• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tungsram getter spots on RF tubes

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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
 
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 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.
 
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
 
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)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.