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Thread: Electrical interference issue, I am OUT of ideas, $20 PayPal to whoever can solve it

  1. #1
    Maximum Bitrate
    Join Date
    Jul 2006

    Electrical interference issue, I am OUT of ideas, $20 PayPal to whoever can solve it

    I posted this in the power supplies thread but wanted to cross-post here since it's relevant.

    I have a P2140 and am having an electrical interference issue that I have not been able to solve despite several attempts.

    What does it look like

    The electrical interference occurs in the monitor as multiple horizontal lines dancing up and down the screen. It occurs on all inputs (VGA, RCA) and across multiple different monitors I have tried.

    What causes it

    It occurs ONLY when the laptop (ThinkPad R60) is running AND being powered by the P2140 at 17V using the supplied additional resistors.

    What makes it go away

    1. When the laptop is powered from the wall in my garage with the stock AC adapter and all other connections unchanged, the interference is gone.

    2. When the laptop is off, the interference is gone. As soon as the laptop boots up, the interference is back.

    3. When I remove or re-insert my PCMCIA sound card, the CPU cycles go up temporarily and the noise is gone for 2-3 seconds but then comes right back.

    What have I tried

    1. Grounding: Single grounding block for the monitor, the laptop, the 5V rail for USB, the PSU, and the amps. Also tried grounding the metal of the laptop chassis to the same grounding block. Grounding block feeds via a 4ga cable to a sanded, solid, single ground point drilled into a seatbelt bolt. I have tried a different ground point in the trunk with no change. Just for testing, I also tried individual ground points for the monitor and laptop with no change. I have no noise in my audio system, no alternator whine, and no static.

    2. Decoupling capacitor Tried both a .01uF and .001uF decoupling capacitor linked between power and ground for the laptop. Also tried both between power and ground for the monitor. No change in intereference.

    3. Disconnecting everything from the laptop All USB devices, sound card, docking station. I left just the VGA output connected and the interference still persists.

    4. Disconnecting the monitor inputs I thought the interference may be coming over the VGA or RCA line, which are run on the opposite side of the car from the power wires. Even with the VGA disconnected, the noise persists on the RCA input (rearview camera), and vice versa. Just the fact that the laptop is on causes interference in the monitor even if there is no video signal going from the laptop to the monitor.

    5. Ferrite cores/beads Have tried them on the power to the laptop, monitor, 5V rail, and the main input to the P2140.

    What now?
    That's what I am hoping someone can help me with. As far as I can gather, the power output of the main rail on the P2140 is CAUSING interference in the power to the monitor, but only when the laptop is on and active. So then I would think - faulty/crappy mobo on the laptop. But plugging it into stock AC adapter from the wall, and all noise is gone. I have searched every thread over the last several years that I could find for a solution, and nothing has helped.

    I am OUT of ideas.

    $20 via Paypal to whoever can give me a solution that works. I am serious
    Last edited by hari-bhari; 01-13-2014 at 12:12 AM.

  2. #2
    Maximum Bitrate
    Join Date
    Sep 2012
    Germany - Munich
    one idea:
    try to change the brightness of the tft backgroundlight.

  3. #3
    Variable Bitrate chris350's Avatar
    Join Date
    Aug 2007
    Queens, NYC
    Sounds like a bad power supply. Have you tried another power supply. ?
    Project "Driver"

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