That kinda reminds me of a time several years ago I got ahold of a big
grab-bag of assorted tantalum capacitors.  They were supposedly all rated
for 20V or higher and had a longer lead to denote the positive side but were
otherwise unmarked.

I happened to have a 12V lead-acid battery just sitting on my desk so I
quickly whipped up a little test circuit on a protoboard with a load
resistor and voltmeter so I could get a rough idea what size each capacitor
was by counting how many seconds it took to discharge to about 9V.

So I went about sorting the capacitors by briefly touching them to the 12V
battery and then plunking them into the protoboard and counting the
discharge time.

Ok .. how many of you out there couldn't see this comming? ... After
measuring a coupple dozen capacitors I was getting a bit bored and tired and
spaced out a bit and touched one of the capacitors to the battery backwards
...  -- POP! -- ... "What the?! ... Doh! .. Oh, well .. plenty more where
that one came from, no big deal.  Cool!  The whole thing blew up!"  (all I
had left was a coupple of leads barely held together by a bit of epoxy but
the body of the capacitor was nowhere to be seen).

I was just about to go back to sorting capacitors when I noticed a fire
break out on the other end of my desk ... it seems that the little
cylindrical core from inside the capacitor was quite hot and had landed on a
stack of papers!  I'm just lucky that that thing flew over there instead of
into my eye!

Ken


>Experiences should be shared.
>
>Just playing with a new small calibrator board over my computer desk,
>taking measurements of the parts, board, LCD, battery etc, to draw the
>physical position of the parts into the new instrument case...
>disconnected the 4 x AA NiCad cells + wire from the circuit, just in
>case, you know... taking measurements from the small 2x16 LCD unit,
>entering it at the CorelDraw, here and there, then suddenly by the very
>corner of the eye I saw something strange like moving at the side,
>physically close to where was the disassembled unit.
>
>I am getting old, so somehow weak eye sometimes "see" things that
>doesn't exist, you know, tired eyes and so on. But this thing was much
>more than an eye tricky ilusion, blinked eyes to "clean" it better, the
>strange thing was there, like moving as a ghost... then probably half
>second after I noticed it by the first time, I turn my eyes back to the
>board, LCD and things, my goodness, everything was on fire, fast one,
>multiwire cable connecting LCD to the Board was transformed into a
>bright lamp, papers below the cable was burning fast, in less than 2
>seconds I got a real fire on my desk, lots of smoke... then I thought
>laughing "Do I call 911 or just disconnect the damn battery + wire from
>the LCD metal face? ... people at home asked me "What a hell is
>happening? It finally worked? hehe.
>
>The real accident in the last 8 years. Cable is complete wasted, Checked
>circuit board and LCD board intact... power it on... working.
>
>Thinking seriously to use a fuse in series with ALL my NiCad batteries
>from now on... they are quite dangerously low impedance units.
>
>The experience was interesting, can you imagine it just happening with
>nobody around?  Fire in the Hole!!!.
>
>Wagner.