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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

    457
    Apr 10, 2014
    WellingtonNZ
    The 6L6GC tubes in my amp died last night after 18 months of light to moderate use. I was hoping for longer! What is reasonable operating life for this type of power tubes? I’m using Mesa branded tubes.
     

  2. JD0x0

    JD0x0 Friend of Leo's

    Age:
    27
    Feb 22, 2009
    New York
    Depends how they're being run. Fixed biased? Cathode biased? Plate Voltage? Plate current? Huge variables.
     

  3. xafinity

    xafinity Friend of Leo's Silver Supporter

    Dec 24, 2015
    my Mom's basement
    2 tubes died at exactly the same time? I think you have other problems
     

  4. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

    Jan 2, 2007
    Virginia, USA
    I had a quartet of Mesa 6l6GCs last me about 15 years in a Mk IV. They still sounded great when I sold it. I wasn't pushing it too hard very often...

    I have some JAN Sylvania 6lGCs that came in my Twin. They're from the early 70's and still work fine. I have a pair of GT 5881's that came in my Bassman Ri... I think they're from the 90's. They still sound great.

    I agee with @xafinity, if both tubes really are faulty and went at the same time, I'd be a tad concerned. Are you sure it's both and not just one?
     
    thegeezer, Jakedog and noah330 like this.

  5. kafka

    kafka Tele-Meister

    336
    Oct 18, 2013
    Maryland
    A pair of 6L6GC's can easily last for decades. I've had many pairs that lasted 25+ years.
     
    thegeezer, Ripradiant and homesick345 like this.

  6. Jakeboy

    Jakeboy Tele-Afflicted

    Jul 26, 2008
    Sedalia, MO
    Lol my Blonde Bassman 6g6b is using Tung Sol 5881s from the late 50s/early 60s that had been used for decades prior to going I to my amp, where they still sound incredibly glorious.

    Something with your amp or tubes is awry.....
     
    thegeezer likes this.

  7. telemnemonics

    telemnemonics Poster Extraordinaire

    Age:
    58
    Mar 2, 2010
    Maine
    Sounds like maybe the Sylvania STR 415 "special tube request" made for Mesa and fender in huge numbers during the '80s.
    Supremely robust and powerful tubes.
    JAN Sylvanias were also built to run long hours in harsh conditions.
    The 5881s are probably the early Sovtek which were a pretty sturdy tube, though not on par with the other sets you mention.

    Given that tube manufacturing requires continuous large scale production to be profitable, the tube makes of today have little reason to make them last for decades.

    There are lots of "STR" tubes in Mesa Fender and other amps today, but special tube request doesn't bring them up to the level tubes were at when the military still used them and lives depended on their reliability.
     
    Axis29 likes this.

  8. radiocaster

    radiocaster Friend of Leo's

    Aug 18, 2015
    europe
    It might depend on your definition of moderate use. Do you mean one hour daily or two hours weekly?
     

  9. radiocaster

    radiocaster Friend of Leo's

    Aug 18, 2015
    europe
    :mad:I hate double posting...:mad:
     

  10. Southpole

    Southpole Tele-Meister

    457
    Apr 10, 2014
    WellingtonNZ
    Varies a bit but on average just a few hours a week. These are STR 440s.

    This is F50 amp and is not driven hard. Clean channel only, drive from pedal board. Fixed bias, cathode biased etc.

    I don’t actually know if it is one or both tubes just assumed I would need to replace with matched pair regardless. But I will take a closer look.

    I have two other Mesa amps that are both 6 years old and still have the original tubes.

    Assumed it was a tube problem but it might be time to get the F50 serviced!
     

  11. bigben55

    bigben55 Friend of Leo's

    May 19, 2010
    Cincinnati, OH
    How did they die? Describe the death.

    What tubes are/were they? New or NOS?

    FWIW, I used to use Tung Sol ri 6V6s in a Z28, and I pushed it hard. 12-18 months was about average replacement time. They would start to not give up the clean tone sparkle, they'd "sound tired." But they never failed.
     
    hrstrat57 likes this.

  12. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

    Jan 2, 2007
    Virginia, USA
    It is better practice to replace both with a matched pair... But, I've seen only one replaced.

    I am relieved that you aren't sure if it's both. Certainly if it's just one, your amp would probably go silent.
     

  13. Southpole

    Southpole Tele-Meister

    457
    Apr 10, 2014
    WellingtonNZ
    Amp fired up ok at start of practice but within 15 mins I could tell I was losing power. Also my clean sound had disappeared and it had a low grade drive sound (clean channel) even with gain set really low. I did my best to compensate but it was sounding pretty dire. After 45 mins output minimal and lots of heavy static sounds so turned it off.

    I have some new Mesa 6L6GCs and so I will swap them out tomorrow and run the amp for a couple of hours to settle them in. Hopefully that will fix it for now.

    But as previous posters have said, short tube life is a bit of a worry. Mind you, the long running Mesa tubes I have are 12AX7s and EL84s. None of the 6L6GCs have lasted for long periods of time (over 3 years etc) I’ve had The amp since 04.

    Whatever happened to the new US made 6L6GCs that were back on the market a few years back? Mesa Gold label or something.
     

  14. uriah1

    uriah1 Doctor of Teleocity Silver Supporter

    Feb 12, 2011
    Around
    I seem to remember an old Mullard or Telefunken vintage ad that hours listed for tubes (11,000 preamp, 7,000 el84, 5000 6l6,EL34,etc,etc)
     

  15. bigben55

    bigben55 Friend of Leo's

    May 19, 2010
    Cincinnati, OH
    I'd take it to a tech for this retube. Dunno if your amp is fixed bias(tech) or cathode bias(plug and play). He could retube it, fire it up, and test stuff based on tgat "tube death description."

    I wasn't aware of recent USA made tubes. NOS tubes will last longer but cost more. My take on tubes is, use NOS preamp tubes, NOS power tubes if you can swing it or score a deal. If not, and you're happy with the tone of new production tubes, I buy a matched quad for fixed bias amps. You can usually get 4 new ones for the price of 2 NOS.
     

  16. homesick345

    homesick345 Poster Extraordinaire

    Jan 20, 2012
    Beirut, Lebanon
    RCA? GE? Pretty much forever
     
    dr_tom likes this.

  17. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Ime and imho, whenever an amp’s sonics change....even if the amp starts to sound fantastic compared to just good...the player needs to immediately take a look at the power tubes. If there is any redplating, shut the amp down. If no tubes are redplating, there is something wrong in the Biasing or power supply. If only one Tube is redplating, then there is a problem with that tube or the circuit associated with that tube. If there is no redplating, then a ‘ touch’ test can be done.....shade tree mechanic kind of thing. One should be able to touch a power tube for part of a second without any severe burning. If one tube is cooler than the other tube/s, then that tube is not conducting current and the sonics will suffer.
    In any case, it is not advisable to continue to play the amp....more severe damage can be done. In your case, Southpole,
    I would advise you NOT to retune and fire that amp up. IMHO, it is tech time. A tech will pull that chassis and survey the situation before installing tubes and firing the amp up. Again....continued operation or ill-advised ‘testing’ with other tubes may lead to more severe damage...and expense. My fingers are crossed for the well-being of the transformers in that amp.
     
    Last edited: Nov 7, 2017

  18. Southpole

    Southpole Tele-Meister

    457
    Apr 10, 2014
    WellingtonNZ
    Thanks for detailed advice! Not easy finding a good tech where I live but probably long overdue.
     
    Wally likes this.

  19. Middleman

    Middleman Friend of Leo's

    Aug 29, 2007
    MV, CA
    I had a pair of RCAs in my 81 vibrolux for 30 years. Changed them out 6 years ago because the amp just was getting a bit lifeless. They still worked however.
     

  20. Ripradiant

    Ripradiant Tele-Holic

    876
    Jul 31, 2014
    Alberta Canada

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