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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


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    Value of B+ on 12at7 Mark3 board?

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    garyb


    Posts : 3
    Join date : 2011-01-06
    Location : Iowa

    Value of B+ on 12at7 Mark3 board? Empty Value of B+ on 12at7 Mark3 board?

    Post by garyb Tue Jan 18, 2011 12:24 pm

    Hi, what should the value of B+ on VTA 12at7 Mark3 board be?
    Thanks
    Gary
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    quad44


    Posts : 21
    Join date : 2009-06-08

    Value of B+ on 12at7 Mark3 board? Empty Re: Value of B+ on 12at7 Mark3 board?

    Post by quad44 Tue Jan 18, 2011 1:35 pm

    The documented value for B+ for the VTA MK3 board is +400VDC. This is the value of the voltage from the power supply.
    The plate voltage for the first 12AT7 is 150VDC and 300VDC for the phase inverter(second 12AT7).
    Hope this helps.
    Bob Latino
    Bob Latino
    Admin


    Posts : 3260
    Join date : 2008-11-26
    Location : Massachusetts

    Value of B+ on 12at7 Mark3 board? Empty Re: Value of B+ on 12at7 Mark3 board?

    Post by Bob Latino Tue Jan 18, 2011 3:26 pm

    On the Mark III with a VTA driver board anything between about 400 VDC to maybe 430 VDC is normal for the B+ line coming into the driver board at the driver board's "B+" eyelet. Solid state rectifiers and/or a higher incoming AC line voltage will give a B+ near the upper end of this range.

    Bob
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    garyb


    Posts : 3
    Join date : 2011-01-06
    Location : Iowa

    Value of B+ on 12at7 Mark3 board? Empty Thanks for your responses

    Post by garyb Wed Jan 19, 2011 3:09 am

    Hi, just wanted to say thanks for your help. The Mark 3 twins have been up and running for a couple of hours and I really like the result. I've had a ST 70 with the VTA high gain board for several months and I was so impressed the twins got the same treatment.
    Many thanks
    Gary

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    Value of B+ on 12at7 Mark3 board? Empty Re: Value of B+ on 12at7 Mark3 board?

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