The 2C39A is a planar design of disc seal construction. This UHF triode was designed for use in a resonant cavity with forced air or water cooling.
The copper anode can be seen through the glass and above is the mesh grid. The cathode is concealed in the metal portion above. The heater and cathode connections are co-axial.
The aluminium radiator fins with the identification. The radiator is 32 mm in diameter.
The co-axial connections for heater, heater + cathode and control grid.
The planar envelope is 19 mm in diameter and 67 mm tall.
