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


Harvey White
 

The guns are indeed the same.  The electrons are the same. However, the shadow mask is the key.  The guns are in a triangle. If each gun were aimed at the exact surface of the screen, then each beam would hit the same spot.  However, the actual point where the beams are focused is a little inside where the phosphor is, so the three beams would cross, and then diverge.  Think three chopsticks making a very small triangle, crossing, and then diverging to the guns.

If you put a mask (with a hole in it at exactly the intersection of the three beams, they get narrowed.  The beam coming through the shadow mask hits a different color phosphor depending on which gun sends out the beam.

It's all in the angles.

Harvey

On 11/16/2020 3:56 PM, n4buq wrote:
Hi Dennis,

I had been to that page yesterday and I didn't quite understand some of it. Particularly, the following image wasn't helping that much.

https://en.wikipedia.org/wiki/Cathode-ray_tube#/media/File:CRT_color_enhanced.png

The reason being that they "paint" the color guns as if they're somehow controlling what color the phosphor will be when, in fact, that was just for clarification to show that the "red" gun was being aimed (through the hole in the mask) at the red phosphor, the "blue" gun at the blue phosphor, and the "green" gun at the green phosphor. The guns are all the same and it is only the phosphor that's different and that was what I was wondering. Perhaps a silly question but it was confusing me nonetheless. I understand it now (actually, Tom Lee helped explain it via a PM).

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <dennis@ridesoft.com>
To: TekScopes@groups.io
Sent: Monday, November 16, 2020 2:38:24 PM
Subject: Re: [TekScopes] Special Offer from Peter Keller to TekScopes Members: The Cathode Ray Tube, Technology,
History, and Applications"

Hi Barry,
As with so many things there is an excellent explanation on Wikipedia of
shadow mask and Trinitron tubes and how they work. It is at
https://en.wikipedia.org/wiki/Cathode-ray_tube.
Scroll down to the section I am referring to. No magic is involved, just a
shadow mask.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of n4buq
Sent: Monday, November 16, 2020 9:43 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Special Offer from Peter Keller to TekScopes
Members: The Cathode Ray Tube, Technology, History, and Applications"

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.

(Hope that made sense...)

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: Monday, November 16, 2020 11:27:46 AM
Subject: Re: [TekScopes] Special Offer from Peter Keller to TekScopes
Members: The Cathode Ray Tube, Technology, History, and Applications"

Hi Barry,

Pete's book mainly covers electrostatically deflected crts. Except for
some very early models, TVs used magnetically deflected crts (to allow
large screens without absurd set depths). The guns are similar, but
the deflection methods are very different because of the different
optimization objectives.

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 11/16/2020 07:18, n4buq wrote:
Does anyone know whether this book covers CRTs that were used for
color TVs (and other color displays)? I ask because I'm not finding
good information on how those work.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <dennis@ridesoft.com>
To: TekScopes@groups.io
Sent: Monday, November 16, 2020 12:15:11 AM
Subject: Re: [TekScopes] Special Offer from Peter Keller to
TekScopes
Members: The Cathode Ray Tube, Technology, History, and
Applications"

Hi Chris,
I don't expect any problems shipping this to Germany.

One correction:
This offer is strictly between Peter Keller and individual members
of the group. I did offer to act as the go-between because I
thought there might be some interest and because I understood how
"sensitive" our members are to price. I was also hoping this would
give Peter some well-deserved cash as we get close to the holidays.

So I told Peter I thought I might be able to pass along 10 orders
for his book. When he said OK I notified TekScopes. That was 36
hours ago. I have orders for over 50 of his books as of this moment.

This brings back memories of when I asked for small donations to
pay Groups.io the annual fee for hosting TekScopes back at the
beginning of the year. Somebody please remind me the next time I
think up something like this to think twice about what happened the
last two times I had a bright idea.
:)

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
ChrisBeee via groups.io
Sent: Sunday, November 15, 2020 8:47 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Special Offer from Peter Keller to
TekScopes
Members: The Cathode Ray Tube, Technology, History, and Applications"

Hi Dennis,
I would be more than glad if I could support the group buy and get
a copy of Peter's book, many thanks for making this possible! My
only concern is if you would ship to Germany too. I will send you a
PM with my contact data.
Cheers
Chris







--
Dennis Tillman W7pF
TekScopes Moderator















--
Dennis Tillman W7pF
TekScopes Moderator







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