RE: 'Scope yes/Fry, no

            RE: 'Scope yes/Fry, no
            Wed, 2 Apr 1997 10:08:26 +1200
            "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
            Wellington Polytechnic, NZ

Hello all,
           Thought I'd add a note to this based on successful 

> -> >From what I've seen so far, even if I turn it on from the next 
room, > -> if it didn't blow, I'd be looking at waveforms. :)
>         - For sure.  And not a bad way to go.   Simply attach a pickup
>                 coil to the 'scope terminals.   Of course such measures
>                 what's floating around in the air, not what is surging
>                 thru the secondary windings.

Beware of pickup *coils* for detecting voltage waveforms. The sods 
can resonate with the scope input capacitance and give a completely 
false picture of what is going on. My favourite technique is a short 
aerial wire hung from the probe (short=wideband at low frequencies)
and a 2-pole LC series-resonant filter at mains frequency connected 
from the probe tip to probe earth lead. The filter uses a small iron-
cored choke (saturation no problem) and two electrolytics in series 
wired back-to-back. Works well.