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AM broadcast transmitters have featured a grounded B+ since the mid-1980s.
One advantage being, that no blocking capacitor is needed (reducing the inductance).
Plate current flows through the pi-network tank coil, to ground through an RF choke
at 50 ohm output, rather than across the high-Z plate. (B-minus HV fed through cathode.)
Main reason for grounded B+ ham rigs: NO lethal voltage topside,
greatly reducing the safety risk for the experimenter.
Had my homebrew grounded B+ amp (four 811-A's) in operation since 2008. :)