The Mullard ECR30 is a small electrostatically deflected cathode ray tube with a medium persistence green phosphor, and was designed for oscilloscope use. Our exhibit has the serial number of 1160.
The electrodes are rigidly held along a series of support rods. The y plates, on the left, diverge in the direction of the screen. The x plates are under the colloidal graphite coating on the extreme left of the picture.
The lettering of this exhibit is still readable. So often all trace of identification is rubbed off down the years.
The B12B base has a substantial locating spigot that houses the evacuation pip and standard sprung pins. The cement holding the base to the envelope has come apart and the base is loose. It is quite often the case that the base is re-attached to the glass by means of adhesive tape.
The screen is smooth and blemish free. The shading is purely due to reflections during photographing.
As with most of the CRT's from this period the heater-cathode insulation is not good and the maximum voltage differential between them is limited to 50 Volts. In practice with the cathode at about -800 Volts, the heater would be fed from its own transformer winding.
The a1,a3 voltage is given as 800 volts and the focus anode a2 would be held at about 135 Volts.
The end window envelope is 70 mm in diameter, and excluding the B12B base pins is 175 mm long. The neck is 40 mm in diameter and the black base is 48 mm in diameter.
References: Data-sheet & 3002. Type ECR30 was first introduced in 1943.