The NU15 is a half wave rectifier designed for 200 mA series connected heaters as found in AC/DC radio receivers. The NU denotes a valve specified by the UK Admiralty for navy use
The maximum reservoir capacitor is 16 µF and the effective minimum series resistance has to be 50 Ω.
The commercial equivalent is the 1D5 and the envelope carries this designation as well.
The anode side view. The anode is 4 mm front to back.
The anode face view. Note the multiple heater wires required for the 40.0 Volt working.
The classic envelope is 45 mm in diameter and, excluding the B5 base pins, is 105 mm tall.
