The U920 is a general purpose triode. The trade name on the envelope is Ostar. Also on the glass are the heater rating. Ostar Ganz made a range of valves with a mains heater.
The valve was made in Austria. The base pins are pierced and form a spring. The base pins on our other U920 are of simple split pin construction.
The mesh anode is supported on both sides. The heater is enclosed in a ceramic tube.
The two folded supports hold the ultra fine tungsten heater wire. The wire can just be seen. The coiled wire has been pulled-out and looks like a fine ripple. The wire enters the ceramic tube through the two small holes.
The cathode connection to the coated tube is on the left. Again at full size the heater wire is just visible.
The identification is etched into the glass.
The control grid is supported along the length by a single rod. Note the closed end of the heater tube.
The triode seen from the closed heater tube end.
Top view of the triode. The heater wire is visible on the right of the image.
The image above laterally reversed and enhanced shows the etched maker name and heater voltage.
The balloon envelope is 50 mm in diameter, and excluding the B5 base pins is 89 mm tall.
References: Data-sheet & 1043. Type U920 was first introduced in 1932. See also1932 adverts.
