My Blues Jr Just Crapped Out

Discussion in 'Glowing Bottle Tube Amp Forum' started by HotRodSteve, Aug 13, 2019.

  1. HotRodSteve

    HotRodSteve Friend of Leo's

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    In case I need to replace the tubes I checked out tubedepot.com to see what they would cost and in the process pulled out the tubes to find out which ones to order if needed. There are two GT-EL84-S tubes but the pre-amp tubes have two GT-12AX7-R tubes and one GT-ECC83-S tube. Are those two models interchangeable? Everything I read says there should be three 12AX7 tubes. What do you guys think?
     
  2. Milspec

    Milspec Friend of Leo's

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    Essentially the same tubes (ECC and AX7), not an issue. I will say that GT tubes are one of my least favorite tubes out there, just find them unreliable. On a Blues Jr., they are often biased on the high side, so JJ tubes actually work very well with those amps and would be my suggestion if you are looking to replace tube sets.
     
  3. HotRodSteve

    HotRodSteve Friend of Leo's

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    Thanks Milspec, I checked out the JJ tubes and can get all five for around $70 (matched and balanced) from tubedepot which I'm going to order. Before the fuse blew I noticed the amp making kind of a buzzing noise so maybe the tubes needed replacing anyway.
     
    Last edited: Aug 15, 2019
  4. Milspec

    Milspec Friend of Leo's

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    That's a good price and a good set of tubes for that amp.
     
  5. JuneauMike

    JuneauMike Friend of Leo's

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    Steve, do you know what version PCB board you have? Should be printed on it somewhere. I'm just curious.
     
  6. Milspec

    Milspec Friend of Leo's

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    Buzzing and new fuse blows....could very well be a shorted tube and being the Chinese tubes, decent odds of it.
     
  7. schmee

    schmee Poster Extraordinaire

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    First, check fuse. Second: check power tubes.
     
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  8. Piggy Stu

    Piggy Stu Friend of Leo's

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    Not that I know much, but if I were the OP I would try to put a hi res pic of the circuitry on here - eagle eyed types to see what they spot as burnt out etc
     
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  9. HotRodSteve

    HotRodSteve Friend of Leo's

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    I don't see any version number on the board, checked pretty good too. I heard the color of the board matters, mine is tan and says "2010 Fender Musical Instruments". It's made in Mexico.
     
    Last edited: Aug 15, 2019
  10. HotRodSteve

    HotRodSteve Friend of Leo's

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    I replaced the fuse as a test, powered it on, after about 15 seconds one of the EL84 tubes started buzzing and popping so I pulled the power plug. The fuse didn't blow. I was watching all the tubes and one of the pre-amp tubes didn't seem to glow, it was the oddball ECC83. Either way, I'll replace all five when they arrive. Thanks again for the advice guys!
     
  11. alnicopu

    alnicopu Friend of Leo's

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    I have had 5 or 6 Blues/Pro Juniors. I have tried my best to like them but All ended up exhibiting quirky issues that made them untrustworthy to gig.
     
  12. jsnwhite619

    jsnwhite619 Friend of Leo's

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    If it ends up too far gone and gets junked, I'd like to call dibs on the chassis!
     
  13. Milspec

    Milspec Friend of Leo's

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    That is farily common with those amps, that ECC tube is in the V1 position right? It takes the brunt of the input power so will likely be the first to go. If that tube isn't glowing, it is like starting a car out in second gear as the input voltage is now hitting V2 without the step down of V1 (laymen terms of course). Replacing that ECC tube just might get you up and running again while you wait for the new JJ tubes to arrive.
     
  14. HotRodSteve

    HotRodSteve Friend of Leo's

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    Yep, the ECC tube is in the V1 spot.
     
  15. Milspec

    Milspec Friend of Leo's

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    Seen it before...I think you will be okay
     
  16. HotRodSteve

    HotRodSteve Friend of Leo's

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    Sounds good, I should have the new JJ tubes early next week. Thanks again!
     
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  17. HotRodSteve

    HotRodSteve Friend of Leo's

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    Well, I got the new tubes today and installed them. When I was pushing one of the EL-84 tubes in I heard a slight cracking noise so I'm wondering if I damaged it. I turned the amp on and let it warm up for 30 minutes and then plugged a guitar in, the amp is making a buzzing noise when you turn up the volume and let the strings ring, it stops when the strings stop ringing, mostly the bass strings make the amp buzz, I tried two guitars, both do it. Do you think I damaged the EL-84 and caused this?
     
  18. JuneauMike

    JuneauMike Friend of Leo's

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    I had previously asked you to give the version number of the PCB board, which would have helped in getting a rough estimate of the age of the amp. Is this a used amp? Is it an old amp? The tan circuit board has been the PCB of record for many many years now so just having the color isn't very helpful.

    (Did you turn the power off when you put the tubes in, or was the power on? The description sounds like maybe the latter, unless you were saying that you wiggled the tubed when the amp was powered up.)

    In addition, I can't see anywhere in this thread where you were able to ascertain what caused the fuse to blow in the first place. If the buzzing noise is on the notes and not just an idle buzz, then there's the possibility that you have one of these amps (I did, it's not fatal);
    https://billmaudio.com/wp/?page_id=267

    I think at this point you would be best served to take it to an amp tech before something inside the circuit really gets goobered up.
     
  19. Matthias

    Matthias Tele-Afflicted

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    From my experience, BJ boards can get damaged when a power tube goes. One of my EL84s went and took out the screen grid resistor. Warranty repair (fortunately it did it in the first year). If you’re getting a weird buzzy/crackly overtone on notes played with any sort of gain, that’s what mine sounded like when I took it in.
     
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  20. HotRodSteve

    HotRodSteve Friend of Leo's

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    The amp is only around five years old, I bought it new.

    The amp was unplugged while putting the tubes in. It had been unplugged for a few days.

    It only buzzes when you play notes, especially on the bass strings.
     
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