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The 054V is a Mullard indirectly heated (4V AC) mains audio output triode that was designed before Mullard's had a satisfactory oxide coating technology and were still largely dependent on the Azide process. Because the azide process broadcast a barium coating everywhere within the anode structure and not just on the cathode surface, it was necessary to design the structure so that all insulating (ie. glass) surfaces and supports were well shielded from flying barium. The classic horizontal arrangement achieved this but made it very difficult to assemble valves with close grid-cathode spacing. Early Mullard indirectly-heated valves therefore had relatively coarse spacings and, as a result, low amplification factors.

There were several triodes in the series differing mainly in grid pitch and therefore in amplification factor.

The first two digits of the type number indicate the μ value and the last two the heater voltage. Thus type 054V has μ = 5 and a 4 V heater. Type 154V had μ = 15, type 164V had μ = 16, and type 152V had an American-style 2.5V heater. Later (oxide-coated) triodes in this series (with more modern vertical electrode structures) continued right up to type 994V (with μ = 125, just to be awkward).

Like many valves kept in the lists for several years, the ratings were improved from time to time.

The side strut supports the glass rod that holds the electrode top support wires. The envelope shows no sign of blackening from the Azide process and is probably of later manufacture.

The mesh anode from the side.

The cathode tube looks to be more modern but the construction without mica supports harks back to earlier methods. This could have been made at the transition point.

The glass rod support and lettering on the dome.

Here the focus point is on the top supports not the glass and looks down inside the mesh anode. The grid winding can be seen to be oval in shape.

The grid winding can be seen to have been pinched at the ends to get the centre section closer to the cathode tube.

The balloon envelope is 48 mm in diameter and, excluding the B5 base pins, is 103 mm tall.

Reference: Data-sheet & ¹⁰⁴³. Type 054V was first introduced in 1931. See also 1931 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Andy Cowley for supplying the above PDF datasheet.