[R-390] Tube Heat Shields

[Harry Joel]

Having followed the ongoing discussion re: heat shields, may I offer this:
For the first three years as electrical engineer I worked for GE (AEG Germany) applicance division. There is had to perform heat related measurements on many of their products. Thermocouples were used almost exclusively to take readings. The small size of a thermocouple junction was an advantage. Drawback was the need to keep the reference for the thermocouple wires in an ice-water jar. A millivolt meter and the calibration chart was all to take very accurate temperature measurements. Now Thermistors could be used for the same purpose. Comparing the efficiency of the various tube heat shield designs could be done using a bead thermistor attached to a heatshield. 

The effect of contact area (with the tube envelope), black or shiny shield color and other mechanical choices could be compared. It seems that with the preponderance of solid state devices, the developement of better heat shields for vaccuum tubes has not been on the front burner in the industry. The demand does not justify the cost of research in this area.

(with a 392 sitting on my work bench waiting for some TLC) I am encouraged by the ongoing discussions in this forum)


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