how to tell when power tubes need replacing?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by bolero, Oct 10, 2004.


  1. bolero

    bolero Member

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    ?


    is it worthwhile to pick up some kind of old tube tester, to check them on once in a while?


    if you just leave them in the amp for years & years, what happens? do they burn out?

    how does the sound degrade as they kack out? ie: over a 6-8month peroid, if they gradually die, how do you know?

    thx
     
  2. RevolutionMan

    RevolutionMan Member

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    A tube tester is not a bad thing, but ultimately an amp is the best tube tester. I've had some tubes that tested average to poor end up sounding great in an amp and lasting a good long time. Also, I've had some new tubes that tested great end up not lasting that long and not having the best tone. Every circuit/tube relationship is different I guess, so I'd say just go by what your ears tell you.

    I've got a few amps that I end up retubing every 6 months or so with regular to heavy use, but I've also got a few old fenders that still have the original tubes and sound great, so I don't retube them as they just don't need it.

    The hard part is that many times the tubes go weak so gradually, that it's easy to just get used to the lesser tone. So every once in awhile instead of just playing through the amp, really give it an objective listen, then decide if the tubes are not sounding up to par.

    Of course you'll always have that time where one just goes out on you, so backups are a necessity. Just my 2 cents.
     
  3. theelectic

    theelectic Guest

    Excessive noise that isn't cured by replacing other tubes (had this one happen to me twice), crappy bass response, general feeling of "damn, this amp doesn't sound like it did new". I can always tell when my amps need a re-tubing, once you've played new tubes it feels "right". Trust your ears! As a runner I always get asked "when should I buy new running shoes?" my reply is always "listen to your feet!" - heel/ankle is sore like it shouldn't be, and the shoes are old? Get new ones.

    What RvolutionMan man said WRT backups is a good idea. If you don't play with expensive NOS tubes (or you can afford it) it's good to have a new, bias matched set as a backup. Think the tubes are getting old? Plug the "new" backup set in for a listen.
     
  4. bolero

    bolero Member

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    thx


    I have an old SFBF twin reverb I'm not liking much lately....got new power tubes a few years ago, but if they're dead I'm surprised, I don't use it much.

    wondering about retubing it, vs. having a look at changing the circuit a bit, or maybe both?


    not in a real rush, just thinkng about different options....I suppose I could sell it & try to find something else?

    but it sure is nice to have all that power + reverb & vibrato in one amp.
     
  5. Shawn Lutz

    Shawn Lutz Member

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    I just use my ears. of the tone starts sounding a little weaker, muddier or I have to turn up the amps volume louder than I normally have to they usualy are due for a change. Its not so much 6-8 months its the hours of use, so if you use it a lot you'll need to change them sooner than if you don't.
     

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