NotTaR of Television Sets : Television receiver fundamentals        
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Television receiver fundamentals

The basic color television receiver must perform the same functions today as 40 years ago. (Since B/W is a subset of the color standard, most references in this document will be for color except as noted). A studio video monitor includes all of the functions of a television receiver except the tuner and IF (which rarely fail except for bad connections or perhaps lightning strikes to the antenna or cable connection). Therefore most of the repair information in this document is applicable to both TVs and studio monitors. Modern computer monitors share many similarities with TVs but the multisync and high scan rate deflection circuitry and more sophisticated power supplies complicates their servicing.

As of this writing, the majority of TVs are still based on the Cathode Ray Tube (CRT) as the display device. Tiny pocket sets, camcorder viewfinders, and the like have started using LCD (Liquid Crystal Display) panels but these are still inferior to the CRT for real time video. There has always been talk of 'the picture on the wall' display and these are now appearing as large screen plasma panel displys but their cost is still high compared to even projection TVs using CRTs. The reason is simple economics - it is really hard to beat the simplicity of the shadow mask CRT. Of course, prices will drop as the technology matures.

Projection - large screen - TVs, on the other hand, are able to take advantage of a novel development in integrated micromachining - the Texas Instruments Inc. Digital Micromirror Device (DMD), now called DLP for "Digital Light Processing". This is basically an integrated circuit with a tiltable micromirror for each pixel fabricated on top of a static memory - RAM - cell. This technology would permit nearly any size projection display to be produced and would therefore be applicable to HDTV. Since it is a reflective device, the light source can be as bright as needed. This technology is already appearing in commercial high performance projectors and is competing for use in totally digital movie theaters to replace the film projector and has begun appearing in high-end consumer projection TV sets - yet.

(From: Kurk MacKay (kurk_mackay@telus.net).)

"DMD TVs have been on the marketplace for about a year now. The DMD is more commonly referred to as DLP (Digital Light Processing) in the marketplace. From what I've heard Samsung has had a DLP TV on the consumer marketplace as of last year in the US and this year here in Canada. My boss was looking at buying one so we went around to view them. The picture quality looks to be between the LCD projection and Plasma. I believe the current Samsung uses a color wheel but they are working on a three color independent system.

For more info or if you want to buy one, see DLP TV Showcase."

As noted, the plasma panel flat screen display has been around for several years in high-end TVs, typically in the 42 inch diagonal range. However, they are very expensive ($5,000 to $15,000 as of Winter, 2003), and their life expectancy may be limited due to the gradual degradation of the active pixel cells - which occurs faster than for a CRT. The physical resolution is also still low enough that visible discrete pixels may be objectionable to some viewers. However, there is little doubt that this or a similar technology will eventually replace the direct view CRT and 3-tube projection TVs in the mid to large screen sizes in the not too distant future.

The remainder of this document concentrates on CRT based analog TVs since these still dominate the market and realistically, these are the only type where there is a good chance of repair without access to specialized test equipment and parts. I wouldn't recommend any sort of attempt at repair of flat screen TVs or monitors - no matter what the size - beyond checking for bad connections, dead power supplies, or other obvious problems. The chance of success is vanishingly small and it's very likely that even with great care, damage could occur to the panels or circuitry.

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