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The Dynaco Tube Audio Forum

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


5 posters

    Another ST-120 build

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    bobgroger


    Posts : 18
    Join date : 2021-02-12

    Another ST-120 build Empty Another ST-120 build

    Post by bobgroger Sun Feb 21, 2021 4:10 pm

    Testing was on hold while I waited for a rectifier, but I remembered there was one in my Scott 299. Fired it up without the outputs first to verify there was audio out of the preamp. Hmm, no left channel. After a bit of troubleshooting I found I had forgotten to solder the center pin of the RCA jack. Then hooked up a dummy load, put the outputs in 1 channel at a time and biased, rebiased with all tubes and glorious music came out. I deviated from the design a bit, I drilled a couple holes and put the second choke where it should be. I wired it in Ultralinear only, and used one of the toggle switches as a standby switch. Note of warning: No matter how careful you are you WILL scratch up the chassis. I covered it entirely in masking tape, only uncovering as needed. Every screwdriver slip makes a nasty gouge. GE 6829 center tube, RCA 12AU7 phase splitters, EH KT88 outputs, RCA\Mullard GZ34.


    Another ST-120 build St120-10
    Another ST-120 build St120-11

    petrnyc likes this post

    Dave_in_Va
    Dave_in_Va


    Posts : 446
    Join date : 2013-04-02
    Location : Mid. VA

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    Post by Dave_in_Va Sun Feb 21, 2021 5:33 pm

    Neat wiring! Congrats.
    Nice rectifier.
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    Rbertalotto


    Posts : 98
    Join date : 2021-02-25

    Another ST-120 build Empty Re: Another ST-120 build

    Post by Rbertalotto Tue Mar 02, 2021 8:31 am

    I deviated from the design a bit, I drilled a couple holes and put the second choke where it should be.

    Can you show what you actually did here?

    Nice build BTW!
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    edman44


    Posts : 24
    Join date : 2021-06-14
    Age : 62
    Location : PENNSYLVANIA

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    Post by edman44 Wed Jun 23, 2021 1:08 pm

    Nice Job, I hope when I build mine it comes out as nice as yours.
    Big Hat
    Big Hat


    Posts : 4
    Join date : 2021-06-24
    Location : West of Weird, Texas

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    Post by Big Hat Mon Jun 28, 2021 7:14 am

    Ignorant n00b question: Why is the left-hand choke generally cocked a a 10 - 30° angle and with only one mounting bolt?

    Outstanding build, bobgroger! Very pretty.
    avatar
    Rbertalotto


    Posts : 98
    Join date : 2021-02-25

    Another ST-120 build Empty Re: Another ST-120 build

    Post by Rbertalotto Mon Jun 28, 2021 7:31 am

    Lots of builders reorient this Xformer to be one with Fengsway......The single hole mounting is just a design decision for easy assembly.
    Big Hat
    Big Hat


    Posts : 4
    Join date : 2021-06-24
    Location : West of Weird, Texas

    Another ST-120 build Empty Re: Another ST-120 build

    Post by Big Hat Mon Jun 28, 2021 7:45 am

    Thanks! I'm all over Feng shui, although if you saw my man cave/workshop you'd never guess it.
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    Rbertalotto


    Posts : 98
    Join date : 2021-02-25

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    Post by Rbertalotto Mon Jun 28, 2021 8:01 am

    Laughing

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