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Life span of 6L6GC tubes

Discussion in 'Amp Central Station' started by Southpole, Nov 6, 2017.

  1. Southpole

    Southpole Tele-Meister

    459
    Apr 10, 2014
    WellingtonNZ
    I’m old enough to remember when all TVs were full of tubes which seemed to last for decades. Can’t recall anyone ever saying “Oh, I need to get my TV re-tubed” !
     

  2. Mutato

    Mutato Tele-Meister

    350
    Sep 16, 2008
    Rhode Island
    My '77 Princeton Reverb still has its rca power tubes.
     
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  3. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    South Pole, there are some differences between tv’s and audio equipment, imho. Experienced and discerning ears know when tubes that function but have lost the ability to yield good sonics have past their prime. So...Ime...’lasting’ is different than sounding good. Conducting current is not the only measure of the usefulness of a tube in an audio circuit.
    That said....your tubes lived a short life...for some reason.
     
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  4. Old Tele man

    Old Tele man Tele-Afflicted

    May 10, 2017
    Tucson, AZ
    GOOD tubes last quite a while...BAD tubes don't.
     
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  5. kafka

    kafka Tele-Meister

    346
    Oct 18, 2013
    Maryland
    RCA definitely. I took one out of a 45 yo Champ amp a few years ago. Tried some other tubes, put it back in. GE's, are great, too. Sylvania. Now they used to know how to make a tube.
     

  6. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    IMO ALL of these are correct.

    Power tube life can't be arbitrarily predicted. There are FAR too many variables.

    NEWER tubes generally do not have nearly the tube life of NOS tubes. I also commonly find BF - even tweed - amps with perfectly good original tubes.

    But is TWO power tubes went bad at the same time after 18 month IMO the amp is either biased far too hot or there are other issues.

    And in TV's and stereos one reason tubes last so long is that the plate voltages are generally FAR lower.
     
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  7. Southpole

    Southpole Tele-Meister

    459
    Apr 10, 2014
    WellingtonNZ
    Bear with me, I’m not an amp expert. Mesa amps are fixed bias and Mesa tubes are designed for this. So something may have gone wrong that has pushed the ‘fixed’ bias too hot? That is sounding like a transformer issue. !&$@$!
     

  8. radiocaster

    radiocaster Friend of Leo's

    Aug 18, 2015
    europe
    Mesa does not use an adjustable bias in their amps, like the Fender Bassman or whatever.

    Instead, they grade their tubes and you have to use the same grade recommended for that amp.
     
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  9. Southpole

    Southpole Tele-Meister

    459
    Apr 10, 2014
    WellingtonNZ

  10. dr_tom

    dr_tom Tele-Meister

    289
    Sep 21, 2013
    Ontario
    My Twin has has RCA 6L6 GC's running since I bought it 20 years ago. Still sounds amazing. I don't think you can go wrong with quality NOS tubes from a reputable vendor.
     
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  11. Southpole

    Southpole Tele-Meister

    459
    Apr 10, 2014
    WellingtonNZ
    Do you ever have to get your amp re-biased? I’m also wondering if you can use just any NOS tubes in a fixed bias amp. Especially a modern tube amp like a Mesa that is probably running hotter than classic Fenders.
     

  12. Dacious

    Dacious Friend of Leo's

    Mar 16, 2003
    Godzone
    Short answer - not safely. Mesa grades it's tubes so that you can plug fresh sets in and the amp will function. But any other matched tubes may still vary in current draw and you may end up with tubes that are outside the parameters Mesa sets it's amps to. That could cause a redplating situation if they pull too much current, or the amp may run the tubes way too cool resulting in less than stellar tone or even blocking distortion which most people think is ugly.

    A lot of NOS tubes sold today are probably yesterday's rejects. With an amp that's adjustable you can make almost any tubes work although you have to watch grid dissipation.

    The other day I was working on my bandmate's HRDx. One of the original GTs had gone bad. It sounded dull and bias was all wrong.

    I tried low mileage Ruby's, a set of new Svetlanas and a set of well-used Sovtek WXT+ before I found a set which biased up to 70mv at the test point or 32ma per tube at 410 volts measured on my probe.

    The other tubes, the adjustable bias pot range only went to 50 and 60ma and at that the tubes would live forever but sounded bland. The WXT+s biased warmish, the amp opened up, sparkled, warmed up, and even reverb sounded better. All three sets the bias match in the amp was good. They were all 6L6s.
     
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  13. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Re: Mesa amps and adjustment...... there are a few very early MKI Boogies that have OEM bias adjustment re is one such amp here. This amp was ordered when Randall Smithh’s Wife was taking orders over the phone and the amps were built in the home garage...$500 was the cost of that one...fully equipped with reverb and Graphi EQ.
     

  14. bigben55

    bigben55 Friend of Leo's

    May 19, 2010
    Cincinnati, OH
    Question...the universally agreed upon best new production 6L6s are the older Winged =C= tubes. No longer made(by the same company) these seem to fetch NOS prices. 1. Are they "as good " as some of the USA NOS tubes and what I REALLY am curious about is, 2) do they LAST as long as USA NOS tubes?
     

  15. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    One might surmise that they have not been around long enough to prove that they can last as long as Old productions tubes??? I do agree that they are the best sounding new production tubes I have used.
     
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  16. Rick330man

    Rick330man Tele-Meister

    398
    Jan 9, 2011
    Florida Keys
    My JAN Philips 6L6WGBs in my Hot Rod Deluxe were manufactured in the 1980s and have been running in my amp over 10 years.
     

  17. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    Many Mesa owners have an unintentional misconception about the term "fixed bias".

    "Fixed" is an electronic term for one of two types of bias circuits ("fixed bias" vs "cathode bias"). It does NOT mean "non-adjustable". In fact it means precisely the opposite. There may not be an "adjustment pot" in your Mesa - but that's only because Mesa sells tubes with their own brand stamp that are "graded" - and tell you if you buy the same number tubes you do not need to have the amp's bias checked or adjusted.

    Horse pucky. :lol:

    First - Mesa tubes are the same imported tubes sold under some other brand names. They do not make tubes. They test them the same way manufacturers do their "tube Town" is not functionally different form any other testing system. But as a proprietary testing/labeling/sales system you are stuck with whatever they want to sell you - unless you learn a bit about amp biasing and tubes.

    I have found their numbered tubes still vary enough that it's smart to have the bias setting at least checked - a very simple, quick job for a qualified tech. And in quite a few cases a slight adjustment can make a significant improvement in the amp's tone. The adjustment can be made by nothing more than resistor swapping, or a pot can be installed to make the bias permanently adjustable.

    Then you can use ANY matched set of tubes you want - ANY brand. Save money buying non-Mesa tubes, or really improve things with longer-lasting and better sounding NOS (new old stock) tubes!

    Bias is a complicated subject, but it has to do with the "idle" point of the amp - which can make a huge difference in the overall tone. It's set by reading the plate voltage and the bias setting and 1) ensuring the setting is in a "safe" zone for the tubes and the amp, and 2) adjusting by ear for the best tone.

    You only need to follow Mesa's extremely arbitrary and VERY proprietary method of "forcing" you to use Mesa tubes if 1) the amp is still under warranty or 2) you want to take the easy way out. But with very minor effort - like finding a good tech and spending a small amount of money - you can have the amp tweaked to your liking and use any compatible power tubes you want.
     
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  18. Southpole

    Southpole Tele-Meister

    459
    Apr 10, 2014
    WellingtonNZ
    Thanks, really helpful.
     

  19. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Ime, I have never installed a set of non-Mesa tubes in a Mesa amp that 1)did not operate at a safe plate dissipation and 2) did not operate at a warmer...higher plate dissipation point...than did the Mesa tubes I took out of the amp. I remember one MK amp that was dissipating at 32% of max plate dissipation with the Mesa tubes. With a set of non-Mesa tubes, the bias warmed up to near 50%. The amp sounded much better at the higher current draw point.
    Boogies with fixed bias are biased to the cold side of things, ime....and that might account for some people not liking what they do. Of course, the tubes last a long time at those lower plate dissipation points.
     
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