Two, the USB device can not be recognized by the computer. We first need to determine whether it is a computer problem or a USB device problem. We can use other USB devices to test the computer has no problem.
If it is a computer problem. If your computer is damaged by a virus, the USB 2.0 driver is not installed properly or the version is not compatible. There is no software conflict (first solve the software problem) generally out of a prompt to install the driver.
If the computer hardware problem. We first use a multimeter to measure the four lines of USB (red +5V white DATA-data - green DATA-data - black ground) multimeter red pen to the ground black pen measurements (white line and strain.) The resistance value is not different 50 ohms. The resistance value does not differ by 50 ohms, these two lines are out of the South Bridge, if the resistance value changes too much can be judged to be the South Bridge problem. Explain the USB in the south bridge inside the module burned.
To look at the outside of the USB device is now a lot of drivers. Even if there is no driver will not come out of the case of unrecognized. There are several cases of unrecognized. A USB cable does not work or poor contact generally contact that place because of the long time may be rusted inside there is swelling things may also have something in the inside blocked. Second, the USB cable does not work. Red line does not work what reaction will not have, white line does not work can not be recognized. The green line is also unrecognizable. The white and green wires cannot be reversed. It can't be recognized. The black line does not work, there is no response, this measurement method has been mentioned above.
Note. The red line 5V low voltage can also lead to unrecognized.
Three USB board internal problems. 1 crystal is bad, not vibration. 2 crystal capacitor is bad (20P) there are two
3 reset capacitor resistor is bad. 2 crystal capacitor is bad (20P) there are two
3 reset capacitor resistance is bad. Reset voltage bottomed out and high 4 Bad triac IC not providing enough voltage to IC 5.
Bad main IC
Good luck!