Tubes with shiny areas on the side?

[amplexus]

Hi.



It is SILVER, damnit .
Just like a working getter flash .


AFAIK, that's not exactly getter flash even though it's origins are usually the same materials, but rather deposits from the mesh screen coating and stray getter material atoms on tubes like EF80 & EF41.
The stray electrons remove and carry them onto the glass.

That kind of a "getter hue" (not a native speaker here so there may be an official word for it) in places there's no getter rings or -cups can be an indication of how much the tube has been used, and especially when buying used tubes and obviously wanting to pay as little as possible, is used as such as can be expected.

However:
A hue like that -EDIT: or the lack of it- doesn't necessarily tell anything about the tube performancewise, unless one has deep knowledge about that particular tube from the same manufacturer and from the same production period.
The amount of certain materials did vary a lot over the years, and so does the deposits.
Economics and profit played obviously a huge part in tube manufacturing, and also new material compounds were developed and tested.

Testing or getting them tested is really the only way to tell how they perform.

Regards,
Sam

I’ll be honest that still looks like getter flashing to me. If you see how it’s “feathered” around the mica “teeth” on the glass it looks exactly like how i’d expect flashing to behave.

Without knowing the specifics of the tube model and brand I would bet that its a heavy dose of getter flashing thats part of a ruggedizing process.

 

[S.Samuelsson]

Hi.

I’ll be honest that still looks like getter flashing to me.

The two issues about it being the getter flash is that there's already thick and uniform flash on the top of the tube, and there isn't any structure on the mid section that would hold and direct the barium vapour onto the more or less full circumference of the glass when flashed during the manufacturing process.

Another is that the getter flash like hue on the mid section of these kind of tubes is usually found on (well) used tubes, unused ones tend not to have them.

IIRC on some tubes the getter cup is indeed located on the waist area and the flash is a dot at the side of the tube (usually when the anode connection is at the top of the tube), but on those tubes there's no flash -nor cup(s) or rings- on the top of the tube.
At least I haven't seen any.

I do know that there was both granular and paste type getter materials, and the latter can obviously be used regardless of the orientation, but AFAIK the former was a way more common.
The paste probably could've been applied onto the outside surface of the mesh screen, but then the actual flash should/would be more uniform then.
And there probably wouldn't be an another flash on the top of the tube.

Also, it would not make much sense economically to have several intentional getter flashes on small and low power tubes.
And even less if the orientation of the tube would have to be altered between the flashings.

BUT, as I said earlier, my focus has always been on the common tubes used on AF-amps, so that extremely narrow take can bias the information I have gathered to a degree.

Regards,
Sam

 

[MagnetoSound]

I just pulled this GE 6L6GC from my Tremolux.

I remembered this thread and thought it might make a good illustration of what soft vacuum looks like, where the getter flash slowly turns white. Oddly enough, the same ‘cardioid’ pattern on both sides of the tube.

 

[Khron]

Well, as i hope can be seen in the photo in my initial post, i don't think any of those example tubes have lost any vacuum (no whitening of the getter that i can see), but some metal seems to have just been blasted / vaporized onto the side walls of the tubes, during however many years of usage those have seen.

 

[MagnetoSound]

I’ve seen lots of EL84s with the black stuff left by the stray electrons that have blasted through the holes in the plates.

 

[Chandra]

To fully remove any traces of oxygen inside the tube, a small piece of magnesium ribbon is placed and ignited. (Any oxygen present will reduce the filament life.)
This causes that traditional shiny mark on the tube.
When some portion of magnesium is not burnt, they stay inside and you can hear it by gently shaking the tube.
Regards.

 

[Khron]

To fully remove any traces of oxygen inside the tube, a small piece of magnesium ribbon is placed and ignited. (Any oxygen present will reduce the filament life.)
This causes that traditional shiny mark on the tube.
When some portion of magnesium is not burnt, they stay inside and you can hear it by gently shaking the tube.
Regards.

Thank you for NOT reading / understanding anything i've written in this thread, OR looking at the photo in the initial post that this thread started with...

 

[Chandra]

Thank you for NOT reading / understanding anything i've written in this thread, OR looking at the photo in the initial post that this thread started with...

Sometimes it is not good to reply to people who think they asked a super intelligent question.

Regards.