🚀 go-pugleaf

   When I (ever so long ago) was in junior high school I built a rudimentary
oscilloscope - it had a 3" screen, the appropriate power supplies, an
audio amplifier and a small piezoelectric microphone.
  
   For some reason I don't understand, the shaft of the focus knob had the
entire G1 voltage present on it - about 40 microfarads of oil-filled
capacitor charged up to 1kv, with a connected power supply capable of
delivering 200ma.  I thought I was safe because there was a bakelite knob
on the shaft - except that the little hex screw affixing the knob to the
shaft wasn't insulated at all... it took about 3 days of playing with this
thing before I finally reached for the focus knob with my right hand while
holding the grounded, metal encased microphone in my left hand.
  
   I found myself laying on the floor about 8 feet from the apparatus, with
deep burns on the thumbs of both my hands - so deep they bled.  The 
microphone cord had broken from my, er, sudden leap backwards, and the
rest of the thing had tipped over on the bench.
  
   After a couple of days had passed I dismantled the 'scope, and almost
got shocked again by the charge left in the capacitor bank.  

   Can't see the scars anymore, but the feeling of 'gee, was I ever lucky'
still remains...

mark olson
mark@lenti.med.umn.edu