How do I get rid of scrolling horizontal line on my VGA monitor?


Dell Precision M6500 laptop, Vista Ultimate, NVidia Quadro FX 2800M, Plugable UGA-2K-A

1900 x 1200 laptop screen + 2 identical 1900 x 1200 external monitors

External monitor #1 on laptop’s built-in VGA port to VGA monitor port

External monitor #2 on UGA-2K-A DVI/DVI

Configuration: laptop primary, external monitor #1 extend right, external monitor #2 extend left

Problem: The VGA monitor exhibits a continuous scrolling horizontal bar, about 0.5 inch high, of slightly different shade than whatever is on the monitor (the UGA-2K-A monitor is fine). This only happens when the UGA-2K-A is functioning - unplugging the UGA-2K-A makes the problem go away. It’s not the monitor because swapping the two identical monitors back and forth makes no difference. The problem goes away when the monitor is switched from VGA to DisplayPort.

Also checked to make sure it’s not the VGA cable … also tried all options for adjusting and tuning the monitor … also called HP support for the monitor and they were no help.


Hi Steve,

That definitely sounds like electrical interference affecting the monitor attached directly to the laptop (when using VGA, being analog). It makes sense that when you switch to DisplayPort (digital) the interference goes away.

You mentioned trying a few things. If you haven’t already, could you try these:

  1. It sounds like the shielding on the VGA cable might be thin. VGA cables vary a lot in the amount of shielding they have - you mention trying something here, but any chance you could track down a thicker VGA cable and see if that helps?

  2. Can you move the 2 external monitors at least 3-4 feet apart, and report if that helps at all?

  3. If you happen to have a powered USB hub, could you connect the UGA-2K-A to that, and use that to get the USB cables, etc. away from the VGA cable?

Thanks for trying these things if possible. The hope is in eliminating the potential for interference. And as for the backup plan of using DisplayPort for the first monitor - is there something in particular that rules that out?

Thanks for letting us know how these things go, and thanks for your patience!


Looks like you nailed the problem - out of my 10 or so VGA cables I found one that was thicker, and swapping that in made the problem about 90% better … good enough for me, so I’m considering this issue solved. Thanks for the assistance.

Since you asked: Can’t use DisplayPort because the connector is too flimsy … my monitors are off my desk and my desk rolls around and goes up and down all day; it would shred the DP connection in a few days unless I could nail the cable to my computer somehow for strain relief … I’m currently looking for a thin, flimsy DP cable that would make this kludge feasible.


Hi Steve - glad that helped. Thanks for finding that thicker VGA cable!


A note about VGAs and anything based off the VESA DB-15 video connector on the PCs. The higher the frequency used in SVGA and above aren’t strictly supported. While you might get an image, you’ll suffer focus (clarity of the image) and other weird anomalies will start to show up, if they’re not upfront and center. The display drive circuit, along with the DACs for in use with SVGA at that resolution and color depth may not be stable or able to correctly drive at that resolution, let alone color depth.

If you’re computer has as DVI-D connector and your monitor also has one, get a cable for it and plug it in, it will look a lot more sharp, your problems should also go away.

Note this is what can be achieved by the DB-15 monitor connection along sans the limitation of your drive circuitry of the computer and DAC frequency:

(Video Graphics Array) VGA 640 x 480
(Super Video Graphics Array) SVGA 800 x 600
(High Definition Television 720i/p) HDTV 1280 x 720
(Extended Graphics Array) XGA 1024 x 768
(Wide Extended Graphics Array) WXGA 1366 x 768
(Super Extended Graphics Array) SXGA 1280 x 1024
(Super Extended Graphics Array+) SXGA+ 1400 x 1050
(Wide Super Extended Graphics Array) WSXGA 1600 x 1024
(Wide Super Extended Graphics Array+) WSXGA+ 1680 x 1050
(High Definition Television 1080i/p) HDTV 1920 x 1080
(Ultra Extended Graphics Array) UXGA 1600 x 1200
(Wide Ultra Extended Graphics Array) WUXGA 1920 x 1200
(Quad Extended Graphics Array) QXGA 2048 x 1536
(Quad Super Extended Graphics Array) QSXGA 2560 x 2048
(Wide Quad Super Extended Graphics Array) WQSXGA 3200 x 2048
(Quad Ultra Extended Graphics Array) QUXGA 3200 x 2400
(Wide Quad Ultra Extended Graphics Array) WQUXGA 3840 x 2400
(Hex Super Extended Graphics Array) HSXGA 5120 x 4096
(Wide Hex Super Extended Graphics Array) WHSXGA 6400 x 4096
(Hex Ultra Extended Graphics Array) HUXGA 6400 x 4800
(Wide Hex Ultra Extended Graphics Array) WHUXGA 7680 x 4800

It appears you’re attempting to use the, “(Wide Ultra Extended Graphics Array) WUXGA 1920 x 1200” standard on your monitor. What you need to do is find out what refresh rates your monitor can handle at this frequency and what refresh rates your card are compatible with. Once you know, pick the lowest one first, then step up to the next, keep going until you get the weird effects. If you get the weird effects on one, test all of them. Pick the one that was least irritating or good and go with that. The DACs aka Digital to Analog converters actually have sweet spots in operation at specific resolution and color depths. It will be different per DAC so playing around with it will help you a great deal.

It’s also a possibility that your monitor while it is advertised that it can do it, it may not do it well. Stick with digital signals if you can. You’re eyes will thank you for it later.


Oops. Grammar error!

"If you’re computer has as DVI-D connector and your monitor also has one, get a cable for it and plug it in, it will look a lot more sharp, your problems should also go away. "

Should read as:

"If your computer has as DVI-D connector and your monitor also has one, get a cable for it and plug it in, it will look a lot more sharp, your problems should also go away. "