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In Reply to: RE: 6gk5 users, what do you do with the internal shield? (nt) posted by Tre' on May 04, 2017 at 19:39:56
I found this image on a Japanese page describing no only the 6HA5 but the 6gk5 as well.Translated, " In the literature *, in 6GK5 and 6HA5, there was explanation that Cpg was decreased by placing a plate of a small area far and focusing the electron flow by the beam plate."
The "beam plates" shown would be the internal shield if a 6gk5 were being depicted.
So, like a planar tube, the cathode to plate current (in the 6ha5 and the 6gk5) only flows from the wide part (top and bottom as shown) of the cathode to the portion of the plate that is closes to the cathode, each side and not off the ends (left and right).
The rest of the plate is "shielded" from not only the grid but also the cathode.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/04/17Follow Ups:
This looks more like a tetrode/pentode. Does that page say what the screen grid is connected to?
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Buy Chinese. Bury freedom.
The page says "However, the figure is [labeled] 6HA5, but with a screen grid it is a 4-electrode tube, so it's not 6HA5. This is a 4-pole tube such as 6CY5, 6EA5, and 6AB9 one unit."The point is, the internal shield of a 6gk5 looks like and does the job of the "Beam Plate" as shown in the mis-labeled image in my previous post.
It forces the tube to behave as a planar tube, conducting only where the plate to cathode spacing is parallel and controlled.
From the book (Amplifier Handbook) "incorporates beam plates to direct the flow of electrons to the desired portion of the plate"
https://books.google.com/books?id=ieFEAAAAIAAJ&focus=searchwithinvolume&q=6ha5
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/05/17
.
Have Fun and Enjoy the Music
"Still Working the Problem"
That makes more sense. You know, there's a large range of tubes of this genre, many different types and many have Gm of 15K. I wonder if anyone here has performed any distortion measurements with these?
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Buy Chinese. Bury freedom.
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