I've got a dismantled FSP250-60PNA here, anyway there is something that i haven't seen before in it, a great big heavy (bigger than the main transformer) inductor, with laminated iron core. It's in series with the neutral, before the rectifier, and has a a capacitor in parallel with it. It's also shorted out by one pole of the selector switch when the PSU is set for 115V. My questions: It is for PFC, right? Why haven't i seen one in a PSU before? (Passive) PFC networks are pretty common in modern power supplies, i think. Also, why isn't it in circuit for 115V use?