1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Ampeg SVT-CL, Blown Power Tube

Discussion in 'Amps and Cabs [BG]' started by jason the fox, Oct 27, 2013.


  1. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    I've got a blown power tube in my SVT CL.

    Turned my amp on yesterday, flipped off standby and I get a nasty loud pop. The LED on the front starts flashing red/green - according to the manual, most likely indicating a power tube problem.

    I took the metal screen off the back to take a look at everything - the power tubes are all glowing, and looking ordinary/normal. I flip the standby switch, and one of them flashes bright blue/white. I verify this by doing it once more, and it did the same thing.

    So my here's my dilemma. The tubes were last changed in April 2011. I only got the amp recently, and the previous owner said there's really not a ton of playing time on them since they were changed. But I don't know what to replace. Should I replace just one triplet set? Or should I bite the bullet and replace the whole tube compliment just so I know for sure that everything is starting at zero miles. I'd prefer not to spend three or four hundred bucks, so I need some opinions. Aside from this, everything was working and sounding great so I know the current tubes were fine (well, except the blown tube).

    I just don't know if it's a better idea to replace just what needs to be replaced, or if it's better to just replace the whole works so everything is even.
     
  2. Replace the triplet (at the most) IMHO and keep the good two as emergency spares. You most likely just suffered "infant mortality" on one out of six. If you already have a working spare plug that one in to be sure you don't have any other troubles with support components in the chassis. With a triplet your chances of "infant mortality" are reduced by 50% ;). Try to find the same brand as the other good three and match any "bias" numbers if available.
     
  3. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis

    I just had the exact same thing happen. Bought a CL, a few months later the same deal. Nasty pop, hum, bright light. I took the tube and one from the other bank out to confirm the problem ( not a good idea to play the thing this way, but it will work). Basically, you can replace all three tubes in that bank with a matched trio and you should be ok. I opted for 6 matched tubes and I took it to a tech. Turns out I blew a few resistors and a couple other things. I would say if you replace those three tubes and you can get the amp to bias up, it sounds normal and has the same volume, you should be good.

    If it were me I would take it to a good tech and have it looked at just to be sure. Otherwise you may just be setting up the new tubes for failure too. Just my opinion.
     
  4. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    By the way, a general check up from the tech should run about $80 and 6 Winged SED's will cost you $350. I went with 6 NOS 6550Bs and I like them a lot. Tubes were $189 for a matched sextet from T/C Tubes.
     
  5. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    Cool, thanks guys.

    Been doing some digging on the internet and searched the the forum too, general consensus seems to agree with just replacing the triplet.

    That's most likely what I'll do.
     
  6. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    If you can get it to bias up you're golden.
     
  7. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    Yeah, it'd be nice to avoid spending a few hundred bucks if it's really not necessary.

    The six 6550's that are in there now are Sovteks. I'm assuming the previous owner just wanted to replace them with the kind they left the factory with. Some people like Sovteks, some don't. I've never had an issue with them, so if I replace the triplet set, I'll buy three more Sovteks since that's what the rest of them are anyway.
     
  8. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada

    Is there any particular reason I might have an issue biasing them?
     
  9. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    That's what was in mine. I liked them fine. I still have 5 good ones, but I think I'll hang on to them.
     
  10. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    Open grid screen resistor, open resistor on the main board, leaking cap, bad OP Amp.

    That's what was keeping mine from biasing. Either the bad parts made the tube blow or the tube blowing roached some parts or some combination of both. All I know is if you can't get it to bias up correctly using the LEDs in the back, you need to take it to a tech. You spent no small amount on the amp, don't take the chance. The more you screw up the more it will cost you later.

    Again, this is my opinion and if you have no noticeable issues you're good to go.
     
  11. I'd always go with a checkup too, replacing the power tubes shouldn't be something you need to do regularly (so wouldn't worry about it being ongoing costs) and a tube failing can be caused by other failing components in the amp. I find it worth having the peace of mind that it's happy and healthy and isn't likely to croak on me at an inconvenient time!
     
  12. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Check this video out. You will find it helpful.

    It would be good to check out the power amp's plate, screen, and cathode resistors. Sometimes when a tube blows, these resistors can go with it.

    The amps will need to be re-biased after the tube change.
     
  13. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    Yikes. Hopefully this is nothing more than a blown tube them.

    Biasing the triplets is pretty easy on this amp. I did it the day after I got it (one set was a little out). I'm just hoping that's all I'll need to do after I put the new tubes in.
     
  14. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    It's just that what happened to your amp is the EXACT same thing that happened to mine.

    Just make sure it biases. Leaky caps smoke trannies. Smoked trannies makes your $1000 CL a $300 CL.
     
  15. Tubes can fry screen resistors when they arc. Like Floyd Eye stated, if they will bias properly chances are very good you're okay. If a screen resistor blows that tube will not function properly and the triplet will not bias properly.
     
  16. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    I was tripping my ass off when it happened to me. When it was all said and done, I paid $189 for the tubes and about $250 to have the amp serviced and repaired. Now I will take it in once every couple years and pay them $75 to have it serviced. T
     
  17. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    Damn. Hoping for the best then. Gonna order three new tubes tonight and go from there.
     
  18. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    Real good chance you'll be fine.;)
     
  19. jason the fox

    jason the fox Often rocks and rarely rolls.

    Jul 2, 2013
    Nova Scotia, Canada
    New tubes arrived yesterday, just went with a matched set of three instead of replacing the whole works. Looks like everything is good. I put them in, let everything get good and warm, biased with no problem and everything sounds great.

    It's a relief to know I didn't have any other issues that would require serious surgery lol.
     
  20. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    That's awesome brother. Might be a good idea every 2 years or so to take it to a good tech for a check up. It will save you money on tubes and progressive amp repairs in the long run.


    Now, go rock that beyotch. :bassist:
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.