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tubes are on fire!!!!!!!!!!!!

Discussion in 'Amps and Cabs [BG]' started by thirdeye, Jul 7, 2002.

  1. I bought a Mesa 400+ 2 weeks ago,first week I jammed with my band,fuses kept blowing,I had to resort to my old amp to finish the practice.

    2nd jam with it today,got new fuses and a surge protector,that fuse blew,so I replaced it and put the fan on high,then the second one blew,I replaced it,turned the amp back on,then a couple of minutes later I had a look at the back of the amp,

    The back row of tubes were glowing bright yellow hot inside,and would probably have gone red hot if left any longer.Yeah......I know tubes have a glow too them when operating,but these were extremely hot.

    New Peavy 6L6GC tubes were installed before I bought it.

    What could the problem be,is it something to do with the bias adjustment?

    Please help.:confused:
  2. monkeyfinger

    monkeyfinger Moderator Staff Member Supporting Member

    Uh, you didn't just pop in a new set of power tubes without re-baising, did you?
  3. steve-o

    steve-o Guest

    Apr 17, 2002
    here is what you do.
    sell it to me and your problems will be over with!
    so how much?

  4. Big String

    Big String Supporting Member

    Apr 22, 2000
    Northwest Indiana
    unless you have your 400+ modified to do so, you cannot bias these amps. They are fixed bias. However you do need to put in the correct 6l6 tube within the mesa specs. I'm no tech but you can contact the tubestore.com or lord valve or anyone like that and get the right tubes for your amp. I think you can get anything between 21 and 28 milliamps, but all the tube experts will tell you that most tube testers are home made and the tolerances vary. But I can tell you from experiance that these people will get you into the RIGHT tube for your amp because they know the specs. I would say you probably got some real hot tubes or maybe the other way and they do not match the correct voltage levels for your amp. Maybe they are the wrong tube all toghether. Better find out or just call Mesa and get their tubes. I can tell you they are expensive and not as good as some you can aquire, but they'll tell you the warranty is void if you use anyone elses's tube. I reccommend the Svetlana 6L6GC and the Electro Harmonics 12ax7 which is a 12ax7eh. Boogie now sells and recommends GC's for the 400+ plus but I doubt if they are Sevtlanas. Good Luck. Oh, and have a tech check you amp for possible damage you may have caused to any other components. Don't screw around with your beautiful 400+. Once you get it dialed in it's super.
  5. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    hmmmm ... Peavey tubes in a Mesa amp ...
  6. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Well, they're both re-labeled...
  7. I live in New Zealand,250 volts at the wall here, USA runs 110V,is that right?anyway could that be a problem if the peavy tubes are made for 110 volts?

    So can only a good tech tell the difference between two 6L6GC tubes or is there some info written on them,then I could compare them with a new amp?

    It's hard to find someone who knows what they're talking about over here.
  8. Also........why is it only the back row of six that are running so hot,are they on a different curcuit or something?
  9. Tapp


    Aug 29, 2001
    USA, Mississippi
    Just so everyone is clear; a "fixed biased" amp can be adjusted. "Fixed bias" refers to a small neg "fixed" DC voltage applied to the grids of the power tubes. In short, this is how the tube is set to keep the plate current within spec. It has nothing to do with adjustment.

    With that said, Big String gives good advise about buying power tubes that meet Mesa's specs. Lord Valve has them (or did in the past). This alleviates having to go inside of the amp and change the resistor that controls the bias voltage. Some techs will go in and add a potentiometer (ala Fender) to be able to adjust the bias voltage; or use "spec'd" tubes like Mesa does.

  10. * ahem *

    there is no country with 250v AC ;)

    there is either 115v or 230v.

    b.t.w. don't tubes need to be " warmed in " ? ( e.g. turn the amp on and leave it on for a while before playing )

  11. yeah,you are right.........my mistake,I meant to say 230v:cool:
  12. jasonbraatz


    Oct 18, 2000
    Oakland, CA
    the tubes just take what the power transformer gives them - there's no "120V" or "230V" tubes. now...if you're plugging a US spec amp into a 230V outlet - no wonder your amp is getting toasted.
  13. No,it is a New Zealand new amp,it says 230v on the back panel.
    And it was only the back row of tubes that were glowing hot
    Could it be something else other than the tubes????
  14. lneal


    Apr 12, 2002
    Lee County, Alabama
    thirdrdeye: I suggest you find a tech. This is not something you can fix yourself. Surely you can find someone over there. Do yourself a favor: call a pro! Lord Valve would be an excellent place to start looking for help.
  15. Thanks for everyones help.

    I found a guy that hopefully will be able to sort out the problem.


  16. Actually nobody uses 115v either;) For anyone who's interested see the link for voltages around the world - it surprised me

  17. Wow neat link. I had no Idea how many different systems theer are. Seems like lots of people on 220v and 50hz. Thanks for the link

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