5881 is an improved 6L6 for sockets which were eating too many 6L6. (Not 6L6GC, which is a different improved 6L6.)
Conceptually you have 5881 marked-up to remind you these will work in 6L6B sockets.
What you actually have, I have no idea. I do not remember that dual-marking back in the day, but I did not buy 6L6 every day, and I know modern marketers are very good at putting new labels on old bottles. (Opposite of what some wine-merchants do.)
Conceptually you have 5881 marked-up to remind you these will work in 6L6B sockets.
What you actually have, I have no idea. I do not remember that dual-marking back in the day, but I did not buy 6L6 every day, and I know modern marketers are very good at putting new labels on old bottles. (Opposite of what some wine-merchants do.)
The 6L6WGB was a 6L6GB stuffed into a small glass envelope with ruggedized mounting of the internals to handle the physical abuse of military applications. The 5881 is very similar, and in many cases are the same tube.
I have a bag full of very well used military pulls from the 60's and early 70's. I went through the whole bag and found an equal mix of 6L6WGB's and 5881's but NONE of them were dual marked.
If your tubes were indeed marked like that by the original manufacturer, then I would assume that the higher screen grid rating of the 5881 applies.
All of the tubes that I have are discolored from heavy use, so I have never even tried them in an amp.
I have a bag full of very well used military pulls from the 60's and early 70's. I went through the whole bag and found an equal mix of 6L6WGB's and 5881's but NONE of them were dual marked.
If your tubes were indeed marked like that by the original manufacturer, then I would assume that the higher screen grid rating of the 5881 applies.
All of the tubes that I have are discolored from heavy use, so I have never even tried them in an amp.
Thanks tubelab. I was hoping you'd provide your opinion. I guess I should try them and see if they hold up at the 350v B+ my amp provides. What am I risking by doing that other than the tubes?
Tung Sol 5881 is ok (max plate, screen 400V) but for 6l6wgb max plate 400, screen is 300V. So you need to drop 50V when B+ is 350V. Use 50V zener bypassed with film cap to test first.
So is the consensus that these are actually remarked 6l6wgb then rather than 5881?
Also, I have no issue sacrificing them I just don't want to sacrifice an output transformer.
Also, I have no issue sacrificing them I just don't want to sacrifice an output transformer.
I agree with Tubelab that these are factory marked, and thus should be OK at the higher voltage. In other words, the factory guaranteed they could replace either.
The new 6L6WGB tubes made in China can withstand Ua ~ 500V (even higher voltage!), And Ug2 ~ 450V without any traces of instability and overheating. The size of the plate is the same as with the 6L6GC tube from JJ, and it behaves almost the same in operation.
Electronic Vacuum Tube Value Tube Low-noise DIY 6L6WGB 6P3P 6L6GC | eBay
Electronic Vacuum Tube Value Tube Low-noise DIY 6L6WGB 6P3P 6L6GC | eBay
