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Old 17th Sep 2020, 5:23 pm   #1
DIY_Swede
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Default Sony KV-1300E: Incorrect colour decoding

With a sticky on the Sony non-PAL decoding (Amazing!) it certainly appears that I've found the right forum. Unfortunately, the sticky is a bit beyond my cognitive abilities.

Some ten years ago I happened to come across a supposedly working Sony KV-1300E. It has been sitting untested in my garage until recently, when I decided to hook up a Chromecast and use it for casting.

Now the problem:
The TV displays the completely wrong colours. When fed with a PM5544 image (from Youtube), the colours are interchanged with each other
When I remove and reconnect the antenna cable, it seems that it displays the (well, at least reasonably) correct colours for a fraction of a second.
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It then immediately switches over to the wrong colour set.
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Also, When I disconnect the antenna cable and hold it just next to the socket, it seems that the TV sometimes manages to decode the colours correct with a sufficiently weak/noisy signal.
This has prompted me to think that there may be some kind of synchronization issue.

What I've tried this far:
Obviously, fiddling with the colour knobs on the front and the colour adjustment screws on the back.
I have tried different sources (VHD player, VHS player, two different types of HDMI converters (cheap Chinese)) and they generate slightly different behavious, but they all result in completely incorrect colour decoding.
I have also tried different balus, different RF modulators, and capacitors in series with the antenna connection to to rule out any DC components on the input.

However, it does seem that something is indeed broken, and that I will have to start poking around inside in order to get this beauty up and running again.

I'm reasonably comfortable with replacing components in vintage audio gear and oscilloscopes, but in a PAL decoder, with no experience of TVs or PAL decoding, and little ability to understand the not-so-pedagogic schematic I have available, I really even don't even have a clue where to start.
Any advice on where to start looking (what boards, what components?) would be highly appreciated.
And yes, I know there are high voltages

Thanks.
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Old 18th Sep 2020, 10:01 am   #2
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Default Re: Sony KV-1300E: Incorrect colour decoding

You are asking a lot when feeding a TV designed to work from a technically perfect PAL encoder to display You Tube or for that matter a Chromecast or any device where a HDMI source is encoded using a $0.1 chip.

My experience when using a DVD player with an extenal RF modulator and an internally RF modulated DVB set top box is that the Sony non PAL decoder requires resetting for each source and, in the case of the DVB box, often needs the tint control to be adjusted on a programme or even scene change. The set top box is encoding a digital display which unlike the DVD player has no PAL encoding at all.

Before I got out the soldering iron, I would start with either a DVD player with a composite video out feeding a RF modulator or better still a Video Recorder. Both of which will produce an acceptable PAL encoded signal. I note that you mention using such but I'm unclear what the results were.

I would be very careful using trial and error repairs to the TV. The Sony Service Manual shows the waveforms expected when a PAL encoded colour bar is input and whilst obvious problems such as blown elelectrolytics or corroded legs on transistors have been mentioned on this site, I've never found the problem to be so obvious.

Chris

Last edited by simpsons; 18th Sep 2020 at 10:10 am.
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Old 18th Sep 2020, 12:22 pm   #3
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Default Re: Sony KV-1300E: Incorrect colour decoding

First question - let's see a black and white picture with the colour turned down. Only when that's perfect will you get any chance with a colour feed wherever it comes from.
This uses the PAL-NTSC decoder described in the sticky thread above which is understandably fussy when faced with a non-broadcast signal.
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Old 18th Sep 2020, 3:54 pm   #4
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Default Re: Sony KV-1300E: Incorrect colour decoding

I agree with WA here, "get it right in black and white" first.
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Old 18th Sep 2020, 5:41 pm   #5
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Default Re: Sony KV-1300E: Incorrect colour decoding

Yes the greyscale needs more green but there is clearly a decoding issue too.

I think the clue here is in the sticky, under the sub-heading "ident". Sony got their decoding scheme to work with a broadcast quality signal, beyond that, all bets are off.
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Old 18th Sep 2020, 5:56 pm   #6
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Default Re: Sony KV-1300E: Incorrect colour decoding

When I did my colour course way back (1970,s) on a Thorn 3000,we were told that if the black and white picture is off,then first things first sort that out.
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Old 18th Sep 2020, 10:46 pm   #7
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Default Re: Sony KV-1300E: Incorrect colour decoding

Quite right Hamish, it would help with the diagnosis to have the grayscale correct, as even the "correct" image in post #1 seems a bit too far removed from YCGMRB, to be right.
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Old 19th Sep 2020, 5:37 am   #8
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Default Re: Sony KV-1300E: Incorrect colour decoding

Everyone who has commented is correct so turn down the colour until a black and white screen and you can then adjust each colour adjustment pot until there is no overshading of that particular one leaving the blacks and white without any signs of any tint at all
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Old 21st Sep 2020, 10:11 pm   #9
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Default Re: Sony KV-1300E: Incorrect colour decoding

Thanks everyone for your suggestions.
I've now tried a somewhat more potent PAL source (Panasonic AG-7650 professional VCR), and managed to get the colours a lot more accurate, so it certainly seems that Chris is right on spot: It could be the PAL decoder just being too demanding on the PAL encoding quality of the source.
Here's a screenshot directly from Youtube:
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and here's the VCR playing the same scene, as good as I could adjust it on the Sony:
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I guess it would have been more useful to have a proper test image available on video tape (or even better, a PM5544 generator), but unfortunately I don't.
Colour tones are by no means perfect, but at least it's possible to get the "base" colours right, whereas when I ran the test image from Youtube via the HDMI->CVBS->RF chain (my first post above), the base colours seemed mutually swapped with each other, and were way beyond any adjustability range.
I will also test it in black and white, but that will need to be done using the conversion chain above since I have no other test pattern available, so I would guess the PAL colour coding of the end result anyhow can't be expected to be correct?

So, assuming that the TV actually works after all, if only the source is right, the next question is how to make it accept a less perfect signal, such as the composite video signal of a HDMI converter.
Perhaps it could slightly improve signal quality, and eliminate two potential sources of error, if I skipped the RF modulation and demodulation steps, and fed the composite video directly to to the right place on the TV tuner board. Would that be possible, and do you think it could improve my chances? Also my RF modulators are cheap Chinese stuff.
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Old 22nd Sep 2020, 9:57 am   #10
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Default Re: Sony KV-1300E: Incorrect colour decoding

Good to see that the TV is at least working and subject to the grey scale being correct displays a good colour picture from a known PAL encoded source.

I'm not sure just what you wish to use the TV for? As far as I know, unless you are prepared to purchase a PAL colour encoder, in my experience, adjusting the internal hue pre set VR303 will give you enough correction for each of the different inputs Chromecast etc. but you will most likely need to re adjust for other sources.

Also, the HDMI converter, again in my experience, when switched to NTSC, tricks the Sony decoder into giving the correct hue.

Should you make any adjustment to VR303, do make sure that you mark the original setting. It is quite critical. Oh. and that goes for where the user hue/tint control was before delving into the innards of the TV which remember, the chassis is live and connected to one side of the mains supply.
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Old 22nd Sep 2020, 10:33 am   #11
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Default Re: Sony KV-1300E: Incorrect colour decoding

To answer your question in post #9, turning the colour control down on the TV should kill the chroma completely, leaving the black and white luminance signal. That will enable you to set up the greyscale as best you can. If the CRT's good - and it's a big if - you should see a marked improvement in the decoded colour signal when you turn the control back up. Only when the set displays a good black and white picture is it worth going anywhere near the decoder presets.
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Old 22nd Sep 2020, 4:17 pm   #12
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Default Re: Sony KV-1300E: Incorrect colour decoding

Adjusting the grey scale is not difficult. On the Sony turn the background controls Red, green & blue shown BKG to their mid position. Leave red alone and adjust blue & green to get a neutral black and white image.

You will find it easier to use a SMPTE colour bar pattern, turning the colour control off and when reducing the brightness and contrast minimise the prominent colour in the darker part of the colour pattern.

Should the image still be too red, reduce the red background as should the green or blue gun emission be poor, then red will be too strong and start again.

Look for suggestions on this and other sites on how to do this if unsure.

Chris
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Old 23rd Sep 2020, 5:55 pm   #13
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Default Re: Sony KV-1300E: Incorrect colour decoding

Thanks again for your suggestions and advice.
Yesterday I did a reasonably successful colour adjustment (using the VCR as source) and managed to obtain a more or less completely B&W picture, which would indicate a healthy picture tube if I've understood it correctly:
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However, I got it with the red screw turned almost all the way down. It seems to me that I have a somewhat weak brightness, which I've compensated for by setting the contrast knob at max. I will try the B&W adjustment again, and aim to get a balanced grayscale with all colour adjustment screws at a more generous setting. Based on the assumption that it could at least slightly help up brightness, but perhaps that's wrong.
Anyhow, here's a photo of the colours after the B&W adjustment:
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They do seem correct, hue-wise, compared to the Youtube screenshot:
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Enter the HDMI converter:
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Roughly, red turns green, green turns red, and blue remains blue.
If I disconnect the RF cable, and allow it to just barely touch the RF output connector of the RF modulator, the TV is able to decode the colours correctly:
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So there's something in the output signal from the HDMI-> PAL conversion which confuses the colour decoding. I will certainly try your suggestion with VR303, Chris.
It would also be attractive to be able to bypass the RF modulation and demodulation steps. Is there any obvious position on the board where I could hook up a baseband signal?

What to use it for? Well, I guess learning at least something about CRT and analog TV along the way is reason enough. And if the alternative is to use it for nothing, and return it to the dusty corner where it came from...
And with an HDMI input, I could use it for Chromecasting, Rasperry Pi and other modern sources, but with that good CRT-and-wood-cabinet feeling.

One more thing, Chris, with regard to your comment on NTSC: The TV does not respond correctly when I switch the HDMI converter to NTSC either. Please note, though, that this is a KV-1300E. I've read somewhere that Sony for patent reasons implemented their PAL encoding differently in the UK models than in the models aimed for the Nordic market; perhaps that could be an explanation.
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Old 23rd Sep 2020, 8:08 pm   #14
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Default Re: Sony KV-1300E: Incorrect colour decoding

The black and white image is a great improvement on the original.

Now, the reason why red was chosen to be the reference colour is that it important to leave one background colour fixed while adjusting the others.

From what you are saying, by reducing the red background to give a b&w picture the brightness is now too low.

OK. What I would do is to see which colour gun is weak and to do this, with the set showing a still picture, the test card for example, is to first adjust the brightness to mid point.

Turn anti clockwise, that is to the minimum, each background colour. The screen should show no image.

Adjust each background control in turn noting when the picture becomes visible. The background control which needs to be advanced most is the weak colour gun.

Set the week colour gun background control to halfway between mechanical central and the max position. This now becomes your reference colour.

Set the other 2 to midpoint and go from there and this should do the trick.

As for the NTSC setting, it could just be down to the HDMI converter I had which cost 5 Euros.

By passing the RF section of the TV, which is quite involved and requires an mains isolation transformer, will have NO effect on the Sony PAL decoder performance.

Chris

Last edited by simpsons; 23rd Sep 2020 at 8:14 pm.
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Old 24th Sep 2020, 5:56 pm   #15
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Default Re: Sony KV-1300E: Incorrect colour decoding

That's a pretty good picture for a KV1300! Your CRT has certainly got some life in it.
I agree with Chris - there's little point in trying to inject video into the TV. Sony did make a version that accepted baseband video and audio (I think the 1300 already has an isolation transformer, but it could be an autotransformer) but they are rare and complicated. I'd try a different HDMI converter or else a different way of conversion. After all, HD isn't exactly an issue here.
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Old 25th Sep 2020, 9:46 am   #16
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Default Re: Sony KV-1300E: Incorrect colour decoding

Thank you both.
Sometimes, a few words of discouragement may be the best advice. I'll drop all thoughts of bypassing RF.
Bringing up the brightness following the suggested procedure was no problem at all, and there seems to be plenty of headroom remaining for further CRT deterioration.
Here's the same scene with increased brightness and more moderate contrast.
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Next step will be to try the hue adjustment on VR303 to see if I can get a decent HDMI picture, but it will be a few days before I will be in a position to try that out.
If it works out well I might consider replacing VR303 with another trim pot on the back panel, to enable accommodating for different sources on the fly.
/Ola
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Old 25th Sep 2020, 3:18 pm   #17
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Default Re: Sony KV-1300E: Incorrect colour decoding

Hi DIY Swede

I've compared the last Shere Khan screen shot with the first one you posted and they are so close that I wonder if this wasn't a duplicate image or the grey scale isn't still a little out.

Any chance of the PM5544 test card image again in colour and monochrome?

Which was the low output gun? I ask this because when bright images are needed, although the grey scale will be ok'ish, highlights will not and especially high contrast images will be tinted or just the wrong hue.

Also, may I suggest for the existing picture increasing the contrast control as the picture is a little washed out, increasing colour - "colour intensity" as Shere Khan is a little pale- lastly, the user hue control to match the orange brown of his coat and see how you get on.

I say this because unintended errors will be really hard to put right should you delve straight into the preset hue control and you may then never get it right.

Chris

Last edited by simpsons; 25th Sep 2020 at 3:27 pm.
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Old 2nd Oct 2020, 8:26 am   #18
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Default Re: Sony KV-1300E: Incorrect colour decoding

So, Ive now spent some more time trying to figure out whats going on.
A few more observations:

The red gun was not possible to turn down to a completely black picture. When I set all guns at the minimum, I still got a red picture. Hence, I turned the red gun up about half-way, and did the adjustments of green and blue from there, which put me in the upper part of the adjustment range for those (albeit with a lot of headroom remaining). Im quite satisfied with the picture when feeding the TV with a signal from the VCR, as illustrated by the latest photos of that source (previous post).
Here's a test image in B&W fed from the out-of-hue HDMI converter:
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There is a slight purplish tint towards the right-hand side, particularly in the bottom-right corner. Would this be likely to be an adjustment issue or a degaussing issue? I do have a tone head demagnetizer available, but Im not sure whether I would risk damaging the shadow mask if I try to use it on the CRT?

I found out that if I switched the HDMI-to-composite converter to NTSC output (resulting in some kind of rainbow coloring of the picture), a hue adjustment option became available in the converters menu. By stepping through all possible values in increments in NTSC output mode, and for each setting checking the picture in PAL output mode, I managed to get a reasonably proper hue on the TV using the signal from the HDMI converter, and also managed to take this photo:
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However, after a minute or so, the hue jumped out of phase again.
By repeatedly flipping between NTSC and PAL mode, I could make the hue sync again, and then shortly thereafter it would jump out of phase again. While I did this a number of times, it also became increasingly difficult to trigger the correct hue until finally, I was again completely unable to obtain the right hue. It was as if something was heating up, or charging up, until the TV could no longer sync properly with the colour burst. Ive twice tried to let it rest over the night, which is of course enough to make it cool down, but not necessarily uncharge. Each time I could again get a correct hue, but for a much shorter period (a few seconds) before jumping back. This suggests that there could be something that gets charged up, and somehow limits the hue syncing ability. It still remains to be found out whether this is a TV issue or a source issue - at least, I always get a correct hue from the VCR. Yesterday I also found my old ZX Spectrum, and connected it to see how the TV would respond to yet another source, but so far I havent loaded any graphics, and the white start screen does not give too much information.

I also tried feeding the TV with crosshatch patterns from Youtube (via the HDMI converter), and got the following pictures:
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(long shutter time, to average out any scan-rate phenomena)
Due to posting limitations I will post close-ups in the next post.
There is some divergence between the colours along the edges, and in particular, the right edge of the screen. However, I'm uncertain whether those minor convergence issues would be rectifyable, or if they should be regarded as good-enough, considering the age and generation of the TV.
There are also some geometric distortions along the edges, so at least I will take a look if there is any convergence strip that on the face of it looks displaced.

In any event, I will refrain from messing up the internal hue control until Im satisfied with the picture.
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Old 2nd Oct 2020, 12:49 pm   #19
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Default Re: Sony KV-1300E: Incorrect colour decoding

Top left:
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Bottom right:
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Centre:
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