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

[Tom Lee]

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.

I’ll try to dig up a link to some RCA advert that shows the anatomy of metal tubes. That drawing matches your and my experience as well. That doesn’t mean that there were not some metal-over-glass tubes, but it does reinforce some skepticism (such as that arising from asking why a manufacturer would do such a thing in the first place).

—Tom

Sent from my iThing, so please forgive typos and brevity.

> On Sep 15, 2021, at 1:10 PM, Rich Post <kb8tad at gmail.com> wrote:
> 
> 
> I have one that I whacked open due to a failed filament, wanting to re-use it as an octal plug.  The bottom button was glass but not the rest.
> 
> Rich KB8TAD
> 
>> On Wed, Sep 15, 2021 at 3:56 PM <frledda at att.net> wrote:
>> All the metal tubes I opened, many years ago, had metal on glass!
>> 
>>  
>> 
>> From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf Of scottjohnson1
>> Sent: Wednesday, September 15, 2021 2:53 PM
>> To: William Cromwell <wrcromwell at gmail.com>; arc5 at mailman.qth.net
>> Subject: Re: [ARC5] A little off-topic: Metal tubes (eg 6SJ7) seem quite valuable ...
>> 
>>  
>> 
>> Not true, unless it is MG (metal- glass) tube.  The rust is just cosmetic.
>> 
>>  
>> 
>>  
>> 
>>  
>> 
>> Sent from my Verizon, Samsung Galaxy smartphone
>> 
>>  
>> 
>>  
>> 
>> -------- Original message --------
>> 
>> From: William Cromwell <wrcromwell at gmail.com>
>> 
>> Date: 9/15/21 11:58 AM (GMT-07:00)
>> 
>> To: arc5 at mailman.qth.net
>> 
>> Subject: Re: [ARC5] A little off-topic: Metal tubes (eg 6SJ7) seem quite valuable ...
>> 
>>  
>> 
>> Hi,
>> 
>> A coupla things.
>> 
>> I have used rusty tubes as-is successfully. Your mileage may vary.
>> 
>> I have been lead to believe that inside that metal shell is a glass 
>> tube. The vacuum is not dependent on the integrity of the metal shell. 
>> Naybe somebody has contradictory information with citations.
>> 
>> 73,
>> 
>> Bill KU8H
>> 
>> bark less - wag more
>> 
>> On 9/15/21 2:10 PM, Leslie Smith wrote:
>> > A link: https://www.ebay.com.au/itm/283973399609 
>> > <https://www.ebay.com.au/itm/283973399609>
>> >
>> > Makes the idea of polishing rusty tubes worth-while.
>> >
>> > Leslie
>> >
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