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Thread: Aaaarrrggghhh! Ignition Noise!

  1. #1
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    Oct 2003
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    Aaaarrrggghhh! Ignition Noise!

    I have my computer hooked up and running pretty smooth. Now I am having ignition/sparkplug noise being transmitted from the computer to my stereo. Noise goes away when I turn off the engine but leave the ignition on. I am also temporarily using an inverter.

    What solutions have you guys used for this problem? I have already installed a ground loop isolator but the ignition part of the noise is still there.

    This is getting frustrating!

    Doug
    Carputer Status: Prototype Install
    EIPS M1000, 80GB HD, 512MB RAM, Win 98 SE
    Lilliput 7" TFT Touchscreen, XM PCR running XM PC-CAR

  2. #2
    2nz
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    Hey dhowse,
    The noise is most likely conducting (through the wires) not transmitting (through the air). If it were your inverter it should still be audible with key on only.
    You could have a bad RCA... or still have a ground loop.
    With engine on and noise present check each chanel at the amp input for the injected noise by unplugging and listening for a change (noise gone/lowered). If it still makes noise with all RCAs unplugged then it's on the DC power side. If one RCA is mostly to blame try replacing it and do the test again.
    Do the same test on the RCAs from carputer to head unit.
    What type of ground loop isolator are we talking; how is it connected?

    I found that my original ground loop was between the sound card (output ground was same as chassis ground) which was also head unit ground but not the same grounding points. I put isolation transformers inline on the RCAs and this cured the problem. But I didn't like the sound - too messy, as the transformers weren't the correct impedence. So I ended up with a 48 kHz fiber optic transfer and it's very clean - full volume engine running and not a peep of engine noise.
    And I also run an inverter - there are other devices I plug in like external drive AC/DC supplies, drill, chargers etc.

    Start here and let me/us know the results.

  3. #3
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    May 2003
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    Quote Originally Posted by dhowse
    I have my computer hooked up and running pretty smooth. Now I am having ignition/sparkplug noise being transmitted from the computer to my stereo. Noise goes away when I turn off the engine but leave the ignition on. I am also temporarily using an inverter.

    What solutions have you guys used for this problem? I have already installed a ground loop isolator but the ignition part of the noise is still there.

    This is getting frustrating!

    Doug
    3Q's

    How much did you pay for the inverter (if less than $100, very likley to be the cause)

    How much did you pay for the power supply (how many Watts)

    You said " I am also temporarily using an inverter", when are you getting rid of it, what are you planing on replacing it with?

    And what the other guy said...

    Cheers,
    Chris

  4. #4
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    Oct 2003
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    I would like to be able to help but I need help myself. Forgive me in using this thread but I think I am in the same ballpark. Anyway, I just assembled a system using the mini-itx board from via. The case is a Morex that came with a 12-volt power supply which is a direct plug-in to the car's cigarette lighter. Is this why I am having this noise? Should I tap into the car radio's power supply to get a cleaner line?

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