Electro Interference

[eschroeter]

I have a monitor on my office desk that has tremendous intermittent interference (all icons turn wavy) from the surrounding electromagnetic interference. My best guess is that the electrical circuits in the walls and the overhead fluorescent lights are not properly shielded (it is an old building). Does anyone know of anything I can put around my monitor to protect it? Mind you, if it costs too much, I might as well try to trade up to an LCD monitor (is an LCD monitor also susceptible to this kind of interference?).

 

[Teq]

Unless you work in an electric generating plant with a radio transmitter on it's roof, it is far more likely that you have a problem either with your monitor or video card. It is extremely unlikely that overhead lighting or wall circuitry is going to cause any noticeable EM interference with your monitor.

First thing...

1) Is the power cord plugged in tightly at both ends?

2) Is the data cord connected snugly to the computer?

3) Are the connections on the data cord clean?
To clean a connector you need nothing more than a bit of alcohol and a soft toothbrush... dip the brush in alcohol and sweep it back and forth across the pins...

4) Are the case top and case bottom cooling vents blocked?
Most monitors need 8 to 10 inches of overhead clearance to allow proper air circulation. You wouldn't be the first person to fry a monitor by jamming it into too small a space or using the top of it as an "inbox".


If it isn't connections or airflow, the easiest way to further diagnose this is to take the monitor to another location and see if the problem moves with the monitor or not.

If it does, you know it's the monitor not the location.

If it doesn't... then you should try trading video cards with another machine and see what happens.

If the problem moves, you've found your culprit.


If you've eliminated all the extrinsic causes...you may have either a bad connection or a failing part in the horizontal deflection part of your monitor. The good news is that most techs could fix a problem like this very inexpensively... even better, if it's under warranty you can get it fixed for free.

While CRT monitors are succeptable to magnetic interference and ALL electronic circuits are vulnerable to radio frequency interference (like from nearby transmitters), these days all but the very cheapest equipment is well enough shielded. With most monitors, to get the effect you describe as a result of EM interference, you would need an enormous field, one that would probably move stuff around on your desk. Even one of those massive ceramic magnets used in stereo speakers has almost no influence unless you get it within a few inches of the monitor...



--->It ain't better if it don't work<---

 

[eschroeter]

Just a quick update. I put another monitor in the near vicinity (which works fine otherwise). It, too, starts to act wavy exactly when the first monitor does. It is like something turning on and off which causes the distortion. It is definately the location.

 

[Teq]

Was it on the same video card?



--->It ain't better if it don't work<---

 

[eschroeter]

Yes, I brought over another computer (the exact same computer) with the same monitor. They sit about 6 feet apart, but both monitors are subject to the waviness at exactly the same times.

 

[Teq]

Move your desk.



--->It ain't better if it don't work<---

 

[GoSharks]

Magnetic interference is the likely cause and you don need a power generator or a transmitter on the roof. Fluorescent lighting and poor electrical wiring are highly suspect.

Anything that creates a magnetic field may influence your monitor. Fans, motors, large speakers, elevators etc. We had a similar problem when we moved into our offices a couple of years ago. What we found was that an unbalanced AC current created the magnetic the fields. Current normally flows along the live and neutral wires, which are close together in the cable and so their magnetic field cancels out. A neutral/earth short can cause current to go in a large loop rather than heading back the intended way creating a magnetic field.

For your problem, there must be significant current flowing past your monitor, and not coming back on an adjacent wire. A neutral/earth short can easily go unnoticed, You might even have a load somewhere erroneously connected between live and earth instead of live and neutral (dangerous!) I think you ought to get the wiring properly checked as soon as possible.


Old Florescent lamps used iron ballast’s these are basically large transformers that create a significant alternating magnetic field.


There simply is no economical way to shield a monitor from magnetic interference, even the magnetic interference from another monitor. The only way to shield magnetic fields is using an alloy called Mumetal. Monitor manufacturers use Mumetal around the yoke to shield as much as possible. The problem is there is no way to keep the fields from coming in the front of the unit.

For more information on Mumetal
http://www.mushield.com/material_specs.html

Jim Witkowski
Chief Hardware Engineer
MonitorsDirect.com


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