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tube flare-up!

Discussion in 'Amps and Cabs [BG]' started by denton57, Apr 2, 2006.

  1. denton57

    denton57 Supporting Member

    Nov 1, 2005
    During practice last night, I noticed a significant loss of power with my YBA-200 (w KT88's). I glanced over at my head and noticed one of the power tubes was glowing about 10 times brighter than the other three. I went back to standby for a few minutes, then flipped it back on. Everything sounded and looked Ok. What happened? I have a gig next weekend and am starting to get a little worried. I let the head warm up for at least 30 minutes last night. I have noticed a popping sound before at home while practicing on another cabinet. Is one of the tubes going bad? They're 2 months old!
  2. throw_this_away


    Mar 30, 2006
    our gear is very similar... I even have new KT88's in my amp. I'm no expert in diagnosis but more information mught be needed. Where was the gain and master on your amp that night?

    The easy guess is that you have one bad tube (what brand did you use)?
  3. denton57

    denton57 Supporting Member

    Nov 1, 2005
    Both gain and master were at 12:00. I have the red glass JJ Kt88's from Eurotubes.
  4. WalterBush


    Feb 27, 2005
    Yuma, Az
    Full disclosure, I'm a certified Fender technician working in a music store that carries Fender, Yamaha, and Ibanez products among others.
    Take it to a tech, NOW! A tube glowing brighter might just indicate that it wants to die young, but a tube glowing brighter with a loss of volume might be a much more serious problem. The fact that it voodoo-fixed itself after a reset isn't good, either. I'd say you need a specialist.
  5. denton57

    denton57 Supporting Member

    Nov 1, 2005
    Psycho Bass Guy...Are you out there? :help:
  6. throw_this_away


    Mar 30, 2006
    Found this on the net... hope it helps


    There are two main types of tube faults: shorts and noise. Both large and small tubes may fall prey to either of these problems but diagnosis and remedy is usually simple.

    If a fuse blows, the problem is most likely a shorted power tube, Shorts can either be mild or severe. In a mildly shorted tube the electron flow has overcome the control grid and excess current flows to the plate. You will usually hear the amp become distorted and begin to hum slightly. If this occurs, quickly look at the power tubes as you switch the amp to STANDBY and try to identify one as glowing red hot. It is likely that two of a pair will be glowing since the "shorted" tube will pull down the bias for its adjacent mates, but one tube may be glowing hotter - and that one is the culprit. The other two are often fine - unless they've been glowing bright red for several minutes.

    Because there is no physical short inside the tube (just electrons rioting out of control) merely switching to STANDBY for a few moments then back to OPERATE will usually cure the problem... at least temporarily. Watch the tubes carefully now. Should the problem recur, the intermittent tube will visibly start to over heat before the others and thus it can be identified. It should be replaced with one from the same color batch, shown on its label. Call us and we will send one out to you.

    The severe short is not nearly so benign. In the worst cases, a major arcing short occurs between the plate and the cathode with visible lightning inside the glass and a major noise through the speaker. If this is seen to happen, IMMEDIATELY turn the amp to STANDBY. By this time the fuse probably will have blown. Such a short is usually caused by a physical breakdown inside the tube including contaminate coming loose or physical contact (or near contact) between the elements. Replace it and the fuse with the proper slo-blo type and power up the amp using the power up procedure as we described earlier in this manual.
  7. denton57

    denton57 Supporting Member

    Nov 1, 2005
    Thank you. Guess Ill be looking for a new pair of tubes. I wonder if the tube is under any warranty?!?
  8. First and foremost, I reccomend that you do not try to play your amp or diagnose the problem yourself at all!!!!!!! Do not use your amp at all. Unplug it and don't mess with it. Let a tech check it out.

    What makes your situation so bad is that Traynor's auto-bias circuitry is trying to compensate for the problem. I agree with jabberwock77, a tube that "glows" brighter with a LOSS of volume is a serious problem. And just so everyone is clear here, that glow is NOT the tube's heater; it's the plates themselves and it means either that single tube has lost bias or is dying and it needs to be replaced immediately.

    Usually, the amount of 'glow' means nothing about a tube's health, EXCEPT in cases of overcurrent, which will make the plates, which are ALWAYS supposed to just be the same gray color they are when the amp is turned off, emit too much and glow red, orange, or yellow. Yellow is almost a guarantee of a dead or useless tube afterwards, BTW.

    If you bought your amp new, get it to your warranty repair center pronto. You MAY have to replace that single power tube, so if it has some kind of warranty, you'll need to get in touch with the place you bought it from should it need replacing. Most reputable dealers warrant their tubes for six months.
  9. BassGreaser


    Aug 22, 2002
    Austin, TX
    PBG what do you think of Traynor's auto-biasing circut?
  10. denton57

    denton57 Supporting Member

    Nov 1, 2005
    Man, that sucks. There are no Traynor repair centers in this area, and the one tech guy in this area isnt too familiar with this head (he said previously). Plus, its gonna cost me 35 dollars to just get it looked at immediately...plus the cost of the repair and labor. I guess Im going to send it in to Traynor. It might take a while, but at least it is still under warranty. Now I have 5 days to come up with alternative amplification before an outdoor wedding party gig. :bawl:
  11. corinpills


    Nov 19, 2000
    Boston, MA

    So sorry to hear about your troubles, but fear not; you'll get it sorted out. If it's any consolation, your #1 request at the wedding in two weeks is still gonna be "could you guys turn down?"

    good luck with all that.
  12. denton57

    denton57 Supporting Member

    Nov 1, 2005
    Nahhh. Their number one request will to be to just leave. We have a tendency to play until there is no one left. Our drunken alter ego Led Zep cover band (Fred Peddlin) always rears its head eventually. Which is fun, but doesnt work real well at a mostly classic country show. :bassist:
  13. chaosMK


    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    I had the same issue with my Mesa Bass 400, using Eurotubes KT-88. One tube flaring up. Might have been loose or some other issue. I relocated it to a different socket and it continues to glow a bit brighter than the rest, but doesnt look like it's melting down. Makes me feel bad abou Eurotubes, hearing the other experiences.
  14. It depends on how they implemented it, and I've never seen one in person. My local Yorkville dealer was supposed to order me one when they first came out and forgot to and now that can't get one in because they sell out so fast. That's OK, because I need another amp like Tombowlus does.

    If it's a warranty repair, it should cost you NOTHING. Yorkville will pay the tech fees; that's the point of a warranty. Is your local tech not Yorkville certified?

    If it was the plate, it's a bias issue. Otherwise, it's probably just a socket issue. JJ's have their fair share of problems, but overall, their failure rate is FAR lower than other current brands I've seen.
  15. BbbyBld


    Oct 13, 2005
    Meridian, MS
    It's funny you say that, because I have noticed problems with JJ octal tube pins recently. They just don't fit sockets very well. At first I noticed it with EL34s, but I was taking the tubes in and out of the sockets while testing an amp, so I blamed the sockets. One of the tubes in that amp lost bias and burned up.

    Later, after trying the JJ KT88s in the Classic 400, I noticed they did not fit as well as other brands, but I blamed the sockets again. Finally, I was just testing some JJ GZ34s a few weeks back, and they just fall right out of the sockets, while 5 other brands of rectifiers did not.

    I'm not saying that's what happened in this case, but I have noticed JJ octal tube pins have a little bit of a fit problem. They are narrower than other brands.
  16. I had completely forgotten about that! Some guitar guys at a tech forum I frequent were discussing this recently. Fortunately, all you have to do is retension the sockets. Also a lot of recent Sovtek tubes have bad solder connections on the internal elements to the pins.
  17. throw_this_away


    Mar 30, 2006
    Of note, the adivce I posted was from a Messa tec FAQ... and those amps are not self-biasing. The traynor is a different breed... but I bet it is just a bad tube.
  18. My Mesa is self biasing...
  19. throw_this_away


    Mar 30, 2006
    What year is your amp... I am not familiar with Messa's but the website says "fixed bias."
  20. No, it isn't.

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