by Ankur Gupta, Provaré Technology
One day I noticed that I wasn’t receiving calls on my Verizon mobile phone at work. Then I realized text messages were also getting lost. When I began receiving emails asking why I was unresponsive I started taking a closer look. In the mornings and evenings my phone was working fine, but during the day nothing incoming was getting through.
I stood up in my cubicle, waved my phone around a bit, walked outside. I found I could make calls from the hallway, the reception desk, conference rooms, or near the windows. When I got back to my desk, nothing. I had never had reception problems with my carrier before.
What in the world could be happening? I suspected that new test PC in my office was spewing EMI.
After a TON of troubleshooting, including changing out literally every piece of the suspected offending custom-built PC, I determined that the problem was, in fact my monitor, an NEC 223WXM-BK connected via DVI port to that PC; and that it was specifically the fact that the monitor was in DVI mode at a refresh rate of 59 Hz.
What led me astray? Several things:
- I had a problem that was dormant because of a feature that wasn’t previously used in any manner. In my case the DVI port of my NEC monitor wasn’t connected in my previous configuration.
- By the time I noticed problem, it was long enough after the change that caused it that I totally missed the correlation.
- The data points indicating the defect were sparse because at the time I wasn’t expecting or making a lot of calls, so they weren’t missed until they began to accumulate over time.
- Motivation to solve the issue was limited since a workaround was available, and it would take time and resources to figure out the problem.
- Several distracting external variables were present such as new office neighbors, outside construction, and new PC hardware.
- Initial rabbit trails seemed like obvious causes: I had two completely new PCs with all new hardware – but both of my monitors had predated the new PCs – and the problem.
- It wasn’t until all of the “obvious” could be ruled out that I could let go of my bias and take an objective approach to troubleshooting the problem. Once I did that, I found the problem pretty quickly.
To read more about my journey, you’re welcomed to download a longer paper on this experience here.
Happy Troubleshooting!
Ankur
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