The Dynaco Tube Audio Forum

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


    10A or 20A Bucker Transformer for M125's?

    Share
    avatar
    cci1492

    Posts : 192
    Join date : 2016-05-09
    Age : 57
    Location : Bergen County NJ

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by cci1492 on Fri Apr 13, 2018 8:40 am

    Thanks! Just order it from Digi-Key, did a little more looking around and concluded the 6.3 TA will do the trick for the reason you stated. Also ordered a couple of inrush current limiters (30A) for the Vairac. Looks like the breaker is tripped because of the sudden current surge when powering up. Intermittent because it depends where the sinusoidal wave form is at when the switch is thrown. At times the current I measured is 0 (when switch thrown), other times between 2 and 3Amps., other times 9A, and this is with no load at all on output of the Variac. The Variac behaves just fine once it's on and didn't trip the breaker. With no load it sits at .08A, it handles just fine loads in excess of 13A with ease. Took it apart, built nicely and clean. I just think it's a beast and needs a soft start of sorts to not trip breakers. I think Square D makes a breaker for this purpose but not going that route for now.
    avatar
    Dave_in_Va

    Posts : 236
    Join date : 2013-04-02

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by Dave_in_Va on Fri Apr 13, 2018 9:44 am

    I post this link every time this subject comes up.
    The simple one will do the trick, in fact mine are even simpler as I couldn't foresee the use of a 12% voltage reduction. I just shrink wrapped those leads.

    https://robrobinette.com/5e3_Modifications.htm#Bucking_Transformer

    Right now I measure 122.6 out of the wall and 115.5 out of the bucker. Close enough, I think.
    avatar
    gktamps

    Posts : 14
    Join date : 2017-07-30
    Location : Santa Rosa, CA

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by gktamps on Fri Apr 13, 2018 10:42 am

    avatar
    LeGrace

    Posts : 258
    Join date : 2016-08-07
    Location : Ontario, Canada

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by LeGrace on Fri Apr 13, 2018 11:21 am

    Mine is also simpler. No lights, switches, or fuses. Just a single 2 plug outlet along with the transformer. And connecting only the lower output leads. Nice compact little box that is easy to tuck out of the way.
    avatar
    cci1492

    Posts : 192
    Join date : 2016-05-09
    Age : 57
    Location : Bergen County NJ

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by cci1492 on Sat May 26, 2018 12:32 pm

    Finished it.






    Stick with Bob's suggestion, use a variac!
    avatar
    LeGrace

    Posts : 258
    Join date : 2016-08-07
    Location : Ontario, Canada

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by LeGrace on Sat May 26, 2018 1:18 pm

    Wow, nicely done!
    avatar
    deepee99

    Posts : 2000
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by deepee99 on Sun May 27, 2018 2:21 pm

    For those of us without a huge parts bin (or the fabricator's electronic/mechanical skills), is there such a thing as an out-of-the-box plug 'n' play bucker out there?

    stewdan

    Posts : 178
    Join date : 2010-03-07
    Age : 80
    Location : Houston Texas

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by stewdan on Sun May 27, 2018 3:24 pm

    David --- there has been a Bucking Transformer listed on the E-Site for the past 6 months or more.

    It usually shows up on a Dynaco Transformer search.

    If I remember right, it is over $100.
    Stew
    avatar
    deepee99

    Posts : 2000
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by deepee99 on Sun May 27, 2018 3:39 pm

    Stew, thanks. Not sure I need one as the Furman I've got clamps everything down at 121 VAC regardless in input voltage. Still a tad high but OK for modern VTA gear. But a guy can never have too much stuff Smile

    Sponsored content

    Re: 10A or 20A Bucker Transformer for M125's?

    Post by Sponsored content


      Current date/time is Wed Sep 19, 2018 1:38 pm