Sovtek 5881 max plate dissipation?

Discussion in 'Glowing Bottle Tube Amp Forum' started by MrCoolGuy, Aug 4, 2020.

  1. schmee

    schmee Doctor of Teleocity Silver Supporter

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    They are re-stamped "Sylvania" lightly on the glass next to the main logo numbering. . I can barely see "B2819" (maybe) on the glass under the Sylvania, . No lettering on the bases anywhere. Test as new. Was going to sell but I may put them in my Blonde Bassman CLone!
     
  2. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    But no... they can't all be true. Regardless of plate voltage, tubes have a maximum plate dissipation. I understand the relationship between plate voltage, current and idle dissipation. I understand you can run them hot or cool... but usually a datasheet will show maximum plate dissipation... which helps you know what is safe.
     
  3. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Yeah, I Went ahead and ordered some old stockTung Sol 5881's. And, no, I didn't buy the Sovteks... they came out of an amp I was working on.
     
  4. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Max ratings are more arbitrary than you might think... they're chosen to balance output versus lifespan. If an RCA 6L6GC was designed to last 5,000 hours at its max rating of 30 watts, maybe it might last 10,000 hours at 20 watts or 2,000 hours at 35 watts. Any of those scenarios might be preferable depending on the use case. Granted, it you run a tube way too hot and cause the internals to melt, that's not safe! But any of the figures thrown out in this thread so far for Sovtek 5881WXTs are safe. :)

    Regardless, those real TS 5881s ought to treat you well!
     
  5. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Thanks for your reply. And I agree, those numbers surely are somewhat arbitrary. But they are there best we have to work with. A frame of reference... that I appreciate and defer to when biasing. Its just a good starting point. And biasing for 30 watt vs 23 watt mpd is a huge difference. But I just aim for about 55% then go by ear until it sounds right, then check again to see what I settled on. It's usually around 63%
     
  6. slider313

    slider313 Tele-Afflicted Silver Supporter

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    Those are exactly what they say printed on the glass: 6L6WGB which is a 5881. Not all bottles are the same size. If you look at the two plates, you'll see they are held together by "clips". Tung Sol 6L6WGB/5881's have welded plates. Sylvania did make their own version as did GE. The RCA labeled 5881's I've seen were all made by Tung Sol. I actually have a few sets of Sylvania branded Tung Sol 5881's.

    [​IMG]
     
  7. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Thanks for the info.
    Are your Sylvania's brown base?
    I was wondering about these because of the oddball "Sylvania" ink stamping, one is partially over the "6L6WGB" etching. Indicating to me it was an after branding.
    I dont remember WGB tubes from the 60-65 ish time frame, seems like you always saw 5881 designation. Is WGB a later thing, or did I just miss it? I've heard WGB's referred to as 5881's but were they really the same tube early on?
    Seems funny they would make a 50 watt Bassman but then put a lower watt tube in it from the factory.... another wonderment!
     
  8. zombiwoof

    zombiwoof Tele-Afflicted

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    As I recall, there was a period after the last current manufacturer of 6V6 tubes shut down years ago, there were no 6V6's at all except NOS ones. GT offered the Russian 6L6GB as a substitution for a 6V6 that would work, even though it was not optimum. After a while, current manufacture 6V6 tubes became available from the East European, Russian, and Chinese tube manufacturers and GT once again offered true CM 6V6's. People forget about how bad it got back then, that's when Fender stopped making any 6V6 amps and all of the amp companies started making EL84 amps instead, as those tubes were still around in quantity. That's when Fender started making the Blues Jr. and Pro Jr.
    Al
     
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  9. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    I didn't realise it got that bad! That's crazy. I guess I've always taken tube availability for granted.
     
  10. vanr

    vanr Tele-Afflicted

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    Sovtek 5881WXTs are virtually indestructible.
     
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  11. zombiwoof

    zombiwoof Tele-Afflicted

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    Not only that, but when Tesla shut down, there were NO EL34's being made. That caused Marshall to switch all their amps to Sovtek 5881's, which Jim Marshall hated to do, he loved the EL34's as "the" Marshall sound. That lasted for a year or two, and the first new EL34's to appear as current manufacture were the Sovtek skinny bottle ones, which Marshall adopted as soon as they determined they would work, and they switched back to EL34's. Those first Sovteks were made on the old RFT machinery, which the Russian factory acquired from the defunct German tube manufacturer. They were OK, but not the greatest for EL34's, definitely not as good as the RFT/Siemens tubes they looked like.
    Around that time, when Tesla shut down, I made a trip to ARS in Van Nuys CA to grab some Tesla EL34's, as I assumed they were going to go up in price. When I got there, the guy said I was out of luck, as Marshall had recently bought up the last 10,000 of them he had for warranty stock, so they could service their older amps with EL34's. It seems funny now, when we have so many current manufacture tubes to choose from, but back then everyone was worried that the time of no available tubes might actually come. It was a strange time for tube amp people.
    Al
     
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  12. ReverendRevolver

    ReverendRevolver Tele-Afflicted

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    When was all this?

    I totally came late to the party, but I don't ever recall worrying about were tubes would come from. My dad was into ham radio, and most of his acquaintances in the late 90s just had random piles of old unused audio tubes. I vaguely remember him saying buying stuff off them was the backup plan if a power tube died while we borrowed tube stuff early on.

    I definitely recall the story of 6v6s not being made for awhile being the reason the Bjr and Pro jr are el84.

    Interesting.
     
  13. Abu Twangy

    Abu Twangy Friend of Leo's

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    I ditched my tube amps for SS in 1979 after having read an article warning about dwindling supplies as companies were winding down tube production. Where I was living 6550s were virtually unavailable and had more than doubled in price if you could find them. I dropped out of music for about 15 years only to discover tube amps were still thriving.
     
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  14. radiocaster

    radiocaster Poster Extraordinaire

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    By the way, the datasheet I posted does list the maximum plate voltage as 250V, although this has been confirmed as not bearing any consequence on forums. I remember reading on a Russian forum that someone used them with 800V on the plate or something like that and had no problems. It's the plate dissipation that you should worry about.
     
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