The TZ40 is a magnificent audio triode that was designed for high power use. In class B a pair would deliver 175 Watts at 5% distortion. The TZ40 was the successor to the T40.
The signal input would be 220 Volts peak to peak between the two grids. The anode load would be 7,000 Ohms. Maximum anode dissipation is 40 Watts.
It is quite possible that the main use for this device would have been modulators for small AM transmitters.
The base cap contains the Type designation and the old UK Government stores code of 110E/37.
The text on the glass gives TZ40 and 110E/37. The insulators are ceramic due to the high voltages involved and the anode is graphite to withstand high temperatures.
The balloon envelope is 51 mm in diameter and, excluding the UX4 base pins, is 144 mm tall.
