USB Diagnostics

Diagnose your USB problems.

USB is one of the more convenient, user friendly innovations of the 1990s. A computer user can connect most common computer devices through one kind of port, instead of having to fumble with a plethora of different serial and parallel connectors. However, modern operating systems and external devices are constantly becoming more sophisticated and occasionally encounter problems. Luckily, most USB problems can be diagnosed and repaired by the layman without much trouble.

Physical Connection

Loose USB cables can cause problems.

The most easily fixed USB problem is an improper connection. This is usually the result of a bad USB cable, not using a cable that is appropriate for the device, or a cable that is not plugged in completely. Check to make sure the the device is properly connected to the computer. Swap out the cable for one that is known to be working If there are still problems after doing this.

Reset

Reset your computer and USB devices.

Turn off the computer and all devices, unplug all the USB devices, wait 30 minutes for the devices to cool down, then plug in only essential USB devices and restart the computer. Plug in the rest of the devices once the computer is running, and check the problematic devices.

Overcurrent

Overcurrent can cause your USB devices to malfunction.

Overcurrent occurs when there are too many USB-powered devices running at the same time. This will cause the computer to not recognize certain devices at all or to recognize them intermittently. Some websites advise users to experiment with connecting the devices in different orders or to start them up in a particular sequence. However, the most reliable way to fix the problem is to provide external power to as many devices as possible and connect the others to a powered USB hub.

Cable Length

Plain USB cables longer than about 16 feet may not transmit data completely.

Plain USB cables longer than about 16 feet may not transmit data completely, which can cause devices to malfunction. This includes when printers or scanners endlessly spit out blank sheets of paper or create pages of random text or distorted images. Use short USB cables whenever possible. Use a USB repeater to prevent data loss where this is not possible.

Wake Up!

Check your computer's USB devices settings.

If the computer's USB devices are initially are recognized, but will not reactivate when the computer is taken out of hibernation, this is probably a problem in the computer's settings. Both PCs and Macs have options that give the operating system permission to turn the USB devices off as a way to conserve power. Unplug the devices and plug them back in to let the computer recognize them, or turn off any settings that allow the OS to deactivate USB devices.

References

• Hassle Free PC: Smart Free Fixes for Your USB Hassles
• Spilling Coffee: USB Device Not Recognized
• USBMan: USB Troubleshooter