I have recently acquired some russian tubes (6P31S) to find out if they have the same nice triode characteristics as the el36 does.
Now I noticed these tubes dont have the barium (or whatever it is) mirror at the top, or side of the tube.
This seems to be normal for these tubes, as i have seen by the pictures on the internet, but i was wondering how these tubes keep their vacuum this way.
They seem to have something instead of a normal gether at the top of the tube, it look like a small cup filled with grey powder.
For a picture, see here: http://www.jogis-roehrenbude.de/EL34-Story/EL34-Story-Dateien/6P31S-EL36-6CA5.jpg
Now I noticed these tubes dont have the barium (or whatever it is) mirror at the top, or side of the tube.
This seems to be normal for these tubes, as i have seen by the pictures on the internet, but i was wondering how these tubes keep their vacuum this way.
They seem to have something instead of a normal gether at the top of the tube, it look like a small cup filled with grey powder.
For a picture, see here: http://www.jogis-roehrenbude.de/EL34-Story/EL34-Story-Dateien/6P31S-EL36-6CA5.jpg
Some russian toobs have these pellet getters. They seem to work fine, but I've never really seen them on western tubes for some unknown reason.
This is a guess but being attached to the anode would allow them to be heated nicely. Another guess would be that they would not be used in small signal valves.
Cheers Matt.
Cheers Matt.
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