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    PAS-3 problem, hum and smells like burning

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    lobby

    Posts : 18
    Join date : 2011-02-15

    PAS-3 problem, hum and smells like burning

    Post by lobby on Fri Nov 06, 2015 3:33 am

    This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud. Switching the input selector did not make the problem go away. Even with the volume down all the way it was still making a loud buzz. I turned the unit off and noticed a smell of burning. I opened up the unit and cannot find any signs of damage. Where should I start troubleshooting?

    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: PAS-3 problem, hum and smells like burning

    Post by peterh on Fri Nov 06, 2015 3:57 am

    lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud.  Switching the input selector did not make the problem go away.  Even with the volume down all the way it was still making a loud buzz.  I turned the unit off and noticed a smell of burning.  I opened up the unit and cannot find any signs of damage.  Where should I start troubleshooting?
    power supply, including filtering caps, selenium diodes etc.

    A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
    http://www.tubenirvana.net/pas3-power-supplies.html
    That would eliminate all of the above components and keep your power for the next decade.

    It could however be that case that your power transformer is bad ( they do stink). You still want to
    replace the above and then consult :
    http://www.triodeelectronics.com/pa2powtrandy.html
    and buy a pa211 ( or pa522 ) to replace the broken one.


    Last edited by peterh on Fri Nov 06, 2015 3:58 am; edited 1 time in total (Reason for editing : spelling)

    lobby

    Posts : 18
    Join date : 2011-02-15

    Re: PAS-3 problem, hum and smells like burning

    Post by lobby on Fri Nov 06, 2015 3:59 am

    peterh wrote:
    lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud.  Switching the input selector did not make the problem go away.  Even with the volume down all the way it was still making a loud buzz.  I turned the unit off and noticed a smell of burning.  I opened up the unit and cannot find any signs of damage.  Where should I start troubleshooting?
    power supply, including filtering caps, selenium diodes etc.

    A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
    http://www.tubenirvana.net/pas3-power-supplies.html
    That would eliminate all of the above components and keep your power for the next decade.

    It could however be that case that your power transformer is bad ( they do stink). You still want to
    replace the above and then consult :
    http://www.triodeelectronics.com/pa2powtrandy.html
    and buy a pa211 ( or pa521 ) to replace the broken one.




    I already did the Z-Mod PAS3 Power Supply Upgrade kit probably about 5 years ago. The transformer seemed kinda hot to the touch, but then again, i dont know how hot it normally gets under operation.

    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: PAS-3 problem, hum and smells like burning

    Post by peterh on Fri Nov 06, 2015 7:21 am

    lobby wrote:
    peterh wrote:
    lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud.  Switching the input selector did not make the problem go away.  Even with the volume down all the way it was still making a loud buzz.  I turned the unit off and noticed a smell of burning.  I opened up the unit and cannot find any signs of damage.  Where should I start troubleshooting?
    power supply, including filtering caps, selenium diodes etc.

    A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
    http://www.tubenirvana.net/pas3-power-supplies.html
    That would eliminate all of the above components and keep your power for the next decade.

    It could however be that case that your power transformer is bad ( they do stink). You still want to
    replace the above and then consult :
    http://www.triodeelectronics.com/pa2powtrandy.html
    and buy a pa211 ( or pa521 ) to replace the broken one.




    I already did the Z-Mod PAS3 Power Supply Upgrade kit probably about 5 years ago.  The transformer seemed kinda hot to the touch, but then again, i dont know how hot it normally gets under operation.
    the transformer is not (very) hot .
    check the voltages on the power supply , they should coincidence with the pas3 manual. If any
    discrepancies you might have found your problem. ( or if both B+ and DC filament is low it hints
    to the transformer)




    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: PAS-3 problem, hum and smells like burning

    Post by PeterCapo on Fri Nov 06, 2015 10:42 am

    lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud.  Switching the input selector did not make the problem go away.  Even with the volume down all the way it was still making a loud buzz.  I turned the unit off and noticed a smell of burning.  I opened up the unit and cannot find any signs of damage.  Where should I start troubleshooting?

    Close the front door  Very Happy

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