Re: Special Offer from Peter Keller to TekScopes Members: The Cathode Ray Tube, Technology, History, and Applications"

Dave Voorhis

On 16 Nov 2020, at 17:43, n4buq <> wrote:

Hi Tom,

My question is probably quite simple but, like I said, I'm not finding a good answer.

As I understand it (and from personal observation when I had a Trinitron TV and I'm primarily wondering about this type of CRT but the question probably applies to others), the screen has groupings of RBG phospher dots and the RGB guns "activate" those dots as needed; however, what I'm not understanding is how a given gun "activates" a given dot. Is a particular phosphor dot sensitive to a property of one of the color guns such that a blue dot ignores a red gun, etc.? If so, then I can somewhat understand it but I'm wondering if I'm way off in that assumption.

The various sites just seem to indicate there are three guns, each of which magically cause a given color to appear but it's not explained how a single color gun causes a corresponding dot to glow without affecting the ones around it.
The three beams are dynamically and statically aligned via a set of magnets and electromagnets arranged around the neck of the tube, in addition to the yoke coils that deflect the three beams together. The beams are aimed at a photo-etched perforated barrier called a shadow mask, which is either etched with holes (conventional colour CRT) or slots (Sony Trinitron) to further refine and align the beam. The combination of the static and dynamic deflection, plus the shadow mask, ensures that each colour gun only illuminates the relevant colour phosphor dots or bars on the face of the tube.

At least, that’s what I recall from about 40 years ago, which is when I last repaired colour televisions.

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