26 Aug
2015
26 Aug
'15
12:13 p.m.
On 8/26/2015 1:20 AM, jwsmobile wrote:
Microdata card extractors were always engaged to a rail that was metal,
and in one site I was at, there was a CE sized hole in the wall behind a
system when the engineer extracted the printer card and the card
extractors came free from the system. Turned out there was a 120v
potential between the "dedicated" power for the computer and the printer
which was plugged into the normal building power.
There was probably as much as an amp going thru the grounds from the
terminals in the building and the ground of the system. Miracle that he
was not severely injured, and also that the system was working at all.
We had a similar thing happen at the 5th out of 9 floors of the State of
Wisconsin Hill Farms State Transportation Building. The power
requirements for stuff in the building outstripped the capacity to put
wire in the risers, so there were some shared neutrals serving multiple
hot circuits. I learned about this when an Intergraph FE was shocked by
a 50V potential between two neutrals between the LSI-11 equipped
graphics terminal and a Versatec printer.
Also, when I was a kid, I was playing around with a Jacob's Ladder I had
made using a old vibrator-equipped Ford spark coil (I may still have
that around), and I had a telegraph key as a switch. Welll, one day I
was adjusting the ladder electrodes when my elbow hit the telegraph key.
I was knocked flat on my back off of my chair, several feet back from
the table.
JRJ