Although the term 'dead pixels' is commonly used to cover all types
of pixel fault, there are actually three distinct subcategories: stuck
pixels, hot pixels and dead pixels. To understand why dead pixels occur,
it helps to know how an LCD monitor works.
In order to
generate all the colours of the spectrum, each pixel is made up of three
subpixels – one each for red, green and blue light. When all three
subpixels are on, the pixel is white, and when all three are off , the
pixel is black.
If one or two of these subpixels remain on, the
pixel will appear as a solid red, green, blue, cyan, magenta or yellow
dot on the screen (depending on which subpixels aren't working). This
type of pixel fault is called a stuck pixel.
When all three
subpixels are stuck on, the pixel will appear to be permanently white.
This type of pixel is known as a hot pixel.
Dead pixels are
either whole pixels or subpixels that do not turn on. These pixels
always look black. When LCD panels first started to become popular,
stuck and dead pixels were quite common and would often appear in
clusters.
Too many faulty pixels can render a monitor worthless,
so the ISO 13406-2 standard was created to define the maximum number of
faulty pixels that are permitted for any given class of display. A
Class One panel can't have any faulty pixels, but a Class Four panel can
have up to 50 permanently white pixels.
Fixing stuck pixles
Stuck
pixels are usually caused by manufacturing defects, and they will often
stay illuminated for the life of the panel. In many cases it's possible
to fix the pixel using either software tools or manual manipulation.
The
software solution will generally flash a series of images that vary in
colour and intensity onto the screen in an effort to unstick the pixel.
Manual
manipulation involves gently pressing on the affected area with
something like a pencil eraser. Doing this compresses the layers of the
panel, forcing the oil within the panel to move.
Be careful,
though: this is by no means guaranteed to work, and it could create even
more stuck pixels or move the problem to elsewhere on the screen rather
than repairing it.
Dead pixels and hot pixels are generally the
result of faults in the circuitry of the panel. It's usually the case
here that the transistor does not switch states properly.
Dead pixels generally mean that the transistor has failed completely, and this is rarely fixable.
Hot
pixels may be due to manufacturing defects. They can often be fixed in
the same way as stuck pixels, but again, success is not guaranteed.
More help
If
you have stuck or dead pixels, we recommend that you try a software
solution and only press on the screen as a last resort, as you could end
up damaging the panel further. UDPixel is a program that tries to find and fix faulty pixels, as does JScreenFix.
If
your screen is new and seems to have an excessive number of faulty
pixels for its class, you should contact the manufacturer for a
replacement instead.
Three ways to try to fix a stuck pixel
1. The pixel method
UDPixel
will attempt to detect and fix problematic pixels for you by changing
the screen colour to highlight any problems. Once a fault has been
found, you can choose the size of the square and the flash speed to
start the fixing process.
2. The browser method
JScreenFix
runs in a browser window and requires the Java Runtime environment. Go
to the JScreenFix site, start the applet and then press [F11] to
maximise for full screen. You should leave the application to run for an
hour or so before viewing the results.
3. The last resort rubber method
In
some cases, stuck subpixels can be fixed by gently pressing on the
affected area using something that won't damage the panel, such as the
tip of a pencil eraser. You should proceed with caution, however. NOTE: this method isn't guaranteed to work, and can make things worse.
Monday, November 17, 2014
How to fix dead pixels on your LCD monitor
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