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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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    Quad Cap Question for ST-70

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    litefootdan


    Posts : 18
    Join date : 2014-03-21

    Quad Cap Question for ST-70 Empty Quad Cap Question for ST-70

    Post by litefootdan Wed Nov 16, 2022 7:17 pm

    Hi All,
    I'm hoping you guys may be able to help clarify something for me.  I have and ST-70 that I've decided to upgrade with the tubes4hifi "classic" board.  I thought it would be a nice time to replace the quad cap while I'm in there.  I removed the wires connected to the cap sections and labeled them accordingly to their sections.  Then I installed my new quad cap in the same orientation that the old one that was removed was.  I re-soldered the wires and thought everything was dandy.  I had printed the wiring diagram from the tubes4hifi site so that I could remove the 6.8k and 22k resistors and add the appropriate resistor between tabs 3 and 4.  Everything looked peachy until I noticed the picture of the orientation of the quad cap on the website.  The can orientation on my amp has the "square" facing the PCB, while the can orientation of the quad cap on the website pic has the "triangle" facing the PCB.  My question is how bad an error have I made.  Do I need to rewire everything.  I sure hope you guys can help me sort this out.  Thanks in advance for any help offered.
    Dan
    I'm sorry, I thought I could insert an image but I don't have any images on the web for me to insert a url....    If anyone wants to have a look at what I've done to my mess of an amp I could text pictures....
    Roy Mottram
    Roy Mottram
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    Posts : 1837
    Join date : 2008-11-30

    Quad Cap Question for ST-70 Empty Re: Quad Cap Question for ST-70

    Post by Roy Mottram Tue Nov 22, 2022 2:40 pm

    with the upgraded quad cap the triangle should face the PCB.
    The upgraded quad cap has an 80uF section that must NOT be connected directed to the rectifier tube.
    Diagram below is supplied with every quad cap that I send out . . . .

    http://www.tubes4hifi.com/80-40-30-20quadST70.jpg
    Quad Cap Question for ST-70 80-40-30-20quadST70

    litefootdan and Tubes4ever like this post

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    litefootdan


    Posts : 18
    Join date : 2014-03-21

    Quad Cap Question for ST-70 Empty Re: Quad Cap Question for ST-70

    Post by litefootdan Wed Nov 30, 2022 3:32 pm

    Thank you very much for your response!!  I was a buffoon and had only slid the quad cap out of the protective bubble wrap that it had been shipped in.  I hadn't noticed the diagram that was included just as you stated.  

    I did re-orient the quad cap on my chassis. I followed the picture located on the website.  The one that is titled "ST-70 internal wiring show with optional stepped attenuator".  There is also a link to a wiring diagram for the VTA amp located just above that picture.  

    The picture and the diagram would suggest that the 2200 resistor be soldered between tabs 3 and 4 of the quad cap.  This differs from the diagram provided with the quad cap.  

    Also, the picture on the website and the diagram on the website would suggest that tabs 1 and 4 of the quad cap be bridged together rather than how it is stated on the diagram that is sent with the quad cap upgrade.  The diagram sent with the quad cap suggests that tabs 1 and 3 be bridged.

    Perhaps I am making this more complicated than it has to be, I'm just cautious.  I know I just want the project to be as correct as possible.  

    Here is a link to the wiring diagram I am referring to
    http://www.tubes4hifi.com/VTA70wiringdiagram3.jpg

    This is how I have things set up.  Perhaps because I am modifying an existing Dynaco ST-70 I need to go back and follow the diagram that you have sent with the Quad cap upgrade.  (the one seen above in your response post)  

    I really appreciate all the help and am thankful for our attention.  So close to having this project done and can't wait to hear how good the results will sound.  

    Thanks again,

    Dan

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