...
>This created sparks because
>of some kind of ground loop. Immediately the LED that the PIC
>was flashing quit.

Sounds like latch-up

I could smell that infamous burnt electronics
>smell.  I cycled the power and the PIC started working again, but
>then faded and quit again.

Hmm.  Maybe the chip was so hot that it used exessive current (or maybe
some part still in latchup?? No...) And after a vhile vas so hot it stopped
working.

...

> If a PIC can survive
>a disaster like this, I am impressed.

Me too.

>Is it normal for switchers from old PC's to have a hot chassis?

There is normally small capacitance high voltage caps from AC in to
chassis, parallelled with one-meg resistor.
Maybe the resistor was broke.

In the oscilloscope there may not be anything like this in order to not
hace noise "from behind", and in that case the osc should be grounded the
best way by the user, because A) noise rejection, B) disable charge
building up between chassis and oscilloscope inner cirquit.

It was an old scope, so maybe there is a resistive path of dust that
charges the chassis/inner cirquit capacitance?
...

>Dan

/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrt@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /