My amp was acting strange at a gig this weekend... help?

Discussion in 'Amps and Cabs' started by jrm, Sep 22, 2008.

  1. jrm

    jrm Member

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    Hey friends:

    This last weekend our band was playing an outdoor, uncovered gig. I had my mesa rectoverb set up and everything was going great... then after about 45 minutes the sound from the amp began to die. I limped through to the second set and about half way through the sound went out completely. The volume would pulse from time to time, but it pretty much just ended in a "hiss". There was a substntial break between the 2nd and 3rd sets, so I turned the amp off for about an hour or so. I got half way through the last set before the amp stopped.

    So... ummm.... what is going on? Did my amp overheat? It was a pretty warm day and without cover the amp was taking the brunt of the sunlight and heat. Did it just overheat? Can I expect some substantial damage?
     
  2. FrankieSixxxgun

    FrankieSixxxgun Member

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    99% of amp problems are tubes. Bet the output tubes took a dump on you. How old is the amp, what kinda tubes, and when were they last changed?
     
  3. Glowing Tubes

    Glowing Tubes Gold Supporting Member

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    Yup, sounds like tubes to me. Have a spare set handy for gigs if possible.
     
  4. clothwiring

    clothwiring Supporting Member

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    Probably the power tubes. Pull out and reseat all the tube throughout for good measure.
     
  5. Adwex

    Adwex Member

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    I'd check the preamp tubes first. They're cheaper, and easier to replace.
     
  6. jrm

    jrm Member

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    Thanks fellas.

    The amp is about 4 years old, the tubes are roughly a year old (JJ 6L6 and the appropriate preamp tubes). I do have a set of spare tubes sitting around (Groove Tube 6L6 and 12ax7), so I'll slap those in and see if there is a change. I've had similar issues before at outdoor gigs though. Shoudl I assume that there is something about the outdoor gigs that is adversely affecting the tubes?
     
  7. jcollins

    jcollins Member

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    From your description, I doubt if it's a power tube problem. When power tubes go, they either short, taking out screen resistors/fuses or crackle or just die completely, but that leaves the other power tubes to keep on rocking.

    My guess is you've got a bad preamp tube, a bad solder joint or some component that is failing under thermal stress.

    Try swapping out your preamp tubes first, starting with the one closest to your power
    tubes.
     
  8. GearHeadFred

    GearHeadFred Member

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    How about the power??? Perhaps you were running on a generator?? Or on a long extension cord run?? Dirty power can cause big problems in amps.
     
  9. FrankieSixxxgun

    FrankieSixxxgun Member

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    Some amps do get so hot that they unsolder stuff, and if you're outdoors in the sunlight running the amp pretty hard, yeah, you're gonna hit that limit if it has one. What kinda amp are we talking here? Combos are more prone to unsolder stuff than heads in my experience. Sometimes the tubes just start to slip out of the sockets too, try reseating them.
     
  10. Belmont

    Belmont Member

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    the problem with the amp is that it's a Mesa Boogie............kidding.It doesn't sound like a tube problem,especially if their only a year old,unless you play loud everyday or every other day.bad power is more likely,you can usually tell quickly because your amp won't have it's usual punch and headroom.you can buy outlet testers at home depot for $5.00,I keep one in my case and before I plug anything in I check the outlet with the tester,I've discovered a few bad outlets this way.
     
  11. jrm

    jrm Member

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    Thanks fellas.

    Power shoudl have been good. I was given a good clean line by the FOH guy... I trust him (very knowledgeable and straightforward fella), but I'm not running a conditioner. All the other times I'v 3ehad this problem (two other times), I know that I was running good power so I doubt that is the problem... but it might be.... hmmmm...

    The amp in question is a Mesa Rectoverb combo. I'll replace the tubes tomorrow when I see the amp again. We'll see if that solves the problem. I'l start with the preamp tubes and see what happens.

    Barring a tube problem, how would I diagnose the next possibility? I live about 150 miles from the nearest amp tech, so that makes it a bit tricky.
     

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