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USB ports not working or system will not switch on after inserting a USB device.



Summary Many PCs and notebooks contain self-healing fuses. If you simply remove the mains power for 10-60 minutes, these fuses may heal themselves!
When you switch on the computer or connect a USB device, the PC or laptop may not switch on correctly or some USB ports (sockets) do not appear to work. 

A typical symptom is that a PC or notebook will not turn on (the power light may briefly flash) or that the front or rear USB ports do not seem to work.
The most likely causes are:
A mechanical issue with one or more USB ports (eg broken, shorted).
A faulty USB peripheral is or has been connected to the USB port.
A blown fuse on the motherboard caused by a faulty peripheral.
A peripheral is or has been connected that required too much power (eg should be used with an AC adapter or connected to two USB ports on the computer).
If a USB plug is inserted into this socket, it will short out the 5V supply!
A user damaged USB socket (note the plastic tongue is missing and the four contacts are shorting on the metal shroud)
Remove all USB peripherals (printers, keyboard, mouse, USB flash memory pens, etc) from the computer. Note that some RM Ones also have a USB Webcam - unplug this from the rear USB port.
Examine all of the USB ports on the computer for damage. Check that the four gold contacts are not bent and that the plastic tongue is present and not broken.
Switch off and unplug the system from the mains supply or AC adapter. Leave for a few minutes and try again. If the same problem exists then leave the system disconnected for at least 60 minutes. This allows time for any self-healing 'polyswitch' fuses to 'heal'. Do not turn on the system before 60 minutes or the fuses will not have time to heal as they will not cool sufficiently.
Re-connect the mains supply.
Switch on the computer and check that no error message is reported. If an error message is reported, then the computer must have a fault (usually damaged/shorted USB ports).
Insert a good known USB keyboard which has Num Lock, Caps Lock and Scroll Lock LEDs (lights) into the rear USB port (if present).
Switch on the system and observe the USB keyboard LEDs - they should flash indicating that the port has power and the USB data lines are working.
Repeat the switch on test with the USB keyboard on each USB port in turn.
Inspect the USB plug of another USB peripheral (eg mouse) and insert it into another USB port on the computer (you now have a USB keyboard and a USB mouse connected) - repeat the switch on test and check they both work correctly in Windows.
Repeat step 9 until all required peripherals have been connected.
If the BIOS or Windows reports an error during testing, this should help to diagnose the cause of the issue.
It is very common for the plastic tongue inside USB plugs and sockets to break if misused (eg a USB pen drive is bent upwards or downwards). This can result in the four USB contacts inside a USB socket being exposed and shorting out, either when another USB plug is connected or if the contacts are permanently bent and touching the metal shroud inside the USB socket.

It is also common to find a damaged plug on a USB lead or peripheral such as a USB Flash memory drive. This can cause the fuse on the PC or notebook to blow. Typically, you may find that several PCs or notebooks all have the same fault - this is a clue that someone is using a USB peripheral that is causing this issue.

Possible Issues
If several computers to appear to develop the same or similar fault within a few days, this is a good indication that a user may have a faulty USB device.

If a USB port has been damaged, check that none of the four contacts are shorting (eg insert two pieces of double-folded clear adhesive tape above and below the four contacts), test the computer still works correctly and then seal the USB port using tape or by filling it with glue to prevent it's use.

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Article details
Article ID: 3
Category: Knowledgebase
Date added: 2013-12-19 14:21:21
Views: 3315
Rating (Votes): Article rated 3.1/5.0 (103)

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