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  1. #1
    New Lounger
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    Exclamation USB Mass Storage Devices not recognized

    Hi All

    Yesterday, I used my home PC and used a small USB disk for some data transfer. But in the same evening, it was not recognizing my cell phone (although cell phone recognized that it has attached to a PC, and offered me to behave like mass storage, which I selected)

    After some tries, I tried the same USB disk I tried earlier, and found that too is not working!?

    Device manager shows all the controllers and hubs, with no hub indicating any attached devices.

    Even uninstalling all controllers/hubs etc. and rebooting the PC didn't help (off course all controllers/hubs came back after rebooting)

    Note that between two events (i.e. working and not working) there is nothing, just some reboots.

    Any help?

    TIA

    Config: Dell Optiplex GX270 (P4), 512 MB RAM, 160GB hard-disk, WinXP SP3 with latest updates.
    [hr]
    Kamran (کامران)
    Islamabad, Pakistan

  2. #2
    5 Star Lounger
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    This is a common problem with XP PCs. The easiest, fastest way to fix it is to do a normal shutdown, then remove the power cord for a few minutes. If its a laptop, also remove the battery. I can't recall the specifics, but it has to do with capacitors needing to discharge.

    There is another method that requires a little more work, but I'll let someone else detail it if they choose.
    Chuck

  3. #3
    New Lounger
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    Thanks Brown

    But situation remains the same after an hour of this condition (i.e. removed all cables etc.)

    Can anybody point me to that "another method that requires a little more work" which Mr. Brown hinted?

    TIA
    [hr]
    Kamran (کامران)
    Islamabad, Pakistan

  4. #4
    5 Star Lounger
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    OK, try this then:

    Got to Start\Run
    Type CMD and press enter.
    Enter the following, one line at a time, and press enter after each line
    set DEVMGR_SHOW_NONPRESENT_DEVICES=1
    start devmgmt.msc

    From the 'View' menu select "Show hidden devices"
    Device manager will now show you every device that has ever been connected
    Non present devices are grayed out
    Delete all the non-working devices, reboot.
    When it comes back up and plug a device in, it should reinstall the device.
    Chuck

  5. #5
    New Lounger
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    Thanks Brown

    Today I am going out-city, will try this tip day after tomorrow.

    Till then, hoping for the best

    Kamran

  6. #6
    New Lounger
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    Ok, I am back to try the method Mr. Brown told in his last post.

    Alas, it didn't work. Although I was amazed to see how many usb-disks/drives have I connected to my PC in last year or so

    But still....

    Any more help will be more than appreciated (for obvious reasons, as I fear that it might be the time to change my PC regardless of my current financial position)

    Kamran
    Islamabad, Pakistan

  7. #7
    Gold Lounger
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    Quote Originally Posted by mks View Post

    Any more help will be more than appreciated
    Kamran
    Kamran,
    Hello...Have you tried connecting to another USB port?... This kind of sounds like a hardware problem. Regards Fred

    PS: Also when in "Disk Management" does the USB show up? ( with a drive letter)
    Last edited by Just Plain Fred; 2011-04-14 at 08:38.
    PlainFred

    None are so hopelessly enslaved as those who falsely believe they are free (J. W. Von Goethe)

  8. #8
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    Have you run a thorough malware scan? USB devices are a notoriously easy way to introduce malware onto a PC.

    Joe

  9. #9
    3 Star Lounger
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    Frequently it is power capability related. Try plug in a different USB outlet of your PC/laptop.
    USB specifications: 5V nominal, 500mA max (note 1). When overloaded, it limits and self protects.
    Electronic digital circuit spec'd that the 5V should not be below 4.5V or above 5.5V, else the logic circuit *would* fail (may 'work through' it though).
    1.
    Some older USB Flash drive, or older small form factor USB hard drive (laptop drive sizes), is already at the max current specification, or marginally close to the max load current of 500mA. When getting older, it draws more current than 500mA. Then, USB supply self limits, causing the 5V supply drops to below 4.5V. Failure would occur. Then the USB device would no longer be recognized.
    2.
    When USB cable is too long, the voltage drop on the long thin wires may cause too much voltage drop. Again, not enough voltage for the logic circuit will cause failure.

    Solution:
    1. Plug in to a different USB outlet of the PC/laptop.
    Each outlet has a slight different power capability. It is mainly due to the slightly different performance of the voltage regulator IC in the USB circuit (note 1), and the slightly longer wire trace from the PC internal power supply going to the that specific USB outlet.
    2. Use shorter USB cable. Or use thicker better cable.
    'Thick' I mean the internal wire is thicker (larger wire gauge), not the plastic sheath.
    3. Use a self powered USB hub. Or, if you use a no-power USB hub, shorten the cable length.
    4. If you use self-powered USB hub, make sure its capability can handle the USB devices plugged in. Remove some devices if the hub cannot handle that many loads.
    5. Use USB 3.0. It has 1A capability. (But not USB3.0 hub to a USB2.0 outlet!)

    Note 1:
    The 500ma capability is not hard and fast.
    The current limit of the linear voltage regulator IC is quite loose. You may have as much as 600mA to 650mA (but never less than 500mA). So, each USB outlet is different. Add to that is the copper trace, or the thin wires from the internal supply, to the USB outlet. At 500mA, the voltage drop across these thin gauge wires may create enough voltage drop that may effect a failure.
    Older laptop-size hard rive may draw around 500mA, just at the USB load threshold. As it ages, or the USB cable gets a tag longer, it causes failure. However, if moved to another USB outlet, the IC on this outlet may provide 600mA, and the internal wire voltage drop is small, then suddenly the USB drive works.
    Newer USB laptop-size hard drive draws less than the USB 2.0 specification, with headroom to boot, making them less likely to fail.

    You should prefer USB hard drives with optional external power connector, just in case the hard drive ages and uses more power.

  10. #10
    New Lounger
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    Thanks scaisson for this detail, it is indeed informative.

    1. I have already tested all the available ports, so it is no good.

    2. I tried more than one USB devices and none is working

    3. The USB flash drive is drawing 200ma current (I have checked it on other PC), so this should not be problem

    Might be that the power supply is itself in trouble?

    Note that when I connect my mobile-phone to this PC, mobile-phone itself feels it and started charging itself (apart from the offer that should it behave like mass-storage, web-cam, or com-port. and no option works, although mobile does behave as it is doing what it is being told).

    So?

    Even I have tried a blower inside the casing to remove extra dirt, to avoid situations like microscopic short-circuits resulting in dropped voltage, but to no avail.

    ?

    Kamran
    Islamabad, Pakistan

  11. #11
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    If you are hardware capable, and have access to Voltmeter (DVM preferred), measure the voltage across the two outer most edge pins (only 4 pins total) on the USB outlet. During measurement, take care not short circuit the probe/pin to the metal sheath, which is ground.
    1.
    But first measure no load voltage.
    It should be >=4.5V, <=5.5V. If it is less than 4.5V, or =4.5V at no load, time for a new laptop. Try on all USB outlets.
    2.
    Then add a resistor across the pins as load (or across your probes, just the same.) Try 20 Ohms first (for 250mA load). You should measure >4.5V at the pins. Then use 11 Ohms. The voltage should still be >4.5V. If it fails, try other USB outlets. If all of them fail ... new laptop.
    3.
    If you have no access to resistors, use a Y USB cable. Connect your 'failed' USB device. On the other Y cable end, measure the voltage. Do it on all the USB outlets. If it is less than 4.5V or equal to 4.5V, time to replace the laptop.
    4.
    If the results are all good, your hardware is OK. Concentrate on software problem. You might even have virus problem.
    5.
    Rare case that the voltage is above 5.5V. It is STILL OK at 5.6V! It is beyond 6V or higher that you have to throw away the laptop. Beyond 6V, some internal components may fail. Worse, it may cause non recoverable failure in external USB devices.

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