The 154V is a Mullard indirectly heated (4V AC) mains 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 154V has μ = 15 and a 4 V heater. Type 054V had μ = 5, 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).
The earliest examples in this 154V series were fitted with B4 base caps, the cathode being brought out to a side terminal. B5 base caps became standard on this series during the early 1930s. The earlier examples were not nearly as good as their Mazda contemporaries such as the AC/HL and AC/P.
Like many valves kept in the lists for several years, the ratings were improved from time to time.
We believe that the exhibit shown may consume 1 A of heater current and may be limited to an anode voltage of 100 Volts.
The electrode assembly lies horizontally within the glass. The internal silvering obscures the view but the filament appears to be a 'V' and the grid is a flattened wire helix.
The balloon envelope is 47 mm in diameter and, excluding the B5 base pins, is 83 mm tall.
Reference: 1043. Type 154V was first introduced in 1929.
Absolute Maximum Operating Conditions¶
Updated August 14, 2019.