General Electric "Universal" X-ray Tube (ca. 1920s)
This "Universal" Coolidge tube was manufactured by General
Electric, probably in the early 1920s. The last patent date on the tube
was January 1917.
The shape of the cathode filament (photo to left) indicates that this is a fine focus tube. The filaments for the fine focus tubes were flat spirals like this one while those for the medium and coarse focus tubes took the form of a slightly conical spiral. The fine focus tube, like the medium focus tube, was intended for general radiographic work.
The maximum high voltage for which it was rated would have been approximately 100,000 volts - this would be more or less equivalent to a 6" spark gap. The maximum rated current would have been approximately 25 milliamps for a 20 second exposure.
long, 7" bulb diameter
The text etched onto the anode arm reads: ""Pat'd Nov 8,'06, Jan 31 '11, Feb 27 '12 Dec 30 '13 May 18 '15 Oct 31 '16 Jan 2 '17. Patents Pending. This tube is not licensed to be re-exhausted or repaired, nor is the metal therein contained licensed to be used except in this particular tube. General Electric Co. Schenectady N.Y. U.S.A."
Copyright 1999, Oak Ridge Associated Universities