Atomarc,
the circuits used in these old tube radios use a variety of Dc voltages, some as high as 270 V. In order to supply these voltages, a power transformer is used, that runs on Ac, and steps up the Ac voltage from 6 volts, to somewhere around 300 v. This Ac voltage is created by the vibrator, which alternately applies 6v to two opposite windings in the transformer primary. It does this using two sets of points, a magnetic coil and a moving armature, much like the one in a door buzzer.
The higher secondary Ac voltage from the power transformer is applied to a rectifier circuit to create the high voltage Dc supply. The OZ4 tube is used in this circuit.
Fred
