So my Mesa TA-15 blew a tube and. .

Discussion in 'Amps and Cabs' started by Antiquo Cantor, Feb 4, 2015.

  1. Antiquo Cantor

    Antiquo Cantor Member

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    I called Mesa's customer service and described what was going on with my amp and he said he was almost positive it was a bad pre-amp tube and told me how to test them. I opened the chassis, replaced the V1 12ax7 and noticed that one of the power tubes was totally dark and the other one was pulsating with these weird flame-like flashes of light inside. So I pulled both of the EL84s and replaced them with some old Dutch ones that I got out of an old organ. This completely fixed it and the amp is working great. So now I have a few questions.

    Is it unusual for a power tube to go bad in a Mesa amp that is less than two years old? Could this be indicative of some other problem with the amp?

    Is it ok to leave these old EL84s in here for a while or do I need to get a set of Mesa EL84s in there? I don't know if these tubes are "matched", but if they are they were matched for an organ that took like 10 or so el84s. I previously had them in a Marshall using Yellowjackets for a couple of years and they worked great in that. :dunno

    I've read that Mesa amps are permanently biased so does that mean you have to use Mesa's tubes for optimal performance?

    And finally, who currently is making Mesa's tubes? Thanks! :D
     
  2. greenhilander

    greenhilander Member

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    I change my tubes every year. Use what ever Mesa recommends or take it to a tech. You don't have to use mesa brand tubes. Personally I would take swap those old tubes out ASAP.
     
  3. guitargod0dmw

    guitargod0dmw Member

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    It's not unusual for a tube to go bad. It's got nothing to do with it being a Mesa, just that they don't make tubes like they used to.

    IIRC, using non Mesa tubes does void the warranty. You may want to read the warranty to be sure on that, but the Mesa rep on another forum very recently posted that it will. I.E. get em' out ASAP if you want to keep the warranty.

    Mesa amps use a fixed bias. Any Mesa tube will drop right in. You can certainly use other tubes, but they would need to fall within that fixed range. Any tube dealer worth their salt should be able to hook you up with a set of tubes that works just fine with a Mesa.

    No idea who is making what. All I know is Shungang was their KT88 supplier last year when the Prodigy came out. There were a bunch of power tube failures and now they've switched to JJ.
     
  4. Antiquo Cantor

    Antiquo Cantor Member

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    Ok so could it really hurt the amp in any way keeping the old tubes in it?
     
  5. greenhilander

    greenhilander Member

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    You will void the warranty. Old tubes could blow quickly and take something else out with it.
     
  6. critter74

    critter74 Supporting Member

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    It's possible yes. If the tubes are not in the correct bias range it could pull too much power and ah minimum take it a fuse of at worst take out some of the power section. Which will not be covered in a warranty repair as others have stated.

    As for your question regarding the india tube failure- that is normal failure rate for EL-84's today. It has nothing to do with the amp itself and has to do with modern EL-84's made today not having a long shelf life (partially also because many amps are designed to push those tubes at the max of their abilities, shortening tube life).
     
  7. Antiquo Cantor

    Antiquo Cantor Member

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    Ok thanks, I'll go ahead and order a new set of Mesa EL84's.

    BTW, these old Dutch tubes sound fantastic in my TA-15. I suppose I could take it to an amp tech and have them scope these tubes to see if they are suitable for the bias on this amp, but it's probably not worth the hassle.

    Does anyone know if the color codes on Mesa tubes mean anything?
     
  8. JackStraw12

    JackStraw12 Supporting Member

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    Just for determining matched pairs/quads. No sonic difference whatsoever.
     
  9. guitarlifestyle

    guitarlifestyle I like guitars. Silver Supporting Member

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    I had a pre-amp tube go out on my Mesa TA-15 within two years as well. I replaced it with a Mesa-branded tube and all has been well since. I suspect the "they don't make them like they used to" argument is true here.
     
  10. ken374

    ken374 Member

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    The old tubes are better anyways! JJ makes a decent El84 over the stock ones
     
  11. omahaaudio

    omahaaudio Senior Member

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    Better than blowing a speaker.

    A motivational speaker...

    (credit: Doug Stanhope)
     
  12. Bobby Wasabi

    Bobby Wasabi Member

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    I use Mesa EL84's in both my Mesa's, but the 12AX7's are JJ's.
     
  13. Antiquo Cantor

    Antiquo Cantor Member

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    May I ask why you prefer JJ's for the pre-amp? Did you need to get any particular tubes spec-wise?
    When I was checking my pre-amp tubes I noticed someone had already replaced the V1 tube with a JJ. I was wondering if there was any special reason for that.
     
  14. ken374

    ken374 Member

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    JJ/Mesa pre's are the same kind of tubes! unless its a 803 long plate
     
  15. kbgear

    kbgear Member

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    Yes, Mesa's 12AX7s are re-labeled JJ ECC83s. Changing them to JJ-labeled ECC83s only really removes Mesa's extra quality screening.
     
  16. Steeltoe

    Steeltoe Member

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    Do you use the 5w setting a lot? This is what likely caused the uneven power tube wear, since the 5w setting turns one EL84 off. This happened to me on my ROV25. Now I don't use the low power setting.
     
  17. ken374

    ken374 Member

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    Bought a Mesa 12ax7 couple years ago and it blew within 30 sec! First time I had a tube fail that fast but it happens
     
  18. C-4

    C-4 Member

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    EL-84 tubes are known to blow more often then their larger counterparts.
     
  19. Antiquo Cantor

    Antiquo Cantor Member

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    Yes I use the 5w about 80% of the time because I live in a condo and I like the fast break-up. I'll have to keep it at 15 more and keep the master really low I guess.
     
  20. Sparky6string

    Sparky6string Member

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    Or maybe every now and again swap the two power tubes around so that they wear more evenly? I'm gonna try it with my TA-15 because these days I use my 5w setting a lot too.
     

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