Quote:
Originally Posted by Chris K
No sir I do not. I just know the basics of the production of a scanned black and white video image based on varying intensity of phosphor luminescence from the intensity and position of the electron beam at any one time on the CRT screen. Is that correct? This scanning from top to bottom horizontally goes back to the top of the screen and creates a new set of beam intensity driven fluorescent intensities on the phosphor...do enough of these scans over a second and you get the illusion of motion. Is that correct?
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The setting of a reference black in a display is a long discussion that is as old as television itself. It is the need to define a black in the display and maintain the black with changes in video content. DC coupling provides this and is the reason that the designers of this set we t to the trouble of providing DC coupling between stages. Notice there are no coupling capacitors between the stages which would block the passing of DC changes .
The video amplifier of this set maintains the black level very well by passing the DC component which sets the black reference. Another method employed by the RCA 630TS which preceded this set was the use of a DC Restorer. Note all modern displays employ black level clamping. Interestingly, thru the1950s and 1960s, sets dispensed with the DC clamping. This meant that the black level drifted upward in dark scenes and blacks were darker in a bright scene.
The topic of DC restoration or lack of in later sets is seen as a problem by many. Just be aware that the strange design of the set with the -120v DC supply and the stacked stages was to provide the proper consistent black reference that later sets did not have.
It is a topic well discussed in this forum.
https://www.videokarma.org/showthread.php?t=248278