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This battery triode was designed in 1926 for the HF stages in broadcast receivers. The filament would be run from a 2.0 Volt accumulator.

The bright anode lies horizontally across the envelope. The thin nickel sheet has been pressed into a series of ridges and points for strength. It appears that the metal has been stamped before being formed into the anode. The image shows that the pattern has been cut at different points in the repeat top and bottom. The grid winding is visible and the three point filament support. The filament being in the form of an open triangle.

The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 83 mm tall.

References: 1931 data-sheet & ¹⁰⁴³. Type PM1HF was first introduced in 1926. See also 1926 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Andy Cowley for supplying the above PDF datasheet.