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Apeg SVT-CL Tubes

Discussion in 'Amps and Cabs [BG]' started by Charr, Dec 21, 2004.


  1. Charr

    Charr

    May 14, 2004
    Copenhagen, Denmark
    okay - need some advice, i seem to have blown 2 power tubes (svetlana 6550's) and obviously they need replacing!

    my questions are :
    1) can i "just" replace the 2 blown tubes?
    2) and are svetlana all that? i know the sovtek are about half price, but are they dependable, and do they mess the sound up??

    hope you can help me :)
     
  2. Ampeg suggest that you replace all six off at a time( ouch ) i know they run in matched sets so im not sure if changing just two is a good idea, maybe AMPEGINSIDER can give a better answer. Im afraid thats the downside to having an all tube amp, hope it can be sorted quickly just watch the bias adjustment or you might blow the other 4 off !!

    Mart
     
  3. Charr

    Charr

    May 14, 2004
    Copenhagen, Denmark
    yeah, it bites pretty hard - especially here near X-mas!
     
  4. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The problem is that the tubes are biased as groups. So if the ones in a group are not matched fairly well, one may pull more current than the others, or it may be loafing and throwing more load on the others.

    There are two groups of three. The left three and the right three. Therefore, they only really need to be matched in groups of three. If the two groups are not balanced, you can get some added harmonics. The balance control on older units could fix that to some degree.

    The manual has instructions on how to set bias via the bias lights on the back, and what to do if the matching isn't perfect. You can even use the lights to determine if the tubes are matched.

    So, if you get two tubes, you can swap around until the matching shows up as good enough. That can be a pain and be a bit fiddly, so your choice.

    It also depends if the two "bad" tubes were in one group, or were one in each group.

    Also......when you say two tubes are "blown", how did you determine that? Tubes are rarely "blown", i.e. really damaged, without something else happening also. But its possible, and the protection in the CL will usually keep damage from happening.

    What was seen that made you decide thet you had two bad tubes?
     
  5. Charr

    Charr

    May 14, 2004
    Copenhagen, Denmark
    well, the tubes were not "blown" (my bad) there were just no lights in either of the tubes, so i switched them with "working" tubes to see if it was the tubes or something else that was the problems - the unlighted tube i switched remained "dead"

    how about other brands of tubes? say some of the sovtek's? with those i can (just barely) afford to replace all 6 tubes at once, which would be the best (at least thats what people have told me)
     
  6. l like Sovteks as well as Svetlanas and also Electro harmonix, stay clear of Groove tubes as they brand other peoples and they charge accordingly.

    I would go for either EH Sovtek or Svets and get at least a matched set of three if money tight and start from there or negotiate a beter price and get all six off and then you set for a few years keep the others as spares for live gig repair tubes etc.

    Mart
     
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The "no light" means filament is open, since you moved them around and the bad tube was always the bad tube. Otherwise it could have been a bad connection on one socket.

    Odd, but possible. I have rarely seen that problem alone (along with other problems, yes), but with the current tubes, a lot of "unusual" stuff is far more common than it used to be.....

    If they have been that way for a while, the otehr tubes have been working harder, and could have had some "faster wear-out" of the emission material.

    Myself, I would be inclined to just replace the two tubes. I'd juggle around until I got them matched up in sets according to the lights (or a measurement).


    But there is always the chance that your particular two won't match up decently, forcing you to get another one or two. You don't want to nickel-and dime yourself to death trying to get away cheap (ok,...$10 yourself to death, they ain't cheap). For that reason, and the possible early wear-out per the above, you certainly won't go wrong replacing all 6.

    With a unit like the SVT, where the tube ratings are "pushed" somewhat, it can certainly be better to have a matched set that will bias up together. How you get there can be with a bought set, or by manually matching per the lights. One is a lot less trouble, but costs more. The other can be troublesome, may not be as accurate, but is cheaper.

    I tend not to be tube-paranoid, since I've been dealing with tubes a long time. Your mileage may vary....
     
  8. Charr

    Charr

    May 14, 2004
    Copenhagen, Denmark
    thanks for your advice!! this place is so cool - theres allways someone who can help out :)

    anyways, i just went to the (not so) local musicstore, and i bought 6 new powertubes, of the sovtek kind, totalling 1250 DKR (approx 190 $) and by our standards that pretty darn cheap - now i just have to put them in my amp :bassist: