Mini Plexi Build

Discussion in 'Building the Classics' started by ibmorjamn, Sep 1, 2019.

  1. ibmorjamn

    ibmorjamn Well-Known Member

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    So , it's been done before . I am using an Antek toroidal transformer for the power stage 6P1P for power tubes , best duplicate I can do of the 1959 SLP 4 hole input pre amp , 2 volumes and same phase inverter values. Doing chassis layout right now. Aluminum dust is good !
     
  2. john hammond

    john hammond Well-Known Member

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    aluminium is good, it does have a couple of drawbacks/ benefits.

    - it's quick, dynamic response is quicker

    - grounds are a pain in the ass, i like using steel...get a small gas torch and pool up 3/8 puddles of solder wherever you know you'll need a ground, and a couple extra just in case.
     
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  3. ibmorjamn

    ibmorjamn Well-Known Member

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    I never had any trouble with grounds but ampscientist says the same thing .
    Thousands of aluminum amp chassis out there .
     
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  4. ampmadscientist

    ampmadscientist Well-Known Member

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    You cannot solder to aluminum but you can TIG ground lugs to the chassis.
     
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  5. john hammond

    john hammond Well-Known Member

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    if youre trying to make nuclear attack proof amps, puddle pools of solder is best.
    but i do agree that you can make decent grounds, ampmads idea is solid, and really...aluminium chassis sound fantastic, nice and fast.
     
  6. john hammond

    john hammond Well-Known Member

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    prob hundreds of thousands
     
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  7. jensvonbustenskjol

    jensvonbustenskjol Active Member

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    Nice! I'm not familiar with the mini plexi. Can you tell me about the power stage and OT?
    Alu-chassis are fine. If you live near by i can tig grd lugs for you.
     
  8. ibmorjamn

    ibmorjamn Well-Known Member

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    It is not my design , some well versed guys did the schematic and the build they did was 8 years ago. The power stage is not designed to be Marshall because of the Russian tubes .
    I am going to use the values for the pre amp on the schematic from Robinette .
    https://photos.app.goo.gl/5cZ5j6riKZK6wkgg6
     
    Last edited: Sep 2, 2019
  9. ibmorjamn

    ibmorjamn Well-Known Member

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    newThrifty Plexi_0600.jpg
     
    Last edited: Sep 3, 2019
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  10. CoyotesGator

    CoyotesGator Well-Known Member

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    Oh tell me you’re going to use 6N2P for the preamp!
     
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  11. ibmorjamn

    ibmorjamn Well-Known Member

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    Of course ! 6p1p power and 6n2p pre amp.
     
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  12. CoyotesGator

    CoyotesGator Well-Known Member

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    Hell Yeah.

    What are your target voltages?
     
  13. ibmorjamn

    ibmorjamn Well-Known Member

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    Of course ! 6p1p power and 6n2p
    not sure because the power was used for a train wreck with these tubes , same transformer. The original Thrifty Plexi pre amp is very close to mark huss 6v6 plexi but he did not use 4 inputs .
    It says 320v at the phase inverter but I doubt that it will be that high. From this schem. :
    https://robrobinette.com/How_the_Marshall_JCM800_Works.htm
     
    Last edited: Sep 3, 2019
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  14. Adieu

    Adieu Well-Known Member

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    What kinda build cost does it come out to?
     
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  15. ibmorjamn

    ibmorjamn Well-Known Member

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    thriftyplexiRG_0603.jpg
    So far about $145.00 but I am using tag strips instead of a turret board. The Power supply is a Antek AS-1T200 $34.57 , Output Trans is a Hammond 1760f $42.80 , chassis came off ebay , forgot what I payed for that and I bought a bunch of pots , cliff jacks and some tag strips from antique electronic supply $35,00 I did not order some parts yet and forgot knobs but have 2 different type.

    All I did yesterday is drill some holes for the pots next to the mounting holes.
     
    Last edited: Sep 3, 2019
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  16. ibmorjamn

    ibmorjamn Well-Known Member

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    I am crossing a couple of hurdles , I realized I needed few a things I didn’t order on the last order . Mean time I am changing the Thrifty Plexi input schematic and hand drawing it 11” x 16” to include the 4 inputs “cliff jacks” and 2 volumes to be able to blend them so when I get to phase inverter and power tubes I will stick to the TP schem.
     
    Last edited: Sep 10, 2019
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  17. ibmorjamn

    ibmorjamn Well-Known Member

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    I am stuck right now because the cheap chassis needs to be welded on the corners . I have a guy to do it but he is out of town .
    I have been looking at a amplified parts 18w chassis with the face plate . Good prices but I got to wait on it. I have had 3 orders of parts lately.
     
    Last edited: Sep 21, 2019
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  18. ibmorjamn

    ibmorjamn Well-Known Member

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  19. ibmorjamn

    ibmorjamn Well-Known Member

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    9C39714F-B9AD-4A85-9466-5BB9DC1C537A.jpeg
    Got it !
     
    Last edited: Oct 27, 2019
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  20. pleximaster

    pleximaster Well-Known Member

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    I am currently building two Marshall inspired 18 watt amp head for Thomas Hinson here on the forum and one for me that we call Clubman from the JTM Club on facebook that we admin... :)

    One channel is true to the original 18 watt and the other is more plexi like

    plexi

    ahgCJncfRhCTyIRIKSJpqQ_thumb_22f3.jpg




     

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