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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.

Visually the electron gun is clearly seen as are the deflection plates. The tube has no connection for post deflection acceleration and so was designed for operation with about 800 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 Cossor 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 attached data-sheet is of the oscilloscope by courtesy of John Evans of The Valve Page. This excellent site now has most of my collection of oscilloscopes.

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

Reference: Data-sheet. Type 23D was first introduced in 1952. See also 1952 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

PDF scanned from an original document held by the museum