Math Formula to calculate DC power supply capacitor value?

[Nigel Goodwin]

Indeed, Nigel, that was the first step.
But eventually they went with fuses embedded inside the transformer itself.

They added thermal fuses inside the transformer, but any sort of 'equipment' still kept a proper mains fuse as well, it was mainly the cheaper wallwarts that dropped the fuse entirely and relied solely on the thermal fuse.

A thermal fuse in the transformer isn't offering the same protection as a mains fuse.