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Sovtek 5881WXT?


 
9/4/2005 8:26 PM
Scott Sovtek 5881WXT?
Hi all,  
 
I wanted to make sure that the Max Plate Dissipation (PaMax) for the Sovtek 5881WXT is indeed 23W. Can anyone confirm this?  
 
Also, any other good subsitutes? 6L6GC?  
 
Thanks in advance,  
-Scott
 
9/4/2005 9:56 PM
Scott
BTW The reason I'm usure is that I've read on a few sites that the Sovtek 5881WXT really isn't a "true" 5881, but something different and actually closer to a 6L6GC.  
 
Also I've seen different PaMax values listed, some show 23W, others claim 30W.  
 
???  
-Scott
 
9/4/2005 10:04 PM
coledavis
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Start with Sovtek's 5881/6L6WGC, the one with the wafer base. This one isn't a true 5881 or 6L6GC, in Russian it's a 6pi33c which was used in MiG fighter jets (as a voltage regulator, I think). Put a full size base on it (so Fender bear claw clamps can grab it) and it's called the 5881WXT. Same tube electrically. IIRC even in the actual Russian datasheet (google around for it) it lists max plate dissipation as 20W, but that's at some ridiculously low voltage (200V or so) in fighter aircraft. I've read that the tube can actually dissipate more than 40W before dying, but I've never tried it myself. I remember having a quad in a Dual Showman biased to around 20W idle and they were fine for years and years. It's a very rugged and hard to kill tube.  
 
A TRUE 6L6GC, like a Svetlana, or Sovtek 6L6WXT+, or JJ, etc. is rated for 30W max.
 
9/4/2005 10:14 PM
coledavis
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Found the datasheets:  
 
http://www.waspware.it/pages/datasheet.php  
 
I think I know where the supposed 23W max comes from; the 2nd datasheet shows a max plate current of 90mA at 250V, which is around 23W max.
 
9/5/2005 4:23 AM
steve
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Actually the Sovtek "5881" is the 6Π3C-EB [6(pi)3S-EV). The E stands for "mechanically ruggedized; the B stands for "extended lifetime, 3,000 - 10,00 hour rating."  
 
Here is the link to a chart for deciphering the Russian/Cyrillic tube naming scheme:  
 
http://www.klausmobile.narod.ru/td/gost_e.htm  
 
Here is a link to the data sheet for the plain run-of-the-mill 6Π3C tube (no E or B rating):  
 
http://www.audiotriodes.com/data/6p3c/data.htm  
 
The EB version is much tougher. For all intents and purposes, it can be considered a 6L6GC, although it produces less power in circuits built around the 6L6GC.  
 
According to my Russian tube chart, there is a 6Π33Π but it crosses to 6CW5/EL86.  
 
steve
 
9/5/2005 12:29 AM
Scott
Thanks for the info. I also found the post mentioning they can handle upto 45W as well.  
 
So I guess I should use the 23W figure when calculating the bias current? Or should I go with 30W? I know a lower setting will make them last longer, but I'm more interested in what will sound better.  
 
I usually go for 70% of max.  
 
-Scott
 
9/5/2005 3:31 AM
coledavis
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Well, with that particular tube, even if the real max is unknown (or unclear) I wouldn't go more than 23W IDLE period. Start cold at 15W idle and go up from there.
 
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