LG Plasma Panel tweaks for better blacks. - Page 37

A friend called to service LG and asked if this trick is safe, here is his reply:

Today I called to two separate services that fix LG Plasma. In both service engineers advised against turning the knobs on the back of the motherboard, because the change in setting changes the parameters of the hybrid systems that LG used in virtually any plasma, and this in turn inevitably leads to overheating of the hybrids, significantly shortening their lifespan - TV can not survive even end of warranty. Such a hybrid system chip costs about 1000 - 1500 zł, so a lot - if damaged. The first service guy said to let it go to get used to but the other guy says he will check gets a special device, which are services for this model LG and maybe then it would be possible to electronically set the parameters so as to improve the black and that there was no side effects. In any case, too discouraged to change the settings of potentiometers - it can bring the effect in the short run.

Translated by google translator from Polish

What do u think about it ? His TV LG 60 PZ 750S

That sounds a bunch of rubbish. Ask him if you should change the flux capacitor ;-)

In my case, anyway, the "tweak" consisted of nothing more than carefully setting the TV to its ideal design operating values as described in LG's own service manuals, and had nothing to do with stressing anything.

And the results were stunning. It's the way LG should have shipped them from the factory if they had the time to invest fine tuning each set. But then it would cost more. I personally prefer to pay less and do it myself, but most people would not feel comfortable doing this.

I cannot remember, did you have to change the other pots much? Those measured with a voltmeter, not setup or down.

Turning the knobs "inevitably" leads to overheating of the components on the motherboard? What, any turning of any knob? Inevitable damage, significantly shortening the lifespan of "virtually any" LG plasma? Why are the knobs there in the first place -- are they self-destruct buttons?

Also, how much shortening counts as "significant"? 1000 hrs off of a 100,000-hr lifespan? 1000 hrs is a lot of viewing time. Etc etc etc etc

No. I set all the pots to the OEM specs on the stickers. Even set_up and set_dn I set using an oscilloscope exactly according to the procedure in the manual. This reduced my MLL from about .027 to .008.

Then I turned set_dn slightly clockwise from this position to get .007 and left it there.

Only set_up/dn really made any difference. They were way off from the values listed in the manual. The other voltages were really close to begin with. When I first bought the TV over a year ago MLL was around .016, so obviously it increased over time as it aged. Since the adjustment it has been rock solid at .007 for the last few months.

Hi,

Thanks everyone for this loooong thread with alot of information.

I'm just done adjusting the set_up pot only on my PK550n. I tried all sources I have, and then turned it off for 3h to let it cool down. Didn't notice any missfires at startup, so I hope it will be fine. And the white got no more noise than the normal plasma noise. My pot was at 12 o'clock and now it's maxed at 16 o'clock.

Noticed as other ppl the more obvious dancing dots, but with a little lowered brightness it feels better but I crush the black a bit :/ But rather crushed than the dancing. And I'm just capable to do a basic calibration since I doesn't have any equipment for a real calibration.

Now it's time to put the cover back on.

Thanks again!!

Hi rob, thanks for the reply.


The output on my HTPC is set to YCbCr 4:4:4. But as playback I'm using ffdshow which does a YCbCr 16-240 -> RGB 16-235 conversion. Doesn't seems to be an option to not do it. When using a normal pattern for calibrating brightness 17 and 18 are also pitch black, 19 got some dancing in it, and 20 some more, after that I see better shades of gray. If I increase brightness even more I get dancing greens over the whole screen. Think this could be fixed with a 20point real calibration, but I lack the skills and the equipment

(If I set gamma to low (using medium) I get too bright grays all the way down to 17, even if I lower brightness, which make me loose alot of depth since dark scene's becomes very bright.)

sorry for going a little of topic here.


The black is better, quite a lot. But I got back the smudges, guess it is what nowdays is called DSE. Since the blacklevels increased the DSE have been harder to notice, now when it's back down it's easier to spot. Still, I'm kinda noticing everything right now Feels like a new set and I'm looking for flaws allover again

If levels 17 and 18 are indistinguishable from black (16) then you are crushing blacks. Normally the fix for this is to simply turn up brightness a bit. Have you tried this?

Yes, when I do this the whole screen get green dancing dots. But it was like this before the tweak also. (gamma medium).

@gamma low = I can hit the black quite good on 16, and at 17 the gray start.. But the starting gray @17 is to bright, which cause the picture in movies to be too bright in dark scenes.

Maybe it's time for me to invest in some calibration hardware and read up a bit.

Btw, MLL for 24p (72hz) is brighter than 60hz on my 60pk550n (scandinavian version).

It appears all over screen, even in black bars. But did so even before the tweak when going too high in brightness. I can get up to 54, but 55 gives the green dancing. Maybe a set_dn tweak could get this better, but I'll try to get it better calibrated first. (If I occupy the tv for myself this weekend my wife would be far more dangerous than me electricute myself on the tv )

update: No missfires this morning after about 6h cooldown.

Confusion alert! I believe the green dancing pixels are completely different from missfires.

The dancing Fade is talking about is the normal plasma dither for near blacks, the missfires issue looks completely different. I have seen both personally.

The brightness adjustment on these set is very sensitive. Typically I run at 54, and even one click higher to 55 and I see all the blacks full of "dancing pixels" of one color or another (usually green).

Gamma affects the curve relating input level to brightness. When you run the low gamma there is a little more difference between the brightness of the lower levels, i.e., the difference between 17 and 16 is increased, so that 17 now breaks through the "all off" threshold and shows up as brighter than 16. The higher gamma has the opposite effect, putting less space between the lower levels and therefore crushing blacks.

I agree that a calibration should be able to fix this, but I would expect you could get fairly close with the default settings. What do you get with medium gamma in standard mode and everything else reset? Can you find a brightness level that allows 16 to be full black but still shows 17 and 18 as brighter? (Even though they are a very ugly sort of brighter. That's just a limitation of this set)

Just writing this to report that my PK540 has a great black level after having adjusted the pots a couple of months ago. In fact I could swear that the black level is darker now than it was after the first time I adjusted the pots. The only anomaly is that I get some red pixel misfires after I first turn on the TV but they disappear after 30 seconds or so. Also, during the time, the picture will suddenly get a bit brighter after 30 seconds. You can easily see it get brighter but the picture looks amazing. Much better than it did a few months ago.

Same thing on my PV350

Are you sure? I'm fairly certain that if I turn up brightness even the parts of the screen that are supposed to be full black will start to brighten up.

Close enough.
I can lower mll even more, but then the bottom of the panel starts to "glow" less than the upper. it's hard to describe. The effect is visible only on bright scenes, but the line (shadow like) goes through the entire bottom panel, statring exactly in the middle of screen horizontaly. It is barely visible, so I do not know you noticed it on your plasmas. For me this undesired result occurs when I set Set_Dn (most influence on the black level on my pv350) clockwise.

It looks exactly like in this picture (if u dont see it the red arrow on right points it), but for me the line starts exactly in the middle of the screen:
http://img828.imageshack.us/img828/4098/1003889.jpg

As far as I know, the only way the plasma can make the near black levels is with dithering. I'll give it a try later on.

Shiatsu, they're on to us!!