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Thread: Noise (from engine and other sources) HELP!!!

  1. #1
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    Noise (from engine and other sources) HELP!!!

    Hi all,

    Please help me as I have engine and other source noise on my system
    I have try many things before I opened this thread, and yes I have use the search button.

    My configuration:

    1) Renault's "Phillips Tunner list" as head unit.
    2) Connects2 adapter that adds RCA input to "Phillips Tunner list" in CD changer menu.
    3) Toshiba Tecra 8200 laptop as carpc. It takes input 15V 4A and max 70W.
    Battery of laptop is just 10.8V , so I have directly connect the power from cigaret lighter (12V to 14V) to laptop.
    4) Lilliput 7'' touch screen , power through the Lilliput's egg and cigaret lighter again.

    Symptoms in Car:
    - I connect just the laptop (power from battery) to RCA of head unit (no power, no screen): Sound clear.
    - I connect power to laptop : noise
    - I disconnect power of laptop and I connect Lilliputs VGA cable: noise
    - I connect laptops power and Lilliput: of course noise

    Symptoms at home:
    - Laptops speakers with or without power adapter: Sound clear
    - I connect laptop powered from battery to home stereo : Sound clear
    - I connect laptop's power adapter (220v) : Sound makes noise
    So I have a damage audio card in laptop?
    BTW this is the second Tecra 8200 that I manage to damage the audio this way.

    Anyway this is a company I work for laptop, so I managed to change the damaged one with another one.
    The new Tecra 8200 now, has perfect sound when it is connected to home stereo and power adapter now.
    But I don't want to damage this one AGAIN.

    I have try to eliminate noise by:
    (eventhough I don't know if laptop was damaged when I tried)
    - RCA ground loop isolator
    - Power filter to eliminate engine noise
    - Common grounds, as laptop and Lilliput uses the cigaret lighter
    - Many other things.....

    Possible Solution Senarios:
    1) Buy laptops power adapter for car and RCA isolator . Will adapter and RCA isolator solve my problem? Does anybody have heard about "epagogic" RCA isolators? Can I order it from internet?
    2) As laptop's sound is good when it takes power from battery, I may add an extra car battery . Lilliput and laptop will be powered from one battery not connected with the engines battery.
    I may have to create a circuit that will swap these batteries for charging reasons.
    Maybe this solution is cheaper too.
    But will it work again?
    3)... H E L P ....

  2. #2
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    quick test:

    youve got a phono to RCA converter, I assume. wrap a wire around the shield around one RCA end and ground it. (this is for your car) See if that helps, no loop isolator no nothing.

    Ive had issues in the past eliminated by grounding this.

    if this does work and you want a more elegant solution, there are ground loop isolators that come with two wire tails, you can ground those tails and use the isolator, and it does the same thing as wrapping a wire around the surround of the RCA plug.

    anyways, thats where I would start.

  3. #3
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    I suppose I should elaborate on my issue so you can see how similar they are. Bench testing a speaker, I had a 12 volt power supply and car amplifier, then my laptop using its regular in house charger. on the battery, the whole thing was perfect. when I plugged in the charger, I got a slight buzzing noise. when I grounded the RCA cable shield to the chassis of the amp, the noise went away. Ive been running like this since.

    might work for you.

  4. #4
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    Thanks for your reply WhiteRabbit.

    There isn't any easy point that I can ground to car body (I must damage a thich plastic cover on my car) .
    I have try to ground RCA with laptops ground cable, but no progress.

    Ground isolator with two wires is a good idea.

    But I'm not sure what has damage my previous 2 laptops.
    Is is an RCA ground current?
    Is it unregullated power of laptop (12V to 14V direct link to cigaret lighter instead of 15V)?
    Is it a ground test from the many I have done?

    Thanks again.

  5. #5
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    I'm no expert, but when you said your battery was a 10.8 volt battery, then said you wired it direct to your charging system, tons of flags went off in my head, I must say. voltage peaks abound in a vehicular environment!

  6. #6
    Constant Bitrate TyBong's Avatar
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    yea, the amps in the car would for shure fry somthing, it may not fry somthing noticable i.e. audio untill you use it, I have fried many laptops by doing this, but I just didnt care at the time. Try getting a real power supply that works with 12Vin on that laptop, i.e. radioshack, worst buy (bestbuy), etc.

  7. #7
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    dont forget to check the date of the thread next time before posting

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