This beautiful tube was originally labelled with a paper label and we believe it to be a Cossor 23D or a variant thereof. Sadly all that remains now of the label is the glue residue. Consequently we have no details about this 2 inch oscilloscope tube that has a maximum diameter of 68 mm.

Visually the electron gun is clearly seen as are the deflection plates. The tube has no connection for post deflection acceleration and so was most probably designed for operation with about 1000 Volts across the tube. The phosphor produced a green display.

Thanks to Jeremy Skertchly for identifying this CRT and supplying the fact that the 23D was used in the Cosor 1039 mini service oscilloscope. The latter was introduced in 1952 for TV service engineers to carry with them. This scope used three 6AM6 valves and one SD61 diode.

The end window envelope is 38 mm in diameter and, excluding the B12B base pins, is 177 mm tall.

This exhibit was last updated on 02 December 2007