[Tech2]

I was browsing some tubes on ebay and came across an auction for a rectifier tube (5U4G) which had the following statement in the description:

"This tube features ribbed black plates and a single side ribbon getter. The green base markings are totally intact and the type number is legible. The getter flash has migrated to the top of the tube through use."

I have highlighted the part in question.

I was not aware that the getter flashing could 'migrate'. I thought it was deposited onto the tube when the tube was flashed, and that the only change over time would be an oxidization of the flashing.

Is this person mistaken?...or can the getter flash actually move about within a tube?

 

[braillediver]

This is my assumption and you know what they say about assumptions:

I believe they are talking about metallic deposits above the filament tubes? It is a shiny material like the getter flash but it's something else all together. I think as the tube is used metal molecules are vaporized and they flow up with the heat and are deposited on the inside of the tube just above the filament holes. This results in a small dot of silvery appearance on the inside top of the tube.

I believe this indicates a used tube and possibly a well used tube.

I don’t have any pictures available to show what I think they are talking about but as far as I know the getter doesn’t move.


Mitch

 

[jamato8]

Most of the times it represents a very used tube. I do have some nice 6J5 ST tubes that have very little use, mostly for heating up and testing that formed this within an hour or so, but most all the time it is from long use and it is, as stated above, not getter.

 

[Tech2]

Thanks guys.

I looked at some of my tubes, and found two that exhibit what you are referring to: One Raytheon that has a couple of faint spots on the glass envelope, right above the heater filaments. One Sylvania tube has a bottom-side getter (the flashing is still there, near the base), but the top of the tube is heavily coated in 'silver'. Very obvious. This is probably what the ebay seller is referring to on his tube.

Should I assume that my Sylvania is a heavily used tube?

 

[jamato8]

I would say most likely it has quite a bit of use. This doesn't mean that it isn't good but it should sell at a vairly reduced price. I prefer tubes that are easily ubtainable to be nos not used.

 

[Tech2]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif I would say most likely it has quite a bit of use. This doesn't mean that it isn't good but it should sell at a vairly reduced price. I prefer tubes that are easily ubtainable to be nos not used.

I prefer NOS also, unfortunately NOS seems to mean different things to different folks, especially on ebay. I've seen 'NOS' tubes on ebay that were obviously used. I think some folks call any old tubes 'NOS', even though used, especially if they have an original box. The Sylvania 5U4G was listed as used, and I paid $5 for it. I wanted to try a Sylvania rectifier tube in my Woo6.

 

[jamato8]

As long as it tests good. A used rectifier that is on the downside of working well will ad a soft sound to the music, not good. But if the tube tests good it should work fine and the Woo doesn't put much strain on a rectifier. Many of the rectifiers for the Woo 6 shouldn't cost a great deal of money. Excluding some of the GZ34's and a few others, there are many good rectifiers to try out. I rarely sell tubes I think I wonh't use after I have gotten rid of or changed the equipment using the tube from that tube as you never know when it might come in handy.