The 4X150D has a heater rated at 26 Volts for working off of 24 Volt vehicle supplies. The 4X150A differs only in having a 6.3 Volt heater.
The 4CX150D beam tetrode is a close relative to the 4CX250B VHF/UHF RF power output valve and has the same finned anode structure. The silver plated fins are contained in an outer ring, and in use air would be forced over the fins for anode cooling. A special base and chimney were designed for the purpose.
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 base is a glass disc with pins protruding through. The evacuation seal is covered by a central metal spigot.
With a little enhancement the STC logo, Type designation and Made in England can be seen. The valve is also marked CV3991 and the maker is STC Paignton.
The glass separating the base from the anode. The locating key on the spigot can be seen as can the green corrosion.
Another view.
The co-axial glass envelope is 32 mm in diameter and, excluding the B8F base pins, is 45 mm tall.
