Only one USB port can be used to connect an external keyboard

Three USB interfaces A USB external keyboard can only respond when plugged into one of them

Judging from my maintenance experience, it cannot be recognized. First, the computer cannot recognize the USB device.

The second is that the USB device cannot be recognized by the computer. We first need to determine whether it is a problem with the computer or the USB device. We can use other USB devices to test whether there are any problems with the computer.

If it is a computer problem. Is your computer damaged by a virus? The USB2.0 driver is not installed properly or the version is incompatible. If there is any software conflict (solve the software problem first), there will usually be a prompt to install the driver.

If it is a computer hardware problem. We first use a multimeter to measure the four USB lines (red 5V, white DATA-data-green DATA-data-black ground wire). The red test lead of the multimeter is measured against the ground black test lead (white line and Lu line. The resistance values ​​are not different by 50 ohms. This Both lines come out of the south bridge. If the resistance changes too much, it can be judged to be a south bridge problem. It means that the USB module inside the south bridge is burned.

Let’s take a look at the USB devices outside. Many of them now require drivers. Even if there is no driver, it will not be unrecognized. There are several situations in which unrecognition occurs. If the USB data cable is blocked or has poor contact, it usually touches that place. Because over time, it may be rusty or swollen, or there may be something blocking it inside. 2. The USB cable is blocked. If the red line is blocked, there will be no response, and if the white line is blocked, there will be no recognition. If the green line is blocked, it cannot be identified. The white wire and green wire cannot be connected reversely. It is also unrecognizable. The black wire is blocked and there is no response. The measurement method has been mentioned above.

Note. The low 5V voltage of the red line may also result in unrecognizability.

Three USB board internal problems. 1. The crystal oscillator is defective and cannot vibrate. 2. The crystal oscillator capacitor is defective (20P). There are two

3 The reset capacitor resistance is defective. The reset voltage is too low and too high. 4 The three-terminal IC is defective and the voltage provided to the IC is not enough. 5.

Bad main IC

Good luck!

My laptop has 3 USB ports, one is usable and two are unusable. What should I do?

Fault analysis: It is recommended to transfer the mouse to another computer for testing. If the mouse is faulty, please repair or replace it. If there is no fault, please repair the system.

1. Turn on the computer and press F8 until the advanced options appear. Release it, select "Last Known Good Configuration" and press Enter to repair.

2. Press F8 on boot to enter safe mode and then exit. Select restart or shutdown before booting to enter normal mode (repair the registry).

3. If the fault persists, please use the system restore that comes with the system to restore it to the time when the fault did not occur (if the normal mode recovery fails, please boot and press F8 to enter the safe mode and use system restore) .

4. If the fault persists, use the system disk to repair it. Open the command prompt and enter SFC /SCANNOW and press Enter (there is a space between SFC and /). Insert the original system disk to repair the system. The system will automatically compare and repair it.

5. If the fault persists, set the CD-ROM drive in the BIOS as the first boot device, insert the system installation disk, and press the R key to select "Repair Installation".

6. If the fault persists, it is recommended to reinstall the operating system.

If that doesn't work, it is recommended to choose repair installation, which will repair the system and prevent the programs and files on the C drive from being lost.

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