Quote:
Originally Posted by jhalphen
Hi David,
Wow! that is severe indeed, the first picture is really revealing.
Just a gut feeling, but i would say that the KV-4000 is not necessarily the culprit.
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It is definitely the TV - Both of my KV-4000's do it.
Quote:
Originally Posted by jhalphen
OK, let's talk about your video sources, the KV is being used as a monitor running from a DVD, correct?
You're using a baseband video signal not an RF channel 3-4 out from the DVD, correct?
I would switch sources: NTSC out from an ATSC box, cable box, a second DVD player. Does the banding occur on other sources?
Is the banding fixed, moving, linked to picture content?
Permanent or random?
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These pictures were taken from an over the air broadcast with the TV tuned to channel VHF 12. The signal was from my DVR - freeze framed during the broadcast - I stopped it on a very bad frame and a perfect frame for the pictures. The banding came and went according to the image on screen. If I looped a portion of the video - the exact image would be shown each time without variation. It also does it with a DVD player on the video input too.
Quote:
Originally Posted by jhalphen
Have an oscilloscope connected to the KV's video input simultaneously and set it up as a WFM display, look at the signal in both H and V scan rates, do the bands show up simultaneously on the Sony and the scope?
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I do not have a scope - I do not do that much work to need one. Not necessary though - see below explanation.
Quote:
Originally Posted by jhalphen
Have you tried the DVD player on another video monitor? - all OK?
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Yes - it is perfect on all the other sets in my collection.
Quote:
Originally Posted by jhalphen
When the banding occurs, if you turn down the Chroma to zero, is it still there?
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Color, Tint, Brightness, Picture controls have no effect.
Quote:
Originally Posted by jhalphen
Do you have an NTSC generator, have you tried it on the Sony?
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Do not have one. Not necessary though - see below explanation.
Quote:
Originally Posted by jhalphen
Try various signals with full black to white content: grey scale, convergence crosshatch. If the banding is related to luminance levels, video amp instability for instance, it could show up.
investigate silly causes: measure if there is a DC potential on the DVD's video out. One of mine did and it played havoc with my Broadcast routing switcher which is DC circuitry throughout. Inserting a big 470 Mfd Cap in the video feed solved the problem: crushed whites, smeary color & noise.
Keep us informed of the results of your tests.
Best Regards
jhalphen
Paris/France
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An accidental discovery:
The fact that these sets have a very large horizontal over-scan keeps bothering me. If you compare the same image on this set and a different model completely, you will see that the KV-4000 has a very stretched horizontal image - a lot is cut off on both sides. I keep thinking that the beam is getting reflected off the internal sides of the CRT.
I was previewing the TV guide built into my DVR to gauge the horizontal stretch. When the guide is displayed, the program content is reduced to a small window at the top right corner of the screen - I accidentally noticed that the image was perfect when it was reduced to this size. I watched 10 minutes of the program this way - no banding or flashing. I then rewound this same portion and watched it full screen - banding and flashing all over the place.
I am convinced that the problem will be eliminated if I can reduce the horizontal over-scan.