The 19H5 high-vacuum rectifier was originally designed by Ediswan Mazda but was supplied to the British Services by several manufacturers. This later manufactured 19H5 from STC is new.
The 19H5 is described as a very low impedance diode for charging and clamping applications in Radar.
The heaters are and straight. Since the 19H5 is a high-voltage rectifier (PIV = 20,000V) it is important that each leg of the filament should be exactly coaxial with the surrounding anode (ie. equal spacing in all directions). This is why the anode structure is subdivided into 4 cylinders. The ends of each heater leg are cooled by their supports and cannot supply the same emission density as the central section. The coils seen encircling the filament supports are in fact electrostatic shields protecting the filament ends from excessive emission demand.
The output current rating of this valve in normal service is 350 mA so a full-wave pair could supply up to 20 kW at around 6 kV DC.
The base is a giant Edison screw and the anode connects to the top cap.
The four cylindrical cavities are 60 mm long and 12 mm in diameter. Each anode cavity contains a single heater. Thus the valve is in fact four rectifiers operated in parallel.
The top of the envelope showing one pair of anode cylinders. In the left anode can just be seen the oxide coating on the cathode.
A view from the side. The lower heater and supports can easily be seen.
One anode with oxide coated cathode. The coating has been applied such that the emissive surface begins inside the length of the anode.
Closer inspection reveals that the heater is insulated and passes inside the cathode tube. The cathode is then oxide coated. At the top end the heater and cathode are compressed together before being welded to the top support.
The wide glass tube envelope is 57 mm in diameter and, excluding the base pins, is 230 mm tall.
Reference: Data-sheet. Type 19H5 was first introduced in 1954.