The QV1-150A beam tetrode is a close relative to the 4CX250B RF power output valve and has the same finned anode structure.
The picture above shows the anode fins clearly. Sadly our exhibit is broken but it does provide a chance to look inside at the construction
Inside the anode structure we can see the copper of the anode proper. The copper and envelope are shaped to present a larger surface area to one another. The slope forms an angle of approximately 45 degrees.
This picture shows the screen grid. The grid itself is 10 mm in diameter and 14 mm high. The construction of vertical rods that form a hatching on the flat top of the structure is the same pattern of construction that is applied to the largest modern cooled anode power valves.
The inclined view of the screen grid reveals the screws that hold it in position. It also shows slots that the screen grid assembly screws fit into. Not only is this a hand assembly operation but the slots are for rotating the screen grid until the vertical rods align with the control grid beneath. This alignment of grids reduces the screen grid current and thereby increases efficiency.
Returning to the external features. The silver plated fins are contained in an outer ring, and in use in a co-axial cavity air would be forced over the fins for anode cooling.
The base is a glass disc with pins protruding through. The evacuation seal is covered by a central metal spigot.
The spigot connects to the control grid g1 the base ring to the screen grid g2 and the finned top section (radiator) to the anode.
The diameter of the tube encasing the heatsink fins is 40 mm diameter. The overall length of this valve is 44 mm including the B8F base pins.