The PY33 is an HT rectifier for television receivers. It operates directly from the mains input and with a series resistance of 25 Ohms it will feed a reservoir capacitor of 200 µF. The 300 mA heater was the standard for TV receivers from the 1960s.
The advantage of the PY33 was a voltage drop across the valve of only 10 Volts made possible by an ultra smooth cathode coating.
The anode has four flanges set at 90° to one another around the central cathode.
The anode plates are stitched together. The heater wire is coiled before being coated with insulation. It is placed in the cathode as a single hairpin.
The wide glass tube envelope is 32 mm in diameter, and excluding the IO base pins, is 96 mm tall.
References: Data-sheet & 1040. Type PY33 was first introduced in 1961. See also1961 adverts.
