the apple..

[ceebee23]

has anyone ever seen the philco single gun "apple" tube ..did they ever get it working properly???

[Sandy G]

Apparently. Sez here that Philco made preproduction quantities of a 21" tube for evaluation around '56. While the results were technically satisfactory, the timing was wrong as the shadow mask tube was becoming well-entrenched & apparently Philco disbanded their efforts. Sony fooled around w/beam-index tubes in 1981 as well.-Sandy G.

[Steve McVoy]

Here is some information:

http://www.earlytelevision.org/apple_crt.html

[ChuckA]

I have been converting a large collection of "Apple" documentation that was acquired from a Philco engineer into PDF documents that can be downloaded from my web site:

http://www.myvintagetv.com/philco_apple_tube.htm

I have maybe 15% of the documentation converted so far.

To answer your question, Philco did produce 12 sample "Apple" sets for evaluation, but regretably they all were destroyed. Over the 10 years they worked on the project there were about 200 CRT's constructed, but none have surfaced. The documentation shows that quite a few were recycled as new procedures were found. With that many units produced I would think that at least one unit should come out.

One big benefit of the "Apple" tube was the increase in brightness due to the tube not using a shadow mask.

The earliest tube used vertical scanning, this was dropped very quickly as the technology to track the beam location and ability to produce the required phospher stripe quality was not available at the time, so they returned to the horizontal scan.

ChuckA

[wa2ise]

A big problem with an indexing color stripe scheme is that you can never have black in the image. If you did have a large black area in the image, you would lose track of which phosper stripe the beam is on at any given moment of time. When you exit the black area of the image, you wouldn't know what stripe the beam is currently on, and thus not know if you need R, G, or B at that point, to feed the electron gun.

So there is a minimum value of darkness, around 5% of peak white. Which makes the image look washed out.

This scheme would get rid of the convergence issue, and require less power for the very high voltage. But the minimum brightness problem, along with the shadow mask CRT already established, pretty much ended this.

[ChuckA]

Actually the "Apple" tube gun generated two beams, the main beam to "paint" the picture on the phosphor screen and the "index" beam. The phosphor layer contains the RGB stripes and also an index stripe laid over all red stripes. The index beam is modulated with a 7.4Mhz signal to mark it. The secondary emission from the index stripe is used to give a constant indication of the position of the writing beam.

In the Apple tube it didn't make any difference what color was shown on the screen, black or white, the system always knew where the beam was located.

There is a good report I have posted on the operation of the system here:

http://www.myvintagetv.com/Apple%20P...report_458.pdf


ChuckA

[ceebee23]

well perhaps this is more than I will ever need to know about the "Apple" ...I imagine quite a bit of the internals of any set using the Apple would have been different ....driving a quite different tube would have been a design challenge.

[andy]

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[wa2ise]

Looking at the block diagrams of that apple TV set, it seems that the level of complexity (and number of tubes likely needed) would be about the same as needed by convential shadow mask color TV sets. And you just end up trading the convergence problem with "the wrong color because some red signal hits the green or blue stripe" problem. Also you have to keep that 37ish MHz local oscillator and its harmonics out of the TV set's front end (tuner). Ever set a TV set right next to the computer? Shielding can get expensive.

And the risks involved in gearing something new for full production (what will bite us in the ass?) for something not likely to cost any less to manufacture probably made it a non starter.

[rca2000]

The projector is neat to watch in operation. on this tube, the beam is guided OPTICALLY, and there ia an index PHOSPOR, which glows green. You can see it looking at the BACK of the tube. I also have the manual.

My projector was a garbage find. the manual cost, I think, less than $10.00 . BTW, the electronics to guide the beam is mostly small scale digital ic's, on a baord about 5x7inches. It is pretty neat to watch in operation.

[andy]

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[rca2000]

It is possible that part of the 18 volt line is scan derived, and so, without the horizontal running, you may NOT see the full 18 volts.

On each side of my Crt, there is photodiode assembley, that picks up the index phospor, to tell the index circuitry where the beam is. In the manual, it says something to the nature, that the index phospor(the green glow at the back of the screen) starts several lines before the view phospor. this is so the circuitry knows where the beam begins, and ends. I will have to go back into my manual to find out more. It does describe the beam index principle, using photo-electrical guidance.

[andy]

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[andy]

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