Power Tube quickie

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by alanfc, Jan 23, 2006.


  1. alanfc

    alanfc Member

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    I run my amp about 4 hours a week at gig volume and was wondering,

    my last power tube change was approx 9 months ago. Last night at rehearsal I THINK I heard my amp get weak and go to half volume. I thought it was cymbal crashes de-sensitizing my ears in this crappy rehearsal room, but,
    I turned everything off, waited a few minutes, powered back up again, and all was normal. My preamp tubes are all fine. (I think).
    Power tubes are SED Winged C's EL34's in a 55w amp.

    so do you think I need a power tube change?
    thanks
     
  2. VaughnC

    VaughnC Supporting Member

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    Difficult to say as tubes are only one of many things that can cause volume change. And don't assume that your preamp tubes are fine....they can go bad at any time, especially modern ones. They don't make them like they used to!
     
  3. Blue Strat

    Blue Strat Member

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    You might want to try cleaning your tube pins and sockets. See the FAQ on my website under Resources.
     
  4. alanfc

    alanfc Member

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    thanks I'll try that,
    all I have at this hour is this electrical parts cleaner I used for cleaning scratchy guitar pickup switches. Is that too harsh or is it bascially the same thing?
    Thanks
     
  5. robbieboyette

    robbieboyette Member

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    When I was playing 7 nights a week doing 5 sets a night I changed my tubes every 3 months and they were still sounding good. I just didn't want to take any chances. So I would say your tubes are gonna last you a few years at 4 hours a week.
     
  6. John Phillips

    John Phillips Member

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    Four hours a week for nine months is only about 150 hours... way less than the life expectancy of even new-production power tubes, unless they're biased far too hot. That doesn't mean it can't be a tube problem, just unlikely to be 'general wear'. In fact, if it went suddenly weak, thin-sounding, possibly harsh, and quiet, chances are that it if it was anything to do with the power tubes at all, it was that one stopped working temporarily. That could be due to a tube fault, or a socket contact problem as Mike said, or - worst case and fairly unlikely, but I ran across this very recently in a Marshall DSL50 - an intermittently faulty output transformer.

    It wouldn't hurt to have a spare set of tubes though - I'd get some new ones, keep the ones you have now in the amp, and if it does it again immediately swap the tubes. If that doesn't cure it, you know it isn't a tube fault. If it does, you still don't know either way unfortunately, until it does or doesn't do it again...
     

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