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Thread: would a VGA "amplifier" solve LCD hum??

  1. #21
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    i rememver you saying those caps dont work >_> . yes i have tried. but with no luck. i dont think it is related with the car at all. all my things are powered from the PSU, and not anything is grounded elswhere. yes the cables are prety far apart. the only point where they "meet" is, that the cable that has the ampere from the alternator, to the back battery, passes about 1m from the PC itself. but that ccant be the source, becouse the noise presists even if the cable is run from outside the car.... if i had to guess, i would say that its the m4-atx that is completly ****ty , and gives all the problems.

  2. #22
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    not that i think its a good idea, but if one where to build an LR low pass filter with an R like this :
    http://www.ebay.com/itm/0-1-Ohm-0-1R...item2569d1472f
    and an L depending on the frequency that one needs to cut.
    would it work? or would the voltage drop be too big? or the power cables are irelevant, and all the noise is produced inside the psu ?>

  3. #23
    FLAC SNOtwistR's Avatar
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    Have you tried powering your screen from another source to see if it is the M4? Process of elimination/trouble tree is always a good route to travel. Just a thought SNO

  4. #24
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    Quote Originally Posted by settra View Post
    i rememver you saying those caps dont work >_> .
    WTF? When did I say that - or is >_> akin to poke or LOL?


    But know that I know you have an M4 - there is your problem.

  5. #25
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    Ok I will repeat what I said...

    If your VGA cables are too long for the video source driving them it will be too weak to show a display properly. Period...

    If your shorter cables fixed the issue then you already verified the problem and have to figure out how to fix it.

    If you use a USB video card your cables are shorter thus the video signal output is strong enough to drive the screen.
    Assuming that you tested your video with a similar quality cable in both a short and long version. You may also isolate the noise from the card as well but that is a different topic all together. Depending on the noise involved you are not likely to affect the monitor unless the noise is very heavy or has frequencies that the monitor will pick up.

    In our case the video driver was just too low powered and the video would have issues keeping Vsync and Hsync all of the time. We ended up having all sorts of issues. It was as if 5-10 frames of every 60 were not being displayed properly. When we boosted the signal the noise went away. We actually split the video to provide a local source at the computer which was fine and a remote display that was 10' away which had the ghosting and other affects until we got an amplifier for it.

    So like I said, assuming your video signal is too weak the USB card would take care of that. Along with the cable picking up spurious noise due to grounding issues etc.

  6. #26
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    well that sucks. amplifier came in today. hooked it up and nothing. same noise.... so i guess an amp wont solve that specific problem. (tossing the m4 of a cliff might)

  7. #27
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    What happened with the amplifier?

    Same noise or otherwise?

    Don't toss it yet.. If it did change the noise you may have multiple sources of noise.

  8. #28
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    i dont know... i had to put an extra cable in the system (Which was of crapy quallity). it did not make any difernece i think.at least is hard to say... maybe it got a bit worse, but just that....

  9. #29
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    so... some extra info, today i was using a speaker , as an osciloscope ( i know, i am poor:P ) just to see if there are AC currents. the results where those:

    There is an AC directly on the Alternator's output.
    there is AC where the power is pluged at th M4-atx.
    when i power the M4, the ac at its input, grows stronger,
    when i power the M4 there is (ofc) loads of AC, in its 12,5,3v rails....

    those AC, do not neccecery have to do with ground loops, do they?

  10. #30
    Raw Wave
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    Inconclusive. All vehicles have AC on their +12V when charging.
    When not charging depends on the loads, but yours will have AC (eg, due to the M4).

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