More Power to You

December 1, 2010

Mike Kernen, chief engineer of the Greater Media Detroit stations, shared some thoughts on a mysterious short-duration dead air problem he encountered. He received a report that WMGC was off the air for about 30 seconds one day. This was too short to trigger alarms and failovers, so he checked the logger to confirm that the silence occurred at 5:06 on a Wednesday afternoon. He could not determine the cause, but suspected it might happen again at some point.

It did. At 5:06 on a Wednesday afternoon two weeks later. He still had no indication of what the cause might be, and at the time he didn't realize it happened at exactly the same time as the interruption two weeks prior. When it happened again two weeks later, again at the same time, he dug through logs and alarm lists and listened to the audio logger until it was finally discovered that a server in the transmitter room had rebooted at the same time. What would that server and the audio dropout have in common? The UPS. This is when Kernen recalled the UPS performs an automatic self-test every two weeks. Running a manual test confirmed the test fails and the load is dropped for about one second. Naturally, this UPS is the one responsible for guaranteeing that the Optimod and several other critical components at the transmitter site never lose power.

Kernen notes the irony of a failing stand-alone UPS. When it inevitably fails, it does the very thing that its sum total purpose in existence is to avoid: It drops the load.

When is the last time you checked your UPSs?

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