The 25Z5 is an American TV rectifier. Within the envelope, sharing a common heater, are two independent rectifiers. The heater current of 0.3 Amps is one of the standard heater chain currents.
The independent rectifiers make three configurations possible: the pair as a full wave rectifier, the pair to produce 250 V from 117 V mains in voltage doubler configuration, and lastly in parallel as a half wave rectifier.
The maximum reservoir capacitor is quoted at 16 µF.
The cylinder that the anode makes around the cathode is about 2 mm in diameter.
The heater is a single strand wire. The insulation looks to be a ceramic tube within the cathode. This arrangement would offer good heater/cathode insulation.
The Triad name pressed into the base cap.
The classic envelope is 38 mm in diameter and, excluding the UX6 base pins, is 88 mm tall.
References: Data-sheet & 1040. Type 25Z5 was first introduced in 1936. See also1936 adverts.
