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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


    New construction st120

    jonny6336
    jonny6336

    Posts : 24
    Join date : 2018-01-31
    Age : 43
    Location : Italy

    New construction st120 Empty New construction st120

    Post by jonny6336 Sat Feb 13, 2021 9:42 am

    Hallo friends
    Almost ready to start my second build, still missing other components that are on the way.This time I will make a ST120 from the very famous Bob Robert Latino, my idea is to use Hammond output transformer model 1650NA, and the power transformer made here in Italy and for the driver card instead I will buy it directly from Bob.New construction st120 20210213
    New construction st120 20210214
    New construction st120 20210215

    Dave_in_Va, 10-E-C, kFish and Section1 like this post

    markeby
    markeby

    Posts : 24
    Join date : 2019-02-13
    Age : 63
    Location : Near Austin, Texas

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    Post by markeby Thu Feb 18, 2021 3:18 pm

    I don't see it on Bob's web site any more, but, the autobias board has been a blessing to my ST120.  I wouldn't build another without it.

    This is the only legit looking place I see it today:  https://www.audioamp.eu/automatic-bias-control-module-for-dynaco-st70-ab-q-st70-st120/

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    jonny6336
    jonny6336

    Posts : 24
    Join date : 2018-01-31
    Age : 43
    Location : Italy

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    Post by jonny6336 Thu Feb 18, 2021 3:56 pm

    at the moment they start with the construction of the st120 as per project, then any tricks in the evaluation phase, however I had read and seen this system. I will evaluate, thanks a lot for the suggestion
    markeby
    markeby

    Posts : 24
    Join date : 2019-02-13
    Age : 63
    Location : Near Austin, Texas

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    Post by markeby Thu Feb 18, 2021 4:31 pm

    Other notes:

    • Upgraded tube sockets, capacitors (C5,C6,C7,C8), and use KT88s for the power tubes.
    • High quality Circuit breaker of the same capacity instead of the slow blow fuse.  Circuit breaker pop delay is same as slow blow fuse.
    • A fuse and MOV at each power tube with the auto bias board. There are micro sockets for the fuse (it saved me the power tube when I had a bad power tube).      
           https://dynacotubeaudio.forumotion.com/t3627p50-auto-bias-board-on-roy-s-website#35422 
    • Don't use a solid state rectifier.  I have used a Telefunken GZ34-TK without any issues.
    jonny6336
    jonny6336

    Posts : 24
    Join date : 2018-01-31
    Age : 43
    Location : Italy

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    Post by jonny6336 Thu Apr 01, 2021 1:13 am

    transformer made in Italy for my ST120New construction st120 20210311
    jonny6336
    jonny6336

    Posts : 24
    Join date : 2018-01-31
    Age : 43
    Location : Italy

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    Post by jonny6336 Thu Apr 01, 2021 1:17 am

    New construction st120 20210312
    peterh
    peterh

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    Location : gothenburg, sweden

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    Post by peterh Thu Apr 01, 2021 4:11 am

    Interesting with an european source of "dynaco" transformers. Who is this source ? Do they have a webpage or contact information ?
    jonny6336
    jonny6336

    Posts : 24
    Join date : 2018-01-31
    Age : 43
    Location : Italy

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    Post by jonny6336 Thu Apr 01, 2021 4:39 am

    I certainly give you the link. If interested, ask what kind of amp model you need to make.
    https://www.raoli.it/
    markeby
    markeby

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    Location : Near Austin, Texas

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    Post by markeby Thu Apr 01, 2021 3:03 pm

    You most certainly will want the metal "shielding" on the bottom of that transformer. 50 cycle hum will drive you nuts to hunt down.
    jonny6336
    jonny6336

    Posts : 24
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    Post by jonny6336 Thu Apr 01, 2021 5:04 pm

    If you are referring to the metal cap, I cannot mount it because it would not fit into the frame. The transformer in turn has a shielding inside, not visible due to the cover with the paper, moreover it will then be connected to the gnd of the electricity network so theoretically I shouldn't have any problems. For example, with the ST-70 I have no problems, also a transformer made in Italy
    Earl
    Earl

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    Join date : 2020-05-10
    Location : Arkansas

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    Post by Earl Thu Apr 01, 2021 5:44 pm

    jonny6336 wrote:This time I will make a ST120 from the very famous Bob Robert Latino,

    I had no idea that Robert was Bob’s middle name. scratch
    jonny6336
    jonny6336

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    Post by jonny6336 Sun Apr 04, 2021 9:30 am

    Driver board ready New construction st120 20210410
    jonny6336
    jonny6336

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    Post by jonny6336 Thu Apr 08, 2021 2:51 am

    Hi friends, the quartet selected and paired for my realization of the ST120. The driver tubes, on the other hand, will obviously be a trio of 12AU7A RCA Black Plate 45 ° Square Getter Tubes Made in the USA '57New construction st120 Img-2010
    jonny6336
    jonny6336

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    Post by jonny6336 Mon Apr 19, 2021 5:34 pm

    Slowly, but construction proceeds
    New construction st120 20210413
    New construction st120 20210414

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    jonny6336
    jonny6336

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    Post by jonny6336 Wed Apr 21, 2021 4:35 pm

    New construction st120 20210415
    jonny6336
    jonny6336

    Posts : 24
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    Post by jonny6336 Tue May 04, 2021 3:43 pm

    Here are other details, quadruple capacitor arrived and I inserted the thermo sheath to isolate the 4 positive branches from the frame if they could accidentally touch. Plus the ESL capacitor.New construction st120 Img-2011
    New construction st120 Img-2012
    Tom Pickett
    Tom Pickett

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    Location : Texas

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    Post by Tom Pickett Tue May 04, 2021 4:31 pm

    jonny6336 wrote:Slowly, but construction proceeds
    New construction st120 20210413
    New construction st120 20210414

    Nice jonny6336..... That power transformer is massive. How much taller is the lamination stack on it compared to the original VTA ST 120 ?

    Tom
    jonny6336
    jonny6336

    Posts : 24
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    Post by jonny6336 Tue May 04, 2021 4:46 pm

    It is a 450mA transformer having 120x100 measures. Without cap it is in line with the condenser
    New construction st120 20210416
    New construction st120 20210417

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    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Tue May 04, 2021 7:07 pm

    jonny6336 wrote:It is a 450mA transformer having 120x100 measures. Without cap it is in line with the condenser
    New construction st120 20210416
    New construction st120 20210417

    Holy God. lol !  I bet it weighs around 10 pounds by itself? lol New construction st120 1f600
    Earl
    Earl

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    Post by Earl Tue May 04, 2021 8:38 pm

    Oh my, that’s a big one!. Shocked

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    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Tue May 04, 2021 11:19 pm

    Earl wrote:Oh my, that’s a big one!. Shocked

    Earl... I 2nd that lol. It's definitely a beast !
    jonny6336
    jonny6336

    Posts : 24
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    Post by jonny6336 Wed May 05, 2021 1:19 am

    For the specifications that Bob said regarding the anode current the reel to hold the copper for 450mA and all tube filaments it took bigger. All in all it fits on the frame and doesn't make a bad impression😊😊😊

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    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Wed May 05, 2021 5:51 pm

    jonny6336 wrote:For the specifications that Bob said regarding the anode current the reel to hold the copper for 450mA and all tube filaments it took bigger. All in all it fits on the frame and doesn't make a bad impression😊😊😊

    "impression".......... Well ? The transformer was standing up there looking like a steel mountain on a small island lol New construction st120 1f605

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    jonny6336
    jonny6336

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    Post by jonny6336 Fri May 07, 2021 3:35 pm

    Another step is completed, pendode / triode selector wiring. Only the exit transfers are missing, and then we can say it's finished.
    New construction st120 20210510

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