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Tungsram getter spots on RF tubes

niculaie

Member
2014-04-02 12:19 pm
Hello colleagues,


What is your opinion on the (new) rf Tungsrams with getter like spots on the side?
How could they appear there by a manufacturing process? I think this producer is the only one to have this.
The image is not mine, is just for example.


1252-2.jpg
 

Sorento

Member
2008-03-12 9:59 pm
After flashing getter condensation takes place on the coolest spot(s).
This is normally the dome section.
But if they use external holders / clamps / fixtures or whatever which keep these spots cooler than the rest of the glass tube some of the vapor can condensate there.
 

Parafeed813

Member
2012-08-15 8:24 am
This isn't the usual barium getter which condenses on the glass close to the dish.
I had some EL84s that had these 'side flashes'.
One cracked, turning the top getter white instantly.
The flashes on the sides (which are in line with the holes of the anode) remained silver.
 

Elvee

Member
2006-09-08 2:04 pm
I have noticed these dark (when the process begins) or silvery patches on some heavily used tubes.
It always occurs in front of an aperture of the anode (or shielding), meaning it is probably some kind of metal sputtering or evaporation originating from the inside, most likely the cathode since it is the hottest spot in the tube.

I have no idea about the exact mechanism leading to that
 

niculaie

Member
2014-04-02 12:19 pm
After flashing getter condensation takes place on the coolest spot(s).
This is normally the dome section.
But if they use external holders / clamps / fixtures or whatever which keep these spots cooler than the rest of the glass tube some of the vapor can condensate there.


This could be an interesting explanation. Maybe other producers used tube holders that do not conduct heat (like if they had a cloth on them), and Tungsram used tube holders that conduct heat (like bare metal)