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The Pen26 is an audio output pentode. The first production was in 1934 with a revised form with 3.0 Watt output introduced in 1935.

The Pen26 was essentially an improved functional replacement for the Pen20, suitable for either AC or DC heater operation and therefore intended for universal AC/DC sets. Note the 200 mA heater rating. It seems to have been based on the same Philips European prototype as the Triotron Type P2060 and the Tungsram Types PP24 (B7) and PP24s (Ct8), all of which have identical ratings.

An interesting feature of these ratings is the unusually low, for an output pentode, screen grid voltage rating (100 V). It was intended to be capable of useful power output when operating from 110 V mains supplies. It is also interesting that unlike, for example, Tungsram, Mullard never marketed a version of this valve fitted with a B7 base cap. The Pen26 seems to have a distinctly European rather than British flavour and was perhaps used only in imported Philips sets.

The anode load impedance should be 3,000 Ohms.

The connection from the control grid to the top cap can be clearly seen. Also the tops of the other grid supports.

Looking over the internal metallising the cathode tube can be seen as white with the three wire grids passing round it. The anode is a wire mesh.

The classic envelope is 45 mm in diameter and, excluding the Ct8 base pins, is 115 mm tall.

References: Data-sheet & ¹⁰⁴³. Type Pen26 was first introduced in 1934. See also 1934 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

PDF scanned from an original document held by the museum