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
