From: bill@thd.tv.tek.com (William K. McFadden)
Newsgroups: sci.electronics
Subject: Shock the Monkey
Date: 21 Jul 92 23:18:41 GMT
Organization: Tektronix TV Products
Originator: bill@thd.tv.tek.com

Here are some more shocking stories posted on behalf of my friend who
doesn't have net access.  The lack of proper tools and equipment often
led to compromise, as the following stories illustrate.



From:    microsoft!timc@cs.washington.edu

As I remember it, most of this happened during my high school years:


   I had built an amp with a 60hz notch filter to try and measure my
brainwaves.  I wired up two copper pennies as probes and used a mixture
of Jergens and salt as a conducting medium.  I was using an AC power
supply with a 15vdc output to drive the op-amps.  I had a meter, an
led, and a speaker connected to the output (I did not have an
oscilloscope).

   I plugged the wires from my temples into the op-amp inputs.  At
first all I heard was a very low 60hz buzz which I thought was coming
from the speaker, but I also thought it strange I was not seeing
anything on the led or meter.

   "Damn, I thought I had that pesky 60hz filtered out.  Oh well," I
thought, "Perhaps a better contact between those pennies and my temples
would help."  So I pushed lightly on my temples.  What happened next
was really scary.  I "heard" 60Hz coming from all directions, and "saw"
brilliant blue flashes superimposed over my bedroom, and felt a slight
tingling in my temples.  I jumped up while ripping out the pennies with
wires attached and sat there for about 30 minutes trying to see if I
had any holes in my memory, or if I had lost any of my faculties.

   After I had recovered, I examined the circuit and discovered that I
had miswired it.  Instead of connecting the pennies to the input, I had
connected them across the power supply!  The 60hz component was
probably caused by the low impedance of my salted skull loading down
the power supply.



   Another time I was just playing around with a voltage to frequency
circuit, using my tongue to vary the voltage, and trying to play a
tune.  While trying to hit a particularly low note, I slipped and
connected about 5 volts between two fillings on either side of my
mouth.  I never heard that note.  I screamed in pain and shot up out of
my chair.  Luckily, the pain was gone as soon as the wires left my
mouth, but it was probably the worst toothache possible for the
fraction of a second it lasted.



   I had built a tube transmitter, and was working on the pi-matching
section between the plate output and the antenna.  The variable
capacitor on the plate had about 400 volts DC on it, with the RF signal
superimposed on the top of that.

   I didn't even think of which side to connect up to the variable
section.  I figured I'd ground the case, and the stationary side of the
capacitor, and hook the plate up to the rotor side.  So now I have
+400vdc /w RF connected to the metal tuning knob of the first
capacitor.  I then hooked up the next variable capacitor between the
inductor of the pi filter and the antenna, but on this one I grounded
the rotary part, and hooked the stationary part up to the antenna and
inductor.  So now I have ground connected to the metal tuning knob of
the second capacitor.

   Everything looked okay, so I powered up the transmitter, and started
tuning the pi network.  I first grabbed the first capacitor knob, tuned
it until I got a dip in the swr meter, then without letting go I
grabbed the second capacitor knob, and had 400vdc across my chest
through my arms.

   I knew I was going to die if I didn't do something soon, so I tried
to jump up, backpedal and let go at the same time.  Jumping up and
backpedalling worked, however letting go was not working.  In a very
short time I had run backwards knocking the transmitter off the table,
and backed far enough away to pull the cord out of the wall.  Now all I
had to do was wait for the 400vdc to discharge through me.  It did not
take very long, and I sat there for a long time thinking about life in
general.

Doc


-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
bill@tv.tv.tek.com, ...!tektronix!tv.tv.tek.com!bill      Phone: (503) 627-6920
How can I prove I am not crazy to people who are?
Newsgroups: sci.electronics