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The NR47 is the UK Navy version of the classic directly heated 25 Watt anode dissipation audio power triode PX25 designed by M-OV.

The box anode is held in a cage with four stout wires at the corners that drop to a collar tightened around the pinch stem.

The thin anode material is ribbed to confer mechanical rigidity. The filament passes through the control grid eight times in a series of loops.

The GEC profession brand logo. Note the glass rod at the top holding the top supports and filament tension springs.

The flat springs have wire hooks welded to them. The filament can be seen to be oxide coated wire.

Seen flat on the geometry of the triode is clear. The anode can be seen to be made from two identical plates welded to the support cage.

The balloon envelope is 65 mm in diameter, and excluding the B4 base pins is 140 mm tall.

References: Data-sheet, ¹⁰⁰⁵ & ¹⁰⁴³.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.