🚀 go-pugleaf

All the stories about 110 volts on the backplane remind me of the
following story with a different outcome:

When I was a physics undergrad in the spring of '73 at Carnegie-Mellon, I
took an advanced lab course where I built and tested some new particle
counters (multi-wire proportional chambers).  One tool they found to help
me in testing my counters was a very old multi-channel analyzer.

A multi-channel analyzer is a special piece of hardware for accumulating
histograms.  There are two inputs, clock and data.  When a clock pulse
arrives, it increments the bin in the histogram selected by the voltage
on the data line, and it constantly displays the histogram on a CRT as
it is accumulated.

This MCA was built in the early '60s and had an 8x8x8 core stack to hold
its histogram (256 bins of 8 bits each).  The machine had long since lost
its cover, and the core stack was a clearly exposed cube about 10 cm on
a side in the center of the box diagonally below the back of the CRT.  The
wires in the core stack looked like they might be 28 guage, and the cores
were correspondingly large, perhaps 2 mm diameter.  The professor I worked
for showed me how to get the thing working, and part of it involved
tweeking some potentiometers mounted on the side of the core stack inside
the box; they were probably factory preset at one time, and never intended
for user adjustment.

One day, the machine stopped working, so I set to work tweeking the pots.
The result was an awful smelling plume of smoke from the core stack.
I was afraid I'd wrecked the machine, but I reflexively centered the pot
before pulling my hand out, and to my surprise, the dumb thing worked
perfectly!

I assume that, over the years since the machine lost its cover, the
core stack had slowly filled with all manner of dust, and I somehow ran
enough current through it to burn out the dust without melting the wires
in the process.
                                        Doug Jones
                                        jo...@herky.cs.uiowa.edu