I think i Blew a Tube....

Discussion in 'Amps and Cabs [BG]' started by MysteryBox, Nov 25, 2005.

  1. MysteryBox


    Feb 28, 2005
    Well i think i blew a tube but the hell if im sure.

    I have A Traynor YBA200 that i just got about 3 weeks or so ago and replaced the Sovtek 12AX7's with JJ/Tesla 12AT7's.

    Anywho i was givener with my Peavey 2x15BW making her go pretty damn loud and getting some killer distortion. When i try to turn it down its still uber fuzzy. I release i smell the smell of burnt something and i look at my Tubes. The Power Amp ones all look fine but looking at the Pre Amp tubes the 2 new ones look great but the Splitter the 12AU7 looks not as bright and looks like the Center part is like really red on both sides and it isnt lit up in the middle.

    So did i blow the Tube or is it something else?
  2. Trevorus


    Oct 18, 2002
    Urbana, IL
    You probably did blow it. Get it replaced, and be nice to it. You may need to get it checked out by a tech to make sure you didn't fry something else near that tube.
  3. That sounds like there is short between the heater filament and the plates internally. Get that tube out of there immediately before it damages your amp!
  4. MysteryBox


    Feb 28, 2005
    why thank you on the compliment.

    Anywho i did change out the tube which wasn't that bad actually (It just looked like it was used). Anywho i realized i was playin on my Carrying around cab which is one Peavey 115BW and i actually think i blew the speaker on it.

    Cause actually after i replaced the tube it still sounded ****ty (but the ****ty sounded better tone wise). So i put it on my 2x15 and it sounded just beautiful.

    I took my other head (a Peavey Mark IV) on the 1x15 and it just was the same fuzz (cause of the Graphic EQ i could dial some of it out by cutting some Mids and Higher Mids).

    But thank you all for the help.
  5. luknfur


    Jan 14, 2004

    read through this thread the other day and had a question but was wanting to wait till it lost gas to take it on a tangent.

    1) Was wondering what part of MB's description led to that diagnosis and what was the potential damage to the amp if that were the case?

    2) I've heard that a tube fogging up is not a good sign (tube not sealed or something) but I was wondering about when they "chrome up" what that's an indication of?

    New to tubes so I'd like to get some basics down so I know what to be concerned about and what not to be when it occurs.

    Also, I buy vintage/used tubes and have no way of checking them out aside from visual inspection before I fire them up, mostly checking all the fillaments are connected, pin condition, just general overall integrity. I've bought about 30 tubes - all pre so far. Most of the guys I've bought from have been pretty reputable and typically have gas/meter read qualifications (which I understand has limitation). But I was wondering if there's anything in particular I need to be looking for?
  6. Preamp tubes are cathode, which means pretty much self, biasing, so if one was glowing red it would either be overdisappation or a short. If the cathode were open (no bias) then the tube wouldn't work anyway, so that leaves the possibility of a short causing the plates to glow red.

    Since preamp tubes are triodes, you could only have a short from heater to plate (it would blow up the amp so not that) from plate to grid (it would make the tube emit LESS) or from heater to grid (it would knock the bias back enough to drive the tube too hot.)

    Since he was talking about the 12AU7 that, IIRC, is the driver tube in that amp. If it were to short itself out, there would be a good possibility it would severely unbalance the output section and cause half the output tubes to go into runaway with oscillations that wouldn't be audible, but would be deadly for the tubes and possibly the output transformer.

    FWIW, I think he still has SERIOUS problems but is ignoring them.

    If they turn frosted white, they're trash.

    The "chrome" is the getter and it's there for good reason, and seing that is a GOOD thing. Leaky or dying tubes start burning that silvery coating away and it turns light brown- THAT's bad.

    Get yourself a tube tester if you start messing with power tubes. They're not perfect, but they also won't blow up with a bad tube like an amp can. As long as you stick to preamp tubes, don't worry about it.
  7. luknfur


    Jan 14, 2004
    Guy I bought the THD Univavle from just sent me some parts to the amp he ran across including a Brit Sylvania EL34 tube.

    I noticed in handling the tube it "rattles." Like a lightbulb but not as pronounced - pronounced enough to where it was obvious in casual handling. None of the other power tubes I've got do that. I've got one you can stick up to you're ear and tap on it and it's a similar sound but faint at that and definitely nothing that would be heard without doing as much.

    Appearance wise, looks fine otherwise. Anyway, thought I'd inquire before firing it up.
  8. Sometimes it happens, im sure one of my power tubes rattles, but, there it isnt microphonic (it doesnt come through the amp), so im hoping alls well
  9. luknfur


    Jan 14, 2004

    tube works fine. Appreciate the feedback. I just wanted some input that I didn't have a pat hand for an impending melt-down.
  10. Trevor.A


    Jan 2, 2005
    Lubbock, TX
    how does it sound with the 12AT7s instead of the 12AX7s? is it a lot tamer? and did the 12AU7 make much of a difference? i like the stock sound but sometimes it can be a bit much. im thinking about changing them but i dont know which tubes to buy.
  11. luknfur


    Jan 14, 2004

    don't have a Traynor but in the Uni the pre tubes make a lot more difference than what I expected from what I've read. I expected it to be more like with mic tube preamps. I've bought some 15 different pre used tubes (12a TXUVZ 7 among others) and just in popping them in to check them out they can alter tone as much as some pup changes (and I've done more than my share of those). I've only swapped out a few power tubes but, without actually sitting down and taking a hard look, seems I'm getting more variation between "some" pre tubes than from switching power tubes.

    In general it seems like the less gain the softer the tone with less top end. But there are so many variations tube type to tube type, manufacturer to manufacturer, and variables of the same tube within a manufacturer (ie. 12ax7LPS whatever) that it gets real thick in a hurry.

    But I can difinitely use a given pre tube to bring out more top end with a given pup or take the harsh top out with another.
  12. On the note of trying different tubes, ive got an urge to try a set of KT-90s in my SVT, i dont know what it'll sound like, but it would be interesting im sure
  13. You'll have to leave its top off. KT90's are too tall to fit inside an SVT II chassis.
  14. That i knew, think you said that before, how would they sound do you think?
    Whats the power output of a KT90 compaired to an 88 or 6550?