Marshall Minor

Discussion in 'Building the Classics' started by Timbo, Sep 4, 2018.

  1. Timbo

    Timbo Member

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    Hi guys, I thought I'd have a bash at one of these....
    I was able to get hold of a cheap power transformer for $4.
    Not your usual. PT is 35v-0-35v@2.5A and doesn't have a heater supply, so another PT will do the heater supply and maybe a relay supply.
    A quadrupler circuit will be used to get the desired HT of around 380v loaded.
    I have used this PT in a JTM60 build and it works well.
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    A recycled chassis so there are a few extra unused holes.
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    I'm getting 412v unloaded.
     
    Geeze, jmp45 and ampmadscientist like this.
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    Quadrupler?
    That is cavalier - wild child ! :applause: Is this a guitar amp, or a TV set? :lol:
     
  3. jensvonbustenskjol

    jensvonbustenskjol Active Member

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    I love it! Some real hands-on engineering!
    Good luck!
     
  4. Timbo

    Timbo Member

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    Hi guys, A couple of progress pics.
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    Just waiting on a couple of components and we're good to go.
     
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  5. ampmadscientist

    ampmadscientist Well-Known Member

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    That is cool in the old style p to p.
     
  6. Timbo

    Timbo Member

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    Hi guys, No problems on start up.
    Haven't had a chance to crank just yet but does sound very marshally.
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    Very happy with the voltages from the MM2026 and think some 6L6s would be a treat.
    This datasheet
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    Shows some similar voltages and proposed power output.
    But when I use the bias calculator https://robrobinette.com/Tube_Bias_Calculator.htm
    The KT88s are not running at max plate dissipation, which I thought that cathode bias was all about.

    I need some educating.
     
  7. Timbo

    Timbo Member

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    Hi guys, All good, power tubes biased to correct plate dissipation.
    I'm not much of a guitarist but it's got awesome Marshall grind and loud, VERY LOUD:applause:
     
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