Gassy roundy has Copper evacuation nipple

[ctc17]

This is a RCA factory 21FJP22 Hi Lite. It was in a CTC16xl I recently acquired. Does anyone know if all these use this? Im looking at the the one in my CTC11 and its the same. No wonder why these thing seem to be going to air.

Im going to look at my hawkeye rebuilds right now.
The rebuilds have the all glass nipple. Only the factory RCA appear to have the copper pressed inside the steal.

[Eric H]

Seems like a really bad way to build a tube.
Almost guaranteed to leak eventually, of course what did they care if it didn't last 50 years, it wasn't intended to.

Maybe some Vacuseal would be a good idea in this application?

[damen]

I looked at a channel master rebuild and a another rebuilt tube I have they look like glass there the best I can tell. That is odd they made them like that back then.

[jr_tech]

At one time the copper pinch off was regarded as a higher quality but more expensive method of tipping off a tube, and was employed on a number of expensive special purpose tubes. The "cold weld" of the copper provides a near perfect seal, and does not out-gas during the seal process as heated glass does. Interesting to note, however that the 15GP22s employed copper pinch off. Does anybody have any data on long term leakage rates of cu pinch vs glass tip offs
jr

[miniman82]

The developmental CRT I have uses this type of seal, I often wonder if it would be a good idea to apply some vacuum sealent to avoid any future dismay.

[Zenith26kc20]

My Admiral has a 12lp4 with the copper seal (gone to air) also. I was wondering about that sealing process......

[TubeType]

Early on, this technique was quite common. The 15GP22 is a perfect example. Just pop off the 20-pin plug and voila.

[NewVista]

Originally Posted by TubeType

.. The 15GP22 is a perfect example. Just pop off the 20-pin plug and voila.

Didn't know this, another source of trouble for a troubled tube.
Those who have good ones are indeed lucky.

[eberts]

crack.JPG

[jeyurkon]

The crack eberts points out is probably caused by the large glass/metal joint. The copper tube is probably joined to something like kovar which matched the CTE of glass better.

Making such a glass/metal seal probably isn't easy.

John

[old_coot88]

Somehow the title of this thread suggests a tubby, flatulent old gal who's into kinky body adornments.

[old_tv_nut]

Scotty thought the pinch would be the problem on my 21ax, but it was the flange

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