I built my PC over 6 years ago, and within the first year the front case USB 2.0 connectors haven't been operable due to frying whatever gets plugged into them. This did not appear to happen until after a few months of putting it together. But then I slowly started discovering that anything I would plug into them would die and I even found evidence that the circuit for the Xbox controller I plugged into it had burned.
I never got around to figuring out how to fix this, but I need to now. There's clearly a short somewhere. I have a multimeter that I could use to test voltage levels out, but really I just need to be able to test the port without destroying whatever it is I plug into it (i.e. I would prefer not to burn through cheap flash drives as my troubleshooting process). If I have the proper troubleshooting procedure, I know I can figure this out.
My electrical knowledge/experience level is barely a pulse. I can't even explain the possibilities as to why this type of shortage may be occurring -- if I could do that, I think I could start exploring possibilities to fix this...
34 Answers
I did this same (or similar) thing, once, as a computer tech. I hadn't realized that the Firewire connections on the motherboard were the same exact spot and looked the same as the USB connections, so I ended up connecting the USB ports to a Firewire connection.
I don't remember the exact results, but it was bad and something ended up getting fried. #learningexperience
If I was you, besides making sure that the voltages are correct and in the correct pin, make sure that you have the USB port plugged into an actual USB receptacle. :-)
4Buy a proper tester, this one costs ten bucks / costs less than a USB thumb drive and will help you confirm it's time to replace those front ports.
I've personally used this one for the past year and it helped me diagnose a faulty Toshiba Satellite and a bad USB hub.
What fries devices more than volts is the AMPs, too many AMPs kills devices and people faster than voltage and trying to slice a USB cable as a multimeter bridge will always leave you wondering what if?
I doubt that it is an actual short. A literal short circuit would damage the port itself, while the connected device would simply not power up, but work fine connected to a different PC.
One test you can do is to grab a USB cable that you can sacrifice, and strip it so that you have the four wires (five, if you count the bare ground wire) bare. The red and black pair are the ones supplying power, and these should have 5 volts between them. Any more than that, . The other pair (green and white) is the data bus. If you have a good multimeter, you should have a voltage between these two as well, but as it's a digital signal this will jump between 0 and 5, so depending on your meter, it can read 0, 5, something in between, or something completely different, so troubleshooting this pair is beyond the scope of this answer.
To sum up: Ensure that the red/black pair has 5 volts between them, with red being the positive.
PS: Be sure not to short any of the wires. While many (most?) boards have built in short protection, you don't want to risk frying the bus.
2Check the voltage, with a reliable testing device such as a multimeter or a USB tester. If you use a multimeter, make sure you don't short out the probes on the outside of the usb case (which is connected to shield or ground). Over-voltage would be the main problem. Or if the pins were swapped somehow.
The voltage should read around 5V. Any more than 5.2V and your going to have issues, the protection diodes in the device will turn on and start to heat up (if no diodes exist then it will start to fry the device.) Check the data pins, the voltage should be near zero. If there is 5V on the data pins you will also have problems.
If these ports are soldered directly to the motherboard then you will probably not be able to fix the problem as you will have to reverse engineer the motherboard circuits. If its a chassis usb or usb that plugs into the motherboard, then check the pinout on the motherboard with the pinout of the cable (if you don't know what the pinout of the cable is, set your meter to ohms mode and probe the cable, when the meter shows zero ohms then you know how its connected)
