UY224 odd structure

Fellow radiophiles,

I came across this strange looking UY224 screen grid AC heated tube in the back of an Atwater Kent 82

Can anyone explain the structure?

Regards,

-Joe

      

 

 

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Dear Joe,

In addition to the standard 24 tetrode, Sibley lists the 24A version, designed for low secondary emission from plate. Maybe that the tube in the pictures above is the 24A. The odd shape can then be explained as a design choice to minimize the effects of the secondary emission. The draft below shows a cylindrical structure A and a square structure B, that approaches the one in your pictures. K are the cathodes and P are the plates. In the boxed structure B electrons extracted from the plate are preferably directed to other segments of the plate itself, so minimizing their action in the grid space.

        

It is only a guess, I know. But it could explain both the boxed plate and the asymmetry of the cathode displacement.
 

Regards, Emilio

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Dear Emilio,

Thanks for the explanation. John Stokes shows a picture of this UY224 as an early version on page 66 of his "70 years of Radio Valves and tubes" book from 1982.

Regards,

-Joe

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