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  1. #1
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    AC Line Noises getting through test equipment

    What can I use to filter out all kinds of different noises and interference's coming from the AC line wall socket into the bench test equipment. If I plug my PC laptop switching power supply in the AC line wall socket, the switching will be picked up on my bench power supply and oscilloscope. I have to turn off the lights on the workshop because there is noise ,interference, high frequency spikes. I have tried EMI/RFI filters, line conditioners and used an Isolation transformer, they help some but still noisy and high frequency spikes when lights are on and if I have switching power supplies plugged into other AC wall sockets. What can I do to solve this problem?

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  2. #2
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    Re: AC Line Noises getting through test equipment

    Quote Originally Posted by lewisP View Post
    If I plug my PC laptop switching power supply in the AC line wall socket, the switching will be picked up on my bench power supply and oscilloscope.
    I had the same thing happen with my equipment.

    Cable TV, audio/video components. These had no problem until I hooked up my laptop AND plugged in the AC adapter. Then 60 cycle hum came through the speakers.

    I tried disconnecting this and that. The hum stopped when I unplugged either (a) incoming cable TV, or (b) laptop adapter.

    In fact, I did not need to pull out the cable plug entirely. If I only pulled it out 1/8 inch, so as to disconnect the outer part (ground), the hum stopped. The center wire (signal) could stay in contact.

    This made me decide the problem was a ground loop.

    used an Isolation transformer
    I believe this would have solved my problem. I didn't try it.

    If it did not help in your case, then the problem could be something else.



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