Computer reboots or shuts down when USB is touched - PSU issue?

[rheynemusic]

Hello,

 

My power supply is an HX850, about 3 months old. Recently, whenever I simply touch one of the two front USB connectors on my case, the computer instantly shuts down or reboots without a clean shutdown. It doesn't happen with my finger, but if the metal connector from any USB device simply touches the metal socket, the computer will instantly shut down or reboot. This does not happen all the time, but it's easy enough to replicate. It is not driver-related, because the device isn't even fully plugged in, and not even half-way plugged in. I took the metal USB plug from a game controller and also from a USB wireless receiver, and simply grazed the ports across the side, and the machine rebooted.

 

My motherboard has two sockets for USB leads from computer cases, labelled USB 1, and USB 2. One of them was not being used, so I took the lead from the front USB ports of my case, disconnected them from USB 1 on the motherboard and tried the second socket. The USB ports work but the random shutdown still occurs if I occasionally graze the front ports with the metal from a USB device's plug.

 

No other processes are running, nothing is draining my CPU, this is happening at idle.

 

edit: I also wanted to add that the PSU responds great under full load, like a full 3D Mark Vantage / 11 sweep. Games / audio apps perform fine, no random shutdowns or anomalies. I'm stressing the power supply with a pair of GTX 470's, and with an overcloked C2Q, the PSU is indeed getting stressed, and there are no issues. The shutdown from the USB ports is happening at idle.

 

Is the power supply defective (Corsair HX850) or is it behaving the way it should due to protecting itself or the computer from another problem?

 

Thanks for any assistance you can provide.

[Wired]

Sounds like you've got a short somewhere. Shutdowns are probably due to power protection from the PSU and/or motherboard.

[rheynemusic]

After more research, it looks like it's static electricty protection. It's winter, and I'm in NJ, so it's dry and there's lots of static discharge when I touch metal. Apparently, I'm discharging into my USB port and the computer is shutting down or rebooting. I'm sitting next to a grounded Yamaha MG12/4 mixer, and as long as my hand is on the mixer when I plug in my USB device, there seems to be no further issues.

 

I'm going to do more research rather than speculate further, and tomorrow I will attempt to contact Corsair to see if such static electricty protection exists in their power supplies. If not, it could be something my motherboard is doing to protect from static electricity (ASUS P5N-D). I've troubleshooted extensively for a short in the system with lots of jiggling of plugs, physical tapping with my finger while devices are connected, checked the lead from the front of the case to the motherboard including the connectors for frayed or disconnected wires, and everything looks clean. The USB port itself seems to be securely fastened to its circuit board, but I definitely will agree that there still could be a physical short and not static electricty related.

 

Thanks again.

[RAM GUY]

Sounds like the board is shorting and the PSU is detecting it. I would try testing the motherboard outside of the case to see if the short is caused by the way that the mobo is mounted. Before doing that, you may want to just disconnect all the devices from the system that you can get away with and see if the problem persists when running with a barebones configuration.

[rheynemusic]

Much appreciated, thanks. I cannot reproduce any sort of anomaly with the front USB ports disconnected from the motherboard over the past 24hrs. I've gone as far as shaking the system, jumped up and down on the floor a few times (my landlord probably loves this) but once the USB port is connected to the motherboard again, it's very easy to get the computer to shut down or reboot once I tap the ports, and again this is if I'm personally holding a little bit of a static charge. Once I ground myself and then touch the USB ports, including tapping the connector of the USB peripheral on my grounded mixer to release any charge, there's no sign of trouble.

 

I'm really leaning towards static electricty protection. Seems the motherboard is working as intended, in this instance. I will keep the ports disconnected for now just to be sure, and if anything further develops, I will post here.

 

Thanks again for the replies.