Oh, an important exception or two. MANY power supplies for computers
and entertainment gadgets are "switchers". Laptop power supplies are
the most obvious.

A switcher rectifies the AC line into DC and then makes AC of
oh 100-500 Kilohertz, has a transformer, then rectifies that
output to the DC needed. Why all that? Cuz that 100+Khz
transformer is TINY and cheap vice a 60Hz one.

Such could care less what the input frequency. [Within limits...]

Further, lots of laptop switchers are rated "100-240V AC in" -
without changing a switch. Others such as desktops have that
{120|240} setting near the cord receptacle.

I'd assume any inverter welder was rated for 50-60 Hz but RTFM.
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