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shaky screen image

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shaky screen image

Postby miccha81 on Sun Apr 27, 2003 9:34 pm

The image on my monitor constantly shakes. I'm thinking its because of noisy and really old electrical wiring in my house. What could I do to fix this besides getting new wiring?

Thanks
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Postby Inertia on Sun Apr 27, 2003 10:03 pm

Make sure that the refresh rate of the monitor is set higher than 60 Hz. At 60 Hz there will be a noticeable flicker as our eyes are sensitive to this frequency (particularly peripheral vision).

Use the settings for the video card to make sure that the video frequency is 75-85 Hz. Not all moniitors support the same frequencies, so make sure that you set it to a frequency that your monitor supports.
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Postby cfitz on Sun Apr 27, 2003 10:37 pm

Also try to reroute any electrical cords that may pass near your monitor or the cables that connect to it. The electro-magnetic interference from cords carrying higher currents can interfere with the electron gun in the monitor. You might even have electrical wiring running through the wall behind your monitor that causes intereference, so it might help to try repositioning your monitor as well. None of these are guaranteed solutions, buy they are cheap and easy to try.

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Postby Inertia on Sun Apr 27, 2003 11:00 pm

More good advice from cfitz. :)

Along these lines (no pun intended), see the troubleshooting ideas at Monitor Interference and Possible Causes.
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Postby Turkeyscore.com on Sun Apr 27, 2003 11:05 pm

How old is the monitor? Do you have dual monitors or your monitor near a tv? I tried a monitor that was given to me for dual monitors but the image was shaky on the free one and it also made my original shaky.
I donated the free one to my friend.... :P
zzzt *pop*
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Postby miccha81 on Mon Apr 28, 2003 8:25 am

The refresh rate and the monitor itself are fine, as the image is fine when i had my computer in my apt. Moving it elsewhere doesn't seem to do much. Maybe I'll try one of those line conditioner/noise blocker things..

Thanks for the ideas
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Postby cfitz on Mon Apr 28, 2003 9:54 am

You're welcome.

If moving your monitor around and reconfiguring the cables and such doesn't help in your current abode, but your monitor was fine in your old apartement, you might want to try hauling it to a friends place to see if it is still okay or if something has gone wrong with it since you moved. There is no sense in spending money on power conditioners if the monitor itself truly has gone bad. It would also be interesting to borrow a friend's known-good monitor and see if it suffers the same problems at your place.

Any chance you are now living near something like high voltage power lines outside your place that might be causing the problems?

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Postby CDRecorder on Mon Apr 28, 2003 10:32 am

I have two monitors next to each other. When they are both on, both of their images look shaky, but when one (either one) is on, the image is perfect.
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Postby cfitz on Mon Apr 28, 2003 10:41 am

That is because they are each interfering with each other. All CRT monitors use fairly powerful electromagnets to scan the electron beam across the screen (and thus light up the phosphor and create the image). Some monitors are better shielded than others and thus are more or less susceptible to interference and at the same time create more or less interference in other devices.

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Postby CDRecorder on Mon Apr 28, 2003 10:46 am

You're right. I have noticed that if I put the thick metal side door of one of my computers between the monitors, they don't do this.
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Postby cfitz on Mon Apr 28, 2003 11:19 am

A little bit of mild steel does wonders for soaking up magnetic flux. Is your case steel or aluminum? I would bet steel, based on what you have described.

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Postby CDRecorder on Mon Apr 28, 2003 11:29 am

You are right; it is steel! :D
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Postby Inertia on Mon Apr 28, 2003 6:47 pm

LiteOnGuy,

Another trick that helps is to make sure that the two side by side monitors are using different refresh rates.

If the monitors use the same refresh rate, the unshielded electromagnetic impulses can set up an interference which is analogous to an audio beat (difference) frequency. That is, although the refresh rates are nominally the same, they will differ slightly in frequency or phase which results in an interference pattern in an adjacent monitor. Like a musical or audio beat frequency, this "new" frequency is equal to the difference between the frequencies of the adjacent monitors. Since the frequencies are almost the same, the difference can be manifested by a slowly moving line repeating over and over across the screen. Very distracting to say the least.
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Postby CDRecorder on Mon Apr 28, 2003 11:44 pm

Thanks, Inertia! You're right; I notice the problem less when one is 75Hz and the other is 60Hz (I have to use low refresh rates because my video cards and one of the monitors can't go higher than that). There are some combinations which do cause the slowly moving line, which is indeed distracting.
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