USB Shorts

From time to time we get called out to our CD ripping clients to help out with computer problems, which is where I've been this morning. The problem sounded simple, after years of normal service our client had plugged in his iPod and his PC had promptly died.

It's something he'd done, well, hundreds of times with no problems. Naturally he assumed that something in iTunes had corrupted his computer and Windows Vista. When I got there the PC was completely dead, as if the power supply had failed. So I checked the power cable, tried the cable from their kettle, no problem in the mains. Screen worked OK, just when you hit the on button absolutely nothing happened. My line of thinking was that this was a dead PC and the only way forward would be a new machine.

The client asked if the iPod had killed the PC or if, even worse, the failure had blown up the iPod. I should explain it was sitting unhappily on his desk. I thought I'd try it in my MacBook just to be sure so I lifted it up to unplug it. As I moved the iPod there was a flicker from the cooling fan inside the PC. I unplugged the iPod (which was undamaged), then unplugged the sync cable. Each move caused a tiny burst from the box. Having unplugged the sync cable I got a real burst of power so I tipped the box up and had a look at the front USB ports.

At that point I could see the cause of the problem. The tiny piece of plastic in the USB connector had broken, exposing the metal prongs that allow data and electricity to flow down the cable. Then, I'd guess when our client put the cable into the port, the prongs had been bent resulting in one of the prongs touching the metal surround.

A dead short.

I dug out my trusty metal comb which was slim enough to be able to lift the offending prong from the surround. At which point the PC burst into life. One happy client.