# 'Unknown Device' in an Empty and Unresponsive USB Port



## Azbulldog (Nov 1, 2009)

So I'm a little stumped. A few weeks ago or so, while still using Windows XP, once while turning on my computer either the mouse or keyboard wasn't responding (I forget which). I didn't think much of it and changed the USB port the device was plugged into. Since then, the USB port that the device was plugged into no longer works. If I plug anything into it, it is not powered, and Windows does not detect anything plugged into it. 

Aside from it not working, Windows instead claims an 'Unknown Device' is plugged into that port. I have tried uninstalling and removing this 'device' as well as uninstalling all the USB controllers and hubs in the device manager, and restarting, but nothing has helped. 'Unknown Device' just appears again, and Windows fails to find any driver for it, etc. 

I'm using Windows 7 now, I can't remember if Windows XP also reported this unknown device. While I still have five of six working ports, it isn't much of an issue, I'd just like to keep this computer _clean_, so to speak, and not have problems like this sitting around.

Any ideas?


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## fwLogCGI (Nov 1, 2009)

Does it work in a Ubuntu LiveCD?


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## Shino (Nov 1, 2009)

hmm... it's unlikely, but it's possible there's a loose cable somewhere inside the compy. Otherwise, the only thing I can think of is (like above) testing it with some sort of Live CD like Knoppix.

Wierd.


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## Aurali (Nov 1, 2009)

If they are all on the same hub, I would suspect hardware, probably a banged up port.
Dunno what that would mean though.


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## Runefox (Nov 1, 2009)

It sounds like something happened to the ports; If it's one of the rear ports, then that means there might be something physically wrong with the motherboard. If it's the front or an expanded port, then the connector inside may have wriggled loose somehow (maybe it wasn't securely connected to begin with).


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## ArielMT (Nov 1, 2009)

My first thought is hardware problem, especially if the port sees a lot of plugging and unplugging.  Inspect it with a flashlight, and see if anything looks bent or out of place.


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## Irreverent (Nov 1, 2009)

ArielMT said:


> My first thought is hardware problem, especially if the port sees a lot of plugging and unplugging.  Inspect it with a flashlight, and see if anything looks bent or out of place.



That was my thought too, but since keyboards don't get unplugged that often, it could be software related.  

OP: did you look in the device manager and are any of the USP devices or  bridges with a yellow exclamation sign next to them?  Might indicate a driver problem.  You can right click on it and attempt a repair.


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## AshleyAshes (Nov 1, 2009)

I'd go into the CMOS, disable the onboard USB controller, start windows, let it boot without any USB devices, then re-enable the USB controller and see how Window's acts afterwards.

Though physical is still possible.  Sometimes things don't quite come out of the factory right and physically fail much sooner than they ever should have.


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## Azbulldog (Nov 2, 2009)

Lucky me, I just had downloaded and burned Ubuntu on a CD to try and run on Windows Virtual PC (didn't work, needs more work I might mess with later). Where do I go to find devices in Linux?

It's a port on the back of the computer, from the outside it looks fine and I say didn't get much use. I have no idea what would cause it to randomly stop working one day when I went to power on the computer, considering it just sits there. The three other ports next to it all work fine. Motherboard is only little over a year old.
Device manager does not report any yellow question marks or anything like that.
I'll try more stuff later.


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## Runefox (Nov 2, 2009)

Irreverent said:


> That was my thought too, but since keyboards don't get unplugged that often, it could be software related.



That's true, but each two-port block is considered by the USB controller as a separate hub; So it's possible bad traces on the board could have been lifted or split as a result of plugging/unplugging from the other port, or even just over time. It's also possible that a spill into the keyboard or otherwise spiking the USB port could cause that hub to fail.

It could even be on the motherboard's end - I had an old Pentium 4/s478 board set up in a temporary computer, and because of blown capacitors, the front USB ports ended up blowing (to the point of actually frying and fusing the internal cable) because of overvoltage on the motherboard's part.


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## Azbulldog (Nov 2, 2009)

Yeah I think something is wrong in the hardware. The port doesn't work in Ubuntu either. I also disabled all USB ports and ran Windows, stumbled around on an old PS/2 keyboard and everything was fine, then booted up again with the USB ports and the unknown device was there again and the port still doesn't work.

No idea how it happened, nothing has ever been spilled on the keyboard.



Runefox said:


> That's true, but each two-port block is  considered by the USB controller as a separate hub


 About this part, device manager only lists two controllers, and two hubs total, yet I have six ports. I'd imagine the two front ones being one hub, and the other_ four_ being the other hub.


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## Rigor Sardonicus (Nov 2, 2009)

Shot in the dark here--do you have carpeting in your computer room?


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## ToeClaws (Nov 2, 2009)

Azbulldog said:


> Yeah I think something is wrong in the hardware. The port doesn't work in Ubuntu either. I also disabled all USB ports and ran Windows, stumbled around on an old PS/2 keyboard and everything was fine, then booted up again with the USB ports and the unknown device was there again and the port still doesn't work.
> 
> No idea how it happened, nothing has ever been spilled on the keyboard.



Hardware can and does fail.  USB controllers sometimes die.  Had it happen in the past back in the USB 1.x days, but very similar to what you were seeing.  You can try doing a re-flash of the BIOS to see if it's just corrupted software causing it, but in all likelihood, you just have a hardware failure.


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## Azbulldog (Nov 2, 2009)

Rigor Sardonicus said:


> Shot in the dark here--do you have carpeting in your computer room?


Yes, but I have never felt static shocks or anything. I'm more concerned about it reporting an unknown device plugged into it.


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## Rigor Sardonicus (Nov 2, 2009)

Azbulldog said:


> Yes, but I have never felt static shocks or anything.


That doesn't matter. It takes 30,000 volts of static for a human to feel the shock. It takes as little as 3,000 volts to damage electronics.


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## AshleyAshes (Nov 2, 2009)

Rigor Sardonicus said:


> That doesn't matter. It takes 30,000 volts of static for a human to feel the shock. It takes as little as 3,000 volts to damage electronics.


 
Static shock shouldn't be a serious threat to the PC when it's plugged in, since it's also grounded while plugged in.  Static shock is really a threat to disconnected things that are thusly not grounded.

More over, the entire I/O plate on the back of a PC and the metal part on the outside of the USB plug and on the inside of the port are insulted from any actual electronic components.  You could electrify the PC case and it wouldn't hurt the PC, assuming everything was installed correctly.

You'd have to have a static shock that not only managed to hit one of the two USB data pins, somehow traveling INTO the port, negating the much closer metal all around the port, but it would also have to have enough kick to actually travel down into the controller.  I just don't see that happening. 

The reason shocks are a threat to open computers is when the shock happens right over the IC's and transsitors.


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## Rigor Sardonicus (Nov 2, 2009)

AshleyAshes said:


> Static shock shouldn't be a serious threat to the PC when it's plugged in, since it's also grounded while plugged in.  Static shock is really a threat to disconnected things that are thusly not grounded.
> 
> More over, the entire I/O plate on the back of a PC and the metal part on the outside of the USB plug and on the inside of the port are insulted from any actual electronic components.  You could electrify the PC case and it wouldn't hurt the PC, assuming everything was installed correctly.
> 
> ...


I did mention it was a shot in the dark, right? >_>;


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