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    PAS 3 Diode Test



    Posts : 91
    Join date : 2009-04-17

    PAS 3 Diode Test

    Post by Bugs on 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?


    Bob Latino

    Posts : 2382
    Join date : 2008-11-26
    Location : Massachusetts

    Re: PAS 3 Diode Test

    Post by Bob Latino on 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.



    Posts : 1268
    Join date : 2008-11-30

    Re: PAS 3 Diode Test

    Post by tubes4hifi on 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.

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