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EMI issue

Discussion in 'General Hardware' started by Deadlyraver, Jun 11, 2013.

  1. Deadlyraver

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    I am having an EMI issue with my computer for the past 6 months, it has been escalating ever since and I've went through many attempts to clear it. Heres what I can tell you:

    -It doesn't matter which outlet I plug in to.
    -The speakers work perfectly when the computer is turned off or in use with another device.
    -I have an EMI filter on the outlet.
    -Headphones work with a faint scratching noise. Can hear HDD rotations, CPU activity, mouse movement, like telepathy to computers.

    I'm beginning to wonder if it's the power supply, as I have swapped sound cards three times in this computer's lifetime and my PSU has mixed reviews. It's a Cooler Master GX750. My motherboard has worked perfectly since the day I bought it.

    Help? Please?
     
  2. c_heater New Member

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    ground loops?

    neutral and ground should only be connected at the service entrance (first breaker panel after the wires coming from the pole).
    any sub-panel (connected after the main panel) needs to have neutral and ground separated.
    many times a sub-panel will have a jumper that ties these 2 together.
    if this is your setup, make sure the jumper has been removed.
    if there is no sub-panel, or a sub panel with the jumper already removed, check all your outlets to make sure the bare wire for the ground is not making contact to neutral.
    if all of this checks out, start unplugging everything that is plugged in throughout the house one at a time.
    a damaged cord or other device could be making a connection to neutral and ground.
    and for gods sake, if you have no experience with lethal voltages, call a electrician.
    at the very least have a trusted friend with a WOODEN baseball bat standing by , that knows cpr, to bust you loose and jumpstart you.
    good luck
     
  3. itsakjt

    itsakjt

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    First of all, check your household electric line. After you become sure it is ok, I think you should try a different PSU.
     
  4. SaiZo

    SaiZo

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    Have had the same issue, was like "static" noise in the backround. My problem was that the only grounded outlets are in the bathrooms and kitchens. But since I got an electricity meter they even changed the old wires and the EMI problem was solved.
     
  5. Widjaja

    Widjaja

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    If you have not, try the onboard sound and see if you get the same result as your dedicated sound card.
     
  6. Deadlyraver

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    Tested the circuit, fully grounded. I tried switching my speaker power sources and found that it gets a lot more static when on the same bar as my PC. Could it be the PSU?
     
  7. McSteel

    McSteel

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    The PSU is probably just part of the problem. And GX750 didn't receive mixed reviews, it received shit reviews all-round. And for good reason too. I'd try to sell it to someone who doesn't know any better, and get myself a Seasonic- or Delta-made PSU.

    Audio card is grounded either directly via the case or through the motherboard. The case is grounded through the PSU. You could try grounding the case to something else, just for testing purposes. I'm not sure if NZXT's paint is conductive, so if it isn't, maybe it's not properly grounded via the PSU. Test it with a continuity check on a DMM. If the paint isn't conductive, try to find an unpainted area on the case, and use a wire to connect it to a large metal object or to an outlet ground socket, see if that makes any difference.

    Alternately, you could shield your sound card with a thin sheet (or a foil) of metal (tin, copper), but make sure it's coated (isolated/non-conductive), Could help with external EM fields that induce unwanted current.
     
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  8. DinaAngel

    DinaAngel

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    i had this issue, psu leaking into cabinet, try unscrewing the psu and make sure it doesnt make contact with cabinet and then try. i had AC 170 V leak into cabinet, it got fixed after a week of use with a grounded power outlet, idk why

    psu i had issue with was corsair 1200i
    but problem is gone now.
    fun fact, having the fan up into cabinet actually did make the psu have lower temps and the power draw went down like 50 watts
    compared to letting the psu get air from under cabinet
     
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  9. 95Viper

    95Viper

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    Could be a possible ground loop... try plugging the speakers , pc, and other devices connected to the PC to the same outlet or power strip.
    This is an Apple/Mac link, but it is informative about ground loops and the noise you describe --> Solutions for noise in the audio signal
    Here is another article --> Solving Computer Audio Problems Banish Them For Good
    Sometimes it takes a little detective work to hunt down the source.

    Another thing you may wish to try, if you haven't, is disconnect all your audio devices (mics, headphones, audio out (TV, amps, etc.)... check the cables (no shorts, opens(on the ground side of connector & cable), or crosses), connectors are secure/snug when plugged in, and, then, plug one device in at a time and see if any of them are the cause.

    You might wanna try setting your CPU Spread Spectrum to "Auto" or "Enabled" in your bios settings.
    This may help with some noise in the circuits.
    If you have modified your bclk changing this (if you disabled it) may affect your OC.

    You may want to save your bios settings and turn off your OC then try the Spread Spectrum adjustment.
     
    Last edited: Jun 12, 2013
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  10. Deadlyraver

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    Did all the test methods like the paper trick, disconnecting headphones, and enabling onboard audio for a shot. Same results. I contacted NZXT and they are sending me free motherboard standoffs due to a past time case they had with them. I am thankful for their service especially when they placed the order as urgent.

    I installed a new PSU to solve half of the problem, a new AX 760 from Corsair. Loving it.
     
  11. McSteel

    McSteel

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    Their sending new standoffs would confirm my thinking that the case doesn't ground the motherboard properly... Hopefully it'll solve your issue.
     
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  12. Deadlyraver

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    I am connected to a pair of Rokit 5s. Possible ground loop with a shielded cable? Cause it has no ferrites on it, I should get some ground lifters.
     
    Last edited: Jun 13, 2013
  13. Deadlyraver

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    UPDATE: I have confirmed that my monitors are experiencing ground loop. I connected my mixer and interface to my laptop instead of my tower and everything worked as advertised. The PC however is a train wreck. I considered installing the standoffs and found that the interference didn't change afterwards and that while the speakers were raging in interference, the headphones were not affected at all! Even with the rear ports! I will purchase an isolator ASAP!

    I would like to thank Techpowerup for helping me with this issue. Thank you for your support!
     

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