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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    Modifying the ST-120, Bypassing the Triode/Pentode Switches

    EddieGnz1
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    EddieGnz1


    Posts : 23
    Join date : 2013-10-16
    • Post n°1

    Modifying the ST-120, Bypassing the Triode/Pentode Switches Empty Modifying the ST-120, Bypassing the Triode/Pentode Switches

    Post by EddieGnz1 Sat Dec 28, 2013 4:39 pm

    I'm building the ST-120 kit from Bob right now. I'm at the point where the Triode/Pentode Switch start to get wired (Step 14 in the Assembly Manual). If I do not want the option to switch from Pentode to Triode and instead I just want to always run it at 60 watts per channel, how would I modify the instructions to fully bypass the two switches?

    1) What are all the steps in the assembly manual that would need to be modified due to this change?
    2) how exactly would those modified steps be different?

    Please keep in mind that I'm an extreme beginner. So far up to this point everything seems to be going well and I'm following along pretty well.

    Kind thanks,
    Eddie
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    Maintarget
    Maintarget
    Maintarget


    Posts : 227
    Join date : 2013-02-10
    • Post n°2

    Modifying the ST-120, Bypassing the Triode/Pentode Switches Empty Re: Modifying the ST-120, Bypassing the Triode/Pentode Switches

    Post by Maintarget Sat Dec 28, 2013 5:09 pm

    Looking at the pictorial included with the kit it shows the wiring without the Triode/Pentode.
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3274
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°3

    Modifying the ST-120, Bypassing the Triode/Pentode Switches Empty Re: Modifying the ST-120, Bypassing the Triode/Pentode Switches

    Post by Bob Latino Sat Dec 28, 2013 5:19 pm

    Maintarget has it correct ... Just wire the amp as shown on the pictorial. The two triode/pentode switches, the four 100 ohm resistors and the two 2 lug terminal strips will not be used.

    The GREEN wire from the LEFT output transformer will go to pin #4 on V3
    The GREEN/WHITE wire from the LEFT output transformer will go to pin #4 of V2
    The GREEN wire from the RIGHT output transformer will go to pin #4 of V6
    The GREEN/WHITE wire from the RIGHT output transformer will go directly to pin #4 of V7

    Bob
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    sKiZo
    sKiZo
    sKiZo


    Posts : 1530
    Join date : 2013-04-01
    Location : Michigan USA
    • Post n°4

    Modifying the ST-120, Bypassing the Triode/Pentode Switches Empty Re: Modifying the ST-120, Bypassing the Triode/Pentode Switches

    Post by sKiZo Sat Dec 28, 2013 7:10 pm

    Then again, if you don't install the switch, you'll never know what you're missing. The triode mode does change the tone of the amp as well as the output. Very smooth for light jazz and orchestral.

    If you decide you don't like it, hey ... don't flip the switches.
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    • Post n°5

    Modifying the ST-120, Bypassing the Triode/Pentode Switches Empty Re: Modifying the ST-120, Bypassing the Triode/Pentode Switches

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