Sunday, December 24, 2006

Make Your Own Triode

Here is a film from Holland showing the making of a simple Deforest type triode vacuum tube capable of rectification and amplification. Notice the vintage Philips refrigerator in the background and the use of Philips lab. I visited Philips a while back and saw their facilities in Best and Eindhoven, Holland.

Here is the video!

Baking elements helps remove residual volatiles and also eliminates the need for a getter. Most tubes you will use have a separate structure in them called a getter. The getter is an element used to accelerate and deposit the trace gases still in the envelope onto the inside surface of the glass. You can see it as a silvery shiny area in many tubes. Often the getter is a small ring shaped object near the top or side of the tube. Halogen lamps get so hot they generate tungsten vapor which clouds the envlope, but the filament and the heat recombine the vapor as long as the envelope is hot enough. This is "self getting" (not gettering!) and is what the Philips people did here to some extent with this the filament in their little triode.

The 12AX7 consists of a pair of very similar triodes in one envelope.


Anonymous said...

I have wanted to do something like this for years. Now I have no excuse.

Anonymous said...

In a similar vein: here is a website for antique light bulbs. I liked the article on the 50 and 75 kw light bulbsbut there is a lot more here including some reproductions of Edison's notebook describing his discovery of the "Edison Effect" ie. thermionic emission from whence the vacuum tube came.