Let's have some fun this month and have a look at a tube which is not usable for audio applications yet very interesting. Please meet the 6EN4.
The 6EN4 is a beam triode designed for shunt regulation of the high voltage power supply in color TV sets. The Cathode ray tube (CRT) of such TV sets needs a very high voltage to accelerate the electron beam towards the front. This voltage is usually in the range of 20kV and more.General Electric data sheet for all specs.
As can be expected from the specs, such a tube has a rather unusual construction.
At the bottom we see the beam forming shield which is internally directly connected to the cathode. The plate has a large cylindrical shape which is not around grid and cathode.
Grid and cathode are mounted horizontally inside the beam forming shield which has a opening on the top to direct the electrons towards the plate.
A close up to grid and cathode:
Very small distance between the grid wires and the cathode and large distance to the plate.
Extremely rugged construction.
The top cap is very solidly tied into the glass without any risk of coming loose as is often the case with other tubes with top caps.
A warning about potential X-rays produced in such tubes directly printed onto the base.
Let's have a look inside this engineering marvel.
The bottom part with cathode and grid inside the beam shield.
The grid got damaged when I broke the glass bulb.
Removing cathode and grid from the shield:
The tiny heater:
Close up to grid and cathode:
What a beast of a tube! I hope you enjoyed it.