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Valves at the 1950 Radio Exhibition

Wireless World, October, 1950.
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Hivac subminiature valves XFY23 beam tetrode (left) and electrometer valve XE2 (right).

Miniaturisation and television were the twin key-notes of the valve displays this year. The Mullard Noval-based valves for television are now well-known, but Ediswan had two new efficiency diodes, U281 and U801, and a new EHT rectifier U24. Subminiature valves for hearing-aids were shown by Mullard and by Hivac, who had an interesting flat sub-miniature beam tetrode, the XFY23, which has been designed as an output valve for the modern hearing-aids using only 15 Volt HT batteries. Hivac also had a subminiature electrometer valve, the XE2, in which the grid connection was brought out at the top of the silicone-treated bulb, thereby obtaining the exceptionally high leakage resistance of 1016 Ohms between it and the other electrodes.

Aluminization was a common feature of many of the television picture tubes on show, although there is still some disagreement on its merits and it has certainly not been adopted to the exclusion of the plain-backed picture tube. Amongst the oscilloscope cathode-ray tubes shown by Cossor, the 89J was interesting for its new beam-trap device intended for use between shots when photographing the screen. This consists of a cup-shaped anode into which the beam can be directed by the X-shift control so that no stray electrons will accidentally irradiate the screen and fog the film.

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