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Ampeg SVT-II distorting problem !

Discussion in 'Amps and Cabs [BG]' started by Catalin, Jul 28, 2009.

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  1. Jul 28, 2009 #1
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    Hello guys !

    I have a little technical problem with my Ampeg SVT-II non pro.
    When i start the amp it sounds beautiful but after 15-20 minutes of playing at medium volume the sound becomes distorted. If i put the amp in stand-by for 2-3 minutes the problem disappears but appears again after 1-2 minutes. I think is something heat related...
    And another question: it is normal for the fan to not work in the stand-by?

    Thanks !
     
  2. Jul 28, 2009 #2
    RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    I don't know, but in standby, you're not generating much heat. What speaker cab are you using?
     
  3. Jul 28, 2009 #3
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    I'm using an Ampeg SVT 810E cabinet. With my Trace Elliot V-Type i don't have this distortion problem so i guess it's not the cabinet.
     
  4. Jul 28, 2009 #4
    RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    In that case, your best bet is the trusty amp tech.
     
  5. Jul 28, 2009 #5
    whoatherechunk

    whoatherechunk

    Apr 4, 2008
    How long have you had the amp? How long have you had the tubes?
     
  6. Jul 28, 2009 #6
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    My problem is that i don't have any good amp tech in my town. I know a very good electronics engineer but he don't know much about tube amps or instrument amplifiers so i need some opinions from someone who know these amps....
     
  7. Jul 29, 2009 #7
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    I just got the amp last month. The seller says he changed the tubes last year.
     
  8. Jul 29, 2009 #8
    rodl2005

    rodl2005

    Jun 1, 2005
    Tasmania, Australia
    IIRC the fan stays on in standby mode- on mine anyway. Sorry I can't help more.
     
  9. Jul 29, 2009 #9
    Dino@Ampeg

    [email protected]

    Mar 27, 2008
    Global Product Specialist - Ampeg
    That fan should be on at all times. If you put the amp on standby after playing, and the fan doesn't stay on, there's nothing there to allow the tubes to cool down properly.

    This could also be part of the reason why you're getting distortion. The tubes might be cooked over the past year of not being allowed to cool down properly.
     
  10. Jul 29, 2009 #10
    RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    In that case, even just replacing tubes won't fix the problem, so unless you're an expirienced amp tech yourself, the best bet is to FIND someone who can hook you up. Hope you get it sorted.
     
  11. Jul 30, 2009 #11
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    Hi

    I think the fan is the problem. When the fan is working the air flow is very weak i almost don't feal any air flow in the back of the amp.
    Could this distortion be a simptom of overheating ?
     
  12. Jul 30, 2009 #12
    MIJ-VI

    MIJ-VI Inactive Supporting Member

    Jan 12, 2009
    Hi Catalin.

    Weak airflow when the fan is on?

    Is the interior of you amp free of the crud which builds up in fan-cooled electronic equipment over time?

    EDIT: Hmm... Is the fan in an SVT II a single speed, or dual speed unit?
     
  13. Jul 30, 2009 #13
    tpmiller08

    tpmiller08

    Mar 15, 2009
    Boston, MA
    If its a good distortion, let it go!

    Doesn't sound like a simple fix. Not sure if Tube Amps have em, but check your fuses if they do. I just went through all sorts of hell over my fuse about to break, then did break once I got to a gig. PAIN IN THE REAR!
     
  14. Jul 30, 2009 #14
    rbonner

    rbonner

    Sep 25, 2008
    The fan not running properly is probably causing the amp to overheat. Some change in bias, or signal path component is causing the distortion.

    The first thing would be check that out and get airflow, then if the problem still exists deal with that.

    BOB
     
  15. Jul 30, 2009 #15
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    I got my amp to a tech today. I hope he will figure it out. Now i'm whaiting patiently... :hyper:
     
  16. Jul 30, 2009 #16
    MIJ-VI

    MIJ-VI Inactive Supporting Member

    Jan 12, 2009
    Good.
     
  17. Jul 30, 2009 #17
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    I have no ideea. I dont even know how much air flow should be :)
    This is the first full tube ampeg head i have seen :)
     
  18. Jul 30, 2009 #18
    BassmanPaul

    BassmanPaul Inactive

    Aug 25, 2007
    Scarborough Ontario Canada
    Let us know what the results are. The information might be of use to someone further down the road.

    Paul
     
  19. Jul 30, 2009 #19
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    Of course .
     
  20. Jul 31, 2009 #20
    Catalin

    Catalin

    Feb 5, 2006
    Europe-Romania-Craiova
    Hello guys !

    I just got my amp back from the tech. He said the probelm was from the very bad power tubes bias. He said that was the worst bias he has ever seen.
    So if you have distortion problems with your amp check the bias :)
     
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