6080 @ 800µA Question ...

[oldeurope]

Hello,
I am using a 6080WC at the input of my preamp. Anode current is 800µA per section.
Anode dissipation is 10mW per section. Since this is fairly low for a 6V3 2A5 heater,
does this cause deterioration of the emission surface?
Or does deterioration only happen if cathode current is switched off completely?
Does the WC have a protection against deterioration of the emission surface?

What do you think?

Kind regards,
Darius

[kenpeter]

I was of the impression that depleting the space charge was
the cause of stripping damage. Never heard of leaving the
cathode area flooded (with electrons) to cause damage?

I am interested to learn if this is true?

[SY]

It is, but it's not stripping, it's the opposite, the cathode gets poisoned and chokes. There's a nice, readable discussion of this in Robert Tomer's excellent book.

[oldeurope]

Thanks for the replies.
It's not poisoned, this is another effect.
I don't know the English word for Zwischenschichtbildung.
I think this happens at no current and does not happen at low current, I don't know.
I am going to measure the apparatus sporadic and will see what happens ...

Kind regards,
Darius

[Rod Coleman]

It's an interesting paragraph in your link Darius!

Zwischenschichtbildung means "formation of interstitial layer" judging from the description.

It suggests that "when the cathode is heated, but no anode current yet flows, a layer forms between the cathode carrier and the active layer, and causes a reduction in emission". The author claims this is a typical limiting factor to a valve's lifetime.

I have not heard of this process before, but would like to know more...

[SY]

That is precisely the poisoning process. Tomer's book may be found at http://www.pmillett.com/technical_books_online.htm along with the much deeper text "Vacuum Tube Design" (RCA). The mechanisms, causes, and cures are discussed in great depth.

[oldeurope]

Hello Rod Coleman,

thanks for "formation of interstitial layer".
Please have a look at the top of the data sheet for the E92CC.

Back to 6080WC, I don't know what WC means.
Attached a scan from the VALVO Taschenbuch '75
Note that the red tubes have a protection against this interstital layer,
the yellow valves not. I didn't find the ECC230 in this book.

Kind regards,
Darius

[kenpeter]

Zwischenschichtbildung [ Bearbeiten ]

Die elektrochemischen Vorgänge in den Kathoden sind der entscheidende, die Lebensdauer limitierende Faktor. Vor allem, wenn die Röhre geheizt wird, jedoch kein Anodenstrom fließt, bilden sich bei einer Oxidkathode schnell sogenannte Zwischenschichten zwischen Kathodenträger und der aktiven Schicht aus, die die Emissionsfähigkeit der Kathode drastisch reduzieren.

Diese Zwischenschicht kann begrenzt durch gezielte, vorsichtige Überheizung bei gleichzeitigem hohen Kathodenstrom wieder rückgebildet werden. Siehe Abschnitt „Regenerierung“.

Regenerierung [Bearbeiten]

Röhren können in gewissem Umfang regeneriert werden. Dazu wird während gewisser Zeiträume die Kathode gezielt überheizt, während gleichzeitig ein begrenzter Anodenstrom fließt.

Bei altersbedingt leuchtschwachen Anzeigeröhren wie z. B. magischen Augen ist eine Regenerierung im Allgemeinen nicht möglich, da die Gründe nicht in einer schwachen Emission der Kathode zu suchen sind, sondern sich fast ausschließlich in einem Taubwerden des Leuchtstoffes zeigen. Es gibt Möglichkeiten[8], durch massive Erhöhung der Anodenspannung wieder eine höhere Leuchtkraft zu erzielen.

Google Translate: German » English

Interlayer education []

The electrochemical processes in the cathodes are crucial, life-limiting factor. Especially when the tube is heated, but no anode current flows, the formation of a so-called fast oxide cathode intermediate layers between cathode-makers and the active layer of the emission capacity of cathode drastically reduced.

This intermediate layer can be limited through targeted, careful about heating, while high cathode rückgebildet power again. See the "regeneration".

Regeneration []

Tubes can to some extent be regenerated. To this end, during certain periods the cathode targeted overheated, while a limited anode current flows.

At age leuchtschwachen display tubes such as magic eye is a regeneration is generally not possible due to reasons not in a weak emission from the cathode to search, but almost exclusively in a Taubwerden light of the substance. There are opportunities [8], by massive increase in the anode voltage a higher luminosity to achieve.

This Patent might hold something of relevance?
http://www.google.com/patents?id=O7t...e+rejuvenation

[SY]

Ken, when I was a kid in the TV repair biz, this was known as "hot-shotting." It was most often applied to picture tubes. And it worked about half the time, though the fix is decidedly temporary. It mostly was useful for tubes that have exhausted the cathode coating, rather than having it poisoned (exceedingly rare in TVs where the heaters were not run in the absence of B+).

[oldeurope]

Ups, wasn't a good idea to make the wikipedia link ...

Anyone able to tell me the meaning of WC (6080WC)?

Darius