Speak to me YOU LITTLE BASTARD!

Discussion in 'Amps and Cabs [BG]' started by Lowbrow, May 17, 2021.


  1. 707GK

    707GK

    Jun 13, 2013
    California
    I had the same noise & volume cut happen to my LB30 when a preamp tube went out. Can’t remember which one, I was not scientific in figuring that out and preamp tubes are cheap...I replaced all of them and it fixed it right up.
     
    Lowbrow likes this.
  2. 808State

    808State Inactive

    Dec 30, 2020
    Very basic test for pre tubes is just make sure they are all seated well.
    They can shake loose from transport.

    If the mute switch functions, well then its not the problem.

    Static crackle is a sound a tube can make if getting old.
    Also a sound you can get from dirty sockets or loose solder connections.

    You can just tap the tubes to see if one has obvious crackle or microphonic.
    then you found your bad boy.
     
  3. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    Probably the route I’ll go as well. I can unplug and plug in tubes .
     
    707GK likes this.
  4. 707GK

    707GK

    Jun 13, 2013
    California
    Nice. Make sure to leave the amp off & unplugged for a couple of days before opening it up.

    There are 3 preamp tubes, they are all covered in little aluminum shields. The 4 you see glowing are your power tubes.

    From my experience with this little amp, the preamp tubes get pushed pretty hard but not so much the power tubes. I’d be willing to bet it’s one of the 3 little guys hiding under the metal shields.

    I have had good luck with JJ brand tubes in this amp as well.
     
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Probably the single easiest and most common way to ruin an otherwise easily repairable amp. The less somebody knows about an amp or electronics, the more common this kind of treatment is recommended it seems.

    Don't do it.
     
    Balog, Haroldo, FunkHead and 7 others like this.
  6. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    So as I understand it, leave the 4 in a row up top alone and swap the other 3.


    ashdown-little-bastard-2739374.jpg
     
    707GK likes this.
  7. Had a similar problem with a Fender amp, although my mute my working.
    Heavy volume drop. I checked the pre tubes and one had a grayish color on the top. I replaced it and was good to go. Be VERY careful if you go in the amp, I’m not familiar with your amp but, it can hold a change of a few hundred volts. Don’t do the contact cleaner thing, it will cause more problems. If you do use just a very very small amount.
    Good luck.
     
  8. One at a time.
     
  9. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    Thanks again, folks. I'll return to this in a few days after the amp has had time to discharge.
    If you don't hear from me I've turned into a pile of ashes.

    PS: That IS NOT my naked big toe in the photo above - this was swiped off the web and it is someone else's big toe.
     
    kesslari likes this.
  10. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    Ashdown site lists LB pre tubes as 1 x ECC83 1 x ECC82. BUT I believe there are 3 tubes in the pre section? Can anyone confirm what tubes I need to buy/how many of each?
     
    707GK likes this.
  11. This is not intended to come off as snarky, so please take it as a legitimate question:

    Why was it successful on all three of my efforts? And I guess more importantly, how will it damage the amp further?
     
    Last edited: May 18, 2021
  12. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    If all you're doing is swapping tubes, you don't need to wait a few days. Five minutes for the tubes to cool is sufficient. Those little guys get hot!

    Of course, if you've opened the underside of the amp chassis and exposed all the circuitry in there, you don't want to be poking your fingers (or anything conductive) in there. I'm not familiar with the construction of the LB, but on my CTM-30 the tubes are safely accessible.
     
  13. 808State

    808State Inactive

    Dec 30, 2020
    I would confirm its a tube issue before shot gunning all the tubes.
    You likely only need one new tube.
     
    Balog, Sid Fang and agedhorse like this.
  14. 707GK

    707GK

    Jun 13, 2013
    California
    To answer your previous question with the toe pic...correct, the 4 in line are the power tubes, I wouldn’t swap those out yet, but remember it is possible the noise is coming from one of those. My experience has been that the power tubes don’t fail on these unless you’re gigging hard and loud often. I’ve gone through a few ECC83 though.

    The amp uses 2 x ECC83 and 1 x ECC82. I can’t remember which is which, but when you pull them out, they will have writing on them to designate the tube type.
     
    Lowbrow and kesslari like this.
  15. 808State

    808State Inactive

    Dec 30, 2020
    The picture posted shows 3 tubes.

    Its common for the preamp to use 12ax7 or ECC83
    and then the phase splitter will be a 12au7 or ECC82

    So likely you only need One 82

    As mentioned in post #22
    You can just tap on the tubes and listen for obvious crackle or pinging
    to narrow down what tube is likely bad.

    You can also just check if the are seated well.
     
  16. Runlikegregg

    Runlikegregg

    Dec 31, 2011
    Brooklyn
    Have you tried a new cord?
     
  17. 707GK

    707GK

    Jun 13, 2013
    California
    upload_2021-5-18_11-24-15.png
     
    Lowbrow likes this.
  18. And if contact cleaner doesn't work then try some carburetor cleaner, hose it all down :thumbsup:
     
    Lowbrow, Sid Fang and agedhorse like this.
  19. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    All the usual stuff like cord, basses, speaker cable, effect of each individual pot & switch, both speaker output jacks checked in advance, yes.
    Tried different straps but that didn't work either.
     
    Last edited: May 18, 2021
  20. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    HOLY COW it says the amp was designed for playing at home, but I wasn't at home!!! That's probably it! ;)
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Aug 5, 2021

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