I can tell you a few things, but this is not exhaustive.
The main difference is the horizontal frequency. It's now about
31.5Khz for the 480p mode and about 33.6Khz for the 1080i mode.
What we're working on now mostly has a scan converter, or a line doubler. Usually this works on the full frame, not just on two or three lines. I have had troubles in these subsystems but that will become a thing of the past in about a year. Well maybe not.
What they did was to sell a whole bunch of HDTVs without the ATSC tuner. They have component inputs, but would need an HD cable box or component tuner to recieve the HD signal. Now we have the situation on our hands that if the cable companies continue to charge extra for HD after February of next year, some people are going to watch a signal that has been down convereted and then up converted.
Anyway, the technology hasn't changed all that much for CRT based sets. If you have worked on computer monitors you are familiar with switching scan modes. However the rest of it is a nightmare. Plasmas, LCDs and DLPs are rarely repairable due to the lack of availability of, and high cost of replacement parts. In a plasma there are so many power supplies it is ridiculous. An LCD direct view is likely to get a power supply problem. In an LCD projection sometimes the heat destroys the light engine after a time. In a DLP (all DLPs are projection) the color wheel gets bent out of shape due to heat.
All of the latter are in additon to the usual changing of the lamp and possibly ballast, which is basically a power supply. Most of these power supplies are deemed a replacable unit by the manufacturer, and individual component parts are largely unavailable, unless you source them yourself.
So a shop that is not an ASC has to operate pretty much like a boneyard, scrapping a large percentage of the units for parts.
As for theory of operation, these LCD projectors almost always use three panels, one for each color. A DLP has an extremely fast refresh rate, which allows them to use only one element, or panel. They run at at least three times the frame rate and display the colors sequentially. And for some of them there are more than three colors. The refresh rate must be commensurately stepped up.
In any projection unit, the bulb not only has to have the right color temperature, it also needs a specific spectral output characteristic. For some reason they just can't use the old movie projector lamps. I believe it is because the US and other TV systems require the exact shades of red, green and blue to provide accurate color rendition. If you do not use those exact colors you must rematrix the signals to the red, green and blue channels.
I believe that within five years CRT technology will be phased out. At one time we thought that would be great, no more deflection, flybacks, complex geometry circuits, all the horseshit that came in with the flatter, squarer CRTs and RPTVs. But when you actually go to service a non CRT based set, you find out different in a hurry. And that is even if you know the theory of operation and have a print !
Even CRT based RPTVs have become unbelievably complex. Entire directories of DWG or PDF files. But even on a paer print it can take some considerable time to get to the section you need. But even with this advantage, manufdacturers have a supposedly valid reason to get out of CRTs.
I doubt a CRT based set will ever be built that can do 1080p. The horizontal scan rate would have to be 67.2Khz. That is fast even for a computer monitor. When you have even a 27" flat widescreen TV the transistors that can push it might not even yet exist, at least in the general market. And RPTVs need alot of deflection current. Many of them are still 70 degree deflection, they just can't make the CRTs much longer. (lengthwise)
Understand this, in magnetic, reactive scanning, the horizontal windings of the yoke being a constant impedance, you must double the pulse voltage to achieve the same deflection angle. They already feed it with around a 1,000 volt pulse. Generate double that. At those ridiculous frequencies to boot ! There is a limit to just how low yoke impedance can go. So then you have to step it up with a transformer, and stepup transformers are avoided like the plague. The flyback is the main exception.
Hope you found this informative.
JURB