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 !

Thursday, January 10, 2013

CREZAR TV12 /2 YEAR 1978.
















































The CREZAR  TV12/2 is a  little portable B/W television has 12 Inches screen format.


Was first CREZAR portable model  featuring a 6 programs tuning keyboard instead of dedicated band button keyboard type as seen in earlier model.

- Tuning search for each preselection is acted in potentiometric way.

The mechanical turret approach to television tuning has been used almost exclusively for the past 60 years. Even though replete with the inherent disadvantages of mechanical complexity, unreliability and cost, such apparatus has been technically capable of performing its intended function and as a result the consumer has had to bear the burdens associated with the device. However, with the " recent "  Broadcast demands for parity of tuning for UHF and VHF channels, the increasing number of UHF and cable TV stations have imposed new tuning performance requirements which severely tax the capability of the mechanical turret tuner. Consequently, attempts are now being made to provide all electronic tuning to meet the new requirements.

 One " " new " " tuning system currently being incorporated in some television receivers uses a varactor tuner which overcomes some of the disadvantages of mechanical turret tuner by accomplishing tuning electronically. As the name indicates, the heart of such a tuner is a varactor diode which is used as a capacitive tuning element in the RF and local oscillator sections. In this system, channel selection is made by applying a given reverse bias voltage to the varactor to change its electrical capacitance. The channel selection biasing can be performed by mechanically or electrically switching approximately 5 or many more preset potentiometers. The problem with such arrangement is that it quite seriously limits the number of channels available to the consumer. Additionally, it suffers from the drawback that all potentiometers require adjusting for the desired channels. The VHF channels are usually factory adjusted while the six UHF channels require on-location adjustment. Moreover, using this arrangement, the only indication--during adjustment--of which channel is selected is by station identification.

It has a Transistorized horizontal deflection circuits  made up of a horizontal switching or output transistor, a diode, one or more capacitors and a deflection winding. The output transistor, operating as a switch, is driven by a horizontal rate square wave signal and conducts during a portion of the horizontal trace interval. A diode, connected in parallel with the transistor, conducts during the remainder of the trace interval. A retrace capacitor and the deflection yoke winding are coupled in parallel across the transistor-diode combination. Energy is transferred into and out of the deflection winding via the diode and output transistor during the trace interval and via the retrace capacitor during the retrace interval.
In some television receivers, the collector of the horizontal output transistor is coupled to the B+ power supply through the primary windings of the high voltage transformer.

This set was featuring discrete picture quality even with a non excellent black level stabilization feedback, and was very reliable and almost  faultless.

Autor Comment about a A Need for Black level clamping on these tv..................

 As its name indicates the purpose of a black -level clamp is to hold the black level of a video signal at a constant level irrespective of changes in the content of the video signal. 
The problem arises when the video signal is a.c. coupled. A simple method of maintaining the black level of the signal with a.c. coupling is to use a d.c. restorer which clamps the sync pulse tips at a constant level, see Fig. I. A d.c. restorer thus holds the black level constant irrespective of changes in picture content but the black level will still vary with overall video signal amplitude. The answer to this is to clamp the black level itself so that it is held at a constant level irrespective of picture content and signal amplitude. 
Clamping is essential with colour receivers of course but this feature has been almost wholly absent from monochrome sets-it is simpler to use a.c. coupling and rely on the picture generally being at a mean level. In my view however the extra expense involved in adding a black -level clamp is well worthwhile: dark pictures look dark instead of like a bright and often streaky fog and the dark detail in bright pictures does not become lost in shadow. Furthermore the general contrast level for the same video drive is improved since once adjusted the brightness control is always at its optimum setting. These features also make the clamp very useful for DX -TV purposes since the brightness level can be set to the optimum level re- quired for photography, independent of the state of the received signal.

Circuit Principle:
The basic action of this clamp circuit is shown in Fig. 2: the heart of the circuit is transistor Q1. This transistor is non conducting during the line period and as the c.r.t. cathode is more negative than the black level DI is reversed biased. The c.r.t. is drawing current however so that Cl charges-the potential at its right- hand side as a result becoming steadily more positive there would be no current flow through CI. To ensure that CI can still charge and the black -level clamp operate under these conditions RI is required. The time -constant of RI, Cl must be shorter than the shortest time -constant in the preceding video stages. These are normally quite high anyway (around 100- 500mS). Now the clamp appears at first sight to have a time -constant of 500mS (C7, R17 in Fig. 3) but the aiming potential of C7 is the h.t. line at + 200V com- pared with a mean signal level of around + 30V to +60V. Thus the effective time -constant is more like 100mS. There is an advantage to be gained in having a short time -constant: if it is appreciably less than 20mS the clamp will effectively remove any mains hum on the video signal. Such hum does tend to be more noticeable when the picture is uniformly dark. A short time - constant also produces horizontal streaking on the picture if there is a ghost present however as the black level at the end of the line sync pulses has superimposed on it the displaced video signal of the ghost. Thus if the clamp has too short a time -constant it is able to follow these unwanted variations in black level. Note that as long as the time -constant Cl, RI (Fig. 2) is reasonably large compared with the line period CI will charge only a fraction of a volt during the line period. There will be no noticeable change in brightness from left to right across the picture therefore due to Cl charging. So much for the basic thinking behind the clamp circuit.



CREZAR was a little Italian manufacturer of cheap television sets and radios in the 70's.
Crezar
was a combination of " Crespi e Zaretti " - Milano -

Tv production defunct  at the end of the 70's !!



These were build in the way as here this tellye in collection shown is cheap & simple.

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