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  #16  
Old 03-15-2009, 11:40 AM
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kx250rider kx250rider is offline
REAL TVs have TUBES!
 
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I agree on the precautionary re-capping... I'll refrain from turning it on until I recap it. I probably got lucky not to blow it up by powering it on the one time for the pictures... I'm glad I quit while still ahead!

And a note on the color fields... I can't explain it either, but also, when I took the photos, I had to take about 25 photos of the screen until I found one that had all 3 colors. Most were either one color, or two with a black band. I also can't hear the horizontal oscillator, which I can hear plainly on most other TVs. I found that strange too....

Charles
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  #17  
Old 03-19-2009, 11:31 PM
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It amazes me what these go for. Nice find by the way! You couldn't have found a nicer one. Is the leaking cap problem what makes them so rare? Or, did they not make many? Or both? I would love to have one but the price always scares me away. Maybe I'll get lucky at an estate sale or something.
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  #18  
Old 03-20-2009, 12:13 AM
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Probably both if you ask me, Mark. These had to be very pricey when they were new! Bet few people would shell over much coin for a portable back then.

Can't explain the technology employed in the set but what's interesting is that you can't hear the horizontal oscillator whine, Charles...Makes me think there's some type of unusual configuration used there which may just explain the unique technology of the tube (?)

Glad you got it, I'm sure it will be in good hands...
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  #19  
Old 03-20-2009, 06:47 AM
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Hello Charles,

Congratulations on the Indextron, & Welcome! to the club of Beam-Index CRT users.

I have the unobtainium full Indextron service manual and schematics. In your mailbox ASAP if you want it.

A few pictures:
- Dead caps, Andy's picture (Thanks!) all the purple ones leak
- Caps changed on ONE of my Indextrons, SAME quantity on unit #2.
- The Indextron CRT seen from the gun side. Note how simple the gun structure
appears.
- Rear view of the KVX-370, open.
- ONE Gun = PERFECT convergence! *

*see this pix & more here:

http://audiokarma.org/forums/showthread.php?t=120906

Best Regards

jhalphen
Paris/France

Last edited by jhalphen; 03-20-2009 at 06:51 AM.
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  #20  
Old 03-20-2009, 11:50 AM
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kx250rider kx250rider is offline
REAL TVs have TUBES!
 
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Thank you for the pics, Jerome! I haven't taken this one apart. But I just got a rock in my stomach: I remember seeing someone selling 2 Sony small tubes on eBay; of which was supposedly color, but I thought they were both 4" B&W tubes by the photo in the ad. Now looking at you pics, I know what the "color" one was an Indextron It sold for $9 new in the box.

Your photo of the leaky caps is encouraging... Not so many as I was imagining, and they're thru-hole!!!!! I pictured about 50 surface-mount caps to be replaced. I'll go at it sooner than later

Charles
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  #21  
Old 03-20-2009, 05:14 PM
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...

Last edited by andy; 12-06-2021 at 11:09 AM.
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  #22  
Old 03-23-2009, 06:23 AM
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Hi to All,

Charles: i sent you the complete Indextron service data yesterday.

Here is a drawing depicting the screen structure of a Beam-Index CRT. This is not the Sony Indextron, but a CRT using similar technology.

Best Regards

jhalphen
Paris/France
Attached Images
File Type: png Beam-Index CRT Screen Structure Detail-01.png (28.4 KB, 33 views)
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  #23  
Old 03-24-2009, 10:52 AM
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REAL TVs have TUBES!
 
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Thank you Jerome for those!!!! I received them, and will print them out. I especially liked being able to better-understand the indexed scan theory!

Charles
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  #24  
Old 03-26-2009, 12:19 AM
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Quote:
Originally Posted by Dave A View Post
To save some search time...the Indextron tube is a straight-line stripe from top to bottom with a black guard band in-between each stripe. No shadow mask or wire mask. Just a RGB switched color beam going to it's matching color stripe.

Black/Red/Black/Blue/Black/Green and so on. It knows where it is by sensing the green stripe from the rear of the tube.
One big problem with this scheme is that you could not allow the tube to have deep blacks in the picture. Else the indexing looses track of which stripe the electron beam will be hitting when the video image scans out of a black region in the picture. Thus a lower limit on darkness, and the picture looks washed out, kinda like older LCD displays where the LCD pixels couldn't block all of the backlight from getting thru in black areas of the picture.

It did get rid of that PITA convergence chore in manufacturing. Which would cut manufacturing costs.

The width of the stripes on your Indextron reminds me of the coarseness of some GE Portacolor CRTs.
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  #25  
Old 03-26-2009, 11:16 AM
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kx250rider kx250rider is offline
REAL TVs have TUBES!
 
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Quote:
Originally Posted by wa2ise View Post

The width of the stripes on your Indextron reminds me of the coarseness of some GE Portacolor CRTs.

You're not kidding!

Charles
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  #26  
Old 03-26-2009, 03:03 PM
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If the indextron tube is used with a OLCI or deep tinted glass faceplate, the black level issue can be resolved at the cost of overall intensity.
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  #27  
Old 03-26-2009, 08:48 PM
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Quote:
Originally Posted by colorfixer View Post
If the indextron tube is used with a OLCI or deep tinted glass faceplate, the black level issue can be resolved at the cost of overall intensity.
Actually, no -the minimum beam current is a certain fraction of the maximum, and that ratio sets the contrast ratio. Darkening the faceplate darkens both highlights and lowlights and keeps the ratio the same in this case. A dark faceplate does imrove poor contrast due to reflection of room light, since it darkens the reflected light twice (light going in and reflection coming back out), while darkening the highlights only once (light coming out).
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  #28  
Old 03-27-2009, 03:52 AM
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Quote:
Originally Posted by old_tv_nut View Post
Actually, no -the minimum beam current is a certain fraction of the maximum, and that ratio sets the contrast ratio. Darkening the faceplate darkens both highlights and lowlights and keeps the ratio the same in this case. A dark faceplate does imrove poor contrast due to reflection of room light, since it darkens the reflected light twice (light going in and reflection coming back out), while darkening the highlights only once (light coming out).

Where the issue is here is the Indextron needs a minimum amount of beam current to excite the index phosphor, to provide the feedback to the color switching circuit, keeping the timing in lock. This made the image appear as if the brightness was too high since it also illuminated the other phosphors as well.

In the very few industrial aviation indextron displays I saw, they placed OLCI glass in the front of the tube face to darken the background, since the high black level would be a nuisance to the pilots in the aircraft. This had the net effect of as you say cutting the maximum brightness, but the OLCI coating on the glass prevented the glare from sunlight from washing out the picture so it was a favorable tradeoff.

These little sets were really pricey when they were new. I remember it was a toss up between one of these, a 8" or a 19" at >$500.
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  #29  
Old 03-30-2009, 01:50 PM
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jhalphen jhalphen is offline
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Good Day, Gentlemen,

Genuine Sony KVX-370 Indextron screen pictures.

Judge for yourself the picture quality...

Courtesy John Folsom Jr (FLA), 2008 - Thank You! John

I have 3 IndexTrons, operating in Europe via NTSC --> PAL Standards Converter, i can confirm obtaining same pix quality.

Best Regards

* Some units repaired by Andy, TX, Thank You! Andy

jhalphen
Paris/France

Last edited by jhalphen; 03-30-2009 at 02:02 PM.
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