Did you turn off the power and pull the plug?

On January 9, 2019 at Computerworld there was a Shark Tank story about following through titled Details, details. The short version is that an information technology security team at a university found someone outside had hacked into one of their servers and was using it for denial-of-service attacks. The server turned out to be in the alumni office. There were databases with lots of personal information still on it. Officially it had been decommissioned months earlier, but no one actually had switched it off or unplugged it from the network.

Half a century ago my father and I also had a problem with something electrical that should have been disconnected long ago. One Friday morning my mother noticed that when she opened the refrigerator door the light didn’t come on, and it wasn’t cold as usual. We found the fuse for that wall outlet had blown, and used an extension cord to plug the refrigerator into another circuit in the adjacent pantry.

That large brick house had been built in Pittsburgh back in 1912, so the wiring for the kitchen outlets circuit was located on the ceiling of the unfinished basement. On Saturday morning we disconnected power upstream of the fuse. Then we began breaking that circuit into branches to isolate and locate the short. This process involved standing on a stepladder, opening overhead junction boxes, unwrapping electrical tape, and unwinding wire splices.  

We were using an analog multimeter to check for resistance between the hot and neutral wires. One branch with low resistance was not the real problem – just the primary winding of a transformer for the back doorbell. Eventually we found the short was in wiring leading through the back wall and underground - out from a long unused safety switch box. The switch mechanism was rusted until it was stuck in the ON position.

We guessed that it had been for the electric motor of a turntable for turning around a car. A neighbor told us the turntable once had been located at the back end of the driveway. It was not still there when we moved in during 1955. But no one ever had disconnected the wiring!