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LG Plasma Panel tweaks for better blacks. - Page 2

post #31 of 1329
11/13/11 at 1:58pm
I don't have the Service Manual of my TV but I found an old manual for a Samsung PDP from 2007.
It mentions Vs, Va, Ve, Vsc voltges on the SMPS (power supply) board and Vb, Vbf on X and Y boards (it says you shouldn't touch these latter two and you should adjust the SMPS-Main voltages according to the printed label inside the TV). And it shows this nice graph -> see the attachment

I couldn't really recognise the pots on the small pictures of the borads. But I wonder if they are still there on D-series PDPs and they can be used just like with these LGs.
LL
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post #32 of 1329
11/13/11 at 2:20pm
I asked in the D7000-thread but it seems nobody cares.

So, I searched already but couldn't find the service manual for D7000 and D8000 but if someone did, it would be cool! Please post it then.
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post #33 of 1329
11/13/11 at 3:23pm
Cool thread!! I am not a service tech and I don’t know the LG driving system but I have a little knowledge on PDP waveforms in general. Just wondering, do you guys know what portion of the waveform does what and for what purpose? It looks a lot like the Panasonic waveform which I know a little.

Cheers
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post #34 of 1329
11/13/11 at 3:52pm
@xrox

Do you know if the amount of light generated by the first sub-field is significantly affected by the initialization or not?

I mean... you may tune down the MLL but keep the brightness of the lowest possible dark shade as the thresholds for the spatial/temporal dithering was optimized for the factory default MLL and first sub-field combination. This could mean some black-crush.

I already have some black-crush on my Samsung when I calibrate it to gamma 2.4 because the darkest possible shades correspond to level ~21. So what if I could tune down the MLL significantly? If the first sub-field remains the same, it could mean crush between level 16 and 28??? May be too much...
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post #35 of 1329
11/13/11 at 4:35pm
Quote:
Originally Posted by janos666 View Post

@xrox

Do you know if the amount of light generated by the first sub-field is significantly affected by the initialization or not?

Do you mean:

1 - The MLL light output impacting the 1st subfield light output (i.e. - MLL(low)+1st subfield being very different from MLL(high)+first subfield?)

or

2 - Changes to the MLL waveform and discharge impacting the 1st subfield waveform and discharge?



If #2 I'd have to see the entire waveform for several subfields.
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post #36 of 1329
11/13/11 at 5:11pm
Quote:
Originally Posted by xrox View Post

1 - The MLL light output impacting the 1st subfield light output (i.e. - MLL(low)+1st subfield being very different from MLL(high)+first subfield?)

2 - Changes to the MLL waveform and discharge impacting the 1st subfield waveform and discharge?

1 mainly, but now that you say 2 would be also good to know.

I am concerned about the "gap" between the MLL and the first sub-field's light outputs because I am neither a black-crush or dither noise fan.
When I read your "Kuro tech explained" I liked the idea of the '14 sub-fields with very low light first' very much. And I would be terrified if I had to place the darkest possible non-MLL shade of my Samsung D-Seres PDP on a gamma curve starting from something like 0.012 cd/m^2 MLL (if the light out of the first sub-field doesn't follow the change linearly or drop even faster - the latter would also be an improvement alone...).
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post #37 of 1329
11/13/11 at 5:41pm
Quote:
Originally Posted by janos666 View Post

I am concerned about the "gap" between the MLL and the first sub-field's light outputs because I am neither a black-crush or dither noise fan.

A valid concern. Pioneer publically has stated (through science journals) that they had the same concerns as you when developing KURO. The larger the gap between the MLL and the 1st subfield the more visible the dither. On the other hand if the MLL is too high AND too close to the 1st subfield then black crush. Ideally the MLL must be very low AND the 1st subfield optimized.

Quote from Pioneer scientists "Decreasing black luminance poses another issue of deteriorations of picture quality particularly at dark scenes because the luminance gap between black and LSB-SF increases. This increased luminance gap causes the noisy dithering or error diffusion picture. Therefore it is very important to reduce the luminance of LSB-SF."

LSB=least significant bit
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post #38 of 1329
11/13/11 at 7:18pm
I completed the adjustments on my PK550 as outlined in this thread. I have watched scenes from different movies, some football, let the set cool off and re-started it.

I can say this:

WOW!!!!!!

What a difference! The picture just pops off the screen! The space scenes at the beginning of Avatar are JAW DROPPING! Watching scenes from Batman Begins (which is a 'dark' movie) take on a new look. Letterbox bars now look closer to the color of the bezel.

Now, I doubt this is close to Kuro blacks (and we know that there is much more to great black level than just adjusting a few pots), but I feel confident in saying that this makes LG plasma's VERY competitive to the other makers in regards to MLL. Also, I am viewing in a light controlled room and my set has been fully calibrated with an i-one display meter/color HFCR so YMMV. (I plan on treating myself this Christmas to the new i-one display 3 meter. I am really looking forward to viewing the picture after that calibration).

All in all, I am extremely pleased with the picture now. Well worth the time in doing this! A big THANKS to all who brought this to the forum!!
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post #39 of 1329
11/13/11 at 8:14pm
Quote:
Originally Posted by keyoctave View Post

I completed the adjustments on my PK550 as outlined in this thread. I have watched scenes from different movies, some football, let the set cool off and re-started it.

I can say this:

WOW!!!!!!

What a difference! The picture just pops off the screen! The space scenes at the beginning of Avatar are JAW DROPPING! Watching scenes from Batman Begins (which is a 'dark' movie) take on a new look. Letterbox bars now look closer to the color of the bezel.

......

All in all, I am extremely pleased with the picture now. Well worth the time in doing this! A big THANKS to all who brought this to the forum!!

I am very close to addressing this same issue as it has been a concern since I purchased my 50PV450. While I'm satisfied with the natural color and the results of a professional calibration, the grey aspect of muddled backgrounds and limited contrast has been frustrating.

Keyoctave would you mind sharing the adjustments you made and the order you made them in (I'm wondering how much the order matters)? It seems like a fairly straightforward procedure, but there's been slight variation of adjustments mentioned on the threads. It sounds to me from your explanation and results that you took the right path.

Thanks to Turrican for getting others involved from your research and application months ago. This may become a prerequisite or at least part of a comprehensive calibration for these sets moving forward.
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post #40 of 1329
11/14/11 at 10:21am
Thread Starter 
Thanks for the input guys,

I'd be interested if any of those who have done the adjustments have actually checked the panel by using even a basic calibration disc like DVE (Digital Video Essentials) or a Spears/Munsil Disc to see if a recalibration is in order.
Also has the timing of the pixel firing affected motion blur or other artifacts, which might not be obvious while being distracted by the better black levels?
Not to be critical, as I'm excited about this as most, but it appears that those who have jumped on the band-wagon, while reporting a better MLLs have not really given us any further information regarding the whole picture gauntlet in any detail.
Reason I bring this up is that IMHO the LG aside from the black levels produce one of the best and most natural color of all the current plasma displays and the reason I personally chose LG over the competition, mind you my blacks are pretty good and close to my brothers Panasonic ST30 so of course I'm curious like everyone else to see how low it can go.
So if indeed nothing else is affected by squeezing out better black levels, such as a shift in gamma, color & grey scale then I guess I should be getting my screwdriver out, that is as soon as I can get help taking the PX down off the wall.
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post #41 of 1329
11/14/11 at 10:28am
Quote:
Originally Posted by Jimdish255 View Post

Thanks to Turrican for getting others involved from your research and application months ago. This may become a prerequisite or at least part of a comprehensive calibration for these sets moving forward.

You're welcome.
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post #42 of 1329
11/14/11 at 10:34am
Quote:
Originally Posted by xrox View Post

A valid concern. Pioneer publically has stated (through science journals) that they had the same concerns as you when developing KURO. The larger the gap between the MLL and the 1st subfield the more visible the dither. On the other hand if the MLL is too high AND too close to the 1st subfield then black crush.

Yes, I know both situations.

After the first voltagebump on my PK350 the darkest shades were consumed by the fog of "black" (what wasn't black).

After the adjusment, the dtail near black is very good to see, but the biggest weakness of LG pdp is more visible than ever: very clumpy noise patterns in the grey shades near black.

Also, the pwm noise bug is more obvious (the shades up to IRE6 don't reach the panel edges left, right and upside!).

I hope, the pwm noise bug will be addressed in the 2012 plasmas from LG.
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post #43 of 1329
11/14/11 at 12:48pm
CalWldLif,
My post on the 850U is in the "Panasonic black levels rising overnight?" thread. Maybe May of 2010. All details are there. Katzman
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post #44 of 1329
11/14/11 at 12:54pm
Quote:
Originally Posted by Turrican4D View Post

After the adjusment, the dtail near black is very good to see, but the biggest weakness of LG pdp is more visible than ever: very clumpy noise patterns in the grey shades near black.

Also, the pwm noise bug is more obvious (the shades up to IRE6 don't reach the panel edges left, right and upside!).

I hope, the pwm noise bug will be addressed in the 2012 plasmas from LG.

Dropping the initialization waveform is probably increasing the discharge delay and reducing the discharge probability. This will cause address failure and unwanted pixel firing and misfiring everywhere (most probably in low level shades).

LG has produced a zero black PDP in the lab but this PDP produced too much unstable pixel behaviour.
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post #45 of 1329
11/14/11 at 2:13pm
Thread Starter 
Here are a few Blu-ray shots and the last being from a HD broadcast on my stock PX950 , not too sure how much I’ll gain with adjusting the pots.
SD and HD broadcast as well as BD look great, the only few times I felt the blacks could be better is when streaming Netflix films from the Apple TV, Podcasts and everything else look fine.
As I mentioned elsewhere the bars when viewing letter box are pretty dark and with brighter scenes and full screen the picture is about perfect.
(Shot with a Canon Powershot G10 ASA 200 f.3.8 on a tripod, no further processing involved)









HD broadcast
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post #46 of 1329
11/14/11 at 2:35pm
Quote:
Originally Posted by Jimdish255 View Post

.

Keyoctave would you mind sharing the adjustments you made and the order you made them in (I'm wondering how much the order matters)? It seems like a fairly straightforward procedure, but there's been slight variation of adjustments mentioned on the threads. It sounds to me from your explanation and results that you took the right path.

I first put a color bar pattern on the screen. I tweeked the Set_up clockwise as far as it would go. I then tweeked the Vy just a hair counter clockwise. I switched to a screen pattern with black background for a minuite then switched back to the color bars. It was then that I had screen artifacts (black dots in the darker colors). I backed off the Set_up (turned counter clockwise) till they dissapeared then repeated the process of switching between screens, turning the Set-up clockwise till I had the the Set_up as far as it would go without inducing any artifacts. An all white screen was fine.

What was interesting was as I turned the Set_up pot clockwise and watched the black area that surrounds the Pluge adjustment in the color bar screen is, I could see the dark area go from dark grey to more black or back to dark grey as I turned it clockwise or counter clockwise. It is subtle when up close but as you step back away from the screen, you really notice the difference.

I did not do a check with my colormeter as I am planning to upgrade in the next month. I did have to reset the brightness up some (using the Pluge adjustment) but that was it. Off hand, I did not notice any other changes to the overall color balance.
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post #47 of 1329
11/14/11 at 2:40pm
Quote:
Originally Posted by Turrican4D View Post

After the adjusment, the dtail near black is very good to see, but the biggest weakness of LG pdp is more visible than ever: very clumpy noise patterns in the grey shades near black.

I noticed them as well. At least you don't see them when you are farther away from the screen (or I don't anyway).

Thank you for sharing this tweek with us. It has made a most noticable difference and increased my viewing enjoyment!
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post #48 of 1329
11/14/11 at 3:09pm
Quote:
Originally Posted by Turrican4D View Post

0.012 cd/m2 ANSI with PK350 aka 10000:1 contrast

Is this for real, UK poster here can this be done on any LG set?
And maybe I'm misreading but surely if LG could produce decent blacks by doing this then why haven't they?
They keep getting panned for not doing so, I just don't get it
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post #49 of 1329
11/14/11 at 4:16pm
Thread Starter 
Quote:
Originally Posted by leedebs View Post

Is this for real, UK poster here can this be done on any LG set?
And maybe I'm misreading but surely if LG could produce decent blacks by doing this then why haven't they?
They keep getting panned for not doing so, I just don't get it

Shouldn't be a problem although you're dealing with a higher (lethal) voltage before the power supply, but the DC at the Sus-Board where most of the adjustments are would be the same.
I believe Turrican has it about right.

Quote:
Originally Posted by Turrican4D View Post

0.00357 ftl


EDIT: The main reason, why LG throw so much room for good MLL away is the way, the power supply works after a cold start of the set. Depending on room temperature it takes the power supply up to two minutes to reach full throttle.

So LG goes the safe way to avoid pixel missfires after a cold start.
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post #50 of 1329
11/15/11 at 4:03am
Quote:
Originally Posted by rob80b View Post

Shouldn't be a problem although you're dealing with a higher (lethal) voltage before the power supply, but the DC at the Sus-Board where most of the adjustments are would be the same.
I believe Turrican has it about right.


Thanks, may give it a whirl when the sets out of warranty
Is the lowest mll obtainable with the LG pot tweak better than Panasonics though?
I mean 0.012 cd/m2 is better than a GT30 isn't it?
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post #51 of 1329
11/15/11 at 6:01am
Yes, but can you also tweak the Panasonics (or Samsungs or even the 9G Kuros - as much as I know, some Kuros have black level adjustment in the user menu...)?
And what about the near-black color precision after this tweaking....?
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post #52 of 1329
11/15/11 at 9:09am
Panasonic has no pots anymore, so you can't tweak them.

Back in 2009 on the S1 it was possible to tweak is just a little bit, but not much, cause otherwise, the set would shut itself off.
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post #53 of 1329
11/15/11 at 9:28am
So I have my new LG plasma on the way and was thinking about doing this out of the box with the great result that most have been getting.

I just had one question has anyone ever noticed any long term effects of doing this to their TV. I don't want to shorten my TV's life span by tweaking something. It just seems odd to me because if this produces such great black levels why wouldn't the factory do right away.

I am sure if they did they would sell more TV's with the black levels some are getting.

it just seems so odd to me that this is possible and they don't take advantage of it so I am thinking there may be some long term effects.
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post #54 of 1329
11/15/11 at 10:20am
There is a variation in methods that has been discussed on the threads that maybe someone can clarify.

One school of thought suggests adjusting VA, VY and Set-UP then possibly Set-Dn.

Another poster referred to Set_Up and VS only.
http://www.avsforum.com/avs-vb/showt...8#post21185708

Is there a choice between the 2 methods or could/should VS (a tick counterclockwise) be considered additionally to what seems to be the consensus of the first method?
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post #55 of 1329
11/15/11 at 10:29am
Quote:
Originally Posted by leedebs View Post

And maybe I'm misreading but surely if LG could produce decent blacks by doing this then why haven't they?
They keep getting panned for not doing so, I just don't get it

I think Turrican4D summed it up pretty well in post #28.
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post #56 of 1329
11/15/11 at 2:23pm
Thread Starter 
Quote:
Originally Posted by DSF767 View Post

So I have my new LG plasma on the way and was thinking about doing this out of the box with the great result that most have been getting.

I just had one question has anyone ever noticed any long term effects of doing this to their TV. I don't want to shorten my TV's life span by tweaking something. It just seems odd to me because if this produces such great black levels why wouldn't the factory do right away.

I am sure if they did they would sell more TV's with the black levels some are getting.

it just seems so odd to me that this is possible and they don't take advantage of it so I am thinking there may be some long term effects.

The tweak is not necessarily for everyone, some are receiving their sets with already respectable black levels, but as a mass produced consumer item it's either hit or miss, but on the whole it looks like LG in general kept the panel voltages at moderate levels to reduce possible problems later on.
The truth is that for the average consumer the black levels on the LGs are fine, yes they are higher than the "better" Panasonics and Samsungs, it's only once you starting searching the forums that you start to question.
Personally I've yet to see LG plasmas fail to compare and do hold their own when seen next to other makes in a retail environment.
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post #57 of 1329
11/15/11 at 3:41pm
I've done the tweaks,maybe I missed something because now the IR is real bad. Any ideas?
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post #58 of 1329
11/15/11 at 3:47pm
Quote:
Originally Posted by spdracer View Post

I've done the tweaks,maybe I missed something because now the IR is real bad. Any ideas?

interesting.
I would think, less volts equals less IR.
I do not have any idea.
wait, if the one is increased, then the other decreased then the first one needs to be backed off. It must be giving too much volts.
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post #59 of 1329
11/15/11 at 4:46pm
I guess you see the IR on MLL black bacgrounds. The residual charge comes from the bright contents, so the equal amount of IR (you didn't decrease the overall brightness but the MLL only which is relatively rare) is much more visible on the significantly darker background.
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post #60 of 1329
11/15/11 at 5:14pm
Quote:
Originally Posted by janos666 View Post

I guess you see the IR on MLL black bacgrounds. The residual charge comes from the bright contents, so the equal amount of IR (you didn't decrease the overall brightness but the MLL only which is relatively rare) is much more visible on the significantly darker background.

That pretty much hits the nail on the head.When changing modes and the screen is black is when you really see it
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