Billboard Causes Computer Crash

Many years ago, I got a call from a client saying its computer had crashed. It followed with the fact that it had been doing that for about a week, but only at the end of the day and always, so far, while it was not being used.

This turned out to be a blessing, as each time it came back without apparent data loss or corruption. I went over the computer with a fine-tooth comb, and all I could discover from the event logs was that it rebooted a few minutes earlier each day. I returned a little before the time it had crashed the night before and started my vigil, monitoring with all my senses.

Nothing happened at the time it had the previous night. A minute or two later, my mind wandered from the bright screen, and I momentarily gazed out the window at the approaching twilight. A billboard lit up across the street, breaking my reverie, and I glanced back to my now dark screen.

With winter approaching, the billboard's photoelectric sensor was turning on the lights a little earlier each night. The culprit was at hand. After a power line analyzer confirmed the source, I contacted the billboard company to make it aware of the problem.

For some time, I had been trying to convince this customer of the value of having its workstations on UPSes. Now, with compelling evidence and a bill for debugging time, it took the plunge and put UPSes on all its appropriate computer and networking equipment. The demon was throttled.

This entry was submitted by Dave Ussell and edited by Jennifer Campbell.

Dave Ussell is a graduate of San Diego State University with a degree in physics. He has worked most of his professional career seeking out problems he has no experience with whatsoever, such as repairing electron microscopes or C-141s. He spent 15 years working at Children's Hospital and Health Center in San Diego supporting evoked potential research. He later founded and is now the principal of ASCII 27, a company that does everything from designing widgets for disabled persons, medical instrumentation, and the fishing industry to computer forensics.

Tell us your experience in solving a knotty engineering problem. Send to Jennifer Campbell for Sherlock Ohms.

Click here to access the Sherlock archives.