Got Some Issues, Tubes Perhaps (video)

Discussion in 'The Workbench' started by Swede, May 14, 2016.

  1. Swede

    Swede Well-Known Member

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    Whats up gents!

    The video called "issues" shows what has happened lately, I turn it on, it makes noise but as i shut it off and on quick it disappears.

    Issues2 shows the horrible sound it the amp makes now, sound like shit.

    More and more often, the bad sound does not go away as I turn off/on.

    Power tubes?







     
  2. solarburnDSL50

    solarburnDSL50 Well-Known Member Platinum Supporting Member

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    Very well could be power tube. I'd start with them. Have you tapped them while on? I've had power tubes make that noise. Could look at preamp too if you find it wasn't the power section but I'm thinking its power tube. Would be an easy fix. Hope it's nothing else.
     
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  3. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

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    agree, Id retube just to rule it out. id start with the p.i. then pre and work my way to the power tubes. Easiest first is my motto. And are them the original cans?.. If so bad ones can do some weird unexplainable shit when the amps playing under load. Even if theyre not the culprit 10 bucks a piece is cheap to rule them out also. But id start at the p.i. / pre amp/ power tubes.
     
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  4. Swede

    Swede Well-Known Member

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    Thanks guys. Im going to get some new power tubes. I have quite a few pre's at home to roll. I have NOS pre's in there Gunner and TAD power tubes. Thanks
     
  5. SG~GUY

    SG~GUY Well-Known Member

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    -where ya been Swede, how do ya like the TAD's?-
     
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  6. johan.b

    johan.b Well-Known Member

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    pull the p.i. tube to eliminate eveything but the power tubes or power supply and in that state, lightly tap the tubes with a shopstick...I kind of get a "loose cable on a mod" or bad ground kind of vibe thou...
    J
     
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  7. Swede

    Swede Well-Known Member

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    Im doing great SG......Love those tubes. I use the TAD EL34-str's
     
  8. Trapland

    Trapland Running Into Walls Silver Supporting Member

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    I always felt like playing an amp with a sudden loud 60/120 cycle hum was akin to driving a car with the oil light on. A sign something bad has or soon will happen. Hope you resolve it.
     
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  9. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    Does it make the sound when no guitar is plugged in?
     
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  10. ampmadscientist

    ampmadscientist Well-Known Member

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    Is one power tube hot and the other cold?
    Bad power tube or blown screen resistor.


    A. Blown plate resistor in phase inverter. maybe...but probably...
    B. Bad filter caps, time to change them all...or...
    C. a bad diode in the B+ rectifier.

    Probably not the power tubes, but they "might need changing."
    I think this amp needs a cap job, quite honestly. Just the electrolytic caps, not the coupling caps.

    When you take out the preamp tubes, does the amp still hum like that?
    It could be one bad preamp tube doing that. Try taking out the preamp tubes and re-test it.

    If the hum goes away it could be a preamp tube or a bad plate resistor in the PI.
    If the hum is still there the caps are probably going bad.

    But do some more testing, don't just change parts randomly.
     
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  11. jack daniels

    jack daniels Well-Known Member

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    Take it to your buddy Aspen Pittman.
     
  12. danfrank

    danfrank Well-Known Member

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    I second this, mainly because it's an intermittent problem. You say sometimes it goes away. I'm in the valley if you're close by. I can take a look at it.
     
  13. Swede

    Swede Well-Known Member

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    Hahahaha
     
  14. Swede

    Swede Well-Known Member

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    Thanks guys, I still havent had time to check it out, but do have tubes coming my way. I will go through the list of things to check all you guys suggested, and hey danfrank, I might take u up on that offer if I cant get it fixed. Im by Downtown btw (USC)
     
  15. jack daniels

    jack daniels Well-Known Member

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    That's exactly what he said.
     
  16. Swede

    Swede Well-Known Member

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    Got my new power tubes in the mail, but going through the checklist you guys provided it turned out to be the P.I that was the culprit...... NOw I have extra power tubes at least.

    Thanks guys
     
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  17. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

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    Glad you found it! Nothing wrong with having a spare set of power tubes..almost a necessity if your gigging with one head.
     
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  18. Trapland

    Trapland Running Into Walls Silver Supporting Member

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    I can't imagine owning an amp without a spare set of tubes. I have dozens of 6l6s from my fender days. Anyone need some new 6973s?

    Funny this thread should start. I haven't had a tube issue in years. Then I got this fun old jcm800 4010.
    It runs a good 100v higher on the plates than any of my other Marshalls. Didn't work when I got it due to a shorted EL34. I had a set of RFTs and biased them up. Those should handle some voltage... I guess they we more used up than I remembered, after playing awhile they sounded odd, weak, sometimes louder or quieter, varying amounts of crunch. Pulled them out and dug out a matched quad of late era TESLAs I've been hoarding. Biased up a pair, they sounded amazing. An hour in, I got that pathetic sound of one tube dying. I look in back to see one very bright red... I can't find anything wrong with the bias supply and the tube is dead. Another one in its place and its running like a top.

    The point being, in a short while I enjoyed all the common symptoms of power tube failure I've missed so long. And I can still keep an amp running. :). Wish that TESLA hadn't died.
     

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