We’ve seen some spectacular thunderstorms already this year. Back in the day of dial-up internet access, each storm would produce a wave of customers with failed modems; these days, with high speed DSL and cable access, such spikes in repair volume are rare. However, one customer who recently took home a shiny top-end iMac, returned shortly after: lightning had struck nearby, taking out many of his home appliances, including the new computer.
The computer presented with no signs of life. When a modern Mac is plugged in, there are diagnostic LEDs at various points inside the computer. One or more of these would normally be illuminated when plugged in to indicate that the machine was receiving power through the power supply. However, this iMac’s LEDs were dark. The first step was to install a new power supply, which did end up lighting the appropriate LEDs. Unfortunately though, the problem went far deeper than the obvious power supply replacement.
The iMac would now make a faint whirring noise when powered up. Removing the glass and screen from the unit revealed fans that would simply twitch when the power button was pressed. The power surge had affected the main logic board. Once the logic board was replaced, the iMac would power on properly but would kernel panic—display a message in several languages asking for a restart—on start up. Despite the recurring kernel panics, now that the computer was powering up, troubleshooting further was much easier.
To begin, the computer was stripped to a minimal configuration. This was accomplished by unplugging all accessories from the logic board, which coordinates every function of the computer, and plugging them back in one by one. This technique is called component isolation. So, the optical drive, hard drive, camera, infrared sensor and everything else was unplugged from the board, and one by one, they were plugged back in in an attempt to isolate the problem.
I was surprised to find that the built-in camera was the cause of the kernel panics. It had been two days since the machine was checked in, so I pulled the camera out of the 27-inch iMac on my desk, and installed it into the customer’s machine to save him from waiting another day for the part to be delivered. With the new camera installed, the iMac successfully booted.
This iMac had been plugged directly into the wall at the customer’s house. Interestingly, an open outlet was available on a power strip under his desk, but for some reason our customer didn’t choose the wise place to power his computer. The printer and other accessories plugged into the power strip were unaffected, but his television, also plugged directly into the wall, was fried as well. As we’re in the midst of thunderstorm season, now is a great time to make sure you’re using protection from power surges and make necessary purchases and adjustments to safeguard your electronics.