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Why does my monitor have 1/2/3 faint horizontal lines on it?
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Your monitor likely uses a Sony Trinitron picture tube. Trinitron 1
tubes can be recognized because they are curved only in the horizontal
plane, but are flat vertically. Typically, the number of lines seen
depends on the monitor size:
< 17" 1 line
17-21" 2 lines
> 21" 3 lines
Because of the technical nature of how CRT's work, few people understand
the details of how they operate. As such, many laymen have viewed Sony's
Trinitron design as being a proprietary black box because they don't
understand Sony's technical documents. A fairly well accepted description
of the way these tubes work follows.
For a description of how a standard shadow mask CRT works, see "What is a
shadow mask?".
Sony's Trinitron design uses a variation of the shadow mask
called the aperture grill (or guard grill). Rows of very fine
metal strips run vertically down the screen, separating columns of
coloured phosphor which are arranged in alternating stripes of red,
green and blue. This configuration allows the phosphor strips to
be placed closer together than conventional dot triads, and the
fine vertical wires block less of the electron beam than traditional
shadow masks, resulting in a brighter image, and less thermal
buildup and distortion. Coupled with changes in the way that the
electron guns are arranged, this design results in a crisp, bright
image. However, the vertical strips are so fine that they can be
set into motion when contacted by the electron beam (thermal
changes) . This would result in a shimmer on the screen which would
be quite distracting. To remedy this, Sony puts horizontal
stabilizing wires across the vertical ones. This reduces shimmer,
but results in one or more fine horizontal lines being visible on
the monitor. As mentioned above, the number of lines increases with
monitor size. Usually, these lines are only visible to a discerning
viewer when looking at a bright, solid background. If you're an
experimentalist, try gently smacking the side of a Trinitron monitor,
and look to see the wires shimmer. Basically, the horizontal lines
are a minor trade-off when compared to the superior brightness
and vertical flatness of the Trinitron screen.
What follows is a statement from Sony about their aperture grille
design:
Since its introduction in 1968, Sony has produced more than 70
million CRT's. Award-winning Trinitron CRT's are used in a
multitude of applications, including high resolution displays for
the computer industry. Today, Trinitron CRT's are used by Sony and
other leading manufacturers to meet the ever increasing demands and
expectations of computer users throughout the world.
One of the unique features of the Trinitron CRT is what is
called the Aperture Grille. An Aperture Grille consists of a
series of long vertical slits fastened with strong vertical tension
to a steel supporting frame. Electron beams pass through the
Aperture Grill to illuminate phosphor on the faceplate. The
vertical tension of the Aperture Grille absorbs any thermal
expansion, thus eliminating the problem of doming or color spill
and resulting in a superior picture quality.
Since the CRT requires a vacuum to function, a damper wire
which is approximately 15 microns in diameter is strategically
placed on the Aperture Grille to reduce susceptibility to
resonance. The "line" that some customers see on the screen is not
a fault but the damper wire which has always been an integral part
of our Trinitron technology.
We hope that our customers will continue to consider the
overall attributes and excellence of the Trinitron system when
evaluating our products.
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