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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


3 posters

    http://www.tubes4hifi.com/MK3.htm

    solderblob
    solderblob


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    Post by solderblob Wed Jun 30, 2021 10:11 pm

    Peter, here is the VTA MkIII.  No schematics.  http://www.tubes4hifi.com/MK3.htm
    peterh
    peterh


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    Post by peterh Thu Jul 01, 2021 1:10 am

    solderblob wrote:Peter, here is the VTA MkIII.  No schematics.  http://www.tubes4hifi.com/MK3.htm
    OK i finally understand, No Dynaco, no schematics, no help from me.
    Bob Latino
    Bob Latino
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    Post by Bob Latino Thu Jul 01, 2021 7:58 am

    Below is the original Dynaco Mark III schematic ..

    Bob


    http://www.tubes4hifi.com/MK3.htm Dynaco-Mark-III-schematic
    peterh
    peterh


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    Post by peterh Thu Jul 01, 2021 8:17 am

    What we need is the VTA MkIII schematics. Pictures show that power tube cathodes has separate sensing resistors and that 2 sense connectors is connected to the front panel.

    "no bias" at the sens connector indicated that no current flows. ( at least that is my guess that the author is measuring at the sens connector)
    Could be a screen stopper that has blown or some bad solders, or in worst case broken output transformer.
    Bob Latino
    Bob Latino
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    Post by Bob Latino Thu Jul 01, 2021 8:32 am

    peterh wrote:What we need is the VTA MkIII schematics. Pictures show that power tube cathodes has separate sensing resistors and that 2 sense connectors is connected to the front panel.

    "no bias" at the sens connector indicated that no current flows. ( at least that is my guess that the author is measuring at the sens connector)
    Could be a screen stopper that has blown or some bad solders, or in worst case broken output transformer.

    OK - I don't have a VTA Mark III schematic .. Maybe Email Roy Mottram directly about this.
    solderblob
    solderblob


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    Post by solderblob Fri Jul 02, 2021 9:22 am

    The MkIII works best if you install the tubes in the correct locations which I didn't do affraid .  A KT88 fits into the same socket as a 5AR4 and vice versa...Problem solved.
    peterh
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    Post by peterh Fri Jul 02, 2021 4:36 pm

    solderblob wrote:The MkIII works best if you install the tubes in the correct locations which I didn't do affraid .  A KT88 fits into the same socket as a 5AR4 and vice versa...Problem solved.
    Glad you found the problem !
    You must be a strong person that can admit mistakes ! We need more such persons !
    solderblob
    solderblob


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    Post by solderblob Fri Jul 02, 2021 5:08 pm

    Thanks for the help Bob and Peter.  Sorry about the confusion!

    BTW, Roy supplies a schematic for the mods with the kit.  Don't think he publishes it per se.

    Dave

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