The U191 is a television efficiency diode. The function of the device is to enable the stored energy of the line scan coils to be returned to the supply rail during flyback.
Most popular valve type designs of this period were shared by BVA member companies as customers insisted on multiple sources of supply and the BVA wanted it to be UK made. The actual implementation of the design was up to the separate company and their preferred manufacturing techniques.
The valve is rated at 5,000 Volts (PIV) and a peak current of 600 mA. For efficiency diodes the cathode connects to the top cap. This means a 5,000 Volt heater/cathode insulation is required.
This exhibit was Made in England. Note the coiled heater separator at the top of the valve.
At the base of the image can be seen the cathode and insulated heater wires. Separating the heater from the cathode tube is a helical wire spacer the runs the length of the cathode.
The wide glass tube envelope is 29 mm in diameter and excluding the IO base pins it is 75 mm in length.
