What's happening to my USB ports and how do I make it stop?
September 9, 2013 9:00 PM Subscribe
My computer's rear panel USB ports periodically stop working -- even after replacing the motherboard. I'm at the limits of my diagnostic abilities here. Has anyone ever seen anything like this?
posted by teraflop to computers & internet (9 answers total) 1 user marked this as a favorite
Apologies for the length, but I want to make sure I list everything I've tried already.
My current PC is one I built myself maybe a year ago. Windows 7, i5-2500K, Radeon 7850 GPU. It's been working fine since I put it together, except that very occasionally it would give the "unrecognized USB device" warning for no apparent reason. But over the last few weeks, it's suddenly started doing this thing where the rear panel USB ports will apparently shut down. The LEDs on my mouse flicker erratically for a few seconds before turning off, and the keyboard/mouse stop responding, but otherwise the machine keeps running as normal. Sometimes re-plugging things into different ports gets them working again; more commonly, I have to put it in standby using the power button and wake it up again. At first this was happening maybe every few days, and now it's more like hourly. I've scoured the Windows error logs and haven't found any log messages that coincide with it. And I've swapped out the keyboard and mouse to confirm that one of them isn't somehow triggering the problem.
Since it was still flaky when running Ubuntu, I figured it had to be a hardware problem, and since the USB ports are physically mounted on the motherboard, it seemed like the obvious culprit. So I went ahead and replaced the motherboard with a new one (a different model from the same manufacturer, ASRock) and reinstalled Windows for good measure. But the exact same thing keeps happening! If anything it's even worse now.
My only other theory is a bad PSU, but my voltmeter shows the USB power supply as a steady 5.01V even when the ports are nonfunctional. And except for the peripherals, the machine is rock solid and stable under heavy load, which doesn't make sense if there's a power supply problem. In any case, if this guess turns out to be wrong too, I'd rather not keep spending money replacing one component after another with no idea what's wrong. Has anyone seen anything like this before?