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1920's "B" Battery Eliminator History
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Author:  Rick Hirsh [ Mar Sat 29, 2014 1:12 am ]
Post subject:  Re: 1920's "B" Battery Eliminator History

Alan Douglas wrote:
So at least one exists. I wonder who bought it?

I just looked up the total emission of a UV201A and it was 45mA. You couldn't run one anywhere near that, with a high plate voltage, or ionic
bombardment would wipe out the thoriated cathode surface. I'm guessing that Kellogg found that out sooner than they expected.
The original UV213 rectifier had a rated output of 10mA but that was quickly increased and the final design of UX213 by the summer of 1924
had a total emission of 350mA. If Kellogg's eliminator was capable of 10mA, which seems likely, it would have been obsolete before it ever
reached the market.

Hi Alan,

I have a couple of questions for you, regarding your comments that you had made ...

1) You had mentioned that the high plate voltage ion bombardment, would wipe out the thoriated tungsten cathode surface of the UV-201A. But, what about the RCA UV-216B (half-wave) and UV-213 (full-wave) rectifier tubes that were developed in 1925, which also uses the same thoriated tungsten cathode filaments ?

2) And isn't oxide-coated cathode (direct-heated) filaments, more susceptible to damage from ion bombardment, than the thoriated tungsten cathode filaments ?

Thanks Rick

Author:  Alan Douglas [ Mar Sat 29, 2014 1:25 am ]
Post subject:  Re: 1920's "B" Battery Eliminator History

I'm getting dangerously close to the limit of my knowledge, but I believe as long as you have enough space charge around the cathode, positive ions don't reach it. When you start pulling more electrons off than the cathode can supply (emission-limited operation) you lose the protection of the space charge. The rectifier cathodes had more surface area and lots of total emission. I'm also under the impression that rectifier cathodes are oxide-coated (the pre-1930 ones flake off pretty commonly) but I have not looked that up.

Author:  Rick Hirsh [ Apr Thu 10, 2014 4:07 am ]
Post subject:  Re: 1920's "B" Battery Eliminator History

Hi Alan,

Sorry for the long delay in response to your last reply, but I have been very busy with work related projects, and I have very little time for anything else.

But as far as "positive ion bombardment" of the RCA UV-201A thoriated-tungsten cathode filaments ...., this was a problem that had occurred, when it was first developed and used on the original 1922 version of the UV-201A tubes. Later versions of the RCA UV-201A tubes had used an "improved design" starting around 1924, which had used a thoriated-tungsten cathode filament with a "carburized"(tungsten carbide) coating on the thoriated-tungsten surface. This improved process had helped reduce evaporation of the thorium atoms on the tungsten surface and also reduced the effects of positive ion bombardment damage. In fact, the RCA UX-213 and UX-216B rectifier tubes that were developed and released in mid-1925, had also used the "same" thoriated-tungsten cathode filaments, for it had much higher thermionic electron emissions than the regular tungsten cathode filaments.

Note: Both of the early versions of the RCA UV-213 and UV-201 tubes, had used the pure tungsten cathode filament design, and had much lower thermionic electron emissions than the thoriated-tungsten cathode filament designs of the RCA UX-213 and UV-201A tubes.



The Dubilier Super-Ducon UV-196 rectifier tube had used (2) separate oxide-coated cathode filaments in its design, which were more susceptible to positive ion bombardment damage, compared to the RCA thoriated-tungsten cathode filament design.



Note: Jerry Whitaker is an audio engineer, who has written and published more than 42 books.

Thanks Rick

Author:  Alan Douglas [ Apr Thu 10, 2014 1:19 pm ]
Post subject:  Re: 1920's "B" Battery Eliminator History

Well it looks as if both were used at various times. From the 1929 GE tube history, the 213 used a thoriated tungsten filament while the 80 was oxide coated. The 216 was thoriated and the 81 was oxide. The 10 was carbonized thoriated tungsten and the 50 was oxide coated. Since the oxide was the final choice for both rectifiers, I presume it had advantages.

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