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blown tube head

Discussion in 'Amps and Cabs [BG]' started by hydrohydra, Jun 9, 2012.


  1. i just recently bought a YBA3 custom and ran it through a 810 perfectly, although i didnt crank it. later that day i went to the jam spot and ran it through a heartke 115 with a pro co rat pedal, it sounded great then all of sudden i realized it was smoking so turned it off properly then after inspecting the tubes i noticed brownish coloration on two of the power tubes. before i left i tried to power it up and the light no longer comes on. suggestions?
     
  2. FC Bass

    FC Bass Alembic and Mesa/Boogie junkie

    Jun 9, 2006
    Holland
    Our guitar player had an amp (almost) on fire not too long ago, we replaced the tubes/fuse and he could finish the gig (happened during soundcheck, one tube redplating like hell)

    He brought the amp in and (if I'm not mistaken) some screen resistors were replaced (minor cost fix)
     
  3. will33

    will33

    May 22, 2006
    austin,tx
    What was the impedence of the Hartke 15 (I'm guessing 8 ohms, although some of them are really 6), and what was your output tap on the amp set to?
     
  4. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Don't assume its just the tubes, unless they have paper labels, not much there to smoke, so likely resistors attached to them have been toasted by them shorting, but it could also be a bias or PI issue (two on one 'half' of the push pull suggests those). Basically, its a leave them in place and a tech trip, not an easy one if you roughly know your way around.
     
  5. will33

    will33

    May 22, 2006
    austin,tx
    If it smelled really strong and lingered for 2 days.....you smoked a resistor.....
     
  6. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Exploded caps smell pretty bad too. But the other stuff says resistor. Shorted PI valve will also redplate two valves, but sounds like it went beyond that subsequently.
     
  7. RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    Answer this, too. it's important to know.
     
  8. tallchris

    tallchris

    Dec 19, 2010
    Seattle
    Were these original/older tubes? Sounds like you probably blew a resistor and that may have borked those power tubes.

    I'd take it to a good tech and have the caps replaced if you haven't already, any resistors that are blown or off value. You could also change the amp to 6550s if you wanted for more headroom (guessing it had EL34s).

    The YBA3s are great amps for bass or really loud guitar. I used a friend's on tour a few months ago and it sounded just as good as my V4-B, if not a little more biting/gainy.
     
  9. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Generally its the tube blowing that kills the resistor. Aside from carbon comps, resistors are pretty stable in intended operating conditions.

    Also putting 6550 in place of EL34 is a really bad plan without a lot of checking, that has blown a lot of amps up.
     
  10. Generally when a tube red plates its bias supply has failed. Time to take it to a tech.
     
  11. No it will not give you more headroom. The change will really garner you nothing useful.
     
  12. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Distorting loads then catching on fire can be cool sometimes.
     
  13. tallchris

    tallchris

    Dec 19, 2010
    Seattle
    I know people who've done it and they claimed it gave them a bit more headroom, or they at least preferred the sound of 6550s for bass over EL34s. This was of course done by qualified tech(s) do that the 6550s were properly biased, definitely wouldn't want to just pop those in there.
     
  14. I'm glad you qualified your first statement! :D
     
  15. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Bias isn't the main thing, filament/heater current draw is.
     
  16. calebbarton

    calebbarton

    Aug 25, 2007
    Oregon
    I manufacture for several companies including but not limited to: Bridge City Sound, Catalinbread, more.
    Its probably the gain block or tone choke.




    anyway.......something tells me impedance is important in this situation.
     
  17. It was a 8ohm cab
     
  18. It has been modded to use 6550's
     
  19. How about the tap in use?
     
  20. 4 ohms
     

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