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    pas power supply question

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    mrich

    Posts : 1
    Join date : 2017-06-07

    pas power supply question

    Post by mrich on Fri Sep 08, 2017 10:19 pm

    I have stock pas3 which i was thinking of refreshing the power supply with the tube nirvana power supply board. My intent is to get it running safely in stock form for now.

    I dont have any experience with preamps but i know i have had suprises with installing modern power caps in old amps in the past... arcing tubes and the addition of screen grid resistors come to mind.

    I dont like suprises so is there anything i should be aware of here installing a new PS but leaving the rest of the original components in place for the time being?

    Is this plug and play or is it alot more technical?

    Thanks
    Mike
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    j beede

    Posts : 412
    Join date : 2011-02-07
    Location : California

    Re: pas power supply question

    Post by j beede on Fri Sep 08, 2017 10:46 pm

    If all you are after is safe operation consider replacing the Selenium stack with 1N4007 and replace the electrolytics with modern Panasonic or Nichicon. You should be good for another 30-40 years.

    My favorite update to the PAS is the Dynakitparts RCA Jack Kit. When you re-wire replace the miserable stock input selector switch and replace the AWG22 bell wire with shielded cable grounded at the RCA jack end only
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    peterh

    Posts : 872
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: pas power supply question

    Post by peterh on Sat Sep 09, 2017 2:50 am

    mrich wrote:I have stock pas3 which i was thinking of refreshing the power supply with the tube nirvana power supply board. My intent is to get it running safely in stock form for now.

    I dont have any experience with preamps but i know i have had  suprises with installing modern power caps  in old amps in the past... arcing tubes and the addition of screen grid resistors come to mind.

    I dont like suprises so is there anything i should be aware of here installing a new PS but leaving the rest of the original components in place for the time being?

    Is this plug and play or is it alot more technical?

    Thanks
    Mike
    As you don't provide a link to which tube nirvana powersupply board i'll comment on one
    simular: https://www.tubular-well.se/index.php/webshop/reservdelar/dynaco-pas-psu-detail

    This one keeps the transformer and 12x4 but replaces can cap and all filament components.

    It's easy to install. I would recommend to make the ground connection on the top side
    of the chassies as this makes shorter cables that may be located close to the steel chassies.
    This is all you need for an unmolested PAS-3 ( no extra tubes).

    You could add a LED replacement for the pilote lamp, of not available at tubenirvana
    you can get it at dynakitparts, it save a lot of power for the tine mains transformer.
    avatar
    Peter W.

    Posts : 527
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: pas power supply question

    Post by Peter W. on Sat Sep 09, 2017 9:25 am

    http://www.quadesl.com/pdf/pas_capboard.pdf

    Is one option that I have used that eliminates the 12X4, and pretty much gets it all on one board. There are several iterations of this board available from several sources, so this is but one option.

    If you are going to mess with the power-supply (generally a good thing if....), then do what you can to reduce the load on the transformer. There is nothing magic about a tube rectifier in the PAS in any case.

    My revised P/S has been in place for just over one year now, and the pre-amp remains dead-silent as it should be. The OEM 12X4 is in the hands of another forum member - I have several, looking for another PAS in the future.

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