Sanyo 3" Beam Index Color TV - A picture at Last!

[Electronic M]

This is really cool. It kinda boggles my mind that we had this technology and it didn't become dominant in large screen sets before LCD/Plasma did.

[etype2]

Thank you gentlemen. I will try and use the video input so we can freeze the motion with a higher quality color image from a DVD and photograph it, hopefully better exposure’s.

Your comment about the set’s geometry, see diagrams below. Sanyo made an effort to correct keystone distortion.

https://visions4netjournal.com/wp-co...AA4853F38.jpeg

https://visions4netjournal.com/wp-co...3C846FBA9.jpeg

[Tube TV]

Wow congratulations on finding such a rare and very cool TV.

[etype2]

Here are the larger screenshots from the Sanyo Index 1. They are actual size if viewed on an iPad Pro 10.5 in portrait mode. Overall, the background has a green cast in all shots, some more than others. You can see the phosphor stripes have a finer pitch compared to the Sony KVX- 370. Because the photo diode reads UV light from from the index stripes, the minimum black level is 6 nits (same as Sony KVX-370) which hurts the contrast ratio. Nevertheless, a remarkable engineering achievement. A single electron beam scanning the raster at high speed landing on the proper color stripe without the aid of a shadow mask or aperture grill.

https://visions4netjournal.com/wp-co...08D09FBA1.jpeg

https://visions4netjournal.com/wp-co...27118D281.jpeg

https://visions4netjournal.com/wp-co...32C0A491A.jpeg

https://visions4netjournal.com/wp-co...3E416F0F4.jpeg

https://visions4netjournal.com/wp-co...9196234AD.jpeg

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https://visions4netjournal.com/wp-co...8D54DD72C.jpeg

[Dave A]

Great! I am wondering if the blue stripe could be a focus/purity setup indicator. Just a guess.

[old_coot88]

Looks like it might have a hard time rendering blacks. Sort of analogous to a tube set without DC restoration. Or maybe there's something in the setup adjustments for it.

[old_tv_nut]

Originally Posted by old_coot88

Looks like it might have a hard time rendering blacks. Sort of analogous to a tube set without DC restoration. Or maybe there's something in the setup adjustments for it.

Probably needs to maintain some minimum brightness so that the index stripes are lit even in black areas.

EDIT: See post #19, 6 nits minimum.

[old_tv_nut]

Originally Posted by Dave A

Great! I am wondering if the blue stripe could be a focus/purity setup indicator. Just a guess.

Puzzling - why not use a UV index stripe for that?

[Dave A]

Wayne, I thought about that. i'm not sure how a line tech could convert the UV stripe to set focus/purity, but a front facing stripe could help. Null it out until it is all blue. Maybe make it go away with a double button push? I am thinking of the factory line needing something faster. A full screen red display would be the best but time consuming needing a source via the A/V or so input. Still guessing.

[old_tv_nut]

Originally Posted by Dave A

Wayne, I thought about that. i'm not sure how a line tech could convert the UV stripe to set focus/purity, but a front facing stripe could help. Null it out until it is all blue. Maybe make it go away with a double button push? I am thinking of the factory line needing something faster. A full screen red display would be the best but time consuming needing a source via the A/V or so input. Still guessing.

Oh! I understand what you meant now. I wasn't thinking about a tech doing an adjustment, but some additional function of the feedback circuit in the set that tracks the index stripes.

As far as using an all-red screen, I can see doing that with the tracking circuit turned off, like zero-beating the subcarrier oscillator in a color set with the PLL disabled. They might also monitor the tracking circuit voltage with a scope, and zero-center it.

[jhalphen]

Hi to all,

@Etype2, Thanks! for the new screen closeup photos, what a remarkable device!

Finding a service manual:
the Index1's chassis # is A6V-TV100, more fun hunting in perspective, if it even exists...

The left screen vertical blue line:
See a page scan of the Theory of Operation of the RCA CKC-21 Beam-Index color viewfinder + detailed screen structure. To ensure correct RGB Color Sync sequence, the electronics must be informed of beam position at the beginning of each line and after each RGB triplet.
And of course at field Start & End.

The RCA VF uses an UV and green emission for the index sync.
The sensors are 2 front-mounted photocells, not an in-CRT side emission like the Sony Indextrons.

The RCA document is interesting because it delves into the inner workings of the Beam-Index operation. The Sony XKV manual shows just PCBs and schematics.

The Philco Apple tube used 2 guns, a low power "search" gun + the main beam.

Best Regards
jhalphen
Paris/France

[old_tv_nut]

Thanks, Jerome.

The RCA document shows UV reference phosphor twice per triplet, so there is a phase ambiguity that must be resolved. This might be done with the green component that occurs once per triplet, and could be augmented by a once-per-triplet UV reference at the beginning of the line. I wonder if the Sanyo blue line is something like that.

Another thing I have not seen explained is how beam index tubes obtain the correct white balance. The tube should be constructed such that it produces normal white if the beam current is constant (a monochrome gray level), but the phosphors do not generally have equal efficacy. So, do they modify the phosphor composition to get equal efficacy? Do they put a color filter in front of the tube? The RCA drawing shows green stripes wider than red and blue, which would make the picture greenish if not compensated in some way.

[etype2]

About the photography: With the Sony A6300, I could not eliminate the frame bar no matter what combination of shutter/fstop. So, used iPhone X with Hallide software to shoot in RAW. The color looks much better with the eyes. Capturing the color information is difficult. With a conventional set, you have three active color beams all “on”. With the Sanyo, you have one beam, so it’s hard to sync the shutter to capture “all” the color information. As I’m shooting, on the phone screen, I see the color dim and brighten, rapidly along with frame flipping, so we took multiple shots “at the right moment”. You may notice that two of the photos (from the Red Shoes) captured the skin color accurately. I got lucky with capturing the full color information. The shot of the ballerina with orange hair is dead on with the stage lighting used, but we have a significant contrast issue in all the shots because of the 6 nit minimum black level requirement. (Note, Sony got the black level issue resolved with their pro IDX-5000 monitor receiver).

I want to correct two misstatements I made earlier. The horizontal scanning is 47 degrees not 45 and the the index stripes are laid down at every forth RGB phosphor stripe like this.

https://visions4netjournal.com/wp-co...F8458826C.jpeg

About the blue line, the below snippet may apply from a tech article from IEEE which is licensed to me only, but if you are a member you can get the full article free. I wonder if the index phosphor formulation differs from Sony causing the blue light, but obviously they are not lit between the RGB stripes?

https://visions4netjournal.com/wp-co...796677277.jpeg

The RGB stripes are 0.21 mm and the beam width is 0.178 mm.

[old_tv_nut]

The velocity modulation explains how they increased the red brightness to get a reasonable white.

[jr_tech]

The blue line seems to be unique to this “flat crt” design, perhaps it is used for adjustment/dynamic control of the geometry correction scheme.

Does the Sanyo have a second photo detector that is sensitive to blue?

jr