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Thread: Humming, Crackling and Lines onscreen

  1. #1
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    Angry Humming, Crackling and Lines onscreen

    Hi,

    I have just finished setting up my second PC install, the system consists of Jetway 2Ghz Mobo, 1gb Ram, 100GB SATA 2.5" HD, Bluetooth Reciever, M2 ATX PSU, GPS USB Receiver and a 7" Touch screen TFT.

    I set the system up inside the house and tested it using a Meanwell 350W 12V PSU, everything was fine EXCEPT for the screen where i could see lines going across it -moving up down like the old tellys. I didnt think much of it.

    now i have the system setup in the car the noise coming from the speakers is horrible - loud humming unless i turn the volume up and i cant hear it. Its NOT alternator noise as i tested it with the car on IGN.

    The ground is a factory ground, both the amp and carpc are using the same point.

    I TRIED different audio cables, moving the cables around, tried it with the internal sound and my external Live 24, tried taking everything USB off (except touchscreen) - all have the interference.

    Could it be that i am using a custom plastic case? or Could it be a dodgy mobo?

    Really p**sing me off now .. . .

    Any ideas are welcome.

    Thanks,

    ZeD

  2. #2
    FLAC
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    http://www.electronixwarehouse.com/c...e-sup/ns50.htm
    get something similar to that at. always worked for me.

  3. #3
    Variable Bitrate
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    What kind of sound are you getting? Do you think it sounds like the hard drive?

  4. #4
    Fusion Brain Creator 2k1Toaster's Avatar
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    THe plastic case could have something to do with it. The standoff screws actually ground those little rings to the case which is in turn grounded.

    Some things that have helped people with the same issues, is to solder a wire from a standoff screw to ground.

    It is a grounding issue like alternator whine, but just not on the post-pc side, it has to do with the pc.

    Also the wavy lines on the screen depends on how you are powering the screen. If you are powering it from the dc-dc psu, then either you are overloading the psu, or the psu is not grounded properly. Or you are running the vga cable too close to power. If powering through the egg, then the wires are insufficient guage. You did run a dedicated wire right? Not just splice off the cig line... If you have a lilliput and arent using an egg, and are not powering it from the dc-dc then you are putting unregulated voltage through it and the waves probably corespond with the rpms.
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  5. #5
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    Thanks for the replies,

    I had a good drive with it today, i found that there is an alternator whine too - this occured after a changed to a cheap mini amp.

    When the engine is off the noise still occurs, it more like a static + humming noise joined together, and a bit of gunfire/helicopter noise thrown in.

    I think it has something to do with the HD TOO as when i acess or click on something i can can hear clicking noise through the speakers like the hard drive is working.

    I dont think the M2 is taxed as i have just have the Jetway + a few USB devices + LCD connected. The screen is connected to the 12V molex on the M2 so its regulated.

    MY wiring is 4AWG to the distrobution block and 8AWG to the PC - the ground on the other hand is 8AWG direct from a factory ground point to the PC via a mini distro where the amp is also connected to. At the factory ground point i just opened the nut shoved in the loose wires and tighted it - as i didnt have an terminals about - could that be a problem?

    Am thinking it could be a grounding issue, how do i go about grounding my motherboard to the HD to the M2??

    Thanks,

    ZeD

  6. #6
    Newbie a_running_pir8's Avatar
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    hey man, i just got done installing my carpc to a semi-working stage (without the touchscreen, still being fabbed) and i have wavy lines, and lots of noise in the speakers, even when the car is "off" (ignition). The noise is mostly in the front speakers, and here is my wondering/question: I have the vga cable running next to the speaker wires for the front speakers. the rear speakers are run a couple feet straight to the amp in the trunk. i also built my box out of wood and carpeted it, and used plastic standoffs, so there is no grounding on the motherboard "rings". but it sounds like we have the SAME exact issue. so.....have you fixed it?

  7. #7
    Maximum Bitrate pRoFiT's Avatar
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    Motherboards put off tons of noise if not grounded properly. At my work we spend thousands of dollars in research on making sure the motherboard is grounded and all of the i/o ports on the motherboard are shielded.

    The previous company i worked for even went as far as putting a motherboard in one box and then another metal box around that just to meet FCC and CE standards. then all the i/o like serial ports and 485 lines had tons of caps on every line. I had to build them there was a crazy amount of screws too.

    Grounding is important to eliminating noise. Metal boxes work best. Wood and plastic does nothing for you.
    Um, I guess this is where you put something witty.WITTY

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  8. #8
    Variable Bitrate Jistari's Avatar
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    Quote Originally Posted by 2k1Toaster View Post
    Also the wavy lines on the screen depends on how you are powering the screen. If you are powering it from the dc-dc psu, then either you are overloading the psu, or the psu is not grounded properly. Or you are running the vga cable too close to power. If powering through the egg, then the wires are insufficient guage. You did run a dedicated wire right? Not just splice off the cig line... If you have a lilliput and arent using an egg, and are not powering it from the dc-dc then you are putting unregulated voltage through it and the waves probably corespond with the rpms.
    I've been wondering if this is part of my problem ? Most of it is in this post (http://www.mp3car.com/vbulletin/revi...t-p-o-s-5.html ) but I really wanted to ask about the power and the vga cable, if you have a sec 2k1?

    I thought my intermittent problem with the Xenarc 700 IDT not displaying anything (even the post) at boot might have been related to the power (it was wired direct to the molex, so it was powered through the psu) so I tried running it directly off the cigarette adapter that they sent with it. No change for me, still wouldnt get display (well the display wakes up when it boots but it looks like a white screen with lines on it, you can tell its running, windows even works fine, you just cant see anything on the screen). Its all in the post above.

    The second question (which I thought of but didn't do anything about yet) was interference into the vga cable. I routed the (proprietary) vga cable from Xenarc (with the two av inputs,usb and vga) along the firewall and around the right side of the vehicle through the wireing chase down the rocker panel and into the back where the pc is (the power cables are in this chase as well as some audio cables that go to the head unit from the pc). The cable provided wasnt long enough so I had to add an extension. The extension I used was a very good quality shielded cable and I went as far as to foil tape the connection between the two vga cables. You're gonna kick me but I also just realized that I routed the extension through the rear speaker enclosure to get it to the back of the car.

    Pineapple that I am, do you think that the shielded vga cable running right behind the speaker like that might be getting scrambled signals to the monitor at boot?

    <rubs head as the lightbulb goes off in head as he types this> Guess I should reroute that cable huh?
    PDP1170/TRS80/Atari800XL/Amiga500/286/486/P2/P4/C2D/i7 still a newb (but an old newb, been doing this a while) working my way up to "Complete Newb"

  9. #9
    Fusion Brain Creator 2k1Toaster's Avatar
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    You arent getting a picture after post, but it works fine before right? Bad video drivers. Giving me grief right now too. The Intel drivers suck *** and I dont know why. Boot into VGA mode and see if it works.
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  10. #10
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    @ a_running_pir8

    I kind of solved the probelm, it didnt seem to be the ground issude, i swapped my case for a a metal one and still had the problem. I moved all th cables round away from each other still had the problem.

    It turned out that it was the cheap amp that i was using. i put my kenwood back in and it all go sorted not a single dodgy noise coming through.

    Maybe you could try a different amp?

    i still get the lines coming down the screen though, my M2 shouldnt be loaded, its running a 2ghz jetway board 25W version i think, 7"tft, 2.5"HD and a few usb devices - thats it.

    hmm interesting...

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