The P440N from Triotron is an indirectly heated output pentode from 1932. The B7 based version was introduced in 1935.
The anode load should be 7,500 Ω and the cathode resistor to achieve correct bias is 500 Ω. The output is given as 2.0 Watts.
This exhibit was made in Austria and the details are on the dome. Inside is a mesh anode, oxide coated cathode and all three grids can be seen clearly.
The construction pre-dates the use of mica sheets and glass beads and rods hold the electrodes in place. There is a small heat sink fin attached to the control grid top support.
Another view of the construction and dome lettering.
The balloon envelope is 50 mm in diameter and, excluding the B5 base pins, is 103 mm tall.
Reference: 1043. Type P440N was first introduced in 1932. See also1932 adverts.
