strange color on monitor

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titus12

On my nephew's computer (CRT) monitor, there is a purple color spot in the
upper left corner. Is the monitor or the video card is going bad? He has
his X-Box connected to the computer.

Thank you,
David
 
titus12 said:
On my nephew's computer (CRT) monitor, there is a purple color spot in the
upper left corner. Is the monitor or the video card is going bad? He has
his X-Box connected to the computer.

Thank you,
David
Click to expand...

CRTs are sensitive to magnetic fields.

When I first got my Sony monitor many years ago, the color
purity (splotching) was terrible. I ended up taking it to a TV/stereo
store, where they had a degaussing coil. The operator switches on the coil,
walks towards the screen of the TV set, and waves the degaussing
coil around the screen. The AC magnetic field from the coil,
helps to degauss any materials that are capable of being
magnetized. The operator walks backwards and away from the set, to
a distance of about ten feet away, turns the coil 90 degrees (so the
center of the donut no longer points at the TV screen), and switches
off power to the coil.

When I had that done, that cured my color purity problems. The
monitor remained fine after that. It appears the monitors were
stored in a location, where they were exposed to a strong magnet.

The CRT also includes a degaussing coil built into the frame
of the monitor. When the CRT powers up, you hear a "hum" for the
first 20 seconds or so. The hum gradually reduces in intensity
(as a thermistor in circuit, heats up). The degauss cycle completes,
when you hear the click of a relay, and that removes power from the
degauss coil.

The degauss built into the monitor, is capable of removing
small magnetization problems. But cannot handle purposeful damage,
such as slapping fridge magnets on the screen or on the side of the
monitor casing.

For more examples of potential problems, there are FAQs around
on adjusting CRTs. As CRT technology has progressed, at least
some of the adjustments are in the OSD. (I can remember some
display devices, that had a large number of pots you could adjust.)
But a certain number of physical phenomena will still be tied
to the tube neck and surrounding structure (coils and magnets
of various descriptions).

http://www.buchanan1.net/purple_spot.shtml
http://an.hitchcock.org/repairfaq/REPAIR/F_tvfaq3.html

(The two types of CRT tubes, used in monitors)

http://en.wikipedia.org/wiki/Shadow_mask
http://en.wikipedia.org/wiki/Aperture_grille

Paul
 
I used to repair TV's and this was a fairly common problem.
It may have become magnetised by a speaker or similar close to the screen.
We used a degaussing wand in the workshop but thats's not practical at home
unless in the unlikely event you have one lying around or know someone who
has .
On TV's there is an automatic degaussing circuit which kicks in every time
it's switched on.
On monitors it's very often done manually by a button on the front of the
monitor. Find it and use it a few times.
An old trick with TV's was to pick it up and turn in circles on the spot to
degauss the screen. If doing this watch you don't get dizzy and drop it.
 
Paul said:
CRTs are sensitive to magnetic fields.

When I first got my Sony monitor many years ago, the color
purity (splotching) was terrible. I ended up taking it to a TV/stereo
store, where they had a degaussing coil. The operator switches on the coil,
walks towards the screen of the TV set, and waves the degaussing
coil around the screen. The AC magnetic field from the coil,
helps to degauss any materials that are capable of being
magnetized. The operator walks backwards and away from the set, to
a distance of about ten feet away, turns the coil 90 degrees (so the
center of the donut no longer points at the TV screen), and switches
off power to the coil.

When I had that done, that cured my color purity problems. The
monitor remained fine after that. It appears the monitors were
stored in a location, where they were exposed to a strong magnet.

The CRT also includes a degaussing coil built into the frame
of the monitor. When the CRT powers up, you hear a "hum" for the
first 20 seconds or so. The hum gradually reduces in intensity
(as a thermistor in circuit, heats up). The degauss cycle completes,
when you hear the click of a relay, and that removes power from the
degauss coil.

The degauss built into the monitor, is capable of removing
small magnetization problems. But cannot handle purposeful damage,
such as slapping fridge magnets on the screen or on the side of the
monitor casing.

For more examples of potential problems, there are FAQs around
on adjusting CRTs. As CRT technology has progressed, at least
some of the adjustments are in the OSD. (I can remember some
display devices, that had a large number of pots you could adjust.)
But a certain number of physical phenomena will still be tied
to the tube neck and surrounding structure (coils and magnets
of various descriptions).

http://www.buchanan1.net/purple_spot.shtml
http://an.hitchcock.org/repairfaq/REPAIR/F_tvfaq3.html

(The two types of CRT tubes, used in monitors)

http://en.wikipedia.org/wiki/Shadow_mask
http://en.wikipedia.org/wiki/Aperture_grille

Paul
Click to expand...

If Paul's suggestion does not work, and you've recently moved things
around, you could have some magnetic item close to that corner too.
Again, something that destroys the normal magnetism of the TV. Like a
clock or speaker, something.
 
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