stepped approximation to a sine wave to pure sine wave

[Szpara]

I got a refurb. UPS from at work 1000va 600w, for like 60$, its HT1000 form APC
when it runs on battery it makes stepped approximation to a sine wave form of power,

I do know the whats pfc and differences of pure vs stepped.

I'm wondering if there is a way to convert stepped to pure

[[XC] Lead Head]

Not really. Some kind of power conditioner with some crazy inductors or something might be able to clean it up, but at that point you might as well just get a better UPS.

Most electric things (except audio amplifiers and induction motors) will accept extremely dirty, nasty power without issue. You could even feed DC into most PC power supplies and they'd work fine.