varia:
...measuring 'stuff' going back down the power line...
In a previous life, the official way of doing this
involved a split ferrite core device, called an
'absorption clamp', lots of trick calibration,
expensive. Basically: a 'sophisticated current
probe'. (There are international standards for
what PCs, etc can 'push back into the line'.
Much Lower than Tesla Coiling is likely to
generate.)
I've no idea what is used for such now. Measuring
this 'sort of thing' as noted, takes a lot of
experiment, understanding, and not trusting the
test equipment without thought.
...as to trashing PCs, etc...
There are standards (also) for what 'line oddities'
a PC 'should' withstand. Tesla Coil Strays,
conducted and radiated are WAY LARGER than 'the
usual spec'. Separate, circuits, added filtering,
both 'source' and 'victim', unplugging are
indicated. PC PSU's are almost always 'sort of on':
unplugging is the safest...