Screen Voltage Limit

Discussion in 'The Workbench' started by z808, Dec 7, 2021.

  1. z808

    z808 New Member

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    Quick question here:

    I have installed JJ 6L6GC tubes in my Marshall. The screen g2 max voltage is 450 volts according to the data sheet from JJ. After biasing, I have a screen voltage of about 453 +/- volts. Is this O.K. since it is over by a few volts?
     
  2. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    Cannot see that will make any difference at all, also consider how accurate your meter is too.

    Data sheets no matter what they are for will always have a tolerance +/-, so 3 volts will be an extremly low tolerance.

    What type of meter are you using??
     
  3. z808

    z808 New Member

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    I was using a Klein Tools TRMS multimeter. I do have a Fluke on hand just need to find it.
     
  4. EADGBE

    EADGBE Well-Known Member

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    [​IMG]
     
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  5. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    Make comparisons then with the Fluke, but at the end of the day you are worrying about nothing.
     
  6. z808

    z808 New Member

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    Thanks Ken, appreciate the feedback.
     
  7. Old Punker

    Old Punker Well-Known Member

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    Not an expert here but won't the HV level vary with the mains voltage anyway? :scratch:

    Even so, you're only over by 0.7%. :thumb:
     
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  8. Pete Farrington

    Pete Farrington Well-Known Member

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    Note that 6L6GC screen grids are good for 500V when UL connected, so from that, it may be inferred that idle voltage is of somewhat limited relevance; class AB amps don’t tend to fail / undergo stress at idle.
    The HT voltages, especially that of the screen grid, will drop, generally significantly so, when the amp generates some output power. That’s when the compliance to its voltage limit needs to be verified. https://tubedata.altanatubes.com.br/sheets/093/6/6L6GC.pdf.
     
    Last edited: Dec 10, 2021
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