How do you know when tubes go bad?

Discussion in 'Amps and Cabs' started by AstroStrat89, Oct 6, 2008.

  1. AstroStrat89

    AstroStrat89 Member

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    When they mug the output transformer of course.

    But seriously, other then total failure how do you judge? I just got my Pro Junior back from warranty work. And he stated all 4 power tubes I had were bad. I gave them the original GTs and some JJ’s I just got a few months ago. I really don’t think the guy was just trying to sell me tubes, he didn’t really push the issue after telling me they were bad.

    I am guessing a lot of us don’t have a tube testing device around, so what do you look or listen for?

    I’ve heard some great things about JJ’s and so I picked some up, but now they are bad already? I remember when I first got them they sounded pretty good, not a whole lot different then the originals. I know they get knock around a bit, but thinking of getting new GTs just to be on the safe side.

    I have to state the amp sounded like crap before I brought it in with the JJ’s in it and I have not had a chance to try it out since I got it back today. I’ll have to swap some tubes around when I get time with some tested old RCAs I have.
     
  2. FrankieSixxxgun

    FrankieSixxxgun Member

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    I usually replace mine when they go microphonic or when I can notice my tone get muddy. What kind of tubes are we talking about and in what amp? Cathode biased EL84 amps chew up power tubes pretty quickly.
     
  3. hathisisfunnyha

    hathisisfunnyha Member

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    when the amp goes from sounding pristine to gassy, like after a chili burger
     
  4. Flux

    Flux Member

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    Many people have a set of 'known good' tubes in reserve. If the old tubes sounds noticeably dull in comparison, then it may be time to replace them.
     
  5. HurricaneJesus

    HurricaneJesus Member

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    Well, if your amp still makes sound then your rectifier is good. When power tubes go south you lose volume, I think, and when preamp tubes die out you get less headroom. That's my understanding, at least.
     
  6. Adwex

    Adwex Member

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    When I first fired up my Marshall Jubilee I got from ebay, it was making a horrible ...... HORRIBLE buzz/hum sound....no guitar at all, just this loud hum that got louder as the master volume went up.
    After I replaced V2, all was well.
     
  7. Shine

    Shine Member

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    When you come home and your liquors gone and your girlfriend is knocked up.
     
  8. soldano16

    soldano16 Member

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    Volume falling off/fading is one sign.
     

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