ValveState40 Reverb Tank Impedance

Discussion in 'The Workbench' started by Phil E, Oct 26, 2020.

  1. Phil E

    Phil E New Member

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    My modded combo ValveState40 (8040) reverb tank has started a weird buzz on the low A on the 6th string is played - just when the reverb is enabled.

    I figured since reverb tanks are pretty cheap I'd install an external replacement on the floor of the cab. But I can't figure out what the input/output impedance would be. It's not on the unit (which is mounted on the mainboard) and despite much Googling, I can't find any methods on how to measure it with a multimeter.

    Does anyone have any idea on what the impedance would be for the reverb tank? It's quite small.
     
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  2. SkyMonkey

    SkyMonkey Well-Known Member

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  3. South Park

    South Park Well-Known Member

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    To find the impedance you need the schematic for that circuit and do some math . I don’t think it has any impedance for the signal
     
  4. Phil E

    Phil E New Member

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    I do have the schematic - although I do mods I'm not at that level yet in terms of electronics. There is quite a large range of input and output impedances listed when you look up reverb tanks so it's probably pretty important.
     
  5. Phil E

    Phil E New Member

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    Thanks - I think the main issue is that the tank (which is actually mounted on the inside of the circuit board and is not external) is quite small so may have an odd impedance or requirements.[/QUOTE]
     
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  6. SkyMonkey

    SkyMonkey Well-Known Member

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    This YT vid may help.
     
  7. Phil E

    Phil E New Member

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    Thanks - there are no codes visible as it's mounted on the circuit board itself
     
  8. Phil E

    Phil E New Member

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    Found out that it's 55 ohm in 200 ohm out.
     
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  9. Phil E

    Phil E New Member

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    NOTE: The above was from a service tech at a 3rd party company. The official word from Marshall: The Specs are :

    8.5X1.5X1ins
    IP=319 OP=2575
    VERTICAL
     

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