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Valves at the 1929 Olympia Show

Wireless World, September 18, 1929.
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With the latest addition of valves to their already extensive range of radio accessories, it is interesting to record that Lissen, Ltd., now manufacture everything required for wireless reception. The full range consists of eight valves with 2-Volt filaments and includes a screen-grid valve and two pentodes, also five triodes. These are the usual HF RCC and LF types and two power output valves the P220 and PX240.

Lissen P220 small type power amplifying valve.

Several new valves will figure among the well-known Mullard PM series this year. Of special interest are the new 5 pin AC valves fitted with indirectly heated cathodes and consuming 1 amp at 4 Volts. These comprise a screen-grid valve type S4V which possesses the extraordinary amplification factor of 1,000 the AC resistance, however, is on the high side, viz, 1.33 MΩ.

Types 354V, 164V and 154V all possess mutual conductances of two or over. The 104V is the super-power output valve and gives an amplification of 10 with an AC resistance of 2,850 Ohms; the mutual conductance being 3.5 mA per Volt.

Mullard S4V a new 5-pin indirectly heated screen-grid valve.

Marconi valves have been overhauled and a few new types introduced. A new pentode PT240 with an AC resistance of 55,000 Ohms and an amplification factor of 90 figures in the 2-volt class, while the 4-volt range has been augmented by pentode PT425 also and a screen-grid valve, the S410. Additions to the 6-volt series include a new screen-grid valve, the S610, and the return of the LS6A, which was for a time withdrawn. The characteristics of the last valve are AC resistance 1,300 Ohms, and amplification factor 3. Its maximum working HT is 400 Volts. A range of AC valves and full- and half-wave rectifiers will be shown on their stands.

Since these valves appear, also, in the Osram list, they will be exhibited on stands 85 to 90 inclusive. The General Electric Co, Ltd.

Trio of Mazda valves. On the left the SG215 centre H210, and right the Pen230.

The Edison Swan Electric Co, Ltd, is now marketing Cosmos BTH and Ediswan valves and specimens of those types that will be retained under the new organisation are to be shown. A new range, under the name of Mazda, has been introduced, and the 2-volt series were reviewed In this journal in the issue of August 28th last. Full details of the composition of the 4-volt series have not come to hand, but we understand that a new 4-Volt pentode is now ready and will be exhibited. A full range of 6-volt valves will be shown and this will include three power valves the P625A P625B and PP3/425, the last mentioned having somewhat similar characteristics to the familiar BTH B12, and will deliver an undistorted power output of three watts.

A high-voltage half-wave rectifier U65/550, and similar to the BTH RHI will be shown, as well as a varied display of AC indirectly heated valves.

The new Cossor valve In the three-electrode series.

The Cossor series have acquired some interesting additions, which will be shown. In all about thirty-five different types will be available for the coming season. The principal new valves are the MSG41 a screen-grid valve, the 41MRC 41MHF 41MLF 41MP and 41XP. All of these are indirectly heated AC valves and require 4 Volts at 1 Amp for the heater. There will be, also, a full range of half- and full-wave rectifiers operating from 250 Volts to 1,200 volts RMS and dissipating from 10 to 65 Watts according to type.

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