Black brightess raises with just one small white spot - AVS Forum
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post #1 of 27 Old 04-17-2010, 03:32 AM - Thread Starter
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Hello, I just received my tv sent for repair (an lg 50ps8000, the european version of the ps80 but without ethernet) due to a brighter patch on the screen.

They replaced the panel but I'm not sure they calibrated it properly (difficult to demonstrate without a colorimeter, but the thx preset doesn't seem right compared to what I saw before).

Anyway, I found that the black level raises with only a small amount of white (or any other color). I know that a plasma screen would do that when there's a lot of bright spots, but not with only a small one, and I don't remember seeing it before.
I prepared a small test video here, that's just a black background with a small white square turning on and off.

While it doesn't happen with the video, I also noticed that sometimes the black level doesn't restore itself back to the "normal" level even with no white spots on the screen! (though it resets if I slowly put on the screen a white patch and take it back again).

Is it normal or does it actually point to a badly calibrated panel?
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post #2 of 27 Old 04-17-2010, 09:40 AM - Thread Starter
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Here is a video of the tv reproducing the test video (the red flashing dot is the reflection of the camera led, I forgot to turn it off).
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post #3 of 27 Old 04-17-2010, 10:47 AM
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A new Lg panel (at least in the USA) comes with all the boards except the power supply and main board which must be swapped from the old panel.

Power supply voltages should have been set to what is on the new panels sticker.

Y-sustain and z-sustain adjustments checked.

And if the shop had a meter, panel reference white balance should have been set.

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post #4 of 27 Old 04-17-2010, 10:58 AM
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Quote:
Originally Posted by olivluca View Post

Hello, I just received my tv sent for repair (an lg 50ps8000, the european version of the ps80 but without ethernet) due to a brighter patch on the screen.

They replaced the panel but I'm not sure they calibrated it properly (difficult to demonstrate without a colorimeter, but the thx preset doesn't seem right compared to what I saw before).

Anyway, I found that the black level raises with only a small amount of white (or any other color). I know that a plasma screen would do that when there's a lot of bright spots, but not with only a small one, and I don't remember seeing it before.
I prepared a small test video here, that's just a black background with a small white square turning on and off.

While it doesn't happen with the video, I also noticed that sometimes the black level doesn't restore itself back to the "normal" level even with no white spots on the screen! (though it resets if I slowly put on the screen a white patch and take it back again).

Is it normal or does it actually point to a badly calibrated panel?

It sounds that you got same irritating "feature" as some Panasonic have. Look in the picture menu and turn all the "picture feature" to "off". This seems like an back level "enhancer" of some sort.

On my pana, the only way to make this fluctuating stop, is to raise brightness above 50 percent or more.

I dont know if it is a feature or a fault. All that I know is that it destroys black level adjustements...
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post #5 of 27 Old 04-17-2010, 11:08 AM - Thread Starter
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Quote:
Originally Posted by poodlehead View Post

A new Lg panel (at least in the USA) comes with all the boards except the power supply and main board which must be swapped from the old panel.

Power supply voltages should have been set to what is on the new panels sticker.

So in principle the new panel could be a different model than the old one?


Quote:
Originally Posted by poodlehead View Post

Y-sustain and z-sustain adjustments checked.

And if the shop had a meter, panel reference white balance should have been set.

And what if they don't have a meter? And what about the THX preset, or by adjusting the white balance it sets itself to the right calibration?
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post #6 of 27 Old 04-17-2010, 11:15 AM - Thread Starter
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Quote:
Originally Posted by surap View Post

It sounds that you got same irritating "feature" as some Panasonic have. Look in the picture menu and turn all the "picture feature" to "off". This seems like an back level "enhancer" of some sort.

All the picture enhancements were turned off already (it was in thx mode and that turns off everything, you cannot even modify contrast/brightness).
I don't remember seeing the problem with the old panel, so I just think there's something wrong with the new one.
Note that I just prepared the test video as an easy way to showcase the problem, I originally saw it during the titles of a movie that I watched previously.
Maybe they didn't set the voltages properly or the panel is of inferior quality
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post #7 of 27 Old 04-17-2010, 11:22 AM - Thread Starter
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@poodlehead, if you have access to eic.lgservice.com could you check that part n. EAJ39979002 (that's what's on the invoice) is the right one for my set?
They also did a "GQI compensation report", is that the white balance adjustment?
The repair was done under warranty.
Thank you.
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post #8 of 27 Old 04-17-2010, 11:40 AM
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Quote:
Originally Posted by olivluca View Post

So in principle the new panel could be a different model than the old one?

Yes, the panel could be different than the old one. I have never seen them specify a replacement that had lower specifications than the original.


And what if they don't have a meter? And what about the THX preset, or by adjusting the white balance it sets itself to the right calibration?

There is no THX preset adjustment listed in the service manual. The service menu white balance is the reference for the set (it is calibrated to itself).

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post #9 of 27 Old 04-17-2010, 11:49 AM
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Quote:
Originally Posted by olivluca View Post

@poodlehead, if you have access to eic.lgservice.com could you check that part n. EAJ39979002 (that's what's on the invoice) is the right one for my set?
They also did a "GQI compensation report", is that the white balance adjustment?
The repair was done under warranty.
Thank you.

I can only access the USA site but they won't get paid for a warranty repair if it is the incorrect panel. So it's probably a safe bet that it is a correct panel.

Not sure what they mean "GQI compensation report". I would just call and tell them you think you have a problem and explain what you're seeing. They should have no problem explaining what they did on the panel swap out. And if the panel is bad you will want it replaced or call LG, after talking to the repair shop and see what they can do.

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post #10 of 27 Old 04-17-2010, 12:04 PM - Thread Starter
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Quote:
Originally Posted by poodlehead View Post

And if the panel is bad you will want it replaced or call LG, after talking to the repair shop and see what they can do.

That's what I intend to do, but before I'd like to check that I'm not seeing things that are not there.
My wife, which isn't fixated as I am on these issues (she actually told me not to have the previous issue fixed, maybe she was right), told me that she saw immediately that the picture is not right, though it's really difficult to explain what isn't right.
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post #11 of 27 Old 04-17-2010, 12:06 PM - Thread Starter
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One more thing: with the previous panel, using the picture wizard, the contrast was set around 80. With this one I have to set it to 97 to obtain the same picture.
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post #12 of 27 Old 04-17-2010, 01:05 PM
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Have you tried another picture-mode except for the one you have a video on? Maybe that one is the only one that have the fluctuating problem?
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post #13 of 27 Old 04-17-2010, 02:24 PM - Thread Starter
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Yes, I did
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post #14 of 27 Old 05-03-2010, 06:15 AM
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Hi, I have the same problem, and like me another Italian user.
I've see the problem after 5/6 months, and the first time I've call LG's Service they told me that is not a problem.
Now after 10 month I play your video test, and.. surprise:
the black don't change but now is costantly bright!!
Probably the same problem of Panasonic PDP ?
now my screen is about 0.22 cd/m2 black...

sorry for my bad English..
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post #15 of 27 Old 05-03-2010, 11:06 AM
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are you sure it isn't just the screen waking up? On an all black screen most plasmas dim the whole thing. The first stimulus then "wakes" the whole panel up returning it to it's working black level.
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post #16 of 27 Old 05-03-2010, 12:19 PM - Thread Starter
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No, I'm sure the old panel didn't do it, and there's some change in brightness even in dark scenes (i.e. not completely black).
I saw it just a couple of times, but it's irritating, since it seems it impairs the overall contrast of the image (it's duller than before).
Edit: and if I make the white dot half the size it doesn't happen, so it's not just the panel waking up.
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post #17 of 27 Old 05-04-2010, 01:37 AM
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I saw the problem in cloverfield, Memoirs of a Geisha (at the first minute of film) and wherever there was very dark scenes.
it cause a low contrast image (the black mesaure 0.22cd/m2 in the most time).
until a some day ago the problem was the same your.
Now in every scenes the black is grey...
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post #18 of 27 Old 05-04-2010, 03:38 PM - Thread Starter
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Well, the service centre told me to wait one month to see if the phosphors stabilize and if the problem persist to call them again.
I don't think it's the phosphors but I'll wait anyway.
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post #19 of 27 Old 05-08-2010, 02:15 AM - Thread Starter
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Quote:
Originally Posted by poodlehead View Post

I can only access the USA site but they won't get paid for a warranty repair if it is the incorrect panel. So it's probably a safe bet that it is a correct panel.

Nevertheless, could you check the part # for the 50ps80 and/or check if you have details about EAJ39979002 on the USA site?
TIA
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post #20 of 27 Old 05-17-2010, 09:19 AM
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LG service didn't see any problem.
the voltage is ok and the black for the service center is normal.
tomorrow they give me it back.
I'm not surprise...
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post #21 of 27 Old 05-17-2010, 10:15 AM - Thread Starter
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Wow, way to go, LG.
Sorry for the outcome of your tv, I fear mine will be the same
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post #22 of 27 Old 06-19-2010, 08:34 AM - Thread Starter
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Well, I got the final answer from LG: according to them the panel is perfectly fine.

I uploaded some videos to youtube so you can check for yourself what LG considers normal.

This is what happens with dark scenes (look around second 7, 15, 17, 18 and 22):



This is the test video I concocted to show the problem:



And this is how it shows on my LG 50PS8000



I can only suggest to stay away from LG plasmas: the odds of getting a defective panel are quite high, and they don't acknowledge those faults.
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post #23 of 27 Old 06-24-2010, 08:23 AM - Thread Starter
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Well, now LG says that the problem in the youtube video is with the original recording, since they tried in on a couple of led TVs and they can see the change of brightness. Unbelievable.
Here is the original recording so you can check it
http://www.megaupload.com/?d=BGBW33MF
You can play it with vlc (http://www.videolan.org/vlc/).

They also say that, since it isn't an original bluray or dvd, the file is surely faulty (obviously, according to them, the BBC doesn't know how to broadcast in HD).
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post #24 of 27 Old 06-24-2010, 09:49 AM
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post #25 of 27 Old 06-24-2010, 09:56 AM - Thread Starter
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Thanks, that will be probably my next step, though LG goes to great lengths to avoid publishing any email address, much less those of PR representatives.
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post #26 of 27 Old 06-25-2010, 03:15 AM - Thread Starter
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Mmh, I found the names of the top brass of LG Spain, unfortunately they don't follow any scheme in their email addresses (I saw firstname.lastname, flastname, fantasy names, etc.), so it will be quite difficult to launch an executive email carpet bomb.
Up to now I only found the email of the director of the consumer electronics division, maybe that's enough.
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post #27 of 27 Old 07-03-2010, 09:56 AM - Thread Starter
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Well, I managed to reproduce the problem with an original dvd (as they asked)



All the time they maintained that the problem was with the original recording, and that with an original blue ray (sic) or dvd it wouldn't happen.
Now that I have shown that it occurs with every source, they now sat that it's not a fault, they say that the panel cannot raise suddenly the brightness and power in an area without the phosphors being affected, as, for example, can do a led tv with local dimming, that's a completely different technology than plasma. (their words).

Except, it can, as the following video shows: it's showing a slide show of white square on a black background, with the square progressively bigger (5% of the screen, 10%, 15% and so on). When it shows the 10% square the background is perfectly black, showing that the panel can "raise the brightness in an area" without affecting the rest of the picture.



In spite of the evidence they don't acknowledge the problem and won't fix it.
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