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Problem with monitor and electromagnetic interference

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  • Graphics Cards
  • Computer
  • Monitors
  • Graphics
Last response: in Graphics & Displays
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Anonymous
a b U Graphics card
a b C Monitor
December 20, 2004 12:03:33 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

I recently got a new computer (Dell 8400) with a 256 MB nVidia GeForce 6800
video card. The monitor is the Dell M993s 19" CRT. I found that I could
not use any refresh rate above 60 Hz. If I set it higher, I had an
unacceptable amount of wobbling in the picture. After trying several things
(different monitors, different resolutions and color depths, new video card
drivers), I finally
moved the monitor, computer, mouse, keyboard, and surge protector to
another room, where everything worked perfectly. I also tried hooking the
computer up with an extension cord to the same plug we had been using before
and, again, everything worked perfectly at all refresh rates. Incidentally,
the image is much nicer at refresh rates of about 75 Hz or higher. I can
definitely tell a difference in comparison to the 60 Hz, though, honestly, I
can't distinguish much difference at >75 Hz. I really would like to be able
use at least a 75 Hz refresh rate. Any suggestions as to how to fix this
problem? I have tried removing various peripheral devices one by one, to no
avail. I also tried a ferrous choke device on the monitor cable, which
worked for a friend of mine, but it did nothing. Moving the whole setup
might solve the problem, but I really don't have another place which would
be great to place the computer. If it's related to the setup of the system
itself (peripherals and so worth), that won't help anyway. Is there any way
to shield the monitor which is inexpensive? Any other suggestions?

Thanks,
m

More about : problem monitor electromagnetic interference

Anonymous
a b U Graphics card
a b C Monitor
December 20, 2004 9:01:02 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

medgirl writes:

> Incidentally, the image is much nicer at refresh rates of about
> 75 Hz or higher.

In what way? You're configured to run non-interlaced, right?

> I can
> definitely tell a difference in comparison to the 60 Hz, though, honestly, I
> can't distinguish much difference at >75 Hz. I really would like to be able
> use at least a 75 Hz refresh rate. Any suggestions as to how to fix this
> problem?

If it definitely wobbles in certain physical locations, your only choice
is to move the monitor or find the source of the interference and
eliminate it. You could try shielding the monitor, but that could get
expensive and awkward.

Odd that it happens only at higher refresh rates; on the rare occasions
when I've seen this, it seemed to occur at any refresh rate. Maybe
someone else can explain why.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
Anonymous
a b U Graphics card
a b C Monitor
December 20, 2004 9:49:14 PM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"Mxsmanic" <mxsmanic@hotmail.com> wrote in message
news:D tmcs0h4t13c1m309pj7vbui6ahqisaacu@4ax.com...
> medgirl writes:
>
>> Incidentally, the image is much nicer at refresh rates of about
>> 75 Hz or higher.
>
> In what way? You're configured to run non-interlaced, right?

There's less glare at 75 Hz. Above that, I can't discern any difference.

>> I can
>> definitely tell a difference in comparison to the 60 Hz, though,
>> honestly, I
>> can't distinguish much difference at >75 Hz. I really would like to be
>> able
>> use at least a 75 Hz refresh rate. Any suggestions as to how to fix this
>> problem?
>
> If it definitely wobbles in certain physical locations, your only choice
> is to move the monitor or find the source of the interference and
> eliminate it. You could try shielding the monitor, but that could get
> expensive and awkward.
>
> Odd that it happens only at higher refresh rates; on the rare occasions
> when I've seen this, it seemed to occur at any refresh rate. Maybe
> someone else can explain why.

Actually I've been doing a lot of reading about this. It seems that
electrical stuff tends to run at 60 Hz and so in some way doesn't distort
the monitor when it's at the same refresh rate (though there can be
different problems at 60 Hz), but when the monitor is running at a different
setting, there is distortion.
Related resources
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 4:20:26 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

On Mon, 20 Dec 2004 18:49:14 -0500, "medgirl"
<medgirl2001@nospamhotmail.com> wrote:

>> In what way? You're configured to run non-interlaced, right?

Interlaced modes for PC monitors haven't been used in over a decade.

>There's less glare at 75 Hz. Above that, I can't discern any difference.

It looks better because there is less flicker. A refresh rate of 60 Hz
bothers most people, 75 Hz is good for some. I need a CRT at least 85
Hz or else I get headaches.

>> Odd that it happens only at higher refresh rates; on the rare occasions
>> when I've seen this, it seemed to occur at any refresh rate. Maybe
>> someone else can explain why.

>Actually I've been doing a lot of reading about this. It seems that
>electrical stuff tends to run at 60 Hz and so in some way doesn't distort
>the monitor when it's at the same refresh rate (though there can be
>different problems at 60 Hz), but when the monitor is running at a different
>setting, there is distortion.

This is usually (but not always) due to interference with the building
electrical wiring. You demonstrated that this is the case by moving
the computer to another room and eliminated the problem. Sometimes
moving the computer and/or monitor just a few inches or changing the
spatial orientation (i.e., rotating it 90 degrees) will lessen or
eliminate the problem. Shielding is usually not very effective.
Different equipment may be less susceptible, and flat panel LCD
monitors are generally immune from this type of interference.
- -
Gary L.
Reply to the newsgroup only
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 4:20:27 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"Gary L." <nospam@sbcglobal.net> wrote in message
news:urtes0d3hqq8aglbcvdcdfm4ikd5tv8ma7@4ax.com...
> On Mon, 20 Dec 2004 18:49:14 -0500, "medgirl"
> <medgirl2001@nospamhotmail.com> wrote:
>
>>> In what way? You're configured to run non-interlaced, right?
>
> Interlaced modes for PC monitors haven't been used in over a decade.

I think you're getting some quoting mixed up - I'm not the one who mentioned
interlaced modes.

> This is usually (but not always) due to interference with the building
> electrical wiring. You demonstrated that this is the case by moving
> the computer to another room and eliminated the problem. Sometimes
> moving the computer and/or monitor just a few inches or changing the
> spatial orientation (i.e., rotating it 90 degrees) will lessen or
> eliminate the problem.

Unfortunately, moving the computer or monitor slightly or to the end of the
desk, etc. has no effect. I think I'm either going to have to move it to an
entirely new spot or give in and get an LCD.

m
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 4:20:28 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

medgirl wrote:

> "Gary L." <nospam@sbcglobal.net> wrote in message
> news:urtes0d3hqq8aglbcvdcdfm4ikd5tv8ma7@4ax.com...
>> On Mon, 20 Dec 2004 18:49:14 -0500, "medgirl"
>> <medgirl2001@nospamhotmail.com> wrote:
>>
>>>> In what way? You're configured to run non-interlaced, right?
>>
>> Interlaced modes for PC monitors haven't been used in over a decade.
>
> I think you're getting some quoting mixed up - I'm not the one who
> mentioned interlaced modes.
>
>> This is usually (but not always) due to interference with the building
>> electrical wiring. You demonstrated that this is the case by moving
>> the computer to another room and eliminated the problem. Sometimes
>> moving the computer and/or monitor just a few inches or changing the
>> spatial orientation (i.e., rotating it 90 degrees) will lessen or
>> eliminate the problem.
>
> Unfortunately, moving the computer or monitor slightly or to the end of
> the
> desk, etc. has no effect. I think I'm either going to have to move it to
> an entirely new spot or give in and get an LCD.

If the problem is noise picked up by the signal cable then an LCD won't
help.

Check very carefully the routing of the monitor signal cable. Is it passing
near the base of a high-intensity lamp (the little "Tensor" lamps that were
popular a while back for example) or any kind of fluorescent lamp? How
about a wall-wart transformer? Anything else that _might_ be generating an
oscillating magnetic field? That's the most common cause of the kind of
problem you describe. Even if you're sure it's not, check--there may be
something there that you didn't notice without being primed to look for it.
>
> m

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 7:05:14 AM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

On Mon, 20 Dec 2004 21:50:04 -0500, "medgirl"
<medgirl2001@nospamhotmail.com> wrote:


>>>> In what way? You're configured to run non-interlaced, right?
>>
>> Interlaced modes for PC monitors haven't been used in over a decade.
>
>I think you're getting some quoting mixed up - I'm not the one who mentioned
>interlaced modes.

I understand that it was "Mxsmanic" that made this comment and not
you. I just wanted to eliminate this red herring.

>> This is usually (but not always) due to interference with the building
>> electrical wiring. You demonstrated that this is the case by moving
>> the computer to another room and eliminated the problem. Sometimes
>> moving the computer and/or monitor just a few inches or changing the
>> spatial orientation (i.e., rotating it 90 degrees) will lessen or
>> eliminate the problem.
>
>Unfortunately, moving the computer or monitor slightly or to the end of the
>desk, etc. has no effect. I think I'm either going to have to move it to an
>entirely new spot or give in and get an LCD.

I did have one system where a defective video card caused this
symptom, but if your system works correctly in another room then EM
interference is the likely culprit. If you do decide to go with a new
monitor, be sure you can return it on the outside chance that the
problem is something in the computer and not the monitor.
- -
Gary L.
Reply to the newsgroup only
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 12:29:11 PM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

Gary L. writes:

> Interlaced modes for PC monitors haven't been used in over a decade.

I still see people running interlaced. Usually some problem at
installation has left them with a default video setting designed to run
on anything, and often that means an interlaced video mode with low
resolution and a low refresh rate.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
Anonymous
a b U Graphics card
a b C Monitor
December 21, 2004 12:30:29 PM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

Gary L. writes:

> I understand that it was "Mxsmanic" that made this comment and not
> you. I just wanted to eliminate this red herring.

It's not a red herring; it's a real problem that I've occasionally had
to fix. A lot of people won't notice that a monitor is running
interlaced unless they are told, but they will have the subjective
impression that the image isn't as clear.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
Anonymous
a b U Graphics card
a b C Monitor
January 5, 2005 8:59:41 PM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"medgirl" <medgirl2001@nospamhotmail.com> wrote in message
news:2audnaRcmObAElrcRVn-2w@giganews.com...
> "Gary L." <nospam@sbcglobal.net> wrote in message
> news:urtes0d3hqq8aglbcvdcdfm4ikd5tv8ma7@4ax.com...
> > On Mon, 20 Dec 2004 18:49:14 -0500, "medgirl"
> > <medgirl2001@nospamhotmail.com> wrote:
> >
> >>> In what way? You're configured to run non-interlaced, right?
> >
> > Interlaced modes for PC monitors haven't been used in over a decade.
>
> I think you're getting some quoting mixed up - I'm not the one who
mentioned
> interlaced modes.
>
> > This is usually (but not always) due to interference with the building
> > electrical wiring. You demonstrated that this is the case by moving
> > the computer to another room and eliminated the problem. Sometimes
> > moving the computer and/or monitor just a few inches or changing the
> > spatial orientation (i.e., rotating it 90 degrees) will lessen or
> > eliminate the problem.
>
> Unfortunately, moving the computer or monitor slightly or to the end of
the
> desk, etc. has no effect. I think I'm either going to have to move it to
an
> entirely new spot or give in and get an LCD.
>
> m

You might try to determine the cause of the field - for example, desktop
fluorescent lamps are notorious for emitting magnetic fields, and can cause
the kind of interference you mention. Look for nearby motors as well, even
on the other side of the wall may cause issues. A nearby TV set could well
be the culprit, or even placing two PC monitors (CRT type, that is) too
close
to each other will cause interaction. Try turning various appliances off &
on to see if there is any effect, and narrow down the possible culprit.

Magnetic field radiators within a home are generally not hard to identify
and move or remove - it's highly unlikely you are seeing any effect from a
radiator beyond your area of influence.

HTH,
NGA
Anonymous
a b U Graphics card
a b C Monitor
January 5, 2005 8:59:42 PM

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

Not Gimpy Anymore wrote:

> "medgirl" <medgirl2001@nospamhotmail.com> wrote in message
> news:2audnaRcmObAElrcRVn-2w@giganews.com...
>> "Gary L." <nospam@sbcglobal.net> wrote in message
>> news:urtes0d3hqq8aglbcvdcdfm4ikd5tv8ma7@4ax.com...
>> > On Mon, 20 Dec 2004 18:49:14 -0500, "medgirl"
>> > <medgirl2001@nospamhotmail.com> wrote:
>> >
>> >>> In what way? You're configured to run non-interlaced, right?
>> >
>> > Interlaced modes for PC monitors haven't been used in over a decade.
>>
>> I think you're getting some quoting mixed up - I'm not the one who
> mentioned
>> interlaced modes.
>>
>> > This is usually (but not always) due to interference with the building
>> > electrical wiring. You demonstrated that this is the case by moving
>> > the computer to another room and eliminated the problem. Sometimes
>> > moving the computer and/or monitor just a few inches or changing the
>> > spatial orientation (i.e., rotating it 90 degrees) will lessen or
>> > eliminate the problem.
>>
>> Unfortunately, moving the computer or monitor slightly or to the end of
> the
>> desk, etc. has no effect. I think I'm either going to have to move it to
> an
>> entirely new spot or give in and get an LCD.
>>
>> m
>
> You might try to determine the cause of the field - for example,
> desktop
> fluorescent lamps are notorious for emitting magnetic fields, and can
> cause the kind of interference you mention. Look for nearby motors as
> well, even on the other side of the wall may cause issues. A nearby TV set
> could well be the culprit, or even placing two PC monitors (CRT type, that
> is) too close
> to each other will cause interaction. Try turning various appliances off &
> on to see if there is any effect, and narrow down the possible culprit.
>
> Magnetic field radiators within a home are generally not hard to
> identify
> and move or remove - it's highly unlikely you are seeing any effect from a
> radiator beyond your area of influence.

Also, look for the _cable_ to be passing close to the source of the field.
>
> HTH,
> NGA

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
!