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

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    EddieGnz1

    Posts : 23
    Join date : 2013-10-16

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

    Post by EddieGnz1 on 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

    Maintarget

    Posts : 209
    Join date : 2013-02-10

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

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

    Looking at the pictorial included with the kit it shows the wiring without the Triode/Pentode.

    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

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

    Post by Bob Latino on 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

    sKiZo

    Posts : 1312
    Join date : 2013-04-01
    Location : Michigan USA

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

    Post by sKiZo on 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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