Announcement

Collapse
No announcement yet.

Shaking image on monitor...

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Shaking image on monitor...

    I'm stumped on this one.

    My customer has three Dell Dimension desktops with integrated video. Two of the units are two years sold, one of the units is 6 months old. Two of the computers have 17" Dell CRTs and the other has a legacy 19" CRT. The images on the displays have started shaking and jiggling on all three computers.

    If I change the refresh on the monitors to 60Hz, the shaking stops. Anything over 60Hz like 72Hz, 75Hz or 85Hz and the image shakes. If I put an LCD monitor on, there is no shaking because the refesh is 60Hz.

    It makes no difference what resolution I set. Most run 1280x768 but I laso tried 800x600 and 1024x768.

    Degausing the monitors made no difference. Booting into safe mode (no drivers loaded) also made no difference. This would be standard VGA mode 640x480 so that rules out an issue with drivers.

    There is a Dell computer in the office with a 17" legacy CRT that does not shake - it is solid as a rock. If I plug that monitor into one of the questionable compuers, the shaking starts.

    Dell replaced the system board on one of the 2 year old computers and also the 6 month old computer, the shaking did not stop.

    The server is plugged into an APC SmartUPS 1000 and does not shake. The UPS conditions the a/c line. I plugged an extension cord into the back of the UPS and tried powering two of the questionable computers this way - the shaking continued so this ruled out bad a/c in the bulding or on this branch of wiring.

    I tried unplugging the office refrigerator, the two large printer copiers, and the a/c adaptors that run some halogeon desk lamps. I made sure no fans or other questionable a/c devices were plugged in.

    I though maybe the PSU was failing and not filtering the DC properly so I tried a brand new Enermax 500 PSU on two of te computers and this had no effect on the shaking.

    I ran the bootable Dell diagnostics CD (video subsystem only) on two of the computers and all tests passed, however the screen image shook for every task in every video mode.

    I can't think of anything else before calling Dell again. If I push the refresh up to 100Hz the shaking image is barely noticeable and acceptable in my opinion. I don't know if that will ruin the monitors or not - cheap as they are.

    I am open to any suggestions. Thanks.
    Network Engineers do IT under the desk

  • #2
    Re: Shaking image on monitor...

    definitely sounds like magnetic interference (which you knew), try moving the whole machine to another location maybe. There may be some large motor somewhere in the building (upstairs/downstairs) that is throwing energy in that direction.
    "...if I turn out to be particularly clear, you've probably misunderstood what I've said” - Alan Greenspan

    Comment


    • #3
      Re: Shaking image on monitor...

      Are these monitors close together? I recently had a similar problem.

      I moved the rear of the CRT's a metre apart and they are now OK.

      Comment


      • #4
        Re: Shaking image on monitor...

        I went back to the customer's site this afternoon for a 3rd round. I moved one computer and monitor to the back of the building and sure enough, it was as solid as a rock. I conclude there is some type of ambient electromagnet interference and it is not coming from the a/c branch wiring or the workstation so it must be extraneous.

        I turned off the florescent lights in the one office. This office and the other office with the bad computer face the front street. Although the customer has a florescent sign, it was not illuminated. Also on the street are sodium vapor lamps which were on, but these are not on during the day when the problem is also evident.

        Now I am asking myself where my responsibilities end as a network support person. If we are into EMI, should I be referring them to an electrician?
        Last edited by RobW; 26th November 2006, 22:24.
        Network Engineers do IT under the desk

        Comment


        • #5
          Re: Shaking image on monitor...

          Had a similar problem when I had a Monitor with a speaker base and it had an external power supply. The external power supply turned out to be the cause of the interference.
          1 1 was a racehorse.
          2 2 was 1 2.
          1 1 1 1 race 1 day,
          2 2 1 1 2

          Comment


          • #6
            Re: Shaking image on monitor...

            If we are into EMI, should I be referring them to an electrician?
            Absolutely. Get this one off your desk ASAP. The only time I ever saw this problem was through EMI; one time it was the guy's clock radio which he put on top of his monitor. One day he got fed up replacing batteries all the time and bought a mains lead... wibble wobble....

            By the way - if the monitor will display at 100Hz, it's fine. It will only damage the monitor if it won't display the picture and doesn't have an error handling circuit.


            Tom
            For my own and your protection, I do not provide support by private message under any circumstances. All such messages will be deleted and ignored.

            Anything you say will be misquoted and used against you

            Comment


            • #7
              Re: Shaking image on monitor...

              Originally posted by Stonelaughter View Post
              Absolutely. Get this one off your desk ASAP.
              Whoa. Passing the buck are we?
              "...if I turn out to be particularly clear, you've probably misunderstood what I've said” - Alan Greenspan

              Comment


              • #8
                Re: Shaking image on monitor...

                Do you have any power sources near the monitor? What about florescent lights? Both will cause your monitor to have the shakes especially if they are near the gun (in the back of the monitor).

                Have you tried lowering the refresh rate?

                Maybe the monitors are too close together.. Though I doubt it unless its a very small room since you said they are in the corners.
                I've had 4 monitors on a table once all on for a LAN thing and they all had lines moving down them (apart from mine for some reason) and if one degaussed then they would all flicker.

                --Kris--

                Comment


                • #9
                  Re: Shaking image on monitor...

                  Originally posted by Eternity View Post
                  Do you have any power sources near the monitor? What about florescent lights? Both will cause your monitor to have the shakes especially if they are near the gun (in the back of the monitor).

                  Have you tried lowering the refresh rate?

                  Maybe the monitors are too close together.. Though I doubt it unless its a very small room since you said they are in the corners.
                  I've had 4 monitors on a table once all on for a LAN thing and they all had lines moving down them (apart from mine for some reason) and if one degaussed then they would all flicker.

                  --Kris--
                  You must have *really* skimmed over this post without gathering all the facts first

                  I believe in my first post I describe in detail my results with changing the refresh rates and I even elaborated on the a/c power sources plugged into the same power bar that run a desktop halogen light.

                  In my second post I gave you the results eliminating the florescent lights in one office and the outside sign.

                  I'm only speaking for myself, but thoroughness is a characteristic that separates the good from the best
                  Network Engineers do IT under the desk

                  Comment


                  • #10
                    Re: Shaking image on monitor...

                    Sorry!! Your right I did, was eating my lunch at the same time

                    Ill try and think of some other possible causes. In work here, and nothing to do so i Have plently of time.

                    --Kris--

                    Comment

                    Working...
                    X