Don't press the big red buttom on the wall!

Chris Dunn chrisdunn1 at
Fri Sep 2 03:08:03 UTC 2016

On Mon, Aug 29, 2016 at 4:51 PM, Sean Donelan <sean at> wrote:

> See that big red button on the wall under the sign "Do Not Push This
> Button!"....
This is going to date me, well, because it happened in my high school years
mid 1970's... but my best power off story was when in senior year we were
working on the school Sperry/Univac Solid State Systems 90 mainframe.  (   Well this thing used a
Mil-Spec 4K DRUM as its main memory. Now being mil-spec means the motor to
spin the drum is 400 cycle AC.  Where do you get 400 cycle AC in a 60 cycle
world? Well you install a 60 cycle motor in the base of this monstrosity,
and connect it via a fan belt to a 400 cycle AC generator that feeds the

We came in to class one day to warm the Univac up (it took about 30 minutes
to fully power up) and noticed the machine being very quiet when we applied
power.  We eventually tracked it down to no power to the drum and it not

And the reason the drum was not spinning?  The fan belt had broken on the
motor/generator set. :)

Lucky, this was a Technical/Vocational high school, and we ran down to the
auto repair class and bummed a new belt off them. :)

Then there was the time an engineer I worked with pressed the lamp test
button on the huge engineering console display for a Burroughs B6700 room
sized mainframe (like 3 foot by 3 foot bank of incandescent register and
status displays) and the inrush caused the entire machine shut down.... but
that's another story. ;)

Chris Dunn
Data Center Operations

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