[Boatanchors] Can someone explain the history of the Heathkit HP-23 power supplies?

[David Colburn]

I see the value of the "grounding plug" with the HP-23B, and read of the 
silly Hewlett-Packard

lawsuit that forced the change from "HP" to "PS", but the reasoning for 
some of the other

changes is unclear to me e.g. removing variable bias and filament center 
tap,  and removing

the front panel power switch.

  *

    *HP-23 (1963–1968):*Original model with single winding transformer
    and dual fuse plug.

  *

    *HP-23A (1968–1973):*Added 120/240VAC dual primary windings and
    circuit breaker protection.

  *

    *HP-23B (1973–1978):*Removed variable bias and filament center tap;
    added grounding plug.

  *

    *HP-23C (1978–1980):*Removed front-panel power switch; relied on
    remote switching.

  *

    *PS-23 (1980–1983):*Renamed successor to HP-23C, discontinued as
    tube radio demand faded.

Just curious.

Thanks,

David, KD4E