while scopes were electrostatic before they went
digital. (Did anyone
ever do a lab scope with magnetic deflection? I'd think the latency of
the magnetic material would preclude fast sweep speeds.)
I wouldn't necessarily call it a 'lab scope' but I think I once saw an
large-screen (about 17" diagonal) 'scope used for lecture demonstrations
that was magnetically deflected. I think the bandwidth was pretty much
limited to audio frequencies. I can't rememebr the manufactuter, maybe
Airmec?
Waht limits the bandwidth of electromagnetic deflection is often the fact
that you have to change the current through the defleciton coils quickly,
and this leads to large back EMFs that you driving amplifier has to be
able to cope with (suppressing them e.g. with clamp diodes or zeners does
you no good at all, it just slows down the response time and thus kills
the bandwidth).
Of course there have been magneticlaly-deflected XY displays used on
vector grahpics systems (the DEC VR14 being an obvious example), but the
defleciton rates were not that high.
-tony