[R-390] OA2 replacement

[Roy Morgan]

At 09:25 AM 10/21/2005, Tim  Shoppa wrote:
> >> I've had several OA2's ...they >> intermittently fail to strike
>...  Do all OA2's have Krypton-85 in them?


Tim,

No, not all 0A2's have any radioactive stuff in them. Only some of them do.

>Looking it up, Krypton-85 has a half-life of 11 years...

That may well explain why these tubes fail to work right.

>Maybe the early/mid-70's OA2's have marginal quantities of
>Krypton-85 in them to begin with and go bad after a decade
>or two?

Possibly. I'd expect they had just the right amount in them, for the 
requirements of the time.  The purpose of the radioactive stuff (Just a few 
different materials were used, as I understand it) is to make them fire 
more reliably. A regulator tube without the radioactive materials and in 
the dark will strike either less reliably or at a higher voltage than 
otherwise.

>I have a sizable stock of OA2WA's and none of them say
>anything about Krypton-85 on them.  Does this mean they
>predate labeling requirements, or maybe they have some
>other means of ensuring they strike?

It most likely means that they don't have any radioactive stuff in 
them.  There may well be other ways employed to make them strike reliably, 
but that's tube makers craft and art I am not familiar with.

Try some in the dark and then in the light. Report the results.

I repeat Morgan's Rule about Radioactive Meters and VR Tubes:

         DON'T BREAK THEM OPEN AND EAT THE INSIDES.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --