The reasons why the computer can't recognize the USB printer are: 1. The USB port is not correctly recognized.

the USB cable does not conform to the specifications, the length is too long, or additional devices such as extension cord, patch cord and * * * enjoyment device are added. 2. Incorrect port selection.

3. The printer driver is not installed correctly, and there will be a port error if a mismatched driver is installed. For example, lj11 printer is equipped with PCL5e driver of the same series 115.

4. the influence of system and USB Host Controller. 5. The port power supply is insufficient.

solution: 1. connect the USB cable correctly, ensure that the length of the USB cable should be less than 2 meters, and the communication quality is good, and cancel the extension cord and * * * enjoyment device and other additional equipment. 2. Check the port options in the printer driver properties. If there are multiple DOT4 ports, the port with higher number is preferred; Check whether there is a USB port, and select the USB port to print the test.

3. completely uninstall the current driver, and then restart or hot plug the USB cable. If the system automatically finds new hardware, cancel. After discovering u *** printing support in device manager, use the "Add Printer Wizard" to add a printer and install a driver that matches the printer language. At this time, USB-X port should be selected. If the system can't detect the new hardware, it is necessary to check whether the system correctly recognizes the USB chipset. The steps are as follows: In Windows 2/XP (the operation steps of Windows 9x/Me are basically similar), click "Start → Settings → Control Panel → System → Hardware → Device Manager" in turn to find and double-click "Universal Serial Bus Controller". At least two types of entries should be listed, one is USB controller, and the other is USB Root Hub.

if the PC motherboard supports USB 2. and the driver is installed normally, the USB 2. Root Hub will generally be displayed here. If Windows does not recognize the USB controller, or "USB controller" appears in "Other devices", then the driver of motherboard chipset or USB 2. has not been installed successfully.

it is recommended to download the latest driver from the official website of the chipset and confirm that Windows can correctly recognize it. 4. It is recommended to install the printer on other computers for testing.

5. ensure that the USB interface gets enough power. A USB device contains a power supply that drives USB communication from a computer through a USB cable.

the computer can detect devices at a low power level of 1mA, but it needs 5mA to maintain the movable disk of high-power USB devices. When the printer can't get sufficient current supply, it may also cause DOT4 to be set incorrectly.

It is suggested to plug the printer directly into the power socket in the house, instead of plugging it into the extension cord to use current with other appliances. At the same time, try to use the power cord attached to HP instead of other power cords that may be unqualified, or add an active USB hub to the computer.

2. What should I do if the computer can't recognize the printer u *** device?

"Unrecognized USB device" is displayed, and the following points should be checked:

1. The front USB cable is wrongly connected.

this kind of fault will happen when the USB cable on the motherboard is connected to the front USB interface on the chassis, which is also very dangerous and easy to cause the USB device to burn out.

2. USB interface voltage is insufficient.

when the printer is connected to the front USB port, the system may fail to recognize the device. The printer has strict requirements on voltage, and the front USB interface may not provide enough voltage.

Solution: replace the power supply of the chassis or plug it into the USB interface at the back of the chassis.

3. System or BIOS problems. If it is a system problem, the best solution is to reinstall the system. If the BIOS problem enters the BIOS, select enable u *** device.

4. system conflict.

solution: restart the computer and print the test.

3. What if the computer can't recognize the printer?

From my maintenance experience, I can't recognize it. First, the computer can't recognize the USB device.

second, USB devices cannot be recognized by computers. We must first judge whether it is the computer or the USB device. We can use other USB devices to test whether there is anything wrong with the computer.

if it's the computer. Is your computer damaged by a virus? Is the driver of USB2. installed well or the version is incompatible? Is there any software conflict (solve the software problem first)? Generally, a prompt will be given to install the driver.

if it is a computer hardware problem. First, we use a multimeter to measure the four wires of USB (red +5V white DATA- DATA- green data-data-black ground wire). The multimeter uses a red stylus to measure the ground with a black stylus (white wire and green wire). The resistance of is not different by 5 Ω, and both lines are from the South Bridge. If the resistance changes too much, it can be judged that it is a South Bridge problem. It shows that the USB module in the south bridge burned out.

Let's take a look at the USB devices outside. Now many of them need drivers. Even if there is no driver, there will be no unrecognized situation. There are several kinds of unrecognizable situations. A USB data cable is blocked or poorly contacted, which usually touches that place because it may rust and swell inside for a long time, and something may block it. Second, the USB cable is not working. There will be no reaction if the red line is blocked, and the white line is blocked and cannot be recognized. The green line is impassable and unrecognizable. The white line and the green line cannot be reversed. It is also unrecognizable. The black line is blocked and there is no response. This measurement method has been mentioned above.

attention. the low voltage of 5V on the red line can also lead to unrecognizable.

internal problems of the three USB boards. 1 crystal vibration is bad, no vibration. 2 bad crystal oscillator capacitor (2P) has two

3 bad reset capacitors. The reset voltage is too high at the bottom. 4. Bad three-terminal IC provides insufficient voltage for IC. 5.

4. The computer connected to the printer suddenly appears unrecognizable u *** device. How to solve it

How to deal with "unrecognizable USB device"

1. The front USB cable is wrongly connected. This kind of fault will happen when the USB cable on the motherboard is connected to the front USB interface on the chassis, which is also very dangerous, because the reverse connection of the positive and negative will probably burn the USB device. Therefore, try to use the USB interface at the back of the chassis, and use less extension cables. It may be that there is a problem with the fracture, so look at it with another USB port. < P > 2. The voltage of the USB interface is insufficient. When the mobile hard disk is connected to the front USB port, it may happen that the system cannot recognize the device. The reason is that the power of the mobile hard disk is relatively high and the required voltage is relatively strict, and the front interface may not provide enough voltage. Of course, the inferior power supply may also cause this problem. The solution is not to connect the mobile hard disk to the front USB interface, replace the inferior low-power power supply or try to use the hard disk box with external power supply, if possible.

3. Compatibility between motherboard and system. Hehe, the most famous fault is the compatibility between NF2 motherboard and USB. If you encounter this problem on the motherboard of NF2, you can first install the latest USB2. driver and patch for nForce2, the latest motherboard patch and operating system patch, or try to refresh the BIOS of the motherboard, which can generally be solved.

4. System or BIOS problems. When you disable USB in BIOS or operating system, it will happen that USB devices cannot be recognized in the system. The solution is to turn on the options related to USB devices. That is, press F2 or DEL to boot, enter BIOS, and select enable u *** device.

5. Be careful when unplugging. Never unplug it when reading or writing, or you may burn the chip. There are more USB device icons in the taskbar of XP. When you open this icon, the USB device will be displayed in the list. Choose to disable this device, and then you can unplug it, which will be safer.

In fact, it is very simple to judge the software and hardware problems. Just try it on another machine or another system (it needs to be driven under 98). Some small problems may be formatted with special software first. And remind everyone to choose FAT instead of FAT32 when formatting under WINDOWS.

5. What should I do if the computer host doesn't recognize the printer?

The problem can be solved according to the following steps:

First, confirm whether the USB interface is good

Method: Insert a USB flash drive into your U-port, and whether devices such as USB mouse can be connected. If so, it means that it is not a USB port problem. You can change a printer line or try changing a U-port on your computer. On the contrary. It's the motherboard that needs to be repaired.

2. Confirm whether the system service is on:

Method: Right-click "My Computer"-"Services and Applications"-"Services"-find the service "Print Spooler" to see if it has been started. If not, click "Start" again. If this service fails to start, I suggest you reinstall the system.

Third, check whether the printer is in normal condition, as follows:

Open "Printers and Faxes" in the control panel and find your printer icon to see what its status is.

1. If it is gray, it means that there is no communication between your printer and your computer. Please refer to Article 1 and Article 4 for the answer.

2. If the status is Paused, double-click the icon, and click Paused in the Printer menu to remove the previous check mark.

3. If the status is Offline, double-click the icon, and in the Printer menu, click "Use printer offline" to remove the previous "check mark".

4. Next, check whether your printer's online motherboard or printer's connecting cable is damaged:

Method: uninstall all the printer driver and driver-related software in the Control Panel, then connect the printer's connecting cable (USB or parallel cable) to the computer, turn on the printer's power, and then click Start Menu-Settings-Open Printers and Faxes in turn, and right-click inside. If the printer can be detected, it means that there is nothing wrong with your printer. On the other hand, it's the problem of the printer's online motherboard, which needs to be sent to the maintenance station for repair.

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If the above can help you solve the problem, I'll tell you a step to install the printer driver correctly:

First, the printer driver, if you don't have a CD.

1. Connect the printer. Connect the power cable and data cable of the printer, and the data cable is connected to the computer (divided into USB port and parallel port).

2. Turn off the printer and install the drive CD. The driver can be installed in the drive disk that comes with the tape or downloaded from the corresponding website. Turn on the printer after installing the driver or when prompted to turn on the printer power during the safety process.

3. click the "start" menu-"control panel"-printers and fax machines-to find the newly installed printer icon and set it as the default printer.

6. What should I do if the printer u *** can't be recognized?

The printer USB can't be recognized. The solutions are as follows:

1. Ensure that the USB interface of the computer is enabled, and also ensure that the USB driver is installed correctly. Press the corresponding button according to the screen prompt to enter CMOS, enter "Basic BIOS Settings", check the integrated USB interface of the motherboard, and set the USB interface to "Enable". Enter the Windows desktop, right-click "My Computer", open the "Properties" dialog box, and enter the "Device Manager" to check and ensure that the "USB driver" is installed correctly.

2. install the device printer driver. Put the printer driver CD into the computer CD-ROM drive and run the driver installation program. In this process, if the program requires to connect to the USB interface of the printer, it will be operated as required. After the driver installation is completed, restart the computer.

3. after the computer is restarted, power on the printer first, and then connect the USB interface. if it goes well, the computer will automatically identify and complete the installation of the printer driver. One way to check whether the printer is installed successfully is to print a test page. If the test page can be printed, the printer is installed successfully. If the printer is still not installed successfully, please read on.

4. Open the Control Panel, double-click Add Printer, select Add Local Printer in the pop-up window, and then select Use Existing Printer Port and select USB Virtual Printer Port in the next operation.

5. select "install from disk" in the "install printer software" window, then locate the directory of the driver and select the corresponding installation file, and click next to install the printer driver. After the installation is completed, click "Print Test Page". If the test page can be printed, the installation is successful; otherwise, restart the computer.

6. reseat the USB interface of the printer and check the installation of the printer driver again. Enter the "Control Panel", find and double-click the "Printer" icon, right-click the installed printer type, select "Set as Default", right-click the printer icon here, select "Print Header Properties", and click "Print Test Page" in the pop-up window. If the printer can print a test page, the printer driver is successfully installed.

7. The printer is connected to the computer, and the computer says that it cannot be recognized

1. Download the driver matching the printer model. The model of the printer can generally be found on the trademark on the surface of the machine. If it cannot be found, it can be determined by looking at the relevant instructions. Of course, for most printers, the driver CD will be attached with the instructions when purchasing.

2. Select "My Computer" on the desktop and select "Manage" with the right mouse button; In the "Administration" window, select the "Services" option under the "Services and Applications" extension project, find the "PrintSpooler" service in the system service list that appears on the right, and then find the "