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EHT or Extra High Tension is the power supplied to the final anode of the cathode ray tube.
The EHT is traditionally generated by the line transformer from the flyback pulse of the line oscillator/amplifier.
The generated high frequency high voltage current was from the outset rectified by a thermionic diode (eg. EY51, EY86) but by the late 1960s/early 1970s technology brought high voltage diodes and semiconductors rapidly replaced the old technology and the output from the line transformer then typically fed the anode via a semiconductor voltage doubler.
The rectified EHT was originally smoothed by a high voltage oil-filled capacitor but that was soon deleted in favour of spraying the outside of the CRT with a metallic paint and grounding it. This became the high voltage smoothing capacitor with the glass of the CRT being the dielectric and the final anode the positive pole...