Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and information about some of the electronic, electrical and electrotechnical technology relics that the Frank Sharp Private museum has accumulated over the years .

Premise: There are lots of vintage electrical and electronic items that have not survived well or even completely disappeared and forgotten.

Or are not being collected nowadays in proportion to their significance or prevalence in their heyday, this is bad and the main part of the death land. The heavy, ugly sarcophagus; models with few endearing qualities, devices that have some over-riding disadvantage to ownership such as heavy weight,toxicity or inflated value when dismantled, tend to be under-represented by all but the most comprehensive collections and museums. They get relegated to the bottom of the wants list, derided as 'more trouble than they are worth', or just forgotten entirely. As a result, I started to notice gaps in the current representation of the history of electronic and electrical technology to the interested member of the public.


Following this idea around a bit, convinced me that a collection of the peculiar alone could not hope to survive on its own merits, but a museum that gave equal display space to the popular and the unpopular, would bring things to the attention of the average person that he has previously passed by or been shielded from. It's a matter of culture. From this, the Obsolete Technology Tellye Web Museum concept developed and all my other things too. It's an open platform for all electrical Electronic TV technology to have its few, but NOT last, moments of fame in a working, hand-on environment. We'll never own Colossus or Faraday's first transformer, but I can show things that you can't see at the Science Museum, and let you play with things that the Smithsonian can't allow people to touch, because my remit is different.

There was a society once that was the polar opposite of our disposable, junk society. A whole nation was built on the idea of placing quality before quantity in all things. The goal was not “more and newer,” but “better and higher" .This attitude was reflected not only in the manufacturing of material goods, but also in the realms of art and architecture, as well as in the social fabric of everyday life. The goal was for each new cohort of children to stand on a higher level than the preceding cohort: they were to be healthier, stronger, more intelligent, and more vibrant in every way.

The society that prioritized human, social and material quality is a Winner. Truly, it is the high point of all Western civilization. Consequently, its defeat meant the defeat of civilization itself.

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

OLD, but ORIGINAL, Well made, Funny, Not remotely controlled............. and not Made in CHINA.

How to use the site:

- If you landed here via any Search Engine, you will get what you searched for and you can search more using the search this blog feature provided by Google. You can visit more posts scrolling the left blog archive of all posts of the month/year,
or you can click on the main photo-page to start from the main page. Doing so it starts from the most recent post to the older post simple clicking on the Older Post button on the bottom of each page after reading , post after post.

You can even visit all posts, time to time, when reaching the bottom end of each page and click on the Older Post button.

- If you arrived here at the main page via bookmark you can visit all the site scrolling the left blog archive of all posts of the month/year pointing were you want , or more simple You can even visit all blog posts, from newer to older, clicking at the end of each bottom page on the Older Post button.
So you can see all the blog/site content surfing all pages in it.

- The search this blog feature provided by Google is a real search engine. If you're pointing particular things it will search IT for you; or you can place a brand name in the search query at your choice and visit all results page by page. It's useful since the content of the site is very large.

Note that if you don't find what you searched for, try it after a period of time; the site is a never ending job !

Every CRT Television saved let revive knowledge, thoughts, moments of the past life which will never return again.........

Many contemporary "televisions" (more correctly named as displays) would not have this level of staying power, many would ware out or require major services within just five years or less and of course, there is that perennial bug bear of planned obsolescence where components are deliberately designed to fail and, or manufactured with limited edition specificities..... and without considering........picture......sound........quality........

..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

Have big FUN ! !
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©2010, 2011, 2012, 2013, 2014 Frank Sharp - You do not have permission to copy photos and words from this blog, and any content may be never used it for auctions or commercial purposes, however feel free to post anything you see here with a courtesy link back, btw a link to the original post here , is mandatory.
All sets and apparates appearing here are property of
Engineer Frank Sharp. NOTHING HERE IS FOR SALE !

Monday, March 28, 2011

PANASONIC TX-25A3C YEAR 1994.




















































































The PANASONIC  TX-25A3C  is the first DIGITAL TELEVISION set From Panasonic TV models.

Until the coming of this model Panasonic was producing excellent analog technology tellyes.

With this model, Panasonic, is , like other high class fabricants, adopting the DIGIVISION ITT Digital Signal Processing Technology, using the ITT DIGIVISION DIGIT2000 Fast chipset improving furthermore picture quality and sound.
The television receiver has an alphanumeric display  which appears on the picture tube screen, to give the user data on the tuned channel number, colour settings and other operating data. The digital processor which generates the characters for display also controls the channel setting, etc., under the control of a digital remote control unit . The processor  has an associated memory circuit  for permanent tuning back up. The control of the capacitance diode tuner  is achieved by the processor  altering the dividing factor of a feedback loop to a phase/frequency comparator . The other input to the comparator is a divided frequency from a quartz oscillator.


The PANASONIC  TX-25A3C  is a DIGITAL Colour television receiver or set , are known in which the majority of signal processing that takes place therein is carried out digitally. That is, a video or television signal is received in a conventional fashion using a known analog tuning circuit and then, following the tuning operation, the received analog television signal is converted into a digital signal and digitally processed before subsequently being converted back to an analog signal for display on a colour cathode ray tube.

In a conventional television receiver, all signals are analog-processed. Analog signal processing, however, has the problems at the video stage and thereafter. These problems stem from the general drawbacks of analog signal processing with regard to time-base operation, specifically, incomplete Y/C separation (which causes cross color and dot interference), various types of problems resulting in low picture quality, and low precision of synchronization. Furthermore, from the viewpoints of cost and ease of manufacturing the analog circuit, a hybrid configuration must be employed even if the main circuit comprises an IC. In addition to these disadvantages, many adjustments must be performed.

In order to solve the above problems, it is proposed to process all signals in a digital form from the video stage to the chrominance signal demodulation stage. In such a digital television receiver, various improvements in picture quality should result due to the advantages of digital signal processing.

Therefore digital television signal processing system introduced in 1984 by the Worldwide Semiconductor Group (Freiburg, West Germany) of International Telephone and Telegraph Corporation is described in an ITT Corporation publication titled "VLSI Digital TV System--DIGIT 2000." In that system color video signals, after being processed in digital (binary) form, are converted to analog form by means of digital-to-analog converters before being coupled to an image displaying kinescope. The analog color video signals are coupled to the kinescope via analog buffer amplifiers and video output kinescope driver amplifiers which provide video output signals at a high level suitable for driving intensity control electrodes of the kinescope.


The PANASONIC  TX-25A3C   Is a multistandard set and relates to a digital multistandard decoder for video signals and to a method for decoding video signals.
Colour video signals, so-called composite video, blanking and sync signals (CVBS) are essentially composed of a brightness signal or luminance component (Y), two colour difference signals or chrominance components (U, V or I, Q), vertical and horizontal sync signals (VS, HS) and a blanking signal (BL).

The different coding processes, e.g. NTSC, PAL and SECAM, introduced into the known colour television standards, differ in the nature of the chrominance transmission and in particular the different systems make use of different colour subcarrier frequencies and different line frequencies.
The following explanations relate to the PAL and NTSC systems, but correspondingly apply to video signals of other standards and non-standardized signals.
The colour subcarrier frequency (fsc) of a PAL system and a NTSC system is fsc(NTSC) = 3.58 MHz or fsc(PAL) = 4.43 MHz.
In addition, in PAL and NTSC systems the relationships of the colour subcarrier frequency (fsc) to the line frequency (fh) are given by fsc(NTSC) = 227.50 * fh or 4•fsc(NTSC) = 910 • fh fsc(PAL) = 283.75 * fh or 4•fsc(PAL) = 1135 • fh so that the phase of the colour subcarrier in the case of NTSC is changed by 180°/line and in PAL by 270°/line.

In the case of digital video signal processing and decoding the prior art fundamentally distinguishes between two system architectures. These are the burst-locked architecture and the line-locked architecture, i.e. systems which operate with sampling frequencies for the video signal, which are produced in phase-locked manner to the colour subcarrier frequency transmitted with the burst pulse or in phase-locked manner with the line frequency, respectively.

The principal advantage of the present invention is a color television receiver is provided having a fully digital color demodulator wherein the luminance signal and the chrominance signals are separated and digitally processed prior to being converted to analog signals in that the all-digital signal processing largely eliminates the need for nonintegratable circuit elements, i.e., particularly coils and capacitors, and that the subcircuits can be preferably implemented using integrated insulated-gate field-effect transistor circuits, i.e., so-called MOS technology. This technology is better suited for implementing digital circuits than the so-called bipolar technology.

 The PANASONIC  TX-25A3C    is a multisound tv digital sound processing.

It has a DTI.(dti digital transient improvement pertains to a circuit for steepening color-signal transitions in color television receivers or the like particularly in DIGIVISION DIGIT2000 . ) circuit arrangement designed for use in digital color-television receivers or the like and contains for each of the two digital color-difference signals a slope detector to which both a digital signal defining an amplitude threshold value and a digital signal defining a time threshold value are applied. At least one intermediate value occurring during an edge to be steepened is stored, and at the same time value of the steepened edge, it is "inserted" into the latter.

The bandwidth of the color-difference channel is very small compared with the bandwidth of the luminance channel, namely only about 1/5 that of the luminance channel in the television standards now in use. This narrow bandwidth leads to blurred color transitions ("color edging") in case of sudden color-signal changes, e.g., at the edges of the usual color-bar test signal, because, compared with the associated luminance-signal transition, an approximately fivefold duration of the color-signal transition results from the narrow transmission bandwidth.

In the prior circuit arrangement, the relatively slowly rising color-signal edges are steepened by suitably delaying the color-difference signals and the luminance signal and steepening the edges of the color-difference signals at the end of the delay by suitable analog circuits. The color-difference signals and the luminance signal are present and processed in analog form as usual. This circuit arrangement is designed for use in digital color-television receivers or the like and contains for each of the two digital color-difference signals a slope detector to which both a digital signal defining an amplitude threshold value and a digital signal defining a time threshold value are applied. At least one intermediate value occurring during an edge to be steepened is stored, and at the same time value of the steepened edge, it is "inserted" into the latter. This is done by means of memories, switches, output registers, and a sequence controller.

Digital Signal Processing DIGVISION ITT in Brief:
 FOR several years now the use of digital techniques in television has been growing. A considerable impetus came initially from the need for high -quality Tv standards conversion. The IBA's DICE (Digital Intercontinental Conversion Equipment) standards converter came into operational use in 1972. It's success demonstrated convincingly the advantages of processing video signals in digital form - digital signals are neither phase nor level dependent. The trend since then has been towards the all - digital studio: digital effects generators have been in use for some time, and digital telecines were announced earlier this year. An earlier example of the application of digital techniques to television was the BBC's sound-in-syncs system, in which the sound signal is converted to digital form so that it can be added to the video signal for network distribution. The sound-in-syncs system first came into use in 1969, and is was  widely employed in pay tv systems alongside with video scrambling methods in the 80's.  Digital techniques have already appeared on the domestic TV scene. The teletext signals are digital, and require digital processing. In modern remote control systems the commands from the remote control transmitter are in digital form, and require digital decoding and digital - to -analogue conversion in the receiver before the required control action can be put into effect. Allied to this, digital techniques are used for the more sophisticated channel tuning systems. The basic TV receiver itself continues to use analogue techniques however. Are we about to see major changes here? 
ITT Semiconductors in W. Germany have been working on the application of digital techniques to basic TV receiver signal processing since 1977 with the supervision of the Engineer Micic Ljubomir, and at the recent Berlin Radio Show presented a set of digital chips for processing the video, audio and deflection signals in a TV receiver. The set consists of a' couple of l.s.i. and six v.l.s.i. chips - and by very large scale integration (v.l.s.i.) we're talking about chips that contain some more 200,000 transistors. What are the advantages? 
For the setmaker, there's reduction in the component count and simpler, automated receiver alignment - alignment data is simply fed into a programmable memory in the receiver, which then adjusts itself. Subsequently, the use of feedback enables the set to maintain its performance as it ages. From the user's viewpoint, the advantages are improved performance and the fact that extra features such as picture -within -a -picture (two pictures on the screen at the same time) and still pictures become relatively simple to incorporate. The disadvantage of course is the need for a lot of extra circuitry. Since the received signals remain in analogue form, analogue -to -digital conversion is required before signal processing is undertaken. As the c.r.t. requires analogue drive signals, digital -to -analogue conversion is required prior to the RGB output stages - the situation is somewhat different in the timebase and audio departments, since the line drive is basically digital anyway and class D amplifier techniques can be used in the field and audio output stages. In between the A -D conversion and the various output stages, handling the signals in digital form calls for much more elaborate circuitry - hence those chips with 200,000 or so transistors. The extra circuitry is all incorporated within a handful of chips of course, but the big question is if and when the use of these chips will become an economic proposition, taking into account reduced receiver assembly/setting up costs, compared to the use of the present analogue technology - after all, colour receiver component counts are already very low. With the present digital technology, it's not feasible to convert the signals to digital form at i.f. So conversion takes place following video and sound demodulation. Fig. 1 shows in simple block diagram form the basic video and deflection signal processing arrangement used in the system devised by ITT Semiconductors. Before going into detail, two basic points have to be considered - the rate at which the incoming analogue signals are sampled for conversion to digital form, and the number of digits required for signal coding. Consider the example shown in Fig. 2. At both (a) and (b) the signals are sampled at times Ti, T2 etc. In (a) the signal is changing at a much faster rate than the sampling rate. So very little of the signal information would be present in the samples. In (b) the rate at which the signal is changing is much slower, and since the sampling rate is the same the samples will contain the signal information accurately. In practice, the sampling rate has to be at least twice the bandwidth of the signal being sampled. Once you've got your samples, the next question is how many digits are required for adequate resolution of the signal, i.e. how many steps are required on the vertical (signal level) scale in Fig. 2 The use of a four -digit code, i.e. 0000, 0001 etc., gives 16 possible signal levels. Doubling the number of digits to eight gives 256 signal levels and so on. ITT's experience shows that the luminance signal requires 8 bits (digits), the colour -difference signals require 6 bits, the audio signal requires 12 bits (14 for hi-fi quality) while 13 bits are required for a linear horizontal scan on a 26inch tube. These digital signals are handled as parallel data streams in the subsequent signal processing. Returning to Fig. 1, the A -D and D -A conversion required in the video channel is carried out by a single chip which ITT call the video codec (coder/decoder). A clock pulse generator i.c. is required to produce the various pulse trains necessary for the digital signal processing, and a control i.c. is used to act as a computer for the whole digital system and also to provide interfacing to enable the external controls (brightness, volume, colour etc.) to produce the desired effects. In addition, the control i.c. incorporates the digital channel selection system. The video codec i.c. uses parallel A-D/D-A conversion, i.e. a string of voltage comparators connected in parallel. This system places a high premium on the number of bits used to code the signal in digital form, so ITT have devised a technique of biasing the converter to achieve 8 -bit resolution using only 7 bits (the viewer's eye does some averaging on alternate lines, as with Simple PAL, but this time averaging luminance levels). The A -D comparators provide grey -encoded outputs, so the first stage in the video processor i.c. is a grey -to -binary transcoder. As Fig. 3 shows, the processes carried out in the video processor i.c. then follow the normal practice, though everything's done in digital form. The key to this processing is the use of digital filters. These are clocked at rates up to 18MHz, and provide delays, addition and multiplication. The glass chroma delay line required for PAL decoding in a conventional analogue decoder consists of blocks of RAM (random-access memory) occupying only three square millimeters of chip area each. As an example of the ingenuity of the ITT design, the digital delay line used for chroma signal averaging/separation in the PAL system is used in the NTSC version of the chip as a luminance/chrominance signal separating comb filter. Fig. 4 shows the basic processes carried out in the deflection processor i.c. This employs the sorts of techniques we're becoming used to in the latest generation of sync processor i.c.s. Digital video goes in, and the main outputs consist of a horizontal drive pulse plus drives to the field output and EW modulator circuits. The latter are produced by a pulse -width modulator arrangement, i.e. the sort of thing employed with class D output stages. The necessary gating and blanking pulses are also provided. A further chip provides audio signal processing. One might wonder why the relatively simple audio department calls for this sort of treatment. The W. German networks are already equipping themselves for dual -channel sound however, and the audio processor i.c. contains the circuitry required to sort out the two -carrier sound signals. These chips represent a major step in digitalizing the domestic TV receiver. It seems likely that some enterprising setmaker will in due course announce a "digital TV set". The interesting point then will be whether the chip yields, and the chip prices as production increases, will eventually make it worthwhile for all setmakers to follow this path (in 1984).



ADVANTAGE - Increased picture sharpness and highly improved signal-to-noise ratio.

The PANASONIC  TX-25A3C was featuring in this model for sirst time  an Adaptive Combifilter Video Processing:
Chrominance and luminance information can be separated by appropriately combing the composite signal spectrum. Known combing arrangements take advantage of the fact that the odd multiple relationship between chrominance signal components andhalf the line scanning frequency causes the chrominance signal components for corresponding image areas on successive lines to be 180.degree. out of phase with each other. Luminance signal components for corresponding image areas on successive linesare substantially in phase with each other.


All PANASONIC BIG sets from this to a time line of 10 12 Years are digital or even 100HZ Scan rate technology.

This set was quickly replaced with models fitting the new CHASSIS EURO-2 using the ITT DIGIT3000 chipset which you already seen here at Obsolete Tecnology Tellye Museum !

These were widely used by Panasonic until they decided in a brief time to drop all digital technology and return to analog CRT TUBE set employing the UOC 1 and the UOC 3 PHILIPS technology and then completely switch off to Flat Panels and Plasma sets.

The PANASONIC  TX-25A3C set here shown has 25 Inches FSQ screen with black matrix and 100 Programs, Teletext, HIFI Stereo sound, Many connectivity sockets, Advanced OSD and many others features.

Needless to say: Picture is superb thanks even to a selected PHILIPS 45AX IMPROVED CRT TUBE, together with sound.

(Heavy set anyway).




Panasonic Corporation ( Panasonikku Kabushiki-gaisha) (TYO: 6752, NYSE: PC), formerly known as Matsushita Electric Industrial Co., Ltd. ( Matsushita Denki Sangyō Kabushiki-gaisha), is a Japanese multinational consumer electronics corporation headquartered in Kadoma, Osaka, Japan. Its main business is in electronics manufacturing and it produces products under a variety of names including Panasonic and Technics. Since its founding in 1918, it has grown to become the largest Japanese electronics producer. In addition to electronics, Panasonic offers non-electronic products and services such as home renovation services. Panasonic was ranked the 89th-largest company in the world in 2009 by the Forbes Global 2000 and is among the Worldwide Top 20 Semiconductor Sales Leaders !

History

Panasonic was founded in 1918 by Konosuke Matsushita first selling duplex lamp sockets. In 1927, it produced a bicycle lamp, the first product it marketed under the brand name National. It operated factories in Japan and other parts of Asia through the end of World War II, producing electrical components and appliances such as light fixtures, motors, and electric irons.
After World War II, Panasonic regrouped and began to supply the post war boom in Japan with radios and appliances, as well as bicycles. Matsushita's brother-in-law, Toshio Iue founded Sanyo as a subcontractor for components after WWII. Sanyo grew to become a competitor to Panasonic.

Name

For 90 years since establishment, the name of the company was always topped with ("Matsushita"). The company's name before 1 October 2008 had been "Matsushita Electric Industrial Co., Ltd.", used since 1935.
In 1927, the company founder adopted a brand name "National" ( National) for a new lamp product, knowing "national" meant "of or relating to a people, a nation."[5] In 1955, the company labeled its export audio speakers and lamps "PanaSonic", which was the first time it used its "Panasonic" brand name.
The company began to use a brand name "Technics" in 1965.[6] The use of multiple brands lasted for some decades.[6]
In May 2003, the company put "Panasonic" as its global brand, and set its global brand slogan, "Panasonic ideas for life."[7] The company began to unify its brands to "Panasonic" and, by March 2004 replaced "National" for products and outdoor signboards, except for those in Japan[7].
On January 10, 2008, the company announced that it would change its name to "Panasonic Corporation" (effective on October 1, 2008) and phase out the brand "National" in Japan, replacing it with the global brand "Panasonic" (by March 2010). The name change was approved at a shareholders' meeting on June 26, 2008 after consultation with the Matsushita family. Panasonic owns RCTI, Global TV and MNC TV.

Electronics

In 1961, Konosuke Matsushita traveled to the United States and met with American dealers. Panasonic began producing television sets for the U.S. market under the Panasonic brand name, and expanded the use of the brand to Europe in 1979.
The company used the National trademark outside of North America during the 1950s through the 1970s. (The trademark could not be used probably due to discriminatory application of trademark laws where brands like General Motors were registrable.) It sold televisions, hi-fidelity stereo receivers, multi-band shortwave radios, and marine radio direction finders, often exported to North America under various U.S. brand names. The company also developed a line of home appliances such as rice cookers for the Japanese and Asian markets. Rapid growth resulted in the company opening manufacturing plants around the world. National/Panasonic quickly developed a reputation for well-made, reliable products.
The company debuted a hi-fidelity audio speaker in Japan in 1965 with the brand Technics. This line of high quality stereo components became worldwide favorites. The most famous product still made today is the SL-1200 record player, known for its high performance, precision, and durability. Throughout the 1970s and early 1980s, Panasonic continued to produce high-quality specialized electronics for niche markets such as shortwave radios, as well as developing a successful line of stereo receivers, CD players, and other components.
Since 2004, Toyota has used Panasonic batteries for its Toyota Prius, an environmentally friendly car made in Japan.

On January 19, 2006 Panasonic announced that, starting in February, it will stop producing analog televisions (then 30% of its total TV business) to concentrate on digital TVs.
On November 3, 2008 Panasonic and Sanyo were in talks, resulting in the eventual acquisition of Sanyo. The merger was completed in December 2009, and resulted in a mega-corporation with revenues over ¥11.2 trillion (around $110 billion). As part of what will be Japan's biggest electronics company, the Sanyo brand and most of the employees will be retained as a subsidiary.
In November 1999, the Japan Times reported that Panasonic planned to develop a "next generation first aid kit" called the Electronic Health Checker. At the time, the target market was said to be elderly people, especially those living in rural areas where medical help might not be immediately available, so it was planned that the kit would include support for telemedicine. The kits were then in the testing stage, with plans for eventual overseas distribution, to include the United States.
In recent years the company has been involved with the development of high-density optical disc standards intended to eventually replace the DVD and the SD memory card.
On July 29, 2010 Panasonic reached an agreement to acquire the remaining shares of Panasonic Electric Works and Sanyo shares for $9.4 billion.

Panasonic and Universal

Panasonic used to own Universal Studios, then known as the Music Corporation of America, since acquiring the company in 1990 but sold it to Seagram in 1995. Universal Studios is now a unit of NBC Universal.


PANASONIC TX-25A3C CHASSIS EURO-1 INTERNAL VIEW.























































































The Panasonic EURO-1 Is the first PANASONIC TV CHASSIS entirely Digital Technology.

IT Is completely based on the ITT DIGIVISION DIGIT2000 Chipset technology but furtherer improved by ITT adding more improvement functions in the original DIGIT2000.


For a complete technology reference of the Digivision ITT DIGIT2000 you can Read HERE

Indeed there are newly named IC's such as:

- VDU2146 Video Display Unit.

- DTI2223 Digital Transient Improvement

- ACVP2205 Adaptive Combifilter Video Processing

- MCU2600 Main Clock Unit

- SPU2243 Secam Processing Unit

- DPU2553 Deflection Processor Unit

- SAD2140 Signal Analog to Digital Conversion

- TPU2735 Teletext Processor Unit

- CCU3000 Computer control Unit

- MN8333 Digital feature Unit (Panasonic)

- ACP2371 Audio Control Processing




Technology overview:ACVP2205 (Adaptive Combifilter Video Processing)
In a chroma control circuit for a digital television receiver, the system clock lies in the range of four-times the chrominance-subcarrier frequency. The originally received color-burst signal is locked in frequency and phase to the system clock by means of an all-digital phase-locked loop. The phase-difference angle between the color-burst signal and the system clock appears as a sine or cosine value in the two standard color-difference signals of the chrominance demodulator during the reception of the color-burst signal. One of the standard color-difference signals, the B-Y signal, is fed through a horizontal-frequency-suppressing loop filter to a digital oscillator. The latter determines the speed of rotation of a hue adjustment angle rotating at approximately constant angular speed. The respective sine and cosine values of the hue adjustment angle are read as data values from first and second read-only memories, respectively, and are fed to the sine and cosine inputs of a hue adjuster in a calculating stage which derives the color-burst signal and the chrominance signal.The ACVP 2205 is a digital real–time signal processor for multistandard color TV sets based on the DIGIT2000
system. It handles composite video signals as well as
S–VHS signals. For PAL and NTSC a 2H adaptive
combfilter is implemented. It considerably improves the
picture quality by a sophisticated luminance and chrominance
separation. A single silicon chip contains the following
functions:
– selectable 7 or 8 bit video input
– code converter and a data demultiplexer for composite
and S–VHS input signals
– 2H adaptive combfilter for PAL and NTSC composite
video signals
– adjustable horizontal and vertical peaking filter for luminance
– selectable luminance filter for enhanced frequency response
– black–level–expander for improving the picture contrast
and the gamma correction
– contrast multiplier with limiter for the luminance signal
– adjustable chrominance filter
– all color signal processing circuits such as automatic
color control (ACC), color killer, PAL identification, decoder
with PAL compensation, hue correction
– color saturation multiplier with multiplexer for the color
difference signals
– IM bus interface for communication with the CCU 2070
or CCU 3000 Central Control Unit
– circuitry for measuring dark current (CRT spot–cutoff),
white level and photo current, and for transferring this
data to the CCU.
The ACVP 2205 is pin compatible to the PVPU 2204 . It
is designed in N–MOS technology and is available in a
40 pin Dil plastic package.
2. Functional Description
Supplied by one of the DIGIT2000 A/D converters (VCU
2136 or SAD 2140), the ACVP 2205 separates the video
signal into luminance and chrominance. These two signals
are processed in different circuits, which will be described
in the following. The output signals are reconverted
to analog signals in the VCU 2136 or VDU 2146.
Their RGB output amplifiers are used to drive the cathodes
of the CRT (see Fig. 2–4). Additionally, the ACVP
2205 performs a number of measurements and control
operations (in conjunction with the VCU 2136 or VDU
2146)relating to picture tube alignment such as spot–
cutoff current adjustment, white level control, beam current
limiting, etc.
For a multistandard application including SECAM, the
SPU 2243 SECAM Chroma Processor must be connected
in parallel to the ACVP 2205 for chroma processing.
The different processing delays Dt can be equalized
in the DTI 2223.

A comb filter arrangement operating at a reduced data rate is provided, which requires comparably fewer storage locations than previous arrangements. A digitized composite video signal of a given codeword rate is applied to a bandpass filter, which produces a filtered signal restricted to a portion of the passband of the composite video signal. The filtered signal is then subsampled at a rate which satisfies the Nyquist criterion for information of the restricted passband. Codewords, now at a reduced data rate, are applied to a one-H delay line, and delayed and undelayed signals are combined to produce a first comb-filtered signal. The first comb-filtered signal is then applied to an interpolator, which provides a sequence of codewords at the codeword rate of the original digitized composite video signal. This sequence of codewords is then combined with the codewords of the composite video signal to produce a second comb-filtered signal.
This invention relates to signal separation systems and, in particular, to a comb filter arrangement for separating the luminance and chrominance components of a digitized video signal at a reduced data rate.

Conventional television broadcast systems are arranged so that much of the brightness (luminance) information contained in an image is represented by signal frequencies which are concentrated about integer multiples of the horizontal linescanning frequency. Color (chrominance) information is encoded and inserted in a portion of the luminance signal spectrum around frequencies which lie halfway between the multiples of the line scanning frequency (i.e., at odd multiples of one-half theline scanning frequency).

Chrominance and luminance information can be separated by appropriately combing the composite signal spectrum. Known combing arrangements take advantage of the fact that the odd multiple relationship between chrominance signal components andhalf the line scanning frequency causes the chrominance signal components for corresponding image areas on successive lines to be 180.degree. out of phase with each other. Luminance signal components for corresponding image areas on successive linesare substantially in phase with each other.

In a comb filter system, one or more replicas of the composite image-representative signal are produced which are time delayed from each other by at least one line scanning interval (a so-called one-H delay). The signals from one line are addedto signals from a preceding line, resulting in the cancellation of the chrominance components, while reinforcing the luminance components. By subtracting the signals of two successive lines (e.g., by inverting the signals of one line and then combiningthe two), the luminance components are cancelled while the chrominance components are reinforced. Thus, the luminance and chrominance signals may be mutually combed and thereby may be separated advantageously.

The composite video signal may be comb filtered in an analog form, a sampled data form, or a digital form. Comb filters using analog signal glass delay lines for the (approximately) one-H delay lines are commonly employed in PAL-type receiversto separate the red and blue color difference signals, taking advantage of the one-quarter line frequency offset of the interlacing of the two signals. An example of a comb filter system for a sampled data signal is shown in U.S. Pat. No. 4,096,516,in which the delay line comprises a 6821/2 stage charge-coupled device (CCD) delay line which shifts signal samples from stage to stage at a 10.7 MHz rate to achieve a one-H delay. The article "Digital Television Image Enhancement" by John P. Rossi,published in Volume 84 of the Journal of the Society of Motion Picture and Television Engineers (1974) beginning at page 37 shows a digital comb filter in which the one-H delay is provided by a digital storage medium for 682 codewords which is accessedat a 10.7 MHz rate.

In the CCD delay line described in the above-referenced U.S. patent, 6821/2 stages are needed to transfer charge packets related to the analog video signal. But in the digital delay line described in the Rossi article, the video signal is inthe form of eight-bit digital codewords. This arrangement requires the use of eight storage locations for each of the 682 codewords in a horizontal line, or a storage medium for 5,456 bits. Moreover, this delay line is only of sufficient size for asystem in which an NTSC color video signal is sampled at a rate of three times per subcarrier cycle (i.e., using a 10.738635 MHz sampling signal). A frequently discussed sampling frequency for digitizing the analog video signal is 14.3181818 MHz, orfour times the color subcarrier frequency. A one-H digital delay line operating at this frequency requires storage for 910 codewords which, at eight bits per codeword, requires a total of 7280 storage locations. Since a storage medium of this capacityis difficult to fabricate economically, it is desirable to provide a digital comb filter system which requires fewer storage locations.

In accordance with the principles of the present invention, a comb filter arrangement operating at a reduced data rate is provided, which requires comparably fewer storage locations than previous arrangements. A digitized composite video signalof a given codeword rate is applied to a bandpass filter, which produces a filtered signal restricted to a portion of the passband of the composite video signal. The filtered signal is then subsampled at a rate which satisfies the Nyquist criterion forinformation of the restricted passband. Codewords, now at a reduced data rate, are applied to a one-H delay line, and delayed and undelayed signals are combined to produce a first comb-filtered signal. The first comb-filtered signal is then applied toan interpolator, which provides a sequence of codewords at the codeword rate of the original digitized composite video signal. This sequence of codewords is then combined with the codewords of the composite video signal to produce a second comb-filteredsignal.

The invention pertains to a chroma control circuit for a digital television receiver.
A chroma control circuit of this kind is described in an INTERMETALL Data Book entitled "Digit 2000 VLSI Digital TV System", Freiburg/Br., June 1985, pages 163 to 174, which explain the CVPU 2210 NTSC comb-filter video processor. The chroma control circuit according to the aforementioned preambles is contained especially in FIG. 10-2 on page 165, which is described in Section 10.1.4 on page 167 and in Section 10.1.6 on page 168.
In the NTSC and PAL television standards, the hue of a picture element can be represented as an angle-coded signal with respect to a transmitter reference system. The different phase angles from 0° to 360° correspond to hues assigned thereto, the zero reference phase being the zero phase of one of the two standard color-difference signals, namely the B-Y signal. The transmitter reference system is the unmodulated chrominance subcarrier, which is suppressed during the horizontal trace period but is transmitted for a short time as a burst signal during the horizontal retrace period, the phase of the burst signal, referred to the B-Y color-difference signal, being
-180° in the case of the NTSC television standard, and
+/-135° in the case of the PAL television standard.
In the prior art chroma circuit, the receiver reference system is the system clock, which has four times the frequency of, and is locked in frequency and phase to, the unmodulated chrominance subcarrier; four successive system-clock pulses, beginning with the zero phase of the B-Y color-difference signal, correspond to the phase angles of 0°, 90°, 180° and 270° of the unmodulated chrominance subcarrier. The latter, which is included in the composite color signal as mentioned above, is fed to the chroma control circuit after the chrominance and luminance components have been separated from the composite color signal by means of the chrominance filter.
In the NTSC and PAL television standards, the zero reference phase of the receiver reference system is the zero phase of the B-Y color-difference signal during the reception of the color burst. In that case, the R-Y color-difference signal is zero, and the phase comparison in the phase-locked loop is very simple.
If this chroma control circuit is to operate correctly, the chrominance subcarrier and the system clock, which has four times the chrominance-subcarrier frequency, must be locked together in frequency and phase. This is accomplished with a phase-locked loop, which causes the system clock to lock with the unmodulated chrominance subcarrier.
During the further development and improvement of this integrated chroma control circuit, the inventors discovered that the action of the phase-locked loop on the frequency and phase of the system clock is disadvantageous. For example, the phase-locked loop requires a voltage-controlled oscillator for the system clock whose deviation from the reference phase during a line period must not exceed 3°. This corresponds to a permissible deviation of the system-clock frequency of only 0.03 per mill from its nominal value if the phase difference at the beginning of the scanned line is zero. Otherwise, the permissible frequency deviation is even smaller. The necessary frequency stability and control accuracy are thus very high, so that tunable crystal oscillators are used for generating the system clock.
In addition, the data resulting from the phase comparison must be fed to the voltage-controlled oscillator, which is a tunable crystal oscillator forming part of a separate monolithic integrated circuit, so that additional terminals and interconnecting leads are required for both integrated circuits.
Another problem arises if such chroma control circuits are used in television receivers with two or more receiving units which present the information from two or more signal sources or television channels on the screen simultaneously. Each of those receiving units requires a separate clock system whose frequency must be synchronized with the frequency of the respective color-burst signal. With the small differences in the frequencies of the various received color-burst signals, interaction of the associated voltage-controlled oscillators is hardly avoidable, which results in interferences on the screen. The greater the lock-in range of the tunable crystal oscillators, the stronger the interaction will be, because the frequency stability of the oscillators decreases with increasing lock-in range.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to improve the prior art chroma control circuit in such a way that the system clock need not be locked to four times the frequency of the originally received chrominance subcarrier, so that it can be locked to other system-related signals, such as a fixed-frequency signal, and that the phase-locked loop is an all-digital circuit.
The fundamental idea of the invention is to achieve the correct adjustment of the frequency and phase between the system clock, which forms the receiver reference system, and the color-burst signal not by locking the system clock to four times the frequency and four times the phase of the color-burst signal by means of a voltage-controlled oscillator, i.e., by analog means, as has been done so far, but by leaving the frequency and phase of the system clock unchanged and taking the necessary locking measures on the received color-burst and chrominance signals. The phase of the digitalized burst signal is, therefore, rotated with respect to the zero phase of the receiver reference system purely digitally by means of a phase-locked loop until it is -180° or +/-135° in accordance with the NTSC or PAL television standard, respectively; at the same time, frequency equality is established between the rotated burst signal and the system clock. The necessary correction angle is then applied to the chrominance signal too. In case of large frequency differences between the original received color-burst signal and the system clock, the correction of the chrominance signals during the scanning line must be interpolated.
A special advantage of the invention that one or more chroma control circuits in accordance with the invention can be added to the prior art chroma control circuit to produce a television receiver for multipicture reproduction that has only a single system clock for all receiving systems.
Another important advantage is that the system clock can be synchronized with signals which are locked to the horizontal frequency or a multiple thereof. This offers advantages during operation of a video recorder and in signal processing for picture enhancement as is performed, for example, to obtain a flicker-free television picture.
Finally, the necessary interpolation of the chroma correction during the scanning line is achieved by the invention in an advantageous manner even in case of large frequency differences between the originally received color-burst signal and the system clock.




CCU 3000, CCU 3000-I Main System Processor
CCU 3001, CCU 3001-I
MICRONAS INTERMETALL

1. Introduction
The CCU 3000, CCU 3000-I, CCU 3001, CCU 3001-I
are integrated circuits designed in 1.2 mm CMOS
technology, with the exception of CCU 3000, TC18 and
TC19, which is designed in 1 mm CMOS technology. The
CPU contained on the chips is a functionally unchanged
65C02-core, which means that for program development,
systems can be used which are on the market; including
high level language compilers.
The pin numbers mentioned in this data sheet refer to
the 68-pin PLCC package unless otherwise designated.
The CCU 3000-I is described separately in an addendum
on page 66.
1.1. Features of the CCU 3000, CCU 3000-I,
CCU 3001, CCU 3001-I
– CCU 3000 = ROM-less version of the CCU 3001
– 65C02 CPU with max. 8 MHz clock
– 32 kByte internal ROM (CCU 3001 only)
– 1344 internal Bytes RAM with stand-by option
– 51 I/O lines (CCU 3001)
– 26 I/O lines (CCU 3000)
– clock generator with programmable clock frequency
– 8 level interrupt controller
– CCU 3000, CCU 3001:
2 Multimaster IM bus interfaces
– CCU 3000-I, CCU 3001-I: 1I2C/IM bus and
1 Multimaster IM bus interface (see addendum)
– IR-input for software-decoded IR-systems
– on-chip power on, stand-by and clock supervision
logic
– on-chip watchdog
– 3 multifunctional timers
– supports memory banking (external 2MBytes)
– power down signal for external memory
– mask option: EMU mode
– programs can be written in Assembler or in “C”
– CCU 3000 TC 18/19: 1.0 mm CMOS technology, (see
addendum)
– application software available.

Functional Description
2.1. ROM
The chip is equipped with 32 kByte mask-programmable
ROM. The ROM uses up the address space from 8000H
to FFFFH. This ROM can be supplemented or replaced
externally. Only the CCU 3001 has an internal ROM.
2.2. RAM
The RAM area is split into three parts:
– page 0 (address 0 to FFH)
– page 1 (address 100H to 1FFH)
– page 3, 4, 5, 6 (address 300H to 63FH)
Page 0 offers a particularly fast access to the 65C02 and
is therefore very valuable for fast, compact programs.
Page 1 contains the stack and must therefore also have
RAM. The remaining RAM-memory follows in pages 3,
4, 5, 6, as page 2 is reserved as I/O address space. The
RAM can be kept in the stand-by mode via stand-by pin.
2.3. CPU
The CPU core is fully compatible with the 65C02 microprocessor.
However, not all the pins of the 65C02 processor
are accessible for the user outside the chip. One
switch in the control register allows the CPU to be
switched off, so that an external processor can take over
its tasks. This external processor can of course also be
an in-circuit emulator, which makes near-hardware
emulation possible, even though the status and control
lines of the internal CPU are not accessible. If an external
processor is used, all hardware blocks of the chip are
as accessible to it as if it were the internal CPU.
2.4. Clock Generator
An integrated two-pin oscillator generates the clock for
the microcontroller. The frequency created by the oscillator
can be programmed to be reduced with a divider
by the factor 1 ... 255. This enables the user to decrease
the current consumption by the controller by reducing
the working frequency as well as to increase the access
time for the (slower) external memory. This divider contains
the value 4 after a reset, so that the system can also
start with a slow external memory. If the mask-option
OSC is set (EMU version), a switch in the control register
makes it possible to receive the internal clock F2 at
XTAL2. In this case the oscillator must be external and
the clock must be fed to the pin XTAL1. In this way, the
user gets a time reference for internal operations in the
microcomputer. This is especially important with the interrupt
controller. The production version of the CCU
does not have this function!
2.5. PORT 1 to PORT 3, PORT 6 to PORT 8
8 ports belong to the system, of which 5 are 8 bits wide,
one 6 bit, one 4 bit and one 1 bit wide. All port lines of
PORTS 1 to 3 and 6 to 8 can be used as inputs or outputs
independently from each other. One register per port
defines the direction. PORT1 to PORT3 have push-pull
outputs and PORT6 to PORT8 have open drain outputs.
Even a line defined as output can be read, the pin level
being important. This property makes it possible for the
software to find desired and undesired short circuits.
Each port reserves a byte for the direction register and
the data in the I/O page. If the corresponding bit in the
direction register is set to 0, the output mode is switched
on. After a reset, all bits of a direction register are set
to 1. The falling edge of bit 7 of PORT 8 generates interrupts
if the priority of the corresponding interrupt controller
source (7) is not set to 0.
2.6. PORT 4
PORT 4 consists of only one line (LSB, P40). After a reset,
PORT 4 operates as an input only. As soon as PORT
4 is written for the first time, it is switched to output mode
(push-pull). Later read accesses read the actual level at
port 4. If bit 3 in the control word is active, P4 is used as
an R/W-line. If the internal CPU is active, R/W is an output
line, otherwise it is an input. But P4 has another, very
important function during RESET. The level at P4 during
RESET decides whether the control word is read from
the internal ROM (FFF9H) or from the external memory.
It is therefore important that the desired level during RESET
is set at P4. An internal pull-down resistor of approx.
100 kW is integrated in the CCU 3001, which ensures
that the control word is read by the internal ROM. The
external control word access is obtained via an external
pull-up resistor of approx. 5 kW. The CCU 3000 has an
internal pull-up resistor at P4 (external ROM access).
The further mode of operation of the CCU 3000, CCU
3001 depends only on the control word though.
Please note that this mode is always necessary for
the CCU 3000 since this device does not have internal
ROM!
2.7. I/O-Lines P50 to P55
The 6 additional I/O-lines have a two-fold function:
– input or output line (open drain output) or
– fully decoded I/O-select lines (push-pull outputs)
As a rule these lines can be used as input or output lines.
As soon as ports 1 to 4 are used as system bus, they are
lost as I/O-channels. However, a total of 48 port lines (24
inputs and outputs each) can be reconstructed without
difficulties (1 housing for 8 lines), if the additional 6 I/Olines
of the CCU 3000, CCU 3001 are switched into the
port select mode. They then represent the select lines of
the original ports 1 to 3. Each line can be defined as I/O
or port select line separately. In the I/O-page three bytes
are needed.


TEA6415C Bus-Controlled Video Matrix Switch
Main Features
20 MHz Bandwidth
Cascadable with another TEA6415C (Internal
Address can
be changed by Pin 7 Voltage)
8 Inputs (CVBS, RGB, Chroma, ...)
6 Outputs
Possibility of Chroma Signal for each Input
by switching off the Clamp with an external
Resistor Bridge
Bus Controlled
6.5 dB Gain between any Input and Output
-55 dB Crosstalk at 5 MHz
Full ESD Protection

Description
The main function of the TEA6415C is to switch 8
video input sources on the 6 outputs.
Each output can be switched to only one of the
inputs, whereas any single input may be connected
to several outputs.
All switching possibilities are controlled through the
I2C bus.

Driving a 75 W load requires an external transistor.
The switches configuration is defined by words of 16 bits: one word of 16 bits for each output
channel.
So, 6 words of 16 bits are necessary to determine the starting configuration upon power-on (power supply: 0 to 10V). But a new configuration needs only the words of the changed output channels.

Using a Second TEA6415C
The programming input pin (PROG) allows two TEA6415C circuits to operate in parallel and to select them independently through the I²C bus by modifying the address byte. Consequently, the switching capabilities are doubled, or IC1 and IC2 can be cascaded.





TEA6420 BUS-CONTROLLED AUDIO MATRIX SWITCH


5 Stereo Inputs
4 Stereo Ouputs

Gain Control 0/2/4/6dB/Mute for each Output
cascadable (2 different addresses) Serial Bus Controlled Very low Noise
Very low Distorsion
DESCRIPTION The TEA6420 switches 5 stereo audio inputs on 4stereo outputs. All the switching possibilities are changed through the I2C bus.



The power Supply is based on TDA4601 (SIEMENS)





Power supply is based on TDA4601d (SIEMENS)

TDA4601 Operation. * The TDA4601 device is a single in line, 9 pin chip. Its predecessor was the TDA4600 device, the TDA4601 however has improved switching, better protection and cooler running. The (SIEMENS) TDA4601 power supply is a fairly standard parallel chopper switch mode type, which operates on the same basic principle as a line output stage. It is turned on and off by a square wave drive pulse, when switched on energy is stored in the chopper transformer primary winding in the form of a magnetic flux; when the chopper is turned off the magnetic flux collapses, causing a large back emf to be produced. At the secondary side of the chopper transformer this is rectified and smoothed for H.T. supply purposes. The advantage of this type of supply is that the high chopping frequency (20 to 70 KHz according to load) allows the use of relatively small H.T. smoothing capacitors making smoothing easier. Also should the chopper device go short circuit there is no H.T. output. In order to start up the TDA4601 I.C. an initial supply of 9v is required at pin 9, this voltage is sourced via R818 and D805 from the AC side of the bridge rectifier D801, also pin 5 requires a +Ve bias for the internal logic block. (On some sets pin 5 is used for standby switching). Once the power supply is up and running, the voltage on pin 9 is increased to 16v and maintained at this level by D807 and C820 acting as a half wave rectifier and smoothing circuit. PIN DESCRIPTIONS Pin 1 This is a 4v reference produced within the I.C. Pin 2 This pin detects the exact point at which energy stored in the chopper transformer collapses to zero via R824 and R825, and allows Q1 to deliver drive volts to the chopper transistor. It also opens the switch at pin 4 allowing the external capacitor C813 to charge from its external feed resistor R810. Pin 3 H.T. control/feedback via photo coupler D830. The voltage at this pin controls the on time of the chopper transistor and hence the output voltage. Normally it runs at Approximately 2v and regulates H.T. by sensing a proportion of the +4v reference at pin 1, offset by conduction of the photo coupler D830 which acts like a variable resistor. An increase in the conduction of transistor D830 and therefor a reduction of its resistance will cause a corresponding reduction of the positive voltage at Pin 3. A decrease in this voltage will result in a shorter on time for the chopper transistor and therefor a lowering of the output voltage and vice versa, oscillation frequency also varies according to load, the higher the load the lower the frequency etc. should the voltage at pin 3 exceed 2.3v an internal flip flop is triggered causing the chopper drive mark space ratio to extend to 244 (off time) to 1 (on time), the chip is now in over volts trip condition. Pin 4 At this pin a sawtooth waveform is generated which simulates chopper current, it is produced by a time constant network R810 and C813. C813 charges when the chopper is on and is discharged when the chopper is off, by an internal switch strapping pin 4 to the internal +2v reference, see Fig 2. The amplitude of the ramp is proportional to chopper drive. In an overload condition it reaches 4v amplitude at which point chopper drive is reduced to a mark-space ratio of 13 to 1, the chip is then in over current trip. The I.C. can easily withstand a short circuit on the H.T. rail and in such a case the power supply simply squegs quietly. Pin 4 is protected by internal protection components which limit the maximum voltage at this pin to 6.5v. Should a fault occur in either of the time constant components, then the chopper transistor will probably be destroyed. Pin 5 This pin can be used for remote control on/off switching of the power supply, it is normally held at about +7v and will cause the chip to enter standby mode if it falls below 2v. Pin 6 Ground. Pin 7 Chopper switch off pin. This pin clamps the chopper drive voltage to 1.6v in order to switch off the chopper. Pin 8 Chopper base current output drive pin. Pin 9 L.T. pin, approximately 9v under start-up conditions and 16v during normal running, Current consumption of the I.C. is typically 135mA. The voltage at this pin must reach 6.7v in order for the chip to start-up.

Semiconductor circuit for supplying power to electrical equipment, comprising a transformer having a primary winding connected, via a parallel connection of a collector-emitter path of a transistor with a first capacitor, to both outputs of a rectifier circuit supplied, in turn, by a line a-c voltage; said transistor having a base controlled via a second capacitor by an output of a control circuit acted upon, in turn by the rectified a-c line voltage as actual value and by a reference voltage; said transformer having a first secondary winding to which the electrical equipment to be supplied is connected; said transformer having a second secondary winding with one terminal thereof connected to the emitter of said transistor and the other terminal thereof connected to an anode of a first diode leading to said control circuit; said transformer having a third secondary winding with one terminal thereof connected, on the one hand, via a series connection of a third capacitor with a first resistance, to the other terminal of said third secondary winding and connected, on the other hand, to the emitter of said transistor, the collector of which is connected to said primary winding; a point between said third capacitor and said first resistance being connected to the cathode of a second diode; said control circuit having nine terminals including a first terminal delivering a reference voltage and connected, via a voltage divider formed of a third and fourth series-connected resistances, to the anode of said second diode; a second terminal of said control circuit serving for zero-crossing identification being connected via a fifth resistance to said cathode of said second diode; a third terminal of said control-circuit serving as actual value input being directly connected to a divider point of said voltage divider forming said connection of said first terminal of said control circuit to said anode of said second diode; a fourth terminal of said control circuit delivering a sawtooth voltage being connected via a sixth resistance to a terminal of said primary winding of said transformer facing away from said transistor; a fifth terminal of said control circuit serving as a protective input being connected, via a seventh resistance to the cathode of said first diode and, through the intermediary of said seventh resistance and an eighth resistance, to the cathode of a third diode having an anode connected to an input of said rectifier circuit; a sixth terminal of said control circuit carrying said reference potential and being connected via a fourth capacitor to said fourth terminal of said control circuit and via a fifth capacitor to the anode of said second diode; a seventh terminal of said control circuit establishing a potential for pulses controlling said transistor being connected directly and an eighth terminal of said control circuit effecting pulse control of the base of said transistor being connected through the intermediary of a ninth resistance to said first capacitor leading to the base of said transistor; and a ninth terminal of said control circuit serving as a power supply input of said control circuit being connected both to the cathode of said first diode as well as via the intermediary of a sixth capacitor to a terminal of said second secondary winding as well as to a terminal of said third secondary winding.
The invention relates to a blocking oscillator type switching power supply for supplying power to electrical equipment, wherein the primary winding of a transformer, in series with the emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, and a secondary winding of the transformer is provided for supplying power to the electrical equipment, wherein, furthermore, the first bipolar transistor has a base controlled by the output of a control circuit which is acted upon in turn by the rectified a-c line voltage as actual value and by a set-point transmitter, and wherein a starting circuit for further control of the base of the first bipolar transistor is provided.
Such a blocking oscillator switching power supply is described in the German periodical, "Funkschau" (1975) No. 5, pages 40 to 44. It is well known that the purpose of such a circuit is to supply electronic equipment, for example, a television set, with stabilized and controlled supply voltages. Essential for such switching power supply is a power switching transistor i.e. a bipolar transistor with high switching speed and high reverse voltage. This transistor therefore constitutes an important component of the control element of the control circuit. Furthermore, a high operating frequency and a transformer intended for a high operating frequency are provided, because generally, a thorough separation of the equipment to be supplied from the supply naturally is desired. Such switching power supplies may be constructed either for synchronized or externally controlled operation or for non-synchronized or free-running operation. A blocking converter is understood to be a switching power supply in which power is delivered to the equipment to be supplied only if the switching transistor establishing the connection between the primary coil of the transformer and the rectified a-c voltage is cut off. The power delivered by the line rectifier to the primary coil of the transformer while the switching transistor is open, is interim-stored in the transformer and then delivered to the consumer on the secondary side of the transformer with the switching transistor cut off.
In the blocking converter described in the aforementioned reference in the literature, "Funkschau" (1975), No. 5, Pages 40 to 44, the power switching transistor is connected in the manner defined in the introduction to this application. In addition, a so-called starting circuit is provided. Because several diodes are generally provided in the overall circuit of a blocking oscillator according to the definition provided in the introduction hereto, it is necessary, in order not to damage these diodes, that due to the collector peak current in the case of a short circuit, no excessive stress of these diodes and possibly existing further sensitive circuit parts can occur.
Considering the operation of a blocking oscillator, this means that, in the event of a short circuit, the number of collector current pulses per unit time must be reduced. For this purpose, a control and regulating circuit is provided. Simultaneously, a starting circuit must bring the blocking converter back to normal operation when the equipment is switched on, and after disturbances, for example, in the event of a short circuit. The starting circuit shown in the literature reference "Funkschau" on Page 42 thereof, differs to some extent already from the conventional d-c starting circuits. It is commonly known for all heretofore known blocking oscillator circuits, however, that a thyristor or an equivalent circuit replacing the thyristor is essential for the operation of the control circuit.
It is accordingly an object of the invention to provide another starting circuit. It is a further object of the invention to provide a possible circuit for the control circuit which is particularly well suited for this purpose. It is yet another object of the invention to provide such a power supply which is assured of operation over the entire range of line voltages from 90 to 270 V a-c, while the secondary voltages and secondary load variations between no-load and short circuit are largely constant.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a blocking oscillator-type switching power supply for supplying power to electrical equipment wherein a primary winding of a transformer, in series with an emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, a secondary winding of the transformer being connectible to the electrical equipment for supplying power thereto, the first bipolar transistor having a base controlled by the output of a control circuit acted upon, in turn, by the rectified a-c line voltage as actual value and by a set-point transmitter, and including a starting circuit for further control of the base of the first bipolar transistor, including a first diode in the starting circuit having an anode directly connected to one of the supply terminals supplied by the a-c line voltage and a cathode connected via a resistor to an input serving to supply power to the control circuit, the input being directly connected to a cathode of a second diode, the second diode having an anode connected to one terminal of another secondary winding of the transformer, the other secondary winding having another terminal connected to the emitter of the first bipolar transmitter.
In accordance with another feature of the invention, there is provided a second bipolar transistor having the same conduction type as that of the first bipolar transistor and connected in the starting circuit with the base thereof connected to a cathode of a semiconductor diode, the semiconductor diode having an anode connected to the emitter of the first bipolar transistor, the second bipolar transistor having a collector connected via a resistor to a cathode of the first diode in the starting circuit, and having an emitter connected to the input serving to supply power to the control circuit and also connected to the cathode of the second diode which is connected to the other secondary winding of the transformer.
In accordance with a further feature of the invention, the base of the second bipolar transistor is connected to a resistor and via the latter to one pole of a first capacitor, the anode of the first diode being connected to the other pole of the first capacitor.
In accordance with an added feature of the invention, the input serving to supply power to the control circuit is connected via a second capacitor to an output of a line rectifier, the output of the line rectifier being directly connected to the emitter of the first bipolar transistor.
In accordance with an additional feature of the invention, the other secondary winding is connected at one end to the emitter of the first bipolar transistor and to a pole of a third capacitor, the third capacitor having another pole connected, on the one hand, via a resistor, to the other end of the other secondary winding and, on the other hand, to a cathode of a third diode, the third diode having an anode connected via a potentiometer to an actual value input of the control circuit and, via a fourth capacitor, to the emitter of the first bipolar transistor.
In accordance with yet another feature of the invention, the control circuit has a control output connected via a fifth capacitor to the base of the first bipolar transistor for conducting to the latter control pulses generated in the control circuit.
In accordance with a concomitant feature of the invention, there is provided a sixth capacitor shunting the emitter-collector path of the first transistor.
Other features which are considered as characteristic for the invention are set forth in the appended claim.
Although the invention is illustrated and described herein as embodied in a blocking oscillator type switching power supply, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

TDA8175 TV VERTICAL DEFLECTION OUTPUT CIRCUIT:

 DESCRIPTION
The TDA8175 is a monolithic integrated circuit in
HEPTAWATT package. It is a high efficiency power
booster for direct driving of vertical windings of TV
yokes. It is intended for use in Color and B & W
television sets as well as in monitors and displays.

 .POWER AMPLIFIER
 .FLYBACK GENERATOR 
.AUTOMATIC PUMPING COMPENSATION 
.THERMAL PROTECTION .
.REFERENCE VOLTAGE

ABSOLUTE MAXIMUMRATINGS
Symbol Parameter Value Unit
VS Supply Voltage (PIn 2) 35 V
V5, V6 Flyback Peak Voltage 60 V
V3 Voltage at PIn 3 +VS
V1, V7 Amplifier Input Voltage +VS
IO Output Peak Current (non-repetitive, t = 2ms) 2.5 A
IO Output Peak Current at :
f = 50 or 60Hz, t 3 10ms
f = 50 or 60Hz, t > 10ms
32
AA
I3 Pin 3 DC Current at V5 < V2 100 mA
I3 Pin 3 Peak-to-peak Flyback Current at f = 50 or 60Hz, tfly 3 1.5ms 3 A
Ptot Total Power Dissipation at Tcase = 70oC 20 W
Tj, Tstg Storage and Junction Temperature -40, +150 oC

PANASONIC TX-25A3C CHASSIS EURO-1 CRT TUBE PHILIPS A59EAK252X21 45AX SYSTEM






















CRT TUBE PHILIPS A59EAK252X21 It has even Digital controlled beam scan velocity modulation (SVM) with a unit fitted on the tube neck.



In beam scan velocity modulation (SVM) system for a television receiver,

a video signal is applied to a differentiator followed by a limiting differential amplifier. A driver amplifier coupled to the limiting amplifier drives an output stage that supplies current to an SVM coil. Certain video signals with large high frequency content may tend to produce excessive dissipation in the devices of the output stage. To prevent this, a current source for the differential amplifier is controlled by a voltage which is a measure of the average current through the output stage. The magnitude of the current source is varied to thereby vary the peak-to-peak signal output from the limiting amplifier to prevent overdissipation of the output devices. The presence of random noise in the video signal can produce unwanted SVM operation which can impair the viewed image. The unwanted noise component in the video signal can be reduced in amplitude by coring. The coring is unaffected by the variable limiting.

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INTRODUCTION:
This type the 45AX FST TUBE BY PHILIPS WAS WIDELY USED AROUND THE WORLD and fabricated form more than 22 YEARS.


Picture display system including a deflection unit with a double saddle coil system
PHILIPS 45AX SYSTEM
Abstract
Self-convergent picture display system with a color display tube and an electromagnetic deflection unit including a field deflection coil and a line deflection coil which are both of the saddle type and are wound directly on a support. The deflection unit includes a pair of magnetically permeable portions which are arranged symmetrically with respect to the plane of symmetry of the field deflection coil on either side of the tube axis. The magnetically permeable portion draws magnetic flux from the end of the yoke ring in order to extend the vertical deflection field. A self-convergent system can be realized with different screen formats by choosing different lengths of the magnetically permeable portions.
What is claimed is:

1. A picture display system including a colour display tube having a neck accommodating an electron gun assembly for generating three electron beams, and an electromagnetic deflection unit surrounding the paths of the electron beams which have left the electron assembly, said deflection unit comprising

a field deflection coil of the saddle type having a front and a rear end for deflecting electron beams generated in the display tube in a vertical direction;

a line deflection coil of the saddle type likewise having a front and a rear end for deflecting electron beams generated in the display tube in a horizontal direction, and a yoke ring of ferromagnetic material surrounding the two deflection coils and having front and rear end faces extending transversely to the tube axis, the electron beam traversing the coils in the direction from the rear to the front ends when the deflection unit is arranged on a display tube, characterized in that the deflection unit also has first and second magnetically permeable portions arranged symmetrically with respect to the plane of symmetry of the field deflection coil on either side of the tube axis, each magnetically permeble portion having a first end located opposite the rear end face of the yoke ring and a second end located at the neck of the display tube in the proximity of the location where the electron beams leave the electron gun assembly, the length of the first and second magnetically permeable portions and their distance to the yoke ring being dimensioned for providing a self-convergent picture display system.
2. A picture display system as claimed in claim 1 characterized in that regions of the rear end of the yoke ring located on either side of the plane of symmetry of the line deflection coil are left free by the rear end of the field deflection coil and in that the first ends of the magnetically permeable portions are located opposite said regions.

3. A picture display system as claimed in claim 1 characterized in that the field deflection coil and the line deflection coil are directly wound on a support.

4. Apparatus for adapting a self-convergent deflection unit of the type mountable on the neck of a display tube and including a saddle type field deflection coil screen end and a gun end extending away from said tube in a plane disposed at an angle to a tube axis, and a yoke ring having a screen end and a gun end, for use with display tubes having different screen formats comprising:

format adjustment means disposed adjacent to the gun end of the yoke ring for coupling flux from the yoke ring to the neck of the tube to supplement the field produced by the vertical deflection coil to uniformly increase the vertical deflection field to produce a raster having a different format from the raster produced by said deflection unit alone.


5. The apparatus of claim 4 wherein said field deflection coil is arranged symmetrically about a plane of symmetry passing through said neck and said format adjustment means comprises first and second magnetically permeable members arranged symmetrically about said plane of symmetry, each of said magnetically permeable members having a first end disposed adjacent the gun end of the yoke ring and a second end disposed adjacent the neck of the display tube.

6. The apparatus of claim 5 wherein each of said first and second magnetically permeablel members comprises a first end located opposite a gun end face of the yoke ring, and a second end located at the neck of the display tube adjacent the location where the electron beams leave the electron gun assembly.

7. The apparatus of claim 6 wherein said first end comprises a portion of said permeable member disposed parallel to the neck of the displaya tube and said second end comprises a portion of said magnetically permeable member located perpepndicular to the neck of the display tube.

8. The apparatus of claim 7 wherein said second endsn of said magnetically permeable members have inwardly extending arms subending a first angle.

9. The appaaratus of claim 8 wherein said angle is large so that the supplemental field has a positive sixpole component.

10. The apparatus of claim 8 wherein said angle is very small, so that said supplemental field has a dipole component and a negative sixpole component.

11. Apparatus for adapting a self-convergent deflection unit of the type used on the neck of a display tube having an electron gun disposed in a neck of said tube, said deflection unit including a field deflection coil of the saddle type having a rear end portion disposed at an angle to the axis of said tube, comprising means disposed adjacent to said neck between said electron gun and said deflection unit, and coupled to said deflection unit for changing the distance between the line and field deflection points for causing said deflection unit to produce a different screen format.
BACKGROUND OF THE INVENTION The invention relates to a picture display system including a colour display tube having a neck accommodating an electron gun assembly for generating three electron beams, and an electromagnetic deflection unit including a field deflection coil of the saddle type having a front and a rear end for deflecting electron beams generated in the display tube in a vertical direction and a line deflection coil of the saddle type likewise having a front and a rear end for deflecting electron beams generated in the display tube in a horizontal direction and yoke ring of ferromagnetic material surrounds the two deflection coils and has front and rear end faces extending transversely to the tube axis, the electron beam traversing the coils in the direction from the rear to the front ends when the deflection unit is arranged on a display tube. FOr some time a colour display tube has become the vogue in which three electron beams are used in one plane; the type of such a cathode ray tube is sometimes referred to as "in-line". In this case, for decreasing convergence errors of the electron beams, a deflection unit is used having a line deflection coil generating a horizontal deflection field of the pincushion type and a field deflection coil generating a vertical deflection field of the barrel-shaped type. Deflection units for in-line colour display tube systems can in principle be made to be entirely self-convergent, that is to say, in a design of the deflection unit which ensures convergence of the three electron beams on the axes, anisotropic y-astigmatism errors, if any, can simultaneously be made zero in the corners without this requiring extra correction means. While it would be interesting from a point of view of manufacture to have a deflection unit which is selfconvergent for a family of display tubes of the same deflection angle and neck diameter, but different screen formats, the problem exists, however, that a deflection unit of given main dimensions can only be used for display tubes of one screen format. This means that only one screen format can be found for a fixed maximum deflection angle in which aa given deflection unit is self-convergent without a compromise (for example, the use of extra correction means). The Netherlands Patent Specification 174 198 provides a solution to this problem which is based on the fact that, starting from field and line deflection coils having given main dimensions, selfconvergent deflection units for a family of display tubes having different screen formats can be assembled by modifying the effective lengths of the field and line deflection coils with respect to each other. This solution is based on the recognition that, if selfconvergence on the axes has been reached, the possibly remaining anisotropic y-astigmatism error (particularly the y-convergence error halfway the diagonals) mainly depends on the distance between the line deflection point and the field deflection point and to a much smaller extent on the main dimensions of the deflection coils used. If deflection units for different screen formats are to be produced while using deflection coils having the same main dimensions, the distance between the line and field deflection points may be used as a parameter to achieve self-convergence for a family of display tubes having different screen formats but the same maximum deflection angle. The variation in the distance between the line and field deflection points necessary for adaption to different screen formaats is achieved in the prior art by either decreasing or increasing the effective coil length of the line deflection coil or of the field deflection coil, or of both - but then in the opposite sense - with the maiin dimensions of the deflection coils remaining the same and with the dimensions of the yoke ring remaining the same, for example, by mechanically making the coil or coils on the rear side smaller and longer, respectively, by a few millimeters, or by positioning, with the coil length remaining the same, the coil window further or less far to the rear (so thata the turns on the rear side are more or less compressed). To achieve this, saddle-shaped line and field deflection coils of the shell type were used. These are coils having ends following the contour of the neck of the tube at least on the gun side. This is in contrast to the conventional saddle coils in which the gun-sided ends, likewise as the screen-sided ends, are flanged and extend transversely to the tube surface. When using saddle coils of the shell type it is possible for the field deflection coil (and hence the vertical deflection field) to extend further to the electron gun assembly than the line deflection coil, if the field design so requires. However, there are also deflection units with deflection coils of the conventional saddle type, which means that - as stated - they have front and rear ends located in planes extending at an angle (generally of 90.degree. ) to the tube axis. (A special type of such a deflection unit with conventional saddle coils is, for example, the deflection unit described in EP 102 658 with field and line deflection coils directly wound on a support). In this case it has until now been impossible to extend the vertical deflection field further to the electron gun assembly than the horizontal deflection field, because the field deflection coil is enclosed between the flanges of the line deflection coil.
SUMMARY OF THE INVENTION The deflection unit has first and second magnetically permeable portions arranged symmetrically with respect to the plane of symmetry of the field deflection coil on either side of the tube axis, each magnetically permeable portion having a first end located opposite the rear end face of othe yoke ring and a second end located at the neck of the display tube in the proximity of the location where the electron beams leave the electron gun assembly. The length of the first and second magnetically permeable portions and their distance to the yoke ring are dimensioned for providing a self-convergent picture display system. The invention is based on the recognition that the first ends of the magnetically permeable portions draw a field deflection flux flux which is taken up is adjusted by means of the distance between the first ends and the yoke ring, and the length of the magnetically permeable portions determines how far the vertical deflection field is extended to the rear. A practical embodiment of the picture display system according to the invention is characterized in that regions of the rear end of the yoke ring located on either side of the plane of symmetry of the line deflection coil are left free by the rear end of the field deflection coil and in that the first ends of the magnetically permeable portions are located opposite said regions. The invention can particularly be used to advanatage if the field deflection coil and the line deflection coil are directly wound on a support. The invention also relates to an electromagnetic deflection unit suitable for use in a picture display system as described hereinbefore. For use in a display tube having a larger screen format than the display tube for which it is designed, the invention provides the possibility of moving apart the deflection points of the horizontal deflection field and the vertical deflection field generated by a given deflection unit having saddle coils and of moving them towards each other for use in a display tube having a smaller screen format. The great advantage of the invention is that only a modification of the length of the magnetically permeable portions (providing or omitting them, respectively) is required to adapt a deflection unit to different screen formats of a display tube family.

CRT TUBE PHILIPS 45AX TECHNOLOGY Method of Production / manufacturing a color display CRT tube and color display tube manufactured according to said method.A ring is provided to correct the convergence, color purity and frame errors of a color display tube which ring is magnetized as a multipole and which is secured in or around the tube neck and around the paths of the electron beams.
The magnetization of such a ring can best be carried out by energizing a magnetization unit with a combination of direct currents thereby generating a multipole magnetic field and then effecting the magnetization by generating a decaying alternating magnetic field which preferably varies its direction continuously.

1. A method of manufacturing a color display tube in which magnetic poles are provided in or around the neck of said tube and around the paths of the electron beams, which poles generate a permanent static multipole magnetic field for the correction of errors in convergence, color purity and frame of the display tube, which magnetic poles are formed by the magnetisation of a configuration of magnetisable material provided around the paths of the electron beams, the method comprising energizing a magnetisation device with a combination of direct currents with which a static multipole magnetic field is generated, and superimposing a decaying alternating magnetic field over said static multipole magnetic field which initially drives said magnetisable material into saturation on either side of the hysteresis curve thereof, said decaying alternating magnetic field being generated by a decaying alternating current. 2. The method as claimed in claim 1, 6 or 7, wherein the decaying alternating magnetic field is generated by means of a separate system of coils in the magnetisation device. 3. The method as claimed in claim 2, wherein the decaying alternating magnetic field varies its direction continuously. 4. The method as claimed in claim 3 wherein the frequency of the decaying alternating current is approximately the standard line frequency. 5. A colour display tube manufactured by means of the method as claimed in claim 4. 6. The method as claimed in claim 1 which further comprises erasing any residual magnetism in said configuration, prior to said magnetisation, with an alternating magnetic field. 7. The method as claimed in claim 6 which further comprises correcting the errors in convergence, color purity and frame of the display picture with a combination of direct currents applied to said magnetisation device and then reversing said direct currents while increasing the magnitudes thereof and applying these adjusted direct currents to said magnetisation device for the magnetisation of said configuration.
Description:
BACKGROUND OF THE INVENTION
The invention relates to a method of manufacturing a color display tube in which magnetic poles are provided in or around the neck of the envelope and around the paths of the electron beams, which poles generate a permanent multipole magnetic field for the correction of the occurring errors in convergence, color purity and frame of the color display tube, which magnetic poles are formed by the magnetisation of a configuration of magnetisable material provided around the paths of the electron beams, which configuration is magnetized by energising a magnetising device with a combination of currents with which a static multipole magnetic field is generated.
The invention also relates to a color display tube manufactured according to said method.
In a color display tube of the "delta" type, three electron guns are accommodated in the neck of the tube in a triangular arrangement. The points of intersection of the axes of the guns with a plane perpendicular to the tube axis constitute the corner points of an equilateral triangle.
In a color display tube of the "in-line" type three electron guns are arranged in the tube neck in such manner that the axes of the three guns are situated mainly in one plane while the axis of the central electron gun coincides substantially with the axis of the display tube. The two outermost electron guns are situated symmetrically with respect to the central gun. As long as the electron beams generated by the electron guns are not deflected, the three electron beams, both in tubes of the "delta" type and of the "in-line" type, must coincide in the center of the display screen (static convergence). Because, however, as a result of defects in the manufacture of the display tube, for example, the electron guns are not sealed quite symmetrically with respect to the tube axis, deviations of the frame shape, the color purity and the static convergence occur. It should be possible to correct said deviations.
Such a color display tube of the "in-line" type in which this correction is possible, is disclosed in Netherlands Pat. application No. 7,503,830 laid open to public inspection. Said application describes a color display tube in which the deviations are corrected by the magnetisation of a ring of magnetisable material, as a result of which a static magnetic multipole is formed around the paths of the electron beams. Said ring is provided in or around the tube neck. In the method described in said patent application, the color display tube is actuated after which data, regarding the value and the direction of the convergence errors of the electron guns, are established, with reference to which the polarity and strength of the magnetic multipole necessary to correct the frame, color purity and convergence errors are determined. The magnetisation of the configuration, which may consist of a ring, a ribbon or a number of rods or blocks grouped around the electron paths, may be carried out in a number of manners. It is possible, for example, first to magnetise the configuration to full saturation, after which demagnetisation to the desired value is carried out with an opposite field. A disadvantage of this method is that, with a combination of, for example, a 2, 4, and 6-pole field, the polarity and strength of the demagnetisation vary greatly and frequently, dependent on the place on the ring, and hence also the polarity and strength of the full magnetisation used in this method. Moreover it appears that the required demagnetising field has no linear relationship with the required correction field. Due to this non-linearity it is not possible to use a combined 2, 4 and 6-pole field for the demagnetisation. It is impossible to successively carry out the 2, 4 and 6-pole magnetisation since, for each magnetisation, the ring has to be magnetised fully, which results in the preceding magnetisation being erased again. The possibility of successively magnetising various places on the ring is very complicated and is not readily possible if the ring is situated in the tube neck since the stray field of the field necessary for the magnetisation again demagnetizes, at least partly, the already magnetised places.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method with which a combined multipole can be obtained by one total magnetisation.
According to the invention, a method, of the kind described in the first paragraph with which this is possible, is characterized in that the magnetisation is effected by means of a decaying alternating magnetic field which initially drives the magnetisable material on either side of the hysteresis curve into saturation. After the decay of the alternating magnetic field, a hard magnetisation remains in the material of the configuration which neutralizes the externally applied magnetic field and is, hence, directed oppositely thereto. After switching off the externally applied magnetic field, a magnetic multipole field remains as a result of the configuration magnetized as a multipole. The desired magnetisation may be determined in a number of manners. By observing and/or measuring the deviations in the frame shape, color purity and convergence, the desired multipole can be determined experimentally and the correction may be carried out by magnetisation of the configuration. If small deviations are then still found, the method is repeated once or several times with corrected currents. In this manner, by repeating the method according to the invention, it is possible to produce a complete correction of the errors in frame, color purity and convergence. Preceding the magnetisation, residual magnetism, if any, in the configuration is preferably erased by means of a magnetic field.
The method is preferably carried out by determining the required correction field prior to the magnetisation and, after the erasing of the residual magnetism, by correcting the errors in the convergence, the color purity and the frame of the displayed picture by means of a combination of currents through the magnetising device, after which the magnetisation is produced by reversing the direction of the combination of currents, increasing the current strength and simultaneously producing the said decaying alternating magnetic field.
The correction field, obtained with the magnetizing device and measured along the axis of the electron beams, is generally longer than the multipole correction field generated by the configuration. So the correction of the deviations will have to be carried out over a shorter distance along the axis of the tube, which is possible only with a stronger field. During the magnetisation, a combination of currents, which in strength and direction is in the proportion of m:1 to the combination of currents which is necessary to generate a correction multipole field with the device, where m is, for example, -3, should flow through the magnetisation device. The value of m depends on the ratio between the length of the correction multipole field, generated by the magnetizing device, to the effective field length of the magnetized configuration. This depends upon a number of factors, for example, the diameter of the neck, the kind of material, the shape and the place of the configuration, etc., and can be established experimentally. If it proves, upon checking, that the corrections with the magnetized configuration are too large or too small, the magnetisation process can be repeated with varied magnetisation currents.
The decaying alternating magnetic field can be generated by superimposing a decaying alternating current on the combination of currents through the magnetisation device (for example, a device as disclosed in Netherlands Pat. application No. 7,503,830 laid open to public inspection). The decaying alternating magnetic field is preferably generated in the magnetisation device by means of a separate system of coils. In order to obtain a substantially equal influence of all parts of the configuration by the decaying alternating field, it is recommendable not only to cause the alternating field to decay but also to cause it to vary its direction continuously. The system of coils therefore consists preferably of at least two coils and the decaying alternating currents through the coils are shifted in phase with respect to each other. Standard line frequency (50 or 60 Hz) has proven to give good results. The phase shift, when using coils or coil pairs, the axes of which enclose angles of 120° with each other, can simply be obtained from a three-phase line.
DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to a drawing, in which
FIG. 1 is a diagrammatic sectional view of a known color display tube of the "in-line" type having an external static convergence unit,
FIG. 2 shows the pinion transmission used therein,
FIGS. 3 and 4 are two diagrammatic perpendicular cross-sectional views of the color display tube with a ring, which has not yet been magnetized, and in which the outermost electron beams do not converge satisfactorily,
FIGS. 5 and 6 are two diagrammatic perpendicular sectional views of a color display tube in which convergence by means of the magnetisation device has been obtained,
FIGS. 7 and 8 show the magnetisation of a ring arranged in the system of electron guns,
FIGS. 9 and 10 show two diagrammatic perpendicular sectional views of a color display tube with a magnetized ring with which the convergence error, as shown in FIG. 4, is removed,
FIGS. 11 and 12 show two types of devices suitable for magnetisation according to the invention, and
FIGS. 13 to 18 show parts of another type of magnetisation unit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a diagrammatic sectional view of a known color display tube of the "in-line" type. Three electron guns 5, 6 and 7, generating the electron beams 8, 9 and 10, respectively, are accommodated in the neck 4 of a glass envelope 1 which is composed of a display window 2, a funnel-shaped part 3 and a neck 4. The axes of the electron guns 5, 6 and 7 are situated in one plane, the plane of the drawing. The axis of the central electron gun 6 coincides substantially with the tube axis 11. The three electron guns are seated in a sleeve 16 which is situated coaxially in the neck 4. The display window 2 has on the inner surface thereof a large number of triplets of phosphor lines. Each triplet comprises a line of a phosphor luminescing green, a line of a phosphor luminescing blue, and a line of a phosphor luminescing red. All of the triplets together constitute a display screen 12. The phosphor lines are normal to the plane of the drawing. A shadow mask 12, in which a very large number of elongate apertures 14 are provided through which the electron beams 8, 9 and 10 pass, is arranged in front of the display screen 12. The electron beams 8, 9 and 10 are deflected in the horizontal direction (in the plane of the drawing) and in the vertical direction (at right angles thereto) by a system 15 of deflection coils. The three electron guns 5, 6 and 7 are assembled so that the axes thereof enclose a small angle with respect to each other. As a result of this, the generated electron beams 8, 9 and 10 pass through each of the apertures 14 at said angle, the so-called color selection angle, and each impinge only upon phosphor lines of one color.
A display tube has
a good static convergence if the three electron beams, when they are not being deflected, intersect each other substantially in the center of the display screen. It has been found, however, that the static convergence often is not good, no more than the frame shape and the color purity, which may be the result of an insufficiently accurate assembly of the guns, and/or sealing of the electron guns, in the tube neck. In order to produce the static convergence, so far, externally adjustable correction units have been added to the tube. They consist of a number of pairs of multipoles consisting of magnetic rings, for example four two-poles (two horizontal and two vertical), two four-poles and two six-poles. The rings of each pair are coupled together by means of a pinion transmission (see FIG. 2), with which the rings are rotatable with respect to each other to an equal extent. By rotating the rings with respect to each other and/or together, the strength and/or direction of the two-, four- or six-pole field is adjusted. It will be obvious that the control of a display tube with such a device is complicated and time-consuming. Moreover, such a correction unit is material-consuming since, for a combination of multipoles, at least eight rings are necessary which have to be provided around the neck so as to be rotatable with respect to each other.
In the Netherlands Pat. application No. 7,503,830, laid open to public inspection, the complicated correction unit has, therefore, been replaced by one or more magnetized rings, which rings are situated in or around the tube neck or in or around the electron guns.
However, it has proved difficult with the magnetising methods known so far to provide a combination of multipoles in the ring by magnetisation.
The method according to the invention provides a solution.
For clarity, identical components in the following figures will be referred to by the same reference numerals as in FIG. 1.
FIG. 3 is a diagrammatic sectional view of a display tube in which the electron beams do not converge in the horizontal direction. As is known, the outermost electron beams can be deflected more or less in the opposite direction by means of a four-pole, for example, towards the central beam or away therefrom. It is also possible to move the beams upwards and downwards. By means of a six-pole the beams can be deflected more or less in the same direction. For simplicity, the invention will be described with reference to a display tube which requires only a four-pole correction. The convergence errors in the horizontal direction of the electron beams 8 and 10 are in this case equally large but opposite.
FIG. 4 is a sectional view of FIG. 3. On the bottom of sleeve 16, a ring 18 is provided of an alloy of Fe, Co, V and Cr (known as Vicalloy) which can be readily magnetized. It will be obvious that the ring may alternatively be provided in other places around the guns or in or around the tube neck. Instead of a ring it is alternatively possible to use a ribbon or a configuration of rods or blocks of magnetisable material.
In FIG. 5 a device 19 for generating a controllable multipole magnetic field is provided around the neck 4 and the ring 18 according to the method of the invention. 2-, 4- or 6-poles and combinations thereof can be generated by means of the device 19. For the tube shown in FIG. 3, only a four-pole correction is necessary. The coils of the device 19, which device will be described in detail hereinafter, are in this case energized as four-poles until the point of intersection S of the three electron beams 8, 9 and 10, which in FIG. 3 was situated outside the tube 1, lies on the display screen 12. The current I through the coils of the device originates from a direct current source B which supplies a current -mI 1 (m being an experimentally determined constant >1) to the coils via a current divider and commutator A. The current can be adjusted per coil so as to generate the desired multipole. In this phase of the method, an alternating current source C does not yet supply current (i=0).
FIG. 6 is a perpendicular sectional view of FIG. 5. The current I 1 is a measure of the strength of the required correction field. The correction field of the multipole of the device 19 extends over a larger length of the electron paths than the magnetic field generated later by the magnetized ring. Therefore the field of the ring is to be m-times stronger.
FIG. 7 shows the step of the method in which the ring 18 is magnetized as a four-pole. As follows from the above, in this preferred embodiment of the method, the current through the coils of the device must be -mI 1 during the magnetisation, so must traverse in the reverse direction and be m-times as large as the current through the coils during the correction. Moreover, the alternating current source C supplies a decaying alternating current (i=i 1 >0) to the device 19, with which current the decaying alternating field is generated. When the alternating current is switched on, it must be so large that the ring 18 is fully magnetized on either side of the hysteresis curve. When the alternating field has decayed, the ring 18 is magnetized, in this case as a four-pole. It is, of course, alternatively possible to magnetise the ring 18 as a six-pole or as a two-pole or to provide combinations of said multipoles in the ring 18 and to correct therewith other convergence errors or color purity and frame errors. It is also possible to use said corrections in color display tubes of the "delta" type.
FIG. 9 shows the display tube 1 shown in FIG. 3, but in this case provided with a ring 18 magnetized according to the method of the invention as shown in FIGS. 5 and 7. The convergence correction takes place only by the magnetized ring 18 present in sleeve 16. The provision of the required multipole takes place at the display tube 1 factory and complicated adjustments and adjustable convergence units (FIG. 2) may be omitted.
FIG. 10 is a cross-sectional view perpendicular to FIG. 9. FIG. 11 shows a magnetisation device 19 comprising eight coils 20 with which the convergence (see FIG. 5) and the magnetisation (see FIG. 7) are carried out. For generating the decaying alternating magnetic field, two pairs of coils 21 and 22, extending in this case at right angles to each other, are incorporated in the device 19. The current i a through the pair of coils 21 is shifted in phase through 90° with respect to the current i b through the other pair of coils 22, so that the decaying alternating magnetic field changes its direction during the decay and is a field circulating through the ring 18. FIG. 12 shows a magnetisation device known from Netherlands Pat. application No. 7,503,830 laid open to public inspection. In this case, the decaying alternating current may be superimposed on the direct current through the coils 23 so that extra coils are not necessary in the device. The coils 23 are wound around a yoke 24.
The magnetisation device 19 may alternatively be composed of a combination of electrical conductors and coils, as is shown diagrammatically in FIGS. 13 to 18.
FIG. 13 is a sectional view of the neck 4 of a display tube 1 at the area of a ring 18 to be magnetised. A two-pole field for corrections in the horizontal direction is generated in this case by causing currents to flow through the conductors 25, 26, 27 and 28 in the direction as shown in the figure. Said conductors may be single wires or wire bundles forming part of one or more coils or turns, and extending parallel to the tube axis at the area of the ring 18.
FIG. 14 shows how, in an analogous manner, a four-pole field for corrections of the outermost beams 8 and 10 in the horizontal direction can be generated by electrical conductors 29, 30, 31 and 32. A four-pole field for corrections of the outermost beams 8 and 10 in the vertical direction is substantially the same. However, the system of conductors 29, 30, 31 and 32 is rotated through 45° with respect to the neck 4 and the axis of the tube 1.
FIG. 15 shows, in an analogous manner, a six-pole for corrections in the horizontal direction with conductors 33 to 38. By means of a combination of conductors (wires or wire bundles) with which 2-, 4- and 6-poles can be generated, all combinations of two-, four- and six-pole fields with the desired strength can be obtained by variations of the currents through said conductors 33 to 38.
The decaying alternating magnetic field in a magnetisation unit with conductors as shown in FIGS. 13, 14 and 15 can be obtained by means of coils positioned symmetrically around the neck 4 and the conductors as shown in FIGS. 16 and 17 or 18. By energizing the coils 39 and 40, shown in FIG. 16, with a decaying alternating current, a decaying alternating magnetic field is generated. A better influencing of the ring 18 by the decaying alternating field is obtained when a system of coils having coils 41 and 42 in FIG. 17 is provided which is rotated 90° with respect to the coils 39. In this case, 40 and the decaying alternating current through the coils 41 and 42 should then preferably be shifted 90° in phase with respect to the decaying alternating current through the coils 39 and 40.
It is alternatively possible to generate the decaying alternating magnetic field with one or more systems of coils as shown in FIG. 18. The coils 43, 44 and 45 are situated symmetrically around the tube axis and are energized with decaying alternating currents which are shifted 120° in phase with respect to each other (for example from a three-phase line).





















CRT TUBE PHILIPS 45AX TECHNOLOGY Method of manufacturing a static convergence unit, and a color display tube comprising a convergence unit manufactured according to the method, PHILIPS 45AX INTERNAL STATIC CONVERGENCE SYSTEM Application technology:
IMACO RING (Integrated Magnetic Auto Converging )

The method according to the invention consists in the determination of data of the convergence errors of a color display tube, data being derived from the said determinations for determining the polarity and the intensity of magnetic poles of a structure. The structure thus obtained generates a static, permanent, multipole magnetic field adapted to the convergence errors occurring, so that the errors are connected.

What is claimed is: 1. A method of producing a magnetic convergence structure for the static convergence of electron beams which extend approximately in one plane in a neck of a color display tube of the kind in which the neck merges into a flared portion adjoined by a display screen, said method comprising
providing around the neck of the color display tube an auxiliary device for generating variable magnetic fields in the neck of the color display tube, activating the color display tube, adjusting the auxiliary device to produce a magnetic field for converging the electron beams, determining from data derived from the adjustment of the auxiliary device the extent and the direction of the convergence error of each electron beam, and using such data to determine the polarity and the intensity of magnetic poles of said magnetic convergence structure for generating a permanent multi-pole static magnetic field for the correction of the convergence errors occuring in the color display tube. 2. A method as claimed in claim 1, wherein the auxiliary device comprises an electromagnet convergence unit which comprises a number of coils, said generating step comprising passing electrical currents through said coils for generating a magnetic field required for the static convergence of the electron beams, and said determining step comprising using the values of the electrical currents for determining the permanent magnetic structure. 3. A method as claimed in claim 2, further comprising storing the data from the auxiliary device in a memory. 4. A method as claimed in claim 2, wherein said using step comprises controlling a magnetizing unit for magnetizing an annular magnetizable convergence structure. 5. A method as claimed in claim 2, further comprising converting the data into a code, and constructing said annular permanent magnetic convergence structure having a desired magnetic field strength from a set of previously magnetized structural parts. 6. A method as claimed in claim 1, further comprising forming the convergence structure from a magnetizable mass which is annularly arranged on at least one wall of the neck of the color display tube. 7. A method as claimed in claim 1, further comprising forming the convergence structure from a magnetizable ring which is arranged on the neck of the color display tube. 8. A method as claimed in claim 1, wherein the convergence structure comprises a non-magnetizable support and a number of permanent magnetic dipoles. 9. A method as claimed in claim 4, wherein said magnetizing step cofmprises polarizing the magnetizable material of the annular convergence structure at one location after the other by means of the magnetizing unit. 10. A method as claimed in claim 4, further comprising assemblying the auxiliary device and the magnetizing unit in one construction, and then enclosing a convergence structure to be magnetized with said magnetizing unit. 11. A method as claimed in claim 10, further comprising displacing said construction with respect to said tube after said determining step.
Description:
The invention relates to a method of manufacturing a magnetic convergence device for the static convergence of electron beams which extend approximately in one plane in a neck of a colour display tube, and to a colour display tube provided with a permanent magnetic device for the static convergence of electron beams in the colour display tube. A known device, described in U.S. Pat. No. 3,725,831, consists of at least four permanent magnetic rings arranged in pairs which generate a magnetic field that can be adjusted as regards position and intensity. The adjustability is obtained by turning the two rings of a pair in the same direction with respect to the electron beams and by turning the one ring in the opposite direction with respct to the other ring. The adjustability necessitates that the rings be arranged on a support which is arranged about the neck of the colour display tube and which should include facilities such that the adjustability of each pair of rings, independent of the position of the other rings, is ensured. The invention has for its object to provide a method whereby a device for converging electron beams can be manufactured which need not be mechanically adjustable, so that it can have a very simple construction, and to provide a colour display tube including such a device.
To this end, the method according to the invention is characterized in that the colour display tube is activated, after which data concerning the extent and the direction of the convergence error of each electron beam are determined, on the basis of which is determined the polarity and intensity of magnetic poles of a structure for generating a permanent, multi-pole, static magnetic field for the correction of the convergence errors occurring in the colour display tube, about the neck of the colour display tube there being provided an auxiliary device for generating variable magnetic fields in the neck of the colour display tube, the auxiliary device being subsequently adjusted such that a magnetic field with converges the electron beams is produced, data being derived from the adjustment of the auxiliary device thus obtained, the said data being a measure for the convergence errors and being used for determining the structure generating the permanent static magnetic field.
Using the described method, a device can be manufactured which generates a magnetic field adapted to the colour display tube and which thus constitutes one unit as if it were with the colour display tube. If desired colour purity errors as well as convergence errors can be eliminated by this method. The convergence errors visible on the screen can be measured and expressed in milimeters of horizontal and vertical errors. The errors thus classified represent data whereby, using magnetic poles of an intensity to be derived from the errors, there can be determined a structure of a magnetic multi-pole which generates a permanent magnetic field adapted to the determined convergence errors.
As a result of the generation of a desired magnetic field by means of an auxiliary device and the derivation of data therefrom, it is possible to determine a device adapted to the relevant colour display tube. Simultaneously, it is ensured that the convergence of the electron beams can be effected.
A preferred version of the method according to the invention is characterized in that for the auxiliary device is used an electromagnetic convergence unit which comprises a number of coils wherethrough electrical currents are conducted in order to generate a magnetic field required for the convergence of the electron beams, the values of the electrical currents producing the data for determining an annular permanent magnetic structure. Because the electrical currents whereby the auxiliary device is actuated are characteristic of the magnetic field generated, the intensity and the position of the poles of the magnetic multi-poles to be used for the colour display tube are determined by the determination of the values of the electrical currents.
The data obtained from the auxiliary device can be used in various manners. The data from the auxiliary device can be stored in a memory, or the data from the auxiliary device can be used immediately for controlling a magnetizing unit which magnetizes an annular magnetizable structure. Alternatively it is possible to convert the data into a code; on the basis thereof an annular permanent magnetic structure having a desired magnetic field strength can be taken or composed from a set of already magnetized structural parts. Obviously, the latter two possibilities can be performed after the data have been stored in a memory.
A simplification of the method is achieved when the device is formed from a magnetizable mass which is provided in the form of a ring on at least one wall of the neck of the colour display tube. The device to be magnetized is thus arranged around the electron beams to be generated. Subsequently, a construction which comprises the auxiliary device and the magnetizing unit is arranged around the neck of the colour display tube. The auxiliary device is then adjusted, after which the construction can possibly be displaced, so that the magnetizing unit encloses the device. The magnetizing unit is actuated on the basis of the data received from the auxiliary device, and magnetizes the device.
In order to make the construction of a magnetizing unit as simple and as light as possible, it is advantageous to polarize material of the structure to be magnetized one area after the other by means of the magnetizing unit. A suitable alternative of the method for which use can be made of the described construction of the magnetizing unit is characterized in that the device consists of a non-magnetizable support and a number of permanent magnetic bipoles. It was found that any feasible magnetic field required for the static convergence of electron beams in a neck of a colour display tube can be comparatively simply generated using at least one eight-pole electromagnetic convergence unit. Similarly, any desired magnetic field can be generated using a twelve-pole electromagnetic convergence unit. It is to be noted that electromagnetic convergence units have already been proposed in U.S. Pat. No. 4,027,219.
The invention will be described in detail hereinafter with reference to a drawing.
FIG. 1 is a diagrammatic representation of a first version of the method according to the invention.
FIG. 2 is a diagrammatic representation of a second version of the method according to the invention.
FIG. 3 shows a preferred embodiment of an auxiliary device.
FIG. 4 is a side elevation of a first embodiment of a device manufactured using the method according to the invention.
FIG. 5 is a cross-sectional view of the embodiment shown in FIG. 4.
FIG. 6 is a side elevation of a further embodiment of a device manufactured using the method according to the invention.
FIG. 7 is a cross-sectional view of the device shown in FIG. 6.
FIG. 8 is a diagrammatic perspective view of a magnetizing device and a convergence unit arranged therein.
FIG. 9a is a cross-sectional view of a convergence unit manufactured using a method according to the invention.
FIG. 9b is a partial side elevation of part of a support of the convergence unit shown in FIG. 9a.
FIG. 9c shows a permanent magnetic structural part of the device shown in FIG. 9a.
The method according to the invention will be described with reference of FIG. 1. An electromagnetic auxiliary device 5 is arranged around the neck 3 of the colour display tube 1. The auxiliary device 5 will be described in detail with reference to FIG. 3. Electrical currents which generate a magnetic field are applied to the auxiliary device 5. When the electrical currents are adjusted to the correct value, a magnetic field adapted to the colour display tube 1 as regards position and intensity is generated. The electrical currents are measured by means of the measuring unit 9. The electrical currents represent data which completely describe the magnetic field generated by the auxiliary device 5. The data are stored in a memory 19 (for example, a ring core memory) in an adapted form (digitally). The data can be extracted from the memory 19 again for feeding a control unit 11. The control unit 11 actuates a magnetizing unit 13. A magnetic field is impressed on the device 15 arranged inside the magnetizing unit 13 (shown to be arranged outside this unit in FIG. 1), the said magnetic field equalling the magnetic field generated by the auxiliary device 5 at the area of the electron beams. The auxiliary device 5 is then removed from the neck 3 and replaced by the device 15.
The method is suitable for the application of an automatic process controller 17. The storage of the data in the memory 19, the retrieval thereof, the determination and the feeding of the data to the control unit 11 are operations which are very well suitable for execution by an automatic controller. Similarly, the process controller 17 can dispatch commands at the correct instants to mechanisms which inter alia arrange the auxiliary device 5 on the display tube 1, arrange the device 15 to be magnetized in the magnetizing unit 13, remove the auxiliary device 5 from the display tube 1, and arrange the device 15 on the neck 3 of the display tube 1. Besides these controlling functions, checking functions can also be performed by the process controller, such as the checking of:
the position of the display tube 1 with respect to the auxiliary device 5.
the determination of the number of data by the measuring unit 9.
the actuation of the magnetizing unit 13.
the position of the device 15 with respect to the display tube 1.
The method shown in FIG. 2 is an alternative to the method described with reference to FIG. 1. The auxiliary device 5 and the magnetizing unit 13 are accommodated together in one construction 6. Before the auxiliary device 5 and the magnetizing unit 13 are arranged around the neck 3 of the colour display tube 1, the as yet unmagnetized device 15 is arranged in a desired position. The auxiliary device 5 is activated and adjuste so that a magnetic field converging the electron beams is produced. Subsequently, the measuring unit 9 determines the necessary data whereby the control unit 11 is adjusted. The auxiliary device 5 may be shifted so that the magnetizing unit 13 encloses the device 15. After the current to the auxiliary device 5 has been interrupted, the magnetizng unit 13 is activated by the control unit 11. After magnetization of the device 15, the auxiliary device 5 and the magnetizing unit 13 are removed. A convergence unit which has been exactly adjusted as regards position and strength has then been arranged on the neck 3 of the tube 1.

FIG. 3 more or less diagrammatically shows an embodiment of an auxiliary device 5. The auxiliary device 5 comprises an annular ferromagnetic core 21 having formed thereon eight pole shoes a, b, c, d, e, f, g, and h which are situated in one plane and radially orientated. Each pole shoe has provided thereabout a winding wherethrough a direct current I to be adjusted is to be conducted.
In the space enclosed by the core 21 an eight-pole static magnetic field is generated whose polarity and intensity can be controlled. The value and the direction of the direct currents Ia, Ib, Ic, Id, Ie, If, Ig and Ih can be adjusted on the basis of the value and the direction of the deviations of the electron beams to be converged. The corrections required for achieving colour purity and convergence can be derived from the value and the direction of the direct currents Ia and Ih which form the data from which the necessary corrections are determined.
A similar embodiment can be used for the magnetizing unit, but because the electrical currents required for converging electron beams are smaller than the currents required for magnetizing the device, the conductors of the coils of the magnetizing unit must be constructed in a different manner which takes account the higher current intensities. If a similar embodiment of the auxiliary device has been made suitable for higher current intensities, it can also operate at lower current intensities. It follows that it is possible also to use the magnetizing unit as the auxiliary device, which is in one case connected to the measuring unit and in the other case to the control unit.
FIG. 4 shows a partly cut-away neck 3 having an envelope 31 of a colour display tube, the flared portion and the adjoining display screen not being shown. At the end of the neck 3 there are provided contact pins 33 to which cathodes and electrodes of the system of electron guns 35 are connected. The device 15 for the static convergence of the electron beams generated by the system of guns 35 consists of a support 15A of synthetic material and a ferrite ring 15B. On the jacket surface of the support 15A is provided a ridge 15c which extends in the longitudinal direction; the ferrite ring 15B is provided with a slot which co-operates therewith and which opens into the edge of the ring on only one side, so that the ring 15B can be secured to the carrier 15A in only one way. FIG. 5 is a cross-sectional view which clearly shows the ridge 15C and the slot of the device 15. The references used in FIG. 5 correspond to those used in FIG. 4.
FIG. 6 shows the same portions of the neck 3 of a colour display tube as FIG. 4. Instead of a support on which a ferrite ring is secured, the device consists only of a layer of ferrite 15 which is secured directly to the inner wall 37 of the neck 3 by means of a binding agent. This offers the advantage that a support which requires space and material can be dispensed with. FIG. 7 is a cross-sectional view and illustrates the simplicity of the device 15. The references used correspond to the references of FIG. 6. The device 15 can also be mounted (not shown in the Figure) on the rear of a deflection unit of the colour display tube. It is alternatively possible to arrange the device on grids or on the cathodes in the neck of the colour display tube.
FIG. 8 diagrammatically shows a magnetizing unit 13 whereby the device 15 arranged thereon is magnetically polarized one location after the other. The extent of the polarization is dependent of the value and direction of the used direct current Im and of the number of ampere-turns of the coil 41 arranged about the core of the magnetizing unit 13. The core consists of two portions 43 and 45 which form a substantially closed magnetic circuit. Between a concave pole shoe 47 and a convex pole shoe 49 of the core portions 43 and 45, respectively, there is a space wherein a portion of the device 15 to be magnetized is arranged. The concave and convex pole shoes 47 and 49 preferably are shaped to follow the curved faces 51 and 53 of the device substantially completely. In order to enable easy arrangement and displacement of the device between the pole shoes 47 and 49, the core portions 43 and 45 are provided with ground contact faces 55 and 57 which are perpendicular to each other. The pole shoes 47 and 49 can be moved away from and towards each other, the core portions 43 and 45 always returning to the same position relative to each other due to the faces 55 and 57 perpendicularly extending to each other. At the same time, the magnetic contact resistance at the faces 55 snd 57 is low and constant, so that the necessary unambiguous relationship between the current Im and the magnetic field generated in the core is ensured.
FIGS. 9a, b and c show a preferred embodiment and details of a static convergence device 15. The device 15 consists of a support 61 of synthetic material, for example, polycarbonate, wherein eight ferromagnetic discs (or "inserts") 63 are equidistantly arranged along the circumference. It will be obvious that this embodiment is particularly suitable for being actuated in a magnetizing unit as shown in FIG. 8. The holes 65 provided in the support 61 are slightly elliptical so as to lock the capsules 63 firmly in the holes 65. To this end, the width b is chosen to be slightly smaller than the height h which equals the diameter d of the round discs (or "inserts") 63. The narrow portions 67 of the support 61 with clamp the disc 63 in the hole 65 due to their elastic action. It is, of course, possible to magnetize the disc 63 before they are arranged in the support 61; the sequence in which the disc 63 are arranged in the support 61 should then be carefully checked.
If a method is used where the most suitable structure is selected from a series of permanent magnetic structures on the basis of the adjusting data, it is advantageous to compose this structure from a number of permanent rings. This will be illustrated on the basis of an example involving superimposition of a four-pole field and a six-pole field. Assume that the magnetic fields can each have M different intensities, and that the on field can occupy N different positions with respect to the other field. If the magnetic structure consists of one permanent magnetic ring, the series from which selection can be made consists of M×M×N rings. If the structure consists of two rings, the series comprises M+M rings, but it should then be possible for the one ring to be arranged in N different positions with respect to the other ring. If the static convergence device is composed as shown in FIG. 9a, b and c or similar, only M kinds of structural parts (discs) having a different magnetical intensity are required for achieving any desired structure.

Color television display tube with coma correction ELECTRON GUN STRUCTURE PHILIPS CRT TUBE 45AX



A color television display tube including an electron gun system (5) in an evacuated envelope for generating three electron beams whose axes are co-planar. The beams converge on a display screen (10) provided on a wall of the envelope and are deflected in the operative display tube across the display screen into two orthogonal directions. The electron gun system (5) has correction elements for causing the rasters scanned on the display screen by the electron beams to coincide as much as possible. The correction elements include annular elements (34) of a material having a high magnetic permeability which are positioned around the two outer beams. In
addition a further correction element (38, 38", 38"') of a material having a high magnetic permeability is provided around the central beam in a position located further from the screen in order to correct field coma errors at the ends of the vertical axis and in the corners to an equal extent. The further element is preferably positioned in, or on the screen side of, the area of the focusing gap of the electron gun.



1. A color display tube comprising an envelope containing a display screen, and an electron gun system for producing a central electron beam and first and second outer electron beams having respective axes which lie in a single plane and converge toward a point on the screen, the electron gun system including an end from which the electron beams exit into a deflection field region of the envelope where a field deflection field effects deflection of the beams in a direction perpendicular to said plane and a line deflection field effects deflection of the beams in a direction parallel to said plane, said line deflection field producing a positive lens action;
characterized in that the electron gun system includes field coma-correcting means comprising:
(a) first and second deflection field shaping means of magnetically-permeable material arranged adjacent the respective outer electron beams, at the end of the electron gun system, for cooperating with the positive lens action of the line deflection field to anisotropically overcorrect the field coma error of said outer electron beams relative to that of the central electron beam; and
(b) a third deflection field shaping means of magnetically-permeable material arranged adjacent the central electron beam, at a position in the electron gun system further from the screen than the first and second field shaping means, for cooperating with the positive lens action of the line deflection field to reverse-anisotropically correct the field coma error of the central electron beam by an amount sufficient to compensate for the overcorrection by the first and second field shaping means, thereby effecting production of a central-electron-beam- produced raster which is substantially identical to the outer-electron-beam-produced rasters.
2. A color display tube comprising an envelope containing a display screen, and an electron gun system for producing a central electron beam and first and second outer electron beams having respective axes which lie in a single plane and converge toward a point on the screen, the electron gun system including at an end thereof a first plate-shaped part including a central and first and second outer apertures from which the respective electron beams exit into a deflection field region of the envelope where a field deflection field effects deflection of the beams in a direction perpendicular to said plane and a line deflection field effects deflection of the beams in a direction parallel to said plane, said line deflection field producing a positive lens action;
characterized in that the electron gun system includes field coma-correcting means comprising:
(a) first and second deflection field shaping means of magnetically-permeable material arranged adjacent the respective outer apertures in the first plate-shaped part for cooperating with the positive lens action of the line deflection field to anisotropically overcorrect the field coma error of said outer electron beams relative to that of the central electron beam; and
(b) a third deflection field shaping means of magnetically-permeable material arranged adjacent a central aperture in a second plate-shaped part of the electron gun for passing the central electron beam, at a position in the electron gun system further from the screen than the first plate-shaped part, for cooperating with the positive lens action of the line deflection field to reverse-anisotropically correct the field coma of the central electron beam by an amount sufficient to compensate for the overcorrection by the first and second field shaping means, thereby effecting production of a central-electron-beam-produced raster which is substantially identical to the outer-electron-beam-produced rasters.
3. A color display tube as in claim 1 or 2 where the third deflection field shaping means comprises first and second strips of magnetically permeable material extending parallel to and symmetrically disposed on opposite sides of said plane. 4. A color display tube as in claim 3 where each of said first and second strips of magnetically permeable material include at opposite ends thereof projecting lugs which extend away from said plane. 5. A color display tube as in claim 3 where the first and second strips of magnetically permeable material comprise integrally formed portions of a cup-shaped portion of the electron gun system, which itself consists essentially of magnetically permeable material. 6. A color display tube as in claim 1 or 2 where the third deflection field shaping means is disposed adjacent an electron-beam-focusing electrode of the electron gun system. 7. A color display tube as in claim 1 or 2 where the first and second deflection field shaping means are disposed on an apertured plate-shaped member closing an end of a centering bush for centering the electron gun system in a neck of the envelope. 8. A color display tube as in claim 7 where the first and second deflection field shaping means comprise ring-shaped elements disposed around respective first and second apertures of said plate-shaped member on a side thereof closer to the screen, and where the third deflection field shaping means comprises a ring-shaped element disposed around a central aperture of said plate-shaped member on a side thereof which is further from said screen. 9. A color display tube as in claim 6 where the third deflection field shaping means comprises a ring-shaped member surrounding a central aperture in the electron-beam-focusing electrode.
Description:
BACKGROUND OF THE INVENTION
The invention relates to a colour television display tube comprising an electron gun system of the "in-line" type in an evacuated envelope for generating three electron beams. The beam axes are co-planar and converge on a display screen provided on a wall of the envelope while the beams are deflected across the display screen into two orthogonal directions by means of a first and a second deflection field. The electron gun system is provided with field shapers for causing the rasters scanned on the display screen by the electron beams to coincide as much as possible. The field shapers comprise elements of a magnetically permeable material positioned around the two outer beams and placed adjacent the end of the electron gun system closest to the screen.
A colour television display tube of this type is known from U.S. Pat. No. 4,196,370. A frequent problem in colour television display tubes incorporating an electron gun system of the "in-line" type is what is commonly referred to as the line and field coma error. This error becomes manifest in that the rasters scanned by the three electron beams on the display screen are spatially different. This is due to the eccentric location of the outer electron beams relative to the fields for horizontal and vertical deflection, respectively. The Patent cited above sums up a large number of patents giving partial solutions. These solutions consist of the use of field shapers. These are magnetic field conducting and/or protective rings and plates mounted on the extremity of the gun system which locally strengthen or weaken the deflection field or the deflection fields along part of the electron beam paths.
In colour television display tubes various types of deflection units may be used for the deflection of the electron beams. These deflection units may form self-convergent combinations with tubes having an "in-line" electron gun system. One of the frequently used deflection unit types is what is commonly referred to as the hybrid deflection unit. It comprises a saddle line deflection coil and a toroidal field deflection coil. Due to the winding technique used for manufacturing the field deflection coil it is not possible to make the coil completely self-convergent. Usually such a winding distribution is chosen that a certain convergence error remains, which is referr
ed to as field coma. This coma error becomes clearly noticeable in a larger raster (vertical) for the outer beams relative to the central beam. The vertical deflection of the central beam is smaller than that of the outer beams. As has been described, inter alia, in the U.S. Pat. No. 4,196,370 cited above, this may be corrected by providing elements of a material having a high magnetic permeability (for example, mu-metal) around the outer beams. The peripheral field is slightly shielded by these elements at the area of the outer electron beams so that these beams are slightly less deflected and the field coma error is reduced.
A problem which presents itself is that the correction of the field coma (Y-coma) is anisotropic. In other words, the correction in the corners is less than the correction at the end of the vertical axis. This is caused by the positive "lens" action of the line deflection coil (approximately, quadratic with the line deflection) for vertical beam displacements. (The field deflection coil has a corresponding lens action, but it does not contribute to the relevant anisotropic effect). The elimination of such an anisotropic Y-coma error by adapting the winding distribution of the coils is a cumbersome matter and often introduces an anisotropic X-coma.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a display tube in which it is possible to correct field coma errors on the vertical axis and in the corners to an equal extent without requiring notable adaptation of the winding distribution of the coils.
To this end a display tube of the type described in the opening paragraph is characterized in that the elements placed at the display screen end of the electron gun system are constructed to overcorrect field coma errors and that the field shapers comprise a further element positioned around the central electron beam at an area of the electron gun system further away from the display screen which operates oppositely to the elements at the end.
The invention is based on the recognition of the fact that the problem of the anisotropic Y-coma can be solved by suitably utilizing the Z-dependence of the anisotropic Y-coma.
This dependence implies that as the coma correction is effected at a larger distance (in the Z-direction) from the "lens" constituted by the line deflection coil the operation of said "lens" becomes more effective, so that the coma correction acquires a stronger anisotropic character. With the coma correction means placed around the outer beams at the gun extremity closest to the screen, the coma is the overcompensated to such a large extent that it is overcorrected even in the corners. The coma is then heavily overcorrected on the vertical axis. The correction is anisotropic. A stronger anisotropic anti-correction is brought about by performing an anti-coma correction at a still greater distance from the lens. By adding this stronger anisotropic anti-correction the coma on the vertical axis can be reduced to zero without the coma in the corners becoming anisotropic. The coma on the vertical axis and the corners is then corrected to an equal extent.
The further element may have the basic shape of a ring and may be mounted around the central aperture of an apertured electrode partition. However, restrictions then are imposed on the positioning of the further element. As will be further described hereinafter, there will be more freedom in the positioning of the further element when in accordance with a preferred embodiment of the invention the further element comprises two strips of a magnetically permeable material which extend parallel to and symmetrically relative to the plane through the electron beam axis around the axis of the central beam.
The effectiveness of these strips may be improved under circumstances when according to a further embodiment of the invention their extremities are provided with outwardly projecting lugs.
The strips may further be separate components or form one assembly with a magnetic material cup-shaped part of the electron gun system, which facilitates mounting.
An effective embodiment of the invention is characterized in that the further element is positioned in, or in front of, the area of the focusing gap of the electron gun. This may be realized in that the further element consists of a ring of magnetically permeable material which is mounted around the central aperture of an apertured partition in the focussing electrode.
The principle of the invention is realised in a given case in that the field shapers adjacent the display screen facing end of the electron gun system consist of two rings mounted on the apertured lid of a box-shaped centering bush, while the further element in that case may advantageously consist of a ring of magnetically permeable material which is mounted around the central aperture in the bottom of the centering bush.
The display tube according to the invention is very suitable for use in a combination with a deflection unit of the hybrid type, particularly when a combination is concerned which should be free from raster correction.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be further described by way of example, with reference to the accompanying drawing figures in which
FIG. 1 is a perspective broken-up elevational view of a display tube according to the invention;
FIG. 2 is a perspective elevational view of an electron gun system for a tube as shown in FIG. 1;
FIG. 3a is an elevational view of a vertical cross-section through part of FIG. 2 ; and
FIG. 3b is a cross-section analogous to FIG. 3a of a further embodiment according to the invention; and
FIG. 3c is a cross-section analogous to FIG. 3a of a further embodiment according to the invention;
FIGS. 4a, b, c and d show the field coma occurring in the different deflection units;
FIG. 4e illustrates the compensation of the field coma according to the invention;
FIG. 5a schematically shows the beam path on deflection in a conventional dislay tube, and
FIG. 5b schematically shows the beam path on deflection in a display tube according to the invention; and
FIGS. 6a, b, c and d are longitudinal sections of different embodiments of an electron gun system for a display tube according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a perspective elevational view of a display tube according to the invention. It is a colour television display tube of the "in-line" type. In a glass envelope 1, which is composed of a display window 2, a cone 3 and a neck 4, this neck accommodates an integrated electron gun system 5 generating three electron beams 6, 7 and 8 whose axes are co-planar prior to deflection. The axis of the central electron beam 7 coincides with the tube axis 9. The inside of the display window 2 is provided with a large number of triplets of phosphor elements. These elements may be dot shaped or line shaped. Each triplet comprises an element consisting of a blue-luminescing phosphor, an element consisting of a green-luminescing phosphor and an element consisting of a red-luminescing phosphor. All triplets combined constitute the display screen 10. Positioned in front of the display screen is a shadow mask 11 having a very large number of (elongated) apertures 12 which allow the electron beams 6, 7 and 8 to pass, each beam impinging only on respective phosphor elements of one colour. The three co-planar electron beams are deflected by a system of deflection coils not shown. The tube has a base 13 with connection pins 14.
FIG. 2 is a perspective elevational view of an embodiment of an electron gun system as used in the colour television display tube of FIG. 1. The electron gun system has a common cup-shaped electrode 20, in which three cathodes (not visible in the Figure) are secured, and a common plate-shaped apertured grid 21. The three electron beams whose axes are co-planar are focused with the aid of a focussing electrode 22 and an anode 23 which are common for the three electron beams. Focussing electrode 22
consists of three cup-shaped parts 24, 25 and 26. The open ends of parts 25 and 26 are connected together. Part 25 is coaxially positioned relative to part 24. Anode 24 has one cup-shaped part 27 whose bottom, likewise as the bottoms of the other cup-shaped parts, is apertured. Anode 23 also includes a centering bush 28 used for centering the electron gun system in the neck of the tube. This centering bush is provided for that purpose with centering springs not shown. The electrodes of the electron gun system are connected together in a conventional manner with the aid of brackets 29 and glass rods 30.
The bottom of the centeri
ng bush 28 has three apertures 31, 32 and 33. Substantially annular field shapers 34 are provided around the apertures 31 and 33 for the outer electron beams. The centering bush is for example 6.5 mm deep and has an external diameter of 22.1 mm and an internal diameter of 21.6 mm in a tube having a neck diameter of 29.1 mm. The distance between the centers of two adjacent apertures in the bottom is 6.5 mm. The annular elements 34 are punched from 0.40 mm thick mu-metal sheet material. (Conventional elements generally have a thickness of 0.25 mm).
FIG. 3a is an elevational view of a vertical cross-section through the cup-shaped part 25 of the electron gun system of FIG. 2 in which the plane through the beam axes is perpendicular to the plane of the drawing. Two (elongated) strips 35 of a magnetically permeable material such as mu-metal are provided symmetrically relative to the aperture 37 for the central electron beam.
FIG. 3b shows a cross-section analogous to the cross-section of FIG. 3a of a further embodiment of the strips 35. In this case each strip has projecting lugs 36.
The strips 35 which produce a coma correction in a direction opposite to the direction of the coma correction produced by the elements 34 are shown as separate components secured to the focussing electrode 22 (for example, by means of spotwelding). If the cup-shaped part 24 has a magnetic shielding function and is therefore manufactured of a magnetically permeable material, the strips 35 may be formed in an alternative manner as projections on the cup-shaped part 24.
FIG. 3c is an elevational view of a cross-section at a different area through the anode 22 in an alternative embodiment of the electron gun system of FIG. 2. In this alternative embodiment the strips 35 are absent. They have been replaced by an annular element 38 of a magnetically permeable material positioned around the center beam. The annular element 38 is provided on an additional apertured partition 39 accommodated between the cup-shaped parts 25 and 26.
In this embodiment there is a restriction that such an additional partition cannot be accommodated in any arbitrary position. The embodiments shown in FIGS. 3a and 3b do not have such a restriction. The strips 35 may be provided in any axial position of the component 22 dependent on the effect to be attained. A plurality of variants based on the embodiment shown in FIG. 3c is, however, possible. For this purpose reference is made to FIG. 6.
The effect of the invention is demonstrated with reference to FIG. 4. In FIG. 4a the rasters of the outer electron beams (red and blue) and the central beam (green) are shown by means of a solid and a broken line, respectively, in a display tube without field shapers and provided with a self-convergent deflection coil. The reference bc indicates the field coma.
Correction of the coma with the means hitherto known results in the situation shown in FIG. 4b. The field coma is zero at the ends of the Y-axis (the vertical axis or picture axis), but in the corners the field coma is still not zero.
Overcompensation of the field coma causes the situation shown in FIG. 4c. Overcompensation is realised, for example, by adapting the external diameter of the annular elements 34 shown in FIG. 2, or by placing them further to the front.
A coma correction in the opposite direction is realised with the aid of the elements 35 or the element 38 in a position located further to the rear in the electron gun system. The effect of this "anti"-coma correction by itself is shown in FIG. 4d.
The combined effect of the corrections as shown in FIGS. 4c and 4d is shown in FIG. 4e. The effect of the invention can clearly be seen; the field coma is corrected to an equal extent on the vertical axis and in the corners.
Elaboration of the step according to the invention on the beam path of the electron beams in a display tube is illustrated with reference to FIGS. 5a and b. FIG. 5a is a longitudinal section through a display tube 40 in which the outer electron beams R, B and the central electron beam G are deflected in a conventional manner. The reference L indicates the position where the "lensing action" of the deflection coils is thought to be concentrated. Upon generating a change in direction, a displacement (ΔY) of the outer beams relative to the central beam occurs in the "lens".
The step according to the invention ensures that there is no displacement in the lens of the outer beams relative to the central beam when generating a change in direction (FIG. 5b).
When using an annular element provided around the central aperture in an apertured partition, such as the element 38, for ensuring an anti-coma correction, there are different manners of positioning the element in a suitable place in addition to the manner of positioning previously described with reference to FIG. 3c. Some of these manners are shown with reference to FIGS. 6a, b, c and d showing longitudinal sections through different electron gun systems suitable for use in a display tube according to the invention. The plane through the axes of the electron beams is in the plane of the drawing.
FIG. 6a shows the same situation as FIG. 3c. An additional apertured partition 39 on which a ring 38 of a magnetically permeable material is mounted around the central aperture is provided between the parts 25 and 26 of the focussing electrode 22 (G3). If no additional partition 39 is to be accommodated, it is possible to provide an anti-coma correction ring 38' around the central aperture on the bottom 41 of the cup-shaped part 24. However, one should then content oneself with the effect that is produced by the ring positioned in this particular place.
As FIG. 6b shows, an alternative manner is to provide an additional partition 42 between the electrode parts 24 and 25 and mount a ring 38' of a magnetically permeable material on it. This is, however, only possible when the cup-shaped part 24 does not have a shielding function.
There is a greater variation in the positioning possibilities of the anti-coma correction element when the electron gun system is of the multistage type, as is shown in FIG. 6c. Broken lines show that one or more rings of a megnetically permeable material may be provided in different positions around the axis of the central beam.
The closer the correction elements 34 around the outer beams are placed towards the display screen, the better it is in most cases. To meet this purpose, an electron gun system having a special type of centering bush as shown in the electron gun system of FIG. 6d can be used. In that case the centering bush 28 is box-shaped and provided with an apertured end 46 on the side facing the display screen.
The apertured end 46 has three apertures 43, 44 and 45. Rings 34 of a magnetically permeable material are mounted on the outside of the end 46 at the aperture 43 and 45 for the outer beams. An optimum position, viewed in the longitudinal direction of the electron gun system, can then always be found for the ring 38 of a magnetically permeable material which is to be positioned around the central beam. This may be the position of ring 38 in FIG. 6d, but also a more advanced position indicated by the ring 38". Even a still more advanced position indicated by ring 38"' is possible. Generally, a position of the ring around the central beam in, or in front of the area of the focusing gap 47 of the electron gun, that is to say, in or in front of the area of the transition from part 26 to part 27 is very suitable. The rings around the outer beams should then be located further to the front, into the direction of the display screen.