Our newer systems back in 1985 used dual MG setup 400 Hz and 50-60 VAC

anyway, one of the tape drive units had failed, IBM arrived and was checking
power connections in the power supply (they call it a power tub).
Other IBM guy (new young pup) kept leaning on the control unit while
the old timer IBM guy was trying to probe the voltages at the breakers.
Almost gave him a large shock before we told him to get off our control unit.

Same young pup wants to get under the floor to unplug the large
power connector russelstoll 30 amp 3 phase, old timer grabs him by
his belt from behind, and saved his life !

IBM guy takes the rubber cord and then gently glances the RS
connector to the floor supports (all metal and gounnded with copper cables)
large sparks when he did this !

Young ibm pup almost pee in his pants.

Turns out somebody on work crew did not wire the ground cables properly
so the floor was HOT HOT HOT ! Good thing it was carpeted flooring in the
computer center.

allen


Rex wrote:

And you reminded me of something too. Not really a problem, but could
have been.

When I was working on mainframe computers in the 70's we installed a new
machine in Europe. The power for the computer was supplied by a big
motor generator with an output of 3-phase 208 V 400 Hz (or was it CPS
back then?) power to the computer. I learned from the customer that they
discovered that a wiring error had routed the motor generator power to
the wall sockets in the computer room.

I told the customer that it was very good they had found this problem
before people used the sockets. If the cleaning lady had come in and
plugged a vacuum cleaner into the 400 Hz power, it would have probably
sucked all the air out of the room. :-)

-Rex, KK6MK