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SVT CL no sound/buzz only

Discussion in 'Amps [BG]' started by doomloop, Jan 26, 2014.


  1. doomloop

    doomloop

    Joined:
    Mar 1, 2011
    Location:
    Portland, OR
    So some of you probably know some of my story already....replaced all my tubes in my SVT, brought it to a tech for piece of mind but everything was good. I played two gigs and practices and everything was great...

    I let my amp sit and cool for about 90 min after a gig loaded it in my van and left it overnight...it was a pretty cold night, maybe 30, but it was covered and the van is pretty well insulated. Brought it in the next day, took it to practice, warmed it up and BUZZZZZ.... :mad: :bawl:

    That's it, lights are green, no changes/sound from playing bass, when I dial the bias lights to red the buzz increases but that's about it, as it would under normal circumstances when there is sound...no output other than that.

    Tried cables, bass and cabinet...

    Thanks for the help!
     
  2. JGbassman

    JGbassman

    Joined:
    May 31, 2011
    Location:
    Midwest
    Sorry to hear the bad luck and dont have much to offer in a diagnosis. The svt cl heads are pretty stout but I always have carried mine in an ata road case and have always brought it inside after a gig. The roadcase insulates it from rain, snow and extreme temp changes, but even after a long gig I drag all electronics back into my house. I used one on the road and it banged around in the back of a truck in all sorts of temp changes without any issues. I'd be surprised if the cold or vibration actually caused the problem. It might have aggravated an existing problem though.
     
  3. doomloop

    doomloop

    Joined:
    Mar 1, 2011
    Location:
    Portland, OR
    Thanks for the response...hoping it's an easy fix!!!! Got some big gigs coming up and I miss my SVT already!!
     
  4. beans-on-toast

    beans-on-toast Supporting Member

    Joined:
    Aug 7, 2008
    First thing, plug your bass into the power amp in jack on the back and see if you get any sound out of it.

    The CL has a number of connectors inside the amp. The cold may have shrunk one loose enough to loosen a contact. Reseating the internal cables might help. While you got it open do the same to the pre-amp tubes.
     
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  6. prd004

    prd004

    Joined:
    Dec 3, 2010
    Same thing happened to my SVT-VR, exact same thing, used it, everything was fine, got home late, left it in my truck, cold night, etc.........
    Next time I tried to use it...........nothing.

    Turns out the cold had nothing to do with it, for whatever reason the thing would not come out of "protection mode"

    Luckily I live in Washington and Hodgy took care of everything!!!!!!!
     
  7. doomloop

    doomloop

    Joined:
    Mar 1, 2011
    Location:
    Portland, OR
    Yeah..Hodgy has helped me out a bunch too! I will try all those suggestions and re-seat all my tubes, check connectors inside, try the pre and power setups with other amps, etc... Mine seems to be out of protect mode... Thanks for the tips!
     
  8. Cirk

    Cirk

    Joined:
    Jan 16, 2011
    Location:
    Newport News, VA
    There's a small chance that on of your preamp tubes took a dive. If the other fixes don't work, get a pre that you're sure is good and switch it out with each of your preamp tubes.
     
  9. beans-on-toast

    beans-on-toast Supporting Member

    Joined:
    Aug 7, 2008
  10. toomanyslurpees

    toomanyslurpees

    Joined:
    Jan 21, 2009
    I would say don't open that thing up unless you know what you're doing, there's enough voltage in that amp to kill you, and it may still be there when it's turned off and unplugged.
     
  11. doomloop

    doomloop

    Joined:
    Mar 1, 2011
    Location:
    Portland, OR
    I've been inside this amp before and am aware of the dangers, that being said I tend to only swap tubes. I can deal with a Laney AOR but the SVT is a pain to navigate.

    All the tubes in the back seem fine, they all glow appropriately and when I hit the stand-by to on they get just a little blue in them in a uniform manner and on all of them...I was considering perhaps the front pre-amps tubes could be an issue just because they are not normally visible and the others seem fine.

    I have a full set of pre's I can swap...would a misaligned power tube cause this symptom and if so would it glow differently, or at all, if in fact misaligned in a socket?

    Thanks again everyone.
     
  12. Cirk

    Cirk

    Joined:
    Jan 16, 2011
    Location:
    Newport News, VA
    Wouldn't hurt to reseat all of the tubes, but that may not be the issue.
     
  13. Jerrold Tiers

    Jerrold Tiers

    Joined:
    Nov 14, 2003
    Location:
    St Louis
    Cold shrinks things.... probably some connection or component opened up.

    A tech would trace the circuit through the unit, checking to see where the signal stops. the problem will be there.

    Checking if you get music out when playing with cord plugged into power amp input will determine if the problem is in preamp or power amp.

    It might even fix the problem, if it is a matter of corrosion on the jacks.... Plug into every jack on the thing a few times (power off, please) and try again. if no joy, take to tech.
     
  14. Mastermold

    Mastermold Supporting Member

    Joined:
    May 5, 2008
    Location:
    Orange County, California
    Disclosures:
    Firemelon
    Sad to hear. My Heritage SVT-CL has been mysteriously going to fault mode from time to time during gigs. So far no rhyme nor reason for it I can figure out. Told Hodgy about it and he thought it might be a bad power tube but they all bias just fine. I'm still using it since 99% of the time it's fine, but it's frustrating when it happens. I have to quick power off and on again. Everything is fine after that for the rest of the night. Weird.
     
  15. beans-on-toast

    beans-on-toast Supporting Member

    Joined:
    Aug 7, 2008

    If there is a problem with a power tube it can be intermittent. This could happen with temperature or vibration. So the amp might indicate that the bias is fine and then something causes the tube to fault out while playing.

    It is important to remember that the line voltage affects the bias and other voltages in the amp. If the wiring at the venue is not up to standards and the line voltage load gets too high when all the equipment is being pushed, the line voltage will sag causing the amp to fault. The only way to know is to monitor the AC line voltage with a data logger while you are playing. Not easy to do without specialized test equipment.

    So the "simplest" fix would be to inspect the tube sockets, their tension, and try a new set of tubes and see how it goes.
     
  16. 10cc

    10cc

    Joined:
    Oct 28, 2013
    This was also happening to mine at a few different venues. So after a lot of investigating and two or three techs looking everything over and coming up empty handed. I found out that my CL and SVT VRI's do not have the same standby mode as the older ones. At particular places if mine was getting voltage that dropped below 118 (if I remember correctly) it would go to standby mode(red light) and be done for the night. So I had a easy mod done to my standby and it's been fine ever since. I've got the schematics and procedure somewhere I could dig it up and send it to you if you need it. I do not know if the heritage is the same. I thought they were built like the old ones with a manual standby? Maybe Jimmy will come to the rescue and help you guys out.

    As far as Doomloop's problem I think this is not it. Maybe though who knows?
     
  17. JimmyM

    JimmyM Supporting Member

    Joined:
    Apr 11, 2005
    Location:
    Apopka, FL
    Disclosures:
    Endorsing: Ampeg Amps
    10cc, that sounds like a different problem than what's happening with doomloop. But as far as I know, it's only a problem with the VR, and 113v is the magic number.

    http://johnkvintageguitars.homestead.com/SVT-VR.html

    This details a fix you can do for it. Hodgy says there's also a fix for it that's different, but I don't know about it. Again, though, I don't know if this will help Mastermold and I doubt this is the problem doomloop is having.
     
  18. doomloop

    doomloop

    Joined:
    Mar 1, 2011
    Location:
    Portland, OR
    I'm guessing that going into protect would be indicated by the flashing red and green lights on the front of the amp?
    Mine is not doing this so I will try visually inspecting some connections, probably won't dig around too much for the obvious reasons, and re-seat my tubes, swap some pre's and try all the jacks as suggested. After that I'm just gonna bring it in again.

    Thanks all! If anyone thinks of something feel free to lemme know!

    btw...here's some of my bands music when my amp IS working fine...lol

    http://disenchanter.bandcamp.com/
     
  19. Mastermold

    Mastermold Supporting Member

    Joined:
    May 5, 2008
    Location:
    Orange County, California
    Disclosures:
    Firemelon
    Thanks for this, I think I am going to take to a tech for a peek and may end up with some new tubes. If it happened every gig I'd be all over it but because it's so hit and miss it's easy to ignore and play on. For now at least.
     
  20. B-string

    B-string Gold Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Here is an old tech trick for your amp tech to find marginal tubes. While the tubes are in a "tube tester" (marginally useful piece of equipment IMO) with the tube fully warmed up and displaying GM or emissions drop the heater voltage one step down. "Good" tubes will display no or very slight loss, weak or questionable/bad tubes will have a notable loss. We used to call this a "life test". My MU-401 has a switch named that, it's major function is heater voltage drop. If you run into low supply voltage or line "sag" this test is useful also.
     
  21. 10cc

    10cc

    Joined:
    Oct 28, 2013
    Yep, maybe not and yep. Maybe not because mine is a CL and it must have been you that posted that link before if so THANK YOU! Since then and since the mod mine has been running great!

    Again sorry doomloop for loosing focus. Hope you get your amp fixed. Hit us up with a follow up after your problem has been found and fixed. I always try and catch up on SVT news because troubleshooting sucks if your looking in the wrong direction.
     

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