No Plate

The DM160 indicator triode has no plate as such; instead it has a spiral grid coated with fluorescent material that glows when hit by the electron stream.

The construction can be though of that of tetrode, with a missing plate. The second grid glows green and is the Anode of this triode.

The back of the tube has a reflective plate to reflect the distributed glow of the grid, and serves as conductive support for the top of the filament. The red vertical streak is the filament.

The gray toned grid that is visible in the second photo is the anode, and the the gray tone comes from the fluorescent coating.. The silver post to the right is the reflective metal tab that also serves as cathode terminal. The copper rod to the left is just a support

The first photo shows both grid structures, with the gray tone anode surrounding the standard control grid.

DM160 (click photo to enlarge)

It is clear that there is green glow on the back side of the anode grid that faces away from the cathode. This means that electrons overshoot the second grid but are atracted back to make the grid glow green. The other side of the anode grid glow is seen by reflection from the polished back tab.

The tube size is quite small at 1.1inchX0.2inch (28mmx5.5mm) This is about half the size of a typical subminiature tube..

These 1200dpi images were collected with an Epson 1200U scanner. The two images with the fluorescent glow were taken with the transparency/negative scanner back-light that iluminates from the side of the scanner lid. I used Google-Translate to read this German language post about using scanners to photograph tubes.

Regards,

-Joe

This article was edited 31.Oct.09 18:27 by Joe Sousa .

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