Sensibly equivalent¶ to:
This exquisite R Type valve is smaller than the usual varieties. This exhibit probably dates from the mid 1920s and is almost certainly of Dutch origin. The envelope is gettered to the point where no internal details can be seen. The etching on the bulb indicates that it was made in Holland but the makers name is not clear. However, on the left of the image is what looks to be a curved X. This looks to be the right side of the Frelat logo.
The filament is open circuit and so we have no way of telling if this was a bright emitter or a thoriated tungsten dull emitter.
One of our other R Types is very similar but is un-gettered and the envelope assembly can be clearly seen in this other valve.
The type designation is missing from the envelope but operating voltages are etched into the glass. The filament is designed to operate on 4 Volts and the anode supply can be between 60 and 100 Volts.
The balloon envelope is 50 mm in diameter and, excluding the B4 base pins, is 78 mm tall.
Reference: Observation. Type R Type was first introduced in 1916.
Absolute Maximum Operating Conditions¶
Updated July 12, 2017. shape:balloon construction:pinch type:triode age:pre.1920 base:b4 heater:4.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f