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Thread: Valve trouble question

  1. #1
    Join Date: Aug 2012

    Location: Great Yarmouth

    Posts: 82
    I'm Tim.

    Default Valve trouble question

    Hi all, I have a question about output/power valves, if my output valves still hold bias voltage steady with plenty of gain left on the pot's does that mean that my valves are still good ?, The reason I ask is because I'm getting a difference in sound from the left channel with the sound going dull in the highs then rising back up to where it should be and I don't know if it's time to re-valve, I'm a little reluctant to buy more valves as I have only had the valves about 4 years .
    Forgot to say that all the valves in the amp look just fine with no visible blue gases
    Any suggestions would be greatly received
    Many thanks in advance
    Tim

  2. #2
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 13,669
    I'm inthescottishmafia.

    Default

    Not necessarily. Swap the output valves to the other channel, see if the problem with the sound follows the valves.

    4 years in what I'm assuming is a PP amp could easily mean they need replaced, that's a fair amount of hours.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  3. #3
    Join Date: Aug 2012

    Location: Great Yarmouth

    Posts: 82
    I'm Tim.

    Default

    Cool,thanks for your help Ali i'll give that a try and see what happens mate.

  4. #4
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

    Default

    A good suggestion from Ali

    If you valves are holding their bias steadily and the gain is as was I would hazard a guess that they are OK.


  5. #5
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 13,669
    I'm inthescottishmafia.

    Default

    No worries, let us know how you get on.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  6. #6
    Join Date: Jan 2017

    Location: Kansas City, Missouri

    Posts: 590
    I'm Nathan.

    Default

    4 years is a pretty good lifespan for valves in an amp that gets regular use.

  7. #7
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,853
    I'm openingabottleofwine.

    Default

    The typical lifetime for an audio power valve is 10,000 hours (though some may have lifetimes exceeding 50,000 hours).

    Assuming you use your amplifier for 5 hours a day, the valves should last at least 5 years. Overbiasing the valves can shorten the life.

    Some enthusiasts replace the valves once a year as a matter of course.
    Barry

  8. #8
    Join Date: Jan 2017

    Location: Kansas City, Missouri

    Posts: 590
    I'm Nathan.

    Default

    I tend to like them under-biased in push-pull. That's probably even worse for them.

  9. #9
    Join Date: Aug 2012

    Location: Great Yarmouth

    Posts: 82
    I'm Tim.

    Default

    Hi All, Thanks for all your advice but I think I must have had a loose or dirty connection Because I swapped the valves around and put them back to were they came from now I don't hear any problems at all.
    So thanks again
    All the best
    Tim

  10. #10
    Join Date: Feb 2008

    Location: Near Accrington, Lancs, UK

    Posts: 307
    I'm Ralph.

    Default

    I do think some of us change valves more often than is necessary. This may be borne out of the desire to do some "tube rolling" but personally I find it unnecessary. I've only ever replaced one set of valves due to ageing in twenty years of ownership of valve equipment and that was more because the amp was second hand and full of cheap unbranded Chinese valves. I usually give my kit a check over once a year, giving the thing a hoover out, cleaning the valve pins and holders and rebiasing where necessary. I'm fortunate that I have a rudimentary valve tester but I only use it when I feel there's something not sounding quite right and some further investigation is required. Apart from that I just get on with the business of listening to the music
    Ralph.

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