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Ampeg SVT-CL popping noise when switching standby off

Discussion in 'Amps and Cabs [BG]' started by KeenVox, Aug 22, 2018.


  1. KeenVox

    KeenVox

    Aug 22, 2018
    Hamburg, Germany
    Hello all,

    I'm new to the forum. Pleased to be part of this awesome community.
    I've got a problem with my Ampeg SVT-CL and couldn't find any answer through the search function.
    Everytime I go from standby to playing I get two short pops from my cabinet. After that everything plays clean and without any noise.
    When I look a the bias light while the popping occurs, they flicker red after that everything is green. I've checked the powertubes with a wooden stick, but don't get any noise or any weird sounds.
    Any suggestion what could be the cause?

    Ps. Sorry for my wonky english.
     
  2. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    I have no idea what the cause is, but I've never found stuff like that to be an issue that should cause much concern. However, you are always welcome to contact Ampeg CS and get their opinion.
     
    KeenVox likes this.
  3. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    +1
    My SVT hums lightly when the cord is remode from the input jack when it's not in standby.
    It's done this for 20 years.
     
  4. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
  5. Wasnex

    Wasnex

    Dec 25, 2011
    IMHO nothing unusual, this is probably just the tubes warming up. I wouldn't worry about it, unless the noise is really loud or constant. Several of my amps do the same thing and it almost always turns out to be a tube that may last for years if you just leave it alone. The bias lights flicker red when the pop occurs because the tubes pull extra current when they make the noise.
     
    KeenVox and agedhorse like this.
  6. Wasnex

    Wasnex

    Dec 25, 2011
    A couple of my amps do this as well, including my Skunk SVT. Next time I open up one of these amps I will check the switching jacks for bent/dirty contacts. I can get the SVT to stop humming if I partially insert a 1/4" plug and jiggle it a bit. Insuring there is no corrosion where the jack screws to the front panel can also help.
     
    Last edited: Aug 23, 2018
  7. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Good idea.
    I should try cleaning the jacks with Deoxit (with 1/4" jack in and out cleaning with a rag).
    Superticious? Maybe, but if it ain't broke...
     
  8. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Usually this issue is due to arc’ing somewhere. The problem is finding it. There are many possibilities.

    A known issue that causes standby related pops in the CL is the high wattage resistors in the power supply. Start by inspecting them carefully, look for any black cabon traces. Replace any if necessary.
     
    SirMjac28 likes this.
  9. BassmanPaul

    BassmanPaul Inactive

    When I have come across this in the past I have wired a 10n 1KV ceramic cap across the Standby switch contacts. This tends to dampen the arc that’s causing the noise.
     
    SirMjac28 likes this.
  10. meatwad

    meatwad

    Apr 9, 2008
    Smallville, USA
    I went through something similar. Had to replace the standby circuit.
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Generally this is not a big problem, applying and removing the plate/screen voltage often causes pops due to the fast rise time of the applied voltage. I have several test fixtures that do this for the same reason.
     
    SirMjac28 likes this.
  12. BossOnBass

    BossOnBass Supporting Member

    Aug 11, 2012
    Houston, TX
    Had the same problem with a different tube amp. Problem turned out to be three bad resistors around the power tubes.
     
  13. KeenVox

    KeenVox

    Aug 22, 2018
    Hamburg, Germany
    Thanks for all the replies. As it seems it's no big problem, I think I'll let it be for the moment. After the two short pops I can play without problems and the pops aren't that loud either. If it can't hurt any other parts I'll be fine.
    I think I'll wait till I need to replace the next set of power tubes to retube the whole thing and if it still persist I'll carry that beast to my tec.
     
    Wasnex likes this.
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This is a possible cause, but not very likely. If doing a re-tube, I always like to check for current sharing between tubes for this reason.
     
  15. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Apr 17, 2021

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