Flickering Monitors?

Anonymous Coward writes "Our SB Office runs a small 2 Server network with 4 workstations in the LAN, each connected to a dedicated APC Surge protector. The building has a backup power generator thus we didn't see the need for a UPS. For some odd reason all our monitors flicker a lot. We've tried everything from changing resolutions/refresh rates/video cards/monitors and spacing the monitors farther apart from each other - all to no avail. Could this be a building power supply problem? Some have suggested there may be some magnetic interference but visually inspecting the surroundings doesn't leave us with a culprit for the cause. Could this be fixed by the simple addition of a good UPS? Any help, tip or information would be gladly appreciated. Thank you."

Comments

Looking with the right tool

[martyb]

I have developed a set of debugging techniques over the years that seems to work in most every situation. It's a matter of looking at a problem from the proper level of abstraction and using the tools I already know how to use:

How do you find a needle in a haystack?

1. Look for a very long time (exhaustive search).
   
2. Improve the odds; make the haystack smaller (process of elimination)
   
3. Improve the odds; make the needle bigger (adding print statements to code)
   
4. Use a magnet! (think outside the box)
   

With all seriousness, pick up a good compass at a sporting goods store and do a survey of your office. Walk around the room and see if there are any deflections. Whether it's an electric current (which induces a magnet field) or an actual magnet in near proximity to the magnet,
a good compass should point you in the right direction (pun intended!)

Things I have experienced in the past which affected my monitors, in no particular order:

• Cheap speakers placed near monitor (speakers have magnets). Ditto for headphones!!
  
• Small desk fan, even though 3 FEET away, had such a dirty magnetic field that it interfered with my monitor!
  
• Power cable from the PC and/or monitor running alongside the video cable induced flicker (60 Hz) into the video signal; when I separated the power cables from the video cables, the problem diminished greatly.
  
• Electrical cables (wires) IN THE WALL! It makes sense to set up the computer and monitor near an electrical outlet. One time, the electrical outlet into which my monitor was plugged was located directly below the back of my monitor. The power cable feeding that monitor was fed across a suspended ceiling and dropped down the wall to the outlet... immediately behind the yoke of my monitor! I moved the monitor 12 inches to the side and the problem disappeared.
  
• If the monitor's video cable is replacable, try using a video cable with a choke coil on it.
  
• Florescent lights' refresh rate (60 Hz) beating with the refresh rate of my monitor. I unscrewed the bulbs in the overhead florescent light fixtures and saw the problem go away.
  

One other thing to try is to bring the PC, monitor, and all peripherals home and see if the problem exists there, too. If so, then it's likely there's something flakey about your equipment. If they are okay, then it would indicate there's some environmental factors at your office.

Good luck! And please fill us in on what you find!