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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

How to remove tube metalization

Next week will receive pair of cheap old tubes with metalization. it is even guided to socket pin.
But i´d like to remove that out, have bare glass. Maybe it will go with knife, but want to do chemical method.
Help anybody ?

coating looks similar


Paid Member
2009-08-20 3:16 pm
KC Metro
As a reformed restorer of 1930's radio sets (hence my user name), I have to totally agree with the gentlemen above.

IIRC (I can't find my Ludwell Sibley tube book at the moment), metallization was introduced by a few tube manufacturers in the early '30's as a means to shield RF tubes without using - are you ready for this? - the separate metal tube shields that were pretty much the standard with most other manufacturers. They're generally remembered as more of a marketing ploy than anything else, and their manufacture in the US declined rapidly with the introduction of metal tubes like the original 6L6.

These look like nice, unique little shielded triodes that would likely work well just as they are. Aside from ruining the resale value of the tubes, removal of the metallization entails the risk of breaking the glass envelope. In addition, there's no telling what was in that "secret recipe" used for the shielding; maybe it's benign, maybe it's not. But I can assure you it's not seven herbs and spices. ;)
this is the end result, sharp knife did it. On top is grey paint, and soft metal sits on glass. will try melt it with soldering iron. (lead/tin electrochemically deposited?)
I´ll see how they sounds, seller has many of them if i change my mind.
in person looks nicer, but not stc3a-110 like

(not a historical telefunken, i´m not that cruel)


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