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Firt time with tubes!

Discussion in 'Amps and Cabs [BG]' started by billsswills, Jul 19, 2012.


  1. billsswills

    billsswills

    Jul 19, 2012
    howdy all, just a simple question: first time tube owner, sunn sonaro, gotta replace the preamp. well since the tube's a million years old all the paint is gone and i have zero idea what number it is and the net isn't helpin me out very much. any idea what i need to buy?
     
  2. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    :)
     
  3. billsswills

    billsswills

    Jul 19, 2012
    thanks a million!
     
  4. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    Before running away and blissfully changing the preamp tube...what makes you think you need to? Is it actually causing problems? In many case 'old' preamp tubes are way better than new ones as long as their functional.
     
  5. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    It uses a 12ax7 for a rectifier?

    And +1 for Burning Skies. Just because it's old doesn't mean it's bad.
     
  6. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    I doubt it...I took it as 1x 12AX7 for the preamp (probably half for the initial gain stage and half for the EQ), and then a 'tube rectifier' of undetermined type.
     
  7. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
  8. The tube layout did change a bit depending on the year. On the inside of the head cab, there should be a tube layout schematic. If it's not there anymore, you can take the chassis out of the cab and post a picture. Might be able to help more.

    My '68 Sunn Sorado uses two 6550, a 5AR4/GZ34 Rectifier, 12AX7 and 6AN8 preamp tubes. I didn't see it at first, but once you take the chassis out, there's a second preamp slot behind the transformer.

    Here you can see all five tube locations of my Sorado:
    photo3-6.
     
  9. billsswills

    billsswills

    Jul 19, 2012
    the hum and popping and horrifying gargling noise that overpowers my speaker tells me it's bad
     
  10. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    Those would definitely be a good sign of 'bad. :D

    Its just that lots of guys get here and talk about how they need to switch out their tubes and its mostly because they're dusty and they're looking for something to tweak with, rather than an actual need.
     
  11. Marial

    Marial weapons-grade plum

    Apr 8, 2011
    Turn down and it won't firt so much.
     
  12. None of those symptoms are truly positive signs of a bad tube. Plate resistors can cause popping/crackling, so can loose tube sockets. Bad electrolytics can cause hum.

    When has this amp been serviced, if ever? A recap job, tightening the tube sockets, and possibly replacing the plate resistors likely will do the amp a world of good. Also check for cracked solder joints, another likely source of all those symptoms.

    I have preamp tubes that are over 60 years old and they are still going strong. Preamp tubes usually do not just wear out (they can be damaged by mechanical vibrations, or electrical abuse).
     
  13. billsswills

    billsswills

    Jul 19, 2012
    nashville bill i have no idea idea what the previous owner did to the thing besides put it on sale and sell it to me. i'll tell you what i'm going to do to get the bottom of it though: replace the tubes. if that doesn't work then i'll make sure to message you personally, how about that
     
  14. BogeyBass

    BogeyBass

    Sep 14, 2010
    Depends on the year some had the 7199 some had the 6AN8
    preamp tube. 12ax7 was used for V1 in both

    Think this was a 40 watt EL34 output stage similar to a Sonic I-40
    that used the 7199

    the later versions I believe switched to 6AN8 and 6550 output tubes for 60 instead of 40 watts.
     
  15. replacing the valves, may be a waste of money, take the amp to a tech and tell him to replace all the out of spec components and clean everything first
     
  16. Lo-E

    Lo-E

    Dec 19, 2009
    Brooklyn, NY
    +1. Ask around and find a tech you can actually trust (many are hacks - far too many) and bring it in and have them give it a good going over.

    There's a very good chance that it needs new filter caps (electrolytics), but it might not even need that. It might only need a good cleaning.

    Shelling out for new tubes is a big investment that may or may not be a solution to your problems. Definitely have a trustworthy expert check it out first. It could save you a bundle and, as others pointed out, the new tubes might not even be as good as the old ones that are in there now.
     
  17. billsswills

    billsswills

    Jul 19, 2012
    unfortunately my area is running very low on recognized amp techs. in fact, i don't believe anyone in the entire city knows a thing about'em, as no one has ever been able to recommend a guy. luckily i ordered the cheapest tubes i could find since i'm not THAT particular. sigh, at the end of the day it was a bigger investment for a gigantic sunn statue in my house.....
     
  18. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    Fill out your profile. Then the people here can see what area and city you're in and might have some suggestions. For all we know you could be in NYC, LA, Beijing, Sau Paulo, Aukland, etc.
     
  19. Lo-E

    Lo-E

    Dec 19, 2009
    Brooklyn, NY
    One way or another, you're going to need to get that thing looked at by a competent tech. If there's none in your area, you might start considering a very long drive (Road trip!!!) or a stop by the nearest UPS depot. Vintage amps are really pretty simple and very, very durable but right now you have no baseline by which to judge the overall health of the amp. Once you get it in top working order it will be super-reliable, but it all has to start with a trip to the doctor for a good checkup.
     
  20. I know people will argue with me on this, and if you're not familiar with amps I also agree on taking it to a tech, but Sunn amps are pretty simple to look at, clean up and do a basic diagnosis.

    Though the old tubes might be good and sound better, having a back up set of tubes is never a bad idea. Whatever you do, don't throw away the old tubes when you get the new ones in. If the sound goes away, you were obviously right about the tubes. If you can take the chassis out of the cab, you can buy spray to clean the pots, inputs and tube sockets in the amp. You don't have to poke around inside or anything and also good to have on hand. Another important thing is the power cord. If it still has the two prong, definitely get it changed if you're not comfortable doing it yourself. That will also eliminate hum. At worst, if it's still doing all the crackling and popping, you've learned the basics of checking out your own amp and it probably needs new caps, at which point, even I would take it to a tech for replacement. From my experience a faulty cap will crack and pop regardless of playing or not playing (though it's the same with tubes, but it's a different type of crackle and pop). You can check the tubes by lightly tapping on them with a pencil while the amp is on and connected. If they are overly noisy then try a different tube (which you said you ordered already).

    Again, I fully agree with taking it to a tech, these are just basic and simple things you can check out or do at home until you get it to a tech.

    Hell, you might already know all this and you were simply just looking for the tube type to throw in there. This is mainly going by what other people are responding. (no offense to them)
     

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