The CV243 (commercially the 4045A) is a directly heated tetrode. The valve was used by the GPO (General Post Office) for telephone repeaters and was there called the POVT145.
The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
The box anode with filament tension spring above the top mica. The electrode assembly is fixed to the pinch stem with a collar.
The collar is clamped with a nut and bolt each side. The centre loop of the filament is held in a fixed loop.
The filament tension springs attached to the hooks that pass vertically into the anode space.
The reverse carries the STC logo and the commercial Type designation.
The box anode and the fixings of the tension springs.
The top mica. The filament can be seen as an oxide coated ribbon.
The filament and support hook.
The screen grid is only just wider than the control grid.
Here the filament ribbon is clear to see.
The balloon envelope is 60 mm in diameter, and excluding the B5 base pins is 137 mm tall.
