[Michael Koster]

Hi,

Perhaps this is OT a little, but I've always been curious.

If one forcibly opens a vacuum tube (shatter the envelope)
there is immediately a strong somewhat unpleasant earthy
pungent odor (sorry for the wine words) almost like garlic
or mercaptan.

I always wondered what the source is? It must be oxidation
of some material or coating because there would be no gas
and therefore no odor in the sealed, evacuated tube.

Anyone know?

Michael

[Sander deWaal]

Michael Koster said:

Hi,

Perhaps this is OT a little, but I've always been curious.

If one forcibly opens a vacuum tube (shatter the envelope)
there is immediately a strong somewhat unpleasant earthy
pungent odor (sorry for the wine words) almost like garlic
or mercaptan.

I always wondered what the source is? It must be oxidation
of some material or coating because there would be no gas
and therefore no odor in the sealed, evacuated tube.

Anyone know?


For your own sake, I hope this wasn't some kind of RF power tube.
Some of them contain berylliumoxide, which is, in particle or dust
form, highly toxic and lethal.

In all likelyhood, what you smelled was the getter material, most
likely some barium-like alloy.

But wrt. BeO: *never* smash tubes on the ground, never attempt to open
them, never ever try to open RF power transistors and the like.
Though manufacturers have the obligation to mention that on the
device, many didn't in the past, or just mentioned the use of BeO in
the datasheet only.

Here is the symbol you should see on a component containing BeO:
http://www.uploadarchief.net/files/download/beo.jpg

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Michael Koster]

Sander deWaal wrote:
Michael Koster said:


Hi,

Perhaps this is OT a little, but I've always been curious.

If one forcibly opens a vacuum tube (shatter the envelope)
there is immediately a strong somewhat unpleasant earthy
pungent odor (sorry for the wine words) almost like garlic
or mercaptan.

I always wondered what the source is? It must be oxidation
of some material or coating because there would be no gas
and therefore no odor in the sealed, evacuated tube.

Anyone know?



For your own sake, I hope this wasn't some kind of RF power tube.
Some of them contain berylliumoxide, which is, in particle or dust
form, highly toxic and lethal.

In all likelyhood, what you smelled was the getter material, most
likely some barium-like alloy.

But wrt. BeO: *never* smash tubes on the ground, never attempt to open
them, never ever try to open RF power transistors and the like.
Though manufacturers have the obligation to mention that on the
device, many didn't in the past, or just mentioned the use of BeO in
the datasheet only.

Here is the symbol you should see on a component containing BeO:
http://www.uploadarchief.net/files/download/beo.jpg

Yes, thanks! NB I'm not recommending anyone do this. I'm remembering
from when I was perhaps 10-12 years old and used to dissect everything.
Back then I didn't worry too much about all of the toxic materials
used; my curiosity dominated...

I'm also curious as to whether all of the materials science for vacuum
tube manufacture has been preserved or if some is lost trade secrets.

Thanks,

Michael

[Sander deWaal]

Michael Koster said:


I'm also curious as to whether all of the materials science for vacuum
tube manufacture has been preserved or if some is lost trade secrets.


Since they're still making tubes in Russia, China, Czechia etc., I
don't think all knowledge is lost completely.

Perhaps it's just the knowledge to make a good, reliable and
long-lasting tube that is lost......... ;-)

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Patrick Turner]

Sander deWaal wrote:

Michael Koster said:

I'm also curious as to whether all of the materials science for vacuum
tube manufacture has been preserved or if some is lost trade secrets.

Since they're still making tubes in Russia, China, Czechia etc., I
don't think all knowledge is lost completely.

Perhaps it's just the knowledge to make a good, reliable and
long-lasting tube that is lost......... ;-)

I think modern tube makers well know how to make great tubes that last OK.

The pressure is always there from bean counters to cheapen the processes.

But users of tubes including many high-end manufacturers do not instal
active protection to prevent tube failure if the bias fails.
DIYers and musos account for much abuse of tubes, both with mis-biasing
and using loads that are too low and not noticing when something is wrong.

Tubes have always got the blame for the stupidity occuring around them.

Patrick Turner.





--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Sander deWaal]

Patrick Turner said:


I'm also curious as to whether all of the materials science for vacuum
tube manufacture has been preserved or if some is lost trade secrets.


Since they're still making tubes in Russia, China, Czechia etc., I
don't think all knowledge is lost completely.

Perhaps it's just the knowledge to make a good, reliable and
long-lasting tube that is lost......... ;-)


I think modern tube makers well know how to make great tubes that last OK.


Oh, they do know for sure,


The pressure is always there from bean counters to cheapen the processes.

But users of tubes including many high-end manufacturers do not instal
active protection to prevent tube failure if the bias fails.
DIYers and musos account for much abuse of tubes, both with mis-biasing
and using loads that are too low and not noticing when something is wrong.


I think you will agree with me that e.g. NOS807s last longer and can
withstand more abuse than those of today.

Also, I used Philips E88CCs in an application where they drew 15 mA
per triode at 90V idle, which is close or above the rated Pa for each
anode.

They lasted 8+ years in that application.

JJ Teslas lasted 3 years in the same application, one shorted cathode
to heater, the other just dies from emission starvation.


Tubes have always got the blame for the stupidity occuring around them.


Not always, Pat.
Geetah geezers, yes, but us knowledgeable bottleheads? ;-)

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Ned Carlson]

Michael Koster wrote:

Yes, thanks! NB I'm not recommending anyone do this. I'm remembering
from when I was perhaps 10-12 years old and used to dissect everything.
Back then I didn't worry too much about all of the toxic materials
used; my curiosity dominated...

It's probably the smell of getter material reacting with the
air. Whether that stuff is dangerous, I don't know, but I wouldn't
intentionall sniff the stuff.


I'm also curious as to whether all of the materials science for vacuum
tube manufacture has been preserved or if some is lost trade secrets.

AFAIK, documents of pretty much everything that's ever been known or
researched about tubes are stored at the US Naval Research Laboratory.
(There's a few things they know they won't tell you about, too)
One of the fellows there compiled a bibliography of the most
important publications, it was pretty extensive.

--
Ned Carlson
SW side of Chicago, USA
www.tubezone.net