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ASUS B85M-E: USB and PS/2 not working

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    ASUS B85M-E: USB and PS/2 not working

    Hi!
    I have an ASUS B85M-E with non-working USB and PS/2 ports.
    GND and 5V are present.
    I have tried other PCI and PCIe USB cards, but it still doesn't work.
    I have reset the CMOS, updated the BIOS, but the problem is still the same.
    What else should I check?
    Half dead chipset ?

    #2
    Check first the data lines, if they are not shorted. USB port should have some small ESD protection devices very close to the USB ports (6-pin), they sometime get shorted by electrostatic discharges, PS/2 might be similar, but I'm not sure. Unfortunatelly these ESD protections not always do their job, so also the USB driver or pch can be shorted internally, depending on what drives the USB ports. In case of pch a repair usually does not make sense, as it is more expensive, than the value of such working old board.
    To check you can just desolder the ESD protection devices, and try if this will bring back the USB port to work (care not to have any electrostatic charges as pch is completely not protected w/o the ESD's). If success, then just replenish the ESD dev's with new/working ones. You can just take some from another mobo for parts and transplant them, best from same vendor and same/similar board generation. When resoldering new ESD's orientation is important, only one orientation is correct.
    Last edited by DynaxSC; 05-20-2025, 02:52 PM.

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      #3
      Originally posted by DynaxSC View Post
      Check first the data lines, if they are not shorted. USB port should have some small ESD protection devices very close to the USB ports (6-pin), they sometime get shorted by electrostatic discharges, PS/2 might be similar, but I'm not sure. Unfortunatelly these ESD protections not always do their job, so also the USB driver or pch can be shorted internally, depending on what drives the USB ports. In case of pch a repair usually does not make sense, as it is more expensive, than the value of such working old board.
      To check you can just desolder the ESD protection devices, and try if this will bring back the USB port to work (care not to have any electrostatic charges as pch is completely not protected w/o the ESD's). If success, then just replenish the ESD dev's with new/working ones. You can just take some from another mobo for parts and transplant them, best from same vendor and same/similar board generation. When resoldering new ESD's orientation is important, only one orientation is correct.
      The data lines do not appear to be shorted (I checked all the TVS).
      I checked the internal USB 2.0 ports (USB1112 and USB1314) and they work while the internal USB 3.0 (USB3_12) does not work.
      Out of curiosity I checked the Ethernet port and it does not work (the LEDs remain off)
      From the Linux terminal I saw that the USB 2.0, 3.0 and Ethernet controllers are correctly enumerated.
      Could it be a partially faulty PCH?
      Should I remove the TVS anyway and see if anything changes?

      Comment


        #4
        Originally posted by DrFalken View Post

        The data lines do not appear to be shorted (I checked all the TVS).
        I checked the internal USB 2.0 ports (USB1112 and USB1314) and they work while the internal USB 3.0 (USB3_12) does not work.
        Out of curiosity I checked the Ethernet port and it does not work (the LEDs remain off)
        From the Linux terminal I saw that the USB 2.0, 3.0 and Ethernet controllers are correctly enumerated.
        Could it be a partially faulty PCH?
        Should I remove the TVS anyway and see if anything changes?
        TVS removed and....all USB are back to work !
        Actually I've found the audio codec (Realtek ALC887) extremely hot and not working.
        I'll look for a donor board to replace all the TVS & codec chip and report back.

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