[Amps] Large or small Tubes, a question of perspective TSPA

[John T. M. Lyles]

At my workplace, small tetrodes are those with handles or glass 
bottles. If they have an eye hook for a crane or hoist, then they are 
larger tetrodes. In other words, if one man can carry them, they are 
small tubes and two (or a hoist device) then they are large. One of 
the bigger amplifiers can be seen in this paper:
go to the website
http://epaper.kek.jp/p01/HTML/AUTHORS.HTM
Search for my surname, Lyles and select the paper MPPF097 for 
details. The last photo shows an old Continental Electronics 
amplifier which uses the Burle (RCA) 7835 triode (oops, not a 
tetrode) and the right side is the prototype amplifier to replace 
that, using the Thales Diacrode (double ended tetrode).

I have a nice side by side photo of the two tubes hanging from 
cranes, that was not included in the report, available on request.

I agree that shunt regulators become impractical on large tetrode 
screen power supplies. I typically use series regulated switcher 
supplies now days, feeding a capacitor, and a large shunt load (power 
resistor). Using tubes with pyrolytic graphite grid material instead 
of wire helps minimize any effects of primary or secondary electron 
emission from the screen with subsequent reverse current.

73
John
K5PRO

On Jul 11, 2005, at 8:29 AM, Phil Clements wrote:

>  Subject: Re: [Amps] Tetrodes
>
>>  For small tetrodes, the safest way to power the screen is through a...
>
>  What is "small"?

Dick -- Those that use screen potentials of under 800v or so.   For
tetrodes with handles, shunt screen regulation is do-able but not very
practical.

cheers
>
>  73, Dick Knol
>  PA3DUV
>
>  Tubes that do not have built-in handles are small; to me anyway.....
>
>  (((73)))
>  Phil, K5PC