THE GREAT MULLARD MAGIC BLOG — INDIRECTLY HEATED

Last time, we only covered half the story about the CATHODE and today we'll look at the indirectly heated type.  These have a construction in which a pure metallic nickel tube is sprayed with an emissive coating admixture comprising of barium and strontium carbonate.    In the picture below, you can see the various stages taken to produce an indirectly heated cathode tube, and working from L to R these are: - cut; reamed; end swaged; pointing for mica location, flattened; lower end pointed; connecting strip welded; etched to allow emissive coating adhesion. Once the cathode tube is coated, a...