[Test-Equipment] Radioactive Tube Stamp (was: re: Nixie project)

[k4pf at juno.com]

> Dave Harmon" <k6xyz at sbcglobal.net> wrote
> I remember buying a used 30L-1 and the 811A tubes 
had a 'radio-active' stamp on them.
I got rid of them quick. 
Don't need an environmental cleanup in the shack!
I've never seen any other 811A's with that stamp.
At AT&T we used some other quick firing tubes with that stamp 
and we were careful not to break one of them.



Hi, Dave

That tube manufacturer was just being extra-cautious 
in his labeling.  All thoriated tungsten filament tubes
such as the 811A, 572B or 3-500Z are mildly radioactive, 
due to the thorium present in the filament.
The thorium reduces the work function of the filament
surface, making it a more efficient electron emitter.

73,
Ed Knobloch