I was winding up one of my old HP spectrum analysers (my best one, as it
happens, been sitting around unused for years) on the variac yesterday.
Got to about 170VAC from 60 over several hours and just got impatient I
admit it. Wanged it straight up to 240 and *POOF* the all too familiar
magic smoke came out. Patience was never my strong point. So my Sunday is
going to be spent trying to find and fix whatever it was that went bang.
I kind of knew something was in the offing when the display started to
twitch. You know how it is with a CRT tube when it starts winking at you.
Any predictions as to the likely culprit? I'll post back later...

Have a look to condensateur "on" the line first.