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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

    Is it OK to bypass the Selenium like this?

    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Is it OK to bypass the Selenium like this?  Empty Is it OK to bypass the Selenium like this?

    Post by bubbasweet Wed Sep 08, 2021 1:29 pm

    Is it OK to bypass the Selenium like this on my MK3s? As opposed to removing it? It seems easier for me to do this than terminal strip thing. Any pro or con?

    THX

    Is it OK to bypass the Selenium like this?  Dsc_1110
    peterh
    peterh

    Posts : 1581
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Is it OK to bypass the Selenium like this?  Empty Re: Is it OK to bypass the Selenium like this?

    Post by peterh Wed Sep 08, 2021 2:13 pm

    The cap seems old.
    Using the Se as tiepoint may be ok, but i would recommend a kit with caps solder tag and diode. dynakitparts.com has it. You can continue to use the amp until the parts arrives.

    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Is it OK to bypass the Selenium like this?  Empty Re: Is it OK to bypass the Selenium like this?

    Post by bubbasweet Wed Sep 08, 2021 2:16 pm

    I did the cap was just asking about bypassing the selenium.. I read where when they fail they go high resistance so the diode bypassing is OK.

    That is my question. Is there a reason electronically why not to do this? Cap has been replaced THX..
    peterh
    peterh

    Posts : 1581
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Is it OK to bypass the Selenium like this?  Empty Re: Is it OK to bypass the Selenium like this?

    Post by peterh Wed Sep 08, 2021 2:29 pm

    bubbasweet wrote:I did the cap was just asking about bypassing the selenium.. I read where when they fail they go high resistance so the diode bypassing is OK.

    That is my question. Is there a reason electronically why not to do this? Cap has been replaced THX..
    Yes there is. A short in the Se, although very rare, will kill your bias. Eliminating a possible source of failure reduces risk of problems .
    In addition to adding the diode you most likely need to adjust the resistors to compensate for the reduced voltage loss. This to make the bias adjustment pot have a reasonable adjustment range.

    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Is it OK to bypass the Selenium like this?  Empty Re: Is it OK to bypass the Selenium like this?

    Post by bubbasweet Wed Sep 08, 2021 4:03 pm

    Pots and achieving Proper 1.56V range seemed not a problem with room to move even with the original 1K Resistor. I think I have a few Terminal strips and remove the selenium rectifiers.
    danielrhall
    danielrhall

    Posts : 4
    Join date : 2021-05-27
    Location : Raymond, NH USA

    Is it OK to bypass the Selenium like this?  Empty Use only one SR tab as a tie point

    Post by danielrhall Thu Sep 09, 2021 3:20 pm

    [Repeating my reply from the AK forum...]

    If you want to leave the selenium rectifier in place for nostalgic purposes, I'd have no qualms about using one of its tabs for a tie point (I did the same with my Dynaco ST-70) but I wouldn't use both tabs, especially the way that diode and SR are electrically in parallel.

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    Is it OK to bypass the Selenium like this?  Empty Re: Is it OK to bypass the Selenium like this?

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