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Weird problem with external monitor

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  • User profile image
    geeky123

    Not sure if this is the best place to post this, but here goes anyway -

    I just bought and connected a 22" monitor to my sony vaio laptop.

    Now although it works fine, I notice that when i connect the power cord to the laptop, the monitor starts getting these very faint wavy lines. Sort of like water. They are more prominent against a dark background.

    However as soon as i disconnect the power cord from the laptop, the monitor becomes fine again.

    The vga cable and power cord are right next to each other.

    Why do you think this problem is being caused? Is there any way to correct this?

  • User profile image
    Massif

    Does the laptop power cable run adjacent to the monitor cable?

    I'm guessing it's interference, either from the cables running parrallel, or from badly shielded connections in the laptop.

    If you're lucky then a bit of adjusting the cables, or something metal to seperate them will fix your problem. If you're unlucky it's internal shielding on the laptop. (If you're not that unlucky it could be a badly shielded connector on either laptop or monitor cable.)

    But then again, I'm not an electrical engineer Big Smile

  • User profile image
    geeky123

    Yup it does run adjacent to the vga cable. Almost stuck to it.

    Alas it seems the interference is internal since no amount putting stuff in between the cables or adjusting them seems to make any difference.

    Just a wild shot but will getting one of those little vga-dvi adapters help my situation in any way, since my monitor also supports dvi?

  • User profile image
    Cannot​Resolve​Symbol

    geeky123 wrote:
    Not sure if this is the best place to post this, but here goes anyway -

    I just bought and connected a 22" monitor to my sony vaio laptop.

    Now although it works fine, I notice that when i connect the power cord to the laptop, the monitor starts getting these very faint wavy lines. Sort of like water. They are more prominent against a dark background.

    However as soon as i disconnect the power cord from the laptop, the monitor becomes fine again.

    The vga cable and power cord are right next to each other.

    Why do you think this problem is being caused? Is there any way to correct this?


    Rearrange your cables, and make sure they're both grounded to the same pair of outlets or power strip.

  • User profile image
    geeky123

    They both are grounded.

    How can i possibly rearrange them when the connectors on the laptop are side by side Sad

  • User profile image
    RichardRudek

    Your probably getting a "beat signal" due to an interaction between the Power Brick's operating Frequency the Display's horizontal rate.

    So if your monitor supports it, try changing the vertical refresh rate, which in turn changes all of the other related timings, including the horizontal. ie For Win XP, 2K or 2K3, right-click Desktop, Properties, Settings tab, Advanced button, Monitor tab, Vertical Refresh.

    The problem should go away using DVI as it's a digital output, but you never know.

  • User profile image
    RichardRudek

    geeky123 wrote:
    
    Just a wild shot but will getting one of those little vga-dvi adapters help my situation in any way, since my monitor also supports dvi?


    I've not read the DVI specs, so I don't fully understand the capabilities DVI. But I don't see how a "simple" VGA to DVI Adapter, one which (mechanically) converts an Analog VGA output port (from laptop) to a DVI input port (to monitor), could fix this.

    Doesn't your laptop already have a DVI port - many do, these days.

  • User profile image
    Massif

    RichardRudek wrote:
    
    geeky123 wrote:
    Just a wild shot but will getting one of those little vga-dvi adapters help my situation in any way, since my monitor also supports dvi?


    I've not read the DVI specs, so I don't fully understand the capabilities DVI. But I don't see how a "simple" VGA to DVI Adapter, one which (mechanically) converts an Analog VGA output port (from laptop) to a DVI input port (to monitor), could fix this.

    Doesn't your laptop already have a DVI port - many do, these days.


    DVI supports analog signals, so I think a VGA->DVI adapter literally reroutes the signals to the relevant pins, and doesn't actually translate the signal to digital.

  • User profile image
    geeky123

    RichardRudek wrote:
    Your probably getting a "beat signal" due to an interaction between the Power Brick's operating Frequency the Display's horizontal rate.

    So if your monitor supports it, try changing the vertical refresh rate, which in turn changes all of the other related timings, including the horizontal. ie For Win XP, 2K or 2K3, right-click Desktop, Properties, Settings tab, Advanced button, Monitor tab, Vertical Refresh.

    The problem should go away using DVI as it's a digital output, but you never know.


    It doesnt support changing refresh rates. Anything above 60hz starts distorting the image.

    Thing is my laptop doesnt have a DVI output Sad

    Also I notice that the wavy lines appear only on certain colors like dark gray/blue.
    They dont seem to be there when seeing a bright color like White.

    Edit: It turns out my monitor only has support for DVI-D so any of the vga to dvi adapters wont work either Sad

  • User profile image
    geeky123

    so doesnt anyone have any solutions or workarounds for my problem Sad

  • User profile image
    RichardRudek

    geeky123 wrote:
    so doesnt anyone have any solutions or workarounds for my problem


    If you can't reconfigure something, then the next logical thing is try  replacements. ie Try a different Power Brick and/or Monitor.

    Obviously, for the power brick, this will require you to do some checking, such as output voltage, maximum supply current, connector polarity, etc.

    Why a different Monitor ?  Well, perhaps the Monitor has a fault. For example, with the Monitor's cable/routing  (grounding, shielding, supressors).

  • User profile image
    geeky123

    By power brick do you mean my laptop's power adapter?

    I dont the problem could be in the monitor since when i run the monitor by itself, ie with my laptop on batteries, it runs fine.

  • User profile image
    RichardRudek

    geeky123 wrote:
    By power brick do you mean my laptop's power adapter?

    Yes.

    geeky123 wrote:
    I dont the problem could be in the monitor since when i run the monitor by itself, ie with my laptop on batteries, it runs fine.


    But, you get a problem which, from your description, sounds like an interference issue. It may not be though.

    In terms of interference, the VGA output from your laptop has a number of signals: Vertical and Horizontal Sync (digital), and the Red, Green and Blue (analog) video signals. Video, in this case, meaning a left to right, top to bottom raster scan.

    With a CRT monitor, the video signal paths are pretty straight forward: apart from some signal conditioning, they are pretty much used directly to render the display. That is, a CRT uses an Electron beam that scans from the top left of the display to the bottom right, line by line - a raster. The timing of this being controlled by the horizontal and vertical synchronisation signals.

    An LCD monitor is, in comparision, a lot more complicated. They typically still use a raster technique, but instead of a single raster, there may be multiple - thats why you can typically point a video camera at an LCD display without having to "GenLock" the syncs bewteen the Camera and Monitor. In other words, the LCD display has to "store" the image it needs to display, "recovering" it from the Video signal, and it's at this point that you can weird effects. - either due to "noise" on the signals or grounds, or the algorithms/circuitry used for this. Typicially, these "effects" (artifacts) are more noticible when your running the LCD monitor at a non-native resolution. ie The video you feed into the Monitor has less "pixels" than the LCD display panel physically has.

    Now, why only when the Power Brick is being used ?

    Well, the Power Brick will be using a switch-mode design. The basic idea is that if you "digitally" switch (on or off) between two voltages, over a certain period of time, you effectively create an "average" voltage, and you can control this by adjusting the "width" of the "pulses" within that time period. In reality, it's a lot more complicated than that, but you should get the idea.

    It's that time period which I suspect is the cause the interference, and it's a design descision made by Sony. ie The only way you can "fix" this is by trying a different design - operating a different frequency.

    Having said that, the power brick is not the only part of this setup that uses switch-mode power supplies. Inside your laptop, there will be separate ones for each of the 12, 5 and 3.3 Volt rails, and one for the CPU core voltage. In addition to these, there will be one or more directly related to the charging of the Batteries, which might be the source of your problem, too. Then there's the switch-mode power supplies within the Monitor, etc.

    In other words, if it's an interference problem, there are so many possible sources - it's not going to be a simple fix. So if you can't fault find by reconfiguring, then you have to start replacing things.

  • User profile image
    geeky123

    Thanks for the detailed explanation Smiley

    I have been thinking of least expensive possible ways to solve this.

    How about connecting my laptop to a docking station and then connecting the vga output to the docking station. Can it possibly have any effect?


    Having said that, the power brick is not the only part of this setup that uses switch-mode power supplies. Inside your laptop, there will be separate ones for each of the 12, 5 and 3.3 Volt rails, and one for the CPU core voltage. In addition to these, there will be one or more directly related to the charging of the Batteries, which might be the source of your problem, too. Then there's the switch-mode power supplies within the Monitor, etc.



    Hmmm... but if it was any of the other components inside the laptop, then disconnecting the power brick should not have had any effect on the display, while currently as i have previously said, disconnecting the laptop from the power supply makes the display run fine.

  • User profile image
    RichardRudek

    geeky123 wrote:
    Thanks for the detailed explanation

    I have been thinking of least expensive possible ways to solve this.

    How about connecting my laptop to a docking station and then connecting the vga output to the docking station. Can it possibly have any effect?


    So your saying that none of the stuff is covered by warranty, and you don't have any other monitors which you can use to test on your laptop ?

    One thing you could try is to power off (not suspend) your laptop, remove the battery, and see if it will run from just the power brick - some laptops won't, though.

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