Build a PC USB 2.0 Hub "Device Unknown"

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Can anyone help? When my computer came out of standby today both USB ports on my laptop did not recognise the external USB hub connected to it. Window XP keeps giving a "Device Unknown" error message. I've tried everything that the Windows trouble shooter has to offer but still the Hub does not work. (This includes a system restore to a point before the USB error.).

What is strange is that individual devices ie mouse, webcam and flash drive work fine on the ports - Just Hubs are not recognised. I've tried the Hub on my other computer and it work fine so the hub is ok.

The following were connected to the hub when I put the computer into standby.

Infra Red transmitter
Logitec Webcam
Flash Drive

Please, Please can someone help !!!


Posts: 6,452   +3
Your hub loses its power during stand-by. When the PC wakes up again, that (permanently connected) device does not draw enough power again to also 'wake up'.
The connections going through that hub are fine. If you want to prevent this in future, you need a USB-hub with its own powersupply, not one that gets power from the PC-port.
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  • #3
I think there is some missunder standing here. There is no problem with the hub and its corresponding power supply. The problem is Windows XP keeps telling me the hub is an "unknown Device" no mater how many times I reboot, unplug, replug the hub back in.

This problem only occured after switching the laptop to standby and then turned it on again. As you rightfully say power was lost to the hub on standby. Perhaps the devices connected to the hub were powered down before windows could properly save the settings during the standby process.

All I know now is the hub isn't recognised anymore as a valid device unlike any individual devices that I plug in.

I'm sure there is a software/driver problem !!!


Posts: 6,452   +3
Go to Control Panel into Add/Remove Hardware (in W2K), I think in XP it's in the System somewhere.
Select UNinstall a Device, when you get the list, tick the box 'Show hidden devices'.
You may see a yellow mark next to it, if not, scroll down until you find your hub (should have a Brand- or Model-name). Uninstall all instances.
Then either reboot, or go to Add/Remove HW again and ADD new hardware.
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  • #5
Problem solved !!!! As I thought when the laptop was powered down to standby the USB hub was powered down at the same time (Thanks for pointing that out). When the computer switches to standby Windiows XP does not fully close all ports, so when the laptop was powered back up, along with the hub, it got confused because the status of each device was not as it was prior to standby.

Without realising it, I cleaned all temporary files off the laptop with McAffe Cleanup and everything now works perfectly. The clean up application must have removed the files associted with the hub that were locking it out.

These computers are never simple are they !!!
check cables!

I have to tell you that I got some problems with my external hard disk too, which was inside a USB 2.0 enclosure. The disk spontaneously turned off and on and windows xp tried to recognise it every time (ruining every job I did at that moment). I tried everything to no effect, I changed performance settings and drivers, I rearranged the drive-enclosure connection and cables, but nothing seemed to work.
Happily, after some thinking, I found the solution and now everything is going OK for a long time.
The problem was due to my USB cable. The one I used was an 1.1 cable. But Hi-speed USB devices need another type of cable, which is identical to 1.1 but has extra shielding. The 1.1 cables are subject to interference. Try to find a 2.0 cable and I am sure many of your problems will vanish automatically...
USB convertor

Luxus72, thanks a lot for your advice. It really works! I was trying for few days with same problem. Also, if you have little bit old laptop (before 2002) which do not support USB 2.0 port than cable 2.0 cable would not work for Hi-Speed USB so the best solution would be to have USB convertor to 2.0.

Thanks again.

Still computer is amazing machine!
SOLVED USB 2.0 cable

Thanks luxus72

You saved me more work doing all the usual "fixes" to get my external hard-drive to be recognized.

The problem seems to have been using a USB1 cable with USB2.0 port. The external drive was recognized on a USB1 port on another PC

A toast to you :)
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