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


    ST70 too bright...why?

    Share

    tygr1

    Posts : 35
    Join date : 2014-12-08

    Re: ST70 too bright...why?

    Post by tygr1 on Mon Dec 22, 2014 9:42 pm

    OK, here's what I've got so far. With my (new) Fluke 27 I'm seeing 415v at the VTA board B+. Does anyone know if this is good, bad or indifferent?

    Just got the meter and haven't had time to take the amp out of my setup to check the main B+ voltage. I suspect my cheap meter wouldn't even read the 415 volts without showing an overload warning so my main B+ may be ok after all. Wall voltage right now is 121.3v.

    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: ST70 too bright...why?

    Post by peterh on Tue Dec 23, 2014 3:49 am

    If you are measuring voltages, please measure the ones mentioned on page 9 in the dynaco st70 manual,

    415V seems reasonable however.

    tygr1

    Posts : 35
    Join date : 2014-12-08

    Re: ST70 too bright...why?

    Post by tygr1 on Tue Dec 23, 2014 10:04 am

    PeterH, I'm seeing 384vac at pin 6 of the rectifier tube and 472vdc at pin 8. This is with 122.2vac at the wall.

    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: ST70 too bright...why?

    Post by peterh on Tue Dec 23, 2014 12:22 pm

    tygr1 wrote:PeterH, I'm seeing 384vac at pin 6 of the rectifier tube and 472vdc at pin 8. This is with 122.2vac at the wall.

    Seems very reasonable with that wallVoltage.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: ST70 too bright...why?

    Post by tubes4hifi on Tue Dec 23, 2014 6:56 pm

    Peter, and everyone,
    anyone who buys a VTA board from me or Bob gets full documentation, with voltage checks and schematics.
    B+ to the board should be around 380-400vdc after going thru the supplied 2.2K dropping resistor.
    All other voltages on the board are marked on the schematic.

    tygr1

    Posts : 35
    Join date : 2014-12-08

    Re: ST70 too bright...why?

    Post by tygr1 on Tue Dec 23, 2014 7:02 pm

    Thanks for that guys!

    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: ST70 too bright...why?

    Post by PeterCapo on Tue Dec 23, 2014 7:53 pm

    tubes4hifi wrote:Peter, and everyone,
    anyone who buys a VTA board from me or Bob gets full documentation, with voltage checks and schematics.
    B+ to the board should be around 380-400vdc after going thru the supplied 2.2K dropping resistor.
    All other voltages on the board are marked on the schematic.

    Understood. I had mentioned it because I was of the impression, perhaps mistakenly, that tygr1 bought the amp second-hand and that the documentation was not included.

    tygr1

    Posts : 35
    Join date : 2014-12-08

    Re: ST70 too bright...why?

    Post by tygr1 on Tue Dec 23, 2014 8:13 pm

    I did buy the amp already modded and do not have the documentation. So, much thanks to everyone who offered info!

    Sponsored content

    Re: ST70 too bright...why?

    Post by Sponsored content Today at 9:49 am


      Current date/time is Tue Sep 27, 2016 9:49 am