[ARC5] A little off-topic: Metal tubes (eg 6SJ7) seem quite valuable ...

[Tom Lee]

I would guess that there are no metal-over-glass vacuum tubes (the 0Z4 
and other gas-regulator tubes are not, technically speaking, vacuum 
tubes, so I'm excluding them). I would be happy to learn of exceptions 
(as well as the engineering reasons for the exceptions, if possible), 
but from my limited knowledge, it's hard to see a practical reason to 
build a glass vacuum tube, and then bond metal to the glass. Shielding 
is far more cheaply provided in other ways, for example.

-- Cheers,
Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 9/15/2021 15:37, William Cromwell wrote:
> Hi,
>
> Looking at the replies regarding glass tubes in metal sleeves it seems 
> that some are and others are not. Maybe most are not. I doubt anybody 
> here has any reason to report other than their experiences opening 
> metal tubes. I may have read some "fake news" once upon a time:)
>
> I was never interested enough to do a post-mortem on dead metal tubes. 
> Tubes that work should not be 'molested'. I did harvest a few octal 
> plugs from dead glass tubes. Low hanging fruit you know.
>
> 73,
>
> Bill KU8H
>
> bark less - wag more
>
> On 9/15/21 4:48 PM, Ben Hall wrote:
>> On 9/15/2021 3:24 PM, Tom Lee wrote:
>>> My experience is the same as yours. I’ve opened several over the
>>> years, and I’ve never seen one that was simply a metal covering over
>>> an otherwise glass tube.
>> Greetings all,
>>
>> Years ago I obtained a large quantity of assorted tubes - all just 
>> thrown into cardboard boxes - all of questionable provenance. After 
>> sorting them out, I had about 30 metal octals that were rusty and 
>> unidentifiable.  I try not to waste anything, so I cut them all apart 
>> to salvage the octal bases. (for what?  I don't know...but I will say 
>> I've made a few of them into test adapters, etc...)
>>
>> Every single one had a glass seal between the octal base and the 
>> metal envelope, but in all of them, there was no further glass. They 
>> were not glass tubes in metal sleeves; once past the glass seal, the 
>> metal envelope was what held the vacuum.  :)
>>
>> Thanks much and 73,
>> ben, kd5byb
>>
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