Maybe, but I can't see how. Projection CRT displays typically use three
powerful picture tubes with lenses attached to them, one for each primary color
of light (RED, GREEN, BLUE), and are converged mechanically to form the color
image on the projection screen. Purity problems due to stray magnetic fields
may not be an issue in this case.
It's an issue for a regular tube TVs, though, because you have three beams
inside one tube that are converged electromagnetically by the deflection yoke
to form the image on the screen. Stray fields can cause the beams to be
deflected in the wrong way, causing purity problems.
However, projection LCD displays don't need degaussing circuits. Totally
different principle which doesn't involve an electromagnetic deflection yoke.
As for plasma displays, I don't see how they will ever get off the ground
further than they are at right now. They are still prohibitively expensive and
seems to have reliability problems. Sets may not last more than two to three
years, or at least from what I've understood from a retailer that sells them
and have had customer complaints. I've seen some LCD projection displays from
Sony and Hitachi that have had superior performance to Pioneer plasma displays
for a fraction of the price. One of the things you would have to worry about,
though, is eventually replacing the projection lamp.
But, despite the advances in display technologies, I don't see picture tube
sets going away anytime soon as the technology is not only very simple with
excellent performance, but very cost-effective as well. It's a proven
technology with an understandably large following. And, you have a shadow mask
or an aperture grille. I prefer aperture grille, or more precisely, Sony
Trinitron. - Reinhart
I have an RCA XL-100 19" CRT TV which I purchased new in 1999.
Great picture on the cable system in my area. I'm staying with CRT
sets as long as they are available, for just the reason the last
poster mentioned--my set has a very good picture, rich, true-to-life
colors, in short, nearly as good as a good photograph or a picture
postcard, not to mention the reliability of the delta-gun and inline
shadow-mask CRTs, which have been around for years (inlines were
introduced some time after delta-gun tubes, of course; I think Sony's
Trinitron was the first inline tube--Sharp followed shortly thereafter
with its Linytron system).
Speaking of in-line CRTs, I wonder. Are they now the industry standard
for this venerable technology (cathode ray tubes), or are some very
inexpensive color sets (Japanese/Korean small-screen off-brands, etc.)
still using delta-gun CRTs? Just curious.
I am sold on RCA TVs, their OB tuner problems notwithstanding. (Mine
had a problem with the tuner shortly after I bought the set, but after
that was resolved [the technician completely resoldered the ground
points after completing the repair], the set has been trouble-free.
It's been over two years since the repair, and I've had no problems
whatsoever with the set since.)
However, I have done some research (mostly on manufacturers' web
sites and forums such as this one) on the LCD vs. plasma issue and
have learned that plasmas have at least one very serious drawback
(image burn-in), which may also be why this type of widecreen TV isn't
too popular yet. I think the manufacturers of plasma sets should
(indeed must) address this problem, and soon. It just now occurred to
me that makers of plasma TVs do not use the same kind of raster
blanking system as has been and is being used on computer monitors
(power management). I don't think it would add that much to the cost
of the set. The blanking circuit could be arranged so that it would
trigger after a certain length of time during which a static image
(test pattern, network logo, etc.) is on the screen, but not during
normal viewing. The blanking circuit could also be set up so that, if
the set were used as a computer monitor, etc. the power-management
system would blank the screen after a period of inactivity. A button
or switch at the set and/or on the remote could be used to restore the
picture manually (or disable the PM circuit altogether) if desired.
One other problem LCD panels and plasmas have that CRT sets do not
is that there is a projection lamp behind the screen which will
eventually burn out and need replacement. Of course, the same problem
exists with CRTs, which also have filaments that eventually open. The
difference is that CRTs often go for many years before the filaments
burn out (most CRTs I've seen go bad from severely decreased cathode
emission, and this ordinarily happens long before the filaments go
bad); with projection lamps used in plasma and LCD panel systems,
however, the life expectancy of the lamps is probably much shorter
because of the brightness of the lamp. For example, I remember
reading on RCA's web site recently that the projection lamp used in
their Scenium TVs is rated for only about 15,000 hours. I would not
expect the lamps in these sets to last even that long if the set is
used many hours a day, of course. Again, CRT sets have the same
problem, if you will--the more the set is used, the weaker the
emission of the tube's three electron guns becomes.
I realize that to incorporate such systems (power management) in
already expensive (prohibitively so as it is, as has already been
mentioned) plasma TVs would make the set even more expensive (and who
needs that?). However, the foregoing are simply some thoughts I had on
the subject--my two cents' worth, if you will.
Thanks for reading.
Kind regards,
Jeff Strieble, WB8NHV (mailto:
[email protected])
Fairport, Ohio
