K50 USB / PSU Issue - Odd one....

Discussion in 'General Hardware' started by grunger, Dec 30, 2014.

  1. grunger

    grunger Ancient Guru

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    Palit GTX970 4GB
    So, I come back home after xmas with a new 970 to install.

    I'd unplugged my machine from the mains while I was away, so I plug it in power it up and get a no keyboard message from the bios...

    I notice that the backlight on the keyboard is lit, but changing colour and flickering...
    All other usb devices are OK

    Try a different port - same result

    Plug in a spare keyboard (old basic Microsoft keyboard) and its fine, so I figure the K50 has a problem.

    But, as a last test I plug it into my Thinkpad and it works perfectly, backlit and working....

    I switch off the backlighting while it is attached to my Thinkpad, and plug it back into my main rig and it works.
    I then hit the backlight button and it reverts to strobing the colours and flickering.


    Last test I remember I have a USB3 card that I never use (U3S6 - I use the SATA ports) I plug it in there and its fine and working normally.

    So the upshot is it won't work with the backlight enabled in the mobo USB ports (any of them)

    I am going to assume the PCE-E U3S6 card is powered off the 12V rail and the mobo USB is on 5V.

    I've checked the voltages in HWmonitor and they are within specs, but the 5V is rapidly jumping between 4.97 and 4.93 (as in all the time up/down up/down)

    Could this be PSU related?

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