The Dynaco Tube Audio Forum

Would you like to react to this message? Create an account in a few clicks or log in to continue.
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

    PAS 3 Diode Test

    Bugs
    avatar
    Bugs


    Posts : 90
    Join date : 2009-04-17
    • Post n°1

    PAS 3 Diode Test Empty PAS 3 Diode Test

    Post by Bugs Mon Sep 26, 2011 3:48 pm

    Hi All,

    How do I test the diode in my PAS 3 to tell if it is blown? It's been awhile since I looked at this unit, but IIRC I burnt through a couple of rectifier tubes and thought it might be the diode. Maybe the question shoulb be what would cause a PAS 3 rectifer tube to go out?

    Thanks
    • Back to top
    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3262
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    PAS 3 Diode Test Empty Re: PAS 3 Diode Test

    Post by Bob Latino Mon Sep 26, 2011 6:42 pm

    To test a diode place your multimeter on the highest resistance setting. This is usually 20 megohms on most multimeters. Place the black (negative) probe of your multimeter on the banded end of the diode and the red (positive) probe on the other end of the diode. You should get a very high resistance - maybe 8 or 10 megohms. Next reverse the leads on your multimeter. With the red probe on the banded end and the black probe on the other end you should get no continuity across a good diode.

    Bob
    • Back to top
    Roy Mottram
    Roy Mottram
    Roy Mottram
    Admin


    Posts : 1839
    Join date : 2008-11-30
    • Post n°3

    PAS 3 Diode Test Empty Re: PAS 3 Diode Test

    Post by Roy Mottram Mon Sep 26, 2011 10:05 pm

    I believe the question is actually how to test the 12X4 rectifier tube.
    That is more difficult, unless you have a variac.
    The 12X4 is probably the most reliable component in the PAS3.
    I've never in 30 years seen one go bad, so I think probably the only thing that would cause it
    to go bad, is a bad or shorted quad capacitor, or bad or shorted filament supply.
    I would replace the quad capacitor with a new one (about $40), or much better, with a new power supply board (about $50),
    that replaces both the quad cap and the dual filament supply capacitors and diode rectifier with one all-in-one solution.
    http://tubes4hifi.com/PAS3-CAT.htm

    PAS 3 Diode Test Z-PS
    • Back to top
    Sponsored content

    Sponsored content


    • Post n°4

    PAS 3 Diode Test Empty Re: PAS 3 Diode Test

    Post by Sponsored content

    • Back to top
      Current date/time is Fri Apr 19, 2024 7:57 am