The normal (clean channel) doesn't have volume only gain control and the boost channel (distortion) does have both while the 8080 also has an overall volume pot, so you must balance out the two first and then can adjust volume with the overall volume pot. not sure if I,m being clear?
     
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  6. SkyMonkey

    SkyMonkey Well-Known Member

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    Clean has Gain only.
    OD has Gain and Volume.
    Master volume for Global control.

    Ideal, if all is well.
     
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  7. Rickybocker

    Rickybocker New Member

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    I have a scope and generator. I've actually replaced all the clean/crunch switch, op amps, pots, diodes, and a few caps in the clean stages.

    I'm getting about half the expected gain from the first op amp. I am also seeing a loading down effect after the 2nd op amp with the gain pot. Before it hits tone circuit/the switching op amp that switches from channel one or two.

    There's a couple of transistors in the switching circuit that I haven't tested. But I don't think they could be effecting gain.


    I guess it's possible when I replaced the gain adjusting op amp that it got damaged. I still had some dc offset that I just cleaned up with caps last week.

    Any suggestions?
     

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