Getting a LG 60PZ850 tomorrow - anything to watch for?

[Th3_uN1Qu3]

Finally decided to get a proper TV for myself - one that i don't have to fix (or at least, so I think ).

It's a 60" LG 1080p plasma: https://www.lg.com/ca_en/tvs/lg-60PZ850-plasma-tv

Went and took a look at it today, it has been very well cared for. There were no dead pixels, no sparklies, no traces of burn-in. It is maybe a bit less bright than i'd expected, but that's a non-issue for me as i only watch shows at evening/night anyway - if anything, i appreciate a screen that can be dimmed to a very low level rather than a very bright one.

I plan to give it a good cleaning inside and a full recap and resolder of the coils and plastic caps on the sustain boards, as I want to wall mount it and with its 38.5kg (without stand) i don't want to have to take it back off anytime soon. The current owner has it wall mounted too. Besides the caps, anything else to watch for on these sets?

Thank you.

[tvtimmy]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

That should do. Make sure to put all the screws back in.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Since this is not a Smart TV, do I have to worry about the main processor overheating and change the heatsink or add a small fan? I've had a couple LG mainboards that i needed to reball or replace the CPU.

[Andrew F. Ali]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

The LG Plasma as far as I am concerned were better made than their LCD TVs so there should be no problem with the CPU to require re-balling. That sounds like a problem with the Z-SUS Bd. When you get it we will go further.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

There should be no problems with the sustain boards, the TV works fine (it better do, given what i'm paying for it!). The not-so-amazing brightness could simply be due to age, it is not dim, it's just not eye-burning bright which is fine with me. Otherwise it has a very nice picture. The reason he's letting it go is upgrading to OLED.

The only thing i did notice which seemed a bit wrong was a slight flicker on the top right when a light gray logo was displayed on a white background, but this was just this one scene, and i was sitting very close to the screen. I would think recapping will make that go away.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Bought it, along with 2 pairs of genuine LG active 3D glasses. Didn't want to spend extra but this does require active glasses, they are pretty hard to come by, and i was offered a better price than what i found on ebay, so... got those as well.

Got it home in one piece. And now, let me start inspecting it closely...

Plugged it in, wired it up to my laptop thru HDMI, and set the input to PC mode. Sharpness is spot-on, colors are vibrant, gamma is maybe a bit off but that can be tuned in software. Viewing angles are phenomenal, not that I expected anything less from a plasma. Black levels are good. Not breathtaking, but good. Color and black uniformity are perfect. There are no scratches on the glass that I can see.

Figured out how to use 3D mode with it and downloaded a demo. It was a bit annoying that it's got separate picture settings for 3D, but I can understand why. There is a noticeable loss of resolution when 3D is activated, but on video it is a non-issue, guess that's all they could do in 2011. The 3D effect is pretty convincing.

Now, for the things that need some work...
It runs warm. Like really warm. So it'll definitely be getting a recap.
There is a tiny bit of burn-in in places. However, it's so minor that it's invisible unless I nearly put my nose onto the screen, and even so, it rarely shows up. Not bothersome in the slightest.
It's got some "snow" on very dark tones. Not enough for me to call them "sparklies", i know how those look like, but there is something that shouldn't be there. Pretty sure that adjusting the panel voltages will fix it tho.
The white limiter is also pretty aggressive. Is this just done to limit power consumption, or is it also a means of protection? Can it be adjusted in any way? If possible, i would like to make it less obvious.

Also, here's something i did not really expect: It flickers! Like CRT-type flicker. Not painful, but noticeable. Does this really run at just 60Hz, or could there be something wrong? Interesting to note is that it does not flicker at all in 3D mode, not even when I take a look at the screen without the glasses.

I'll be back with pictures.

[lookimback]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Check the large inductor coils on the sustain boards. They are prone to dry joints. Also, make sure you put every screw back in the sus boards or some MOSFETs/IGBTs won't have a path to ground and will fry instantly.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Will do, will also touch up the grounding points with fresh solder while i'm at it.

Have figured out the flicker issue, it's a 60Hz set so it's normal that it flickers slightly, but if i feed it 50Hz or 24p it switches to a higher refresh rate (likely 100Hz/72Hz respectively) and no more flicker. Unfortunately the picture looks really bad in these modes, it's very grainy. New caps and tuning of the panel voltages will hopefully make it look great.

[Moreno83]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Why would you want to replace the caps?

These sets are only known for bad solder on the ss board. ( coils ). Not bad caps , or am i wrong?
New caps wont get rid of the heat. Plasma gets hot..... 60 degrees is normal for a plasma screen.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

It's 6 years old, it runs hot and I want to wall mount it and not take it back down anytime soon. Reason enough. I'll have to take the back off anyway to tune the panel voltages.

Besides, there are some slight issues which I could blame on power delivery.
One is that the white limiter is very aggressive and the second is that I get a little picture bounce, like an old TV losing vertical sync, but much more subtle. This only happens once in a while, and only when the contrast is turned up to a level where the white limiter engages. It will stop bouncing right away if I turn the contrast down, put it into energy saving mode (which does the same thing) or bring the menu up (which dims the picture underneath it) so it is definitely related to the panel's power consumption.

[Moreno83]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Since you got the panel off anyways i would probably do the same. Was just wondering if it was a hardware issue

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Picture is good with 60Hz input from my laptop, just some subtle grain/dancing pixels on the darkest tones and black level a bit higher than it should be able to achieve, but overall good, and these little imperfections are not noticeable at the intended viewing distance of 3 meters.

However, all other modes, 50Hz, 24p, 3D show a very grainy picture and weak, grayish whites. These modes have all something in common - they run the panel at a multiple of the refresh rate set to avoid flicker. There is visible flicker at 60Hz but none at 50Hz so it's definitely running it at 100 instead. My guess is that there's some voltage drops under the higher load of the faster refresh, so replacing all large electrolytics before getting into tuning the panel drive seems like a good idea to me.

Edit: Here is the bouncing picture, watch the text closely. At about 00:41 i put it into power save mode and then it looks perfect. https://vimeo.com/280519908

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Here are the complete schematics for this set.

[Andrew F. Ali]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

To help with cooling you could probably add a fan to expel the hot air. I normally use a 4" or 5.5" if I can get and run it of the 12Vdc or you could install a separate PSU to drive the fan.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

It does seem like it's either the caps or the solder joints on the inductors that you guys have been talking about.

Last night when I turned it on, the grainy whites in the other modes were gone, the picture was perfectly stable, zero flicker and if I'm not mistaken it also came up brighter than I remembered it. Even the flicker in 60Hz mode was more tolerable. It had been really hot during the day.

Now, after the room has been colder overnight, it gets the grainy look in the other modes, the slight picture bounce in 60Hz mode every now and then and it's also slightly flickery in the other modes too, where the refresh is supposed to be invisible (and it was like that last night).

I've got a bunch of other stuff to fix but i'll definitely open 'er up this weekend.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Just noticed i've been reading the spec sheet wrong - this panel is supposed to scan at 600 not 60 Hertz, so visible flickering, in any mode at all, isn't something that's supposed to happen with this set.

And thus, we come back to suspecting bad caps.

I'll do a set of voltage measurements before I pull the boards for capacitor removal.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

No bad caps found. Guess i'll be recapping it next year maybe... I still noted down all the values and dimensions.

However, you guys were right - the soldering on the Z-Sus board, especially those large inductors, was HORRIBLE. I have redone a lot of soldering on both the Y-Sus and Z-Sus. A few interesting things have happened however, not all of them good.

The voltages measured on the power supply and the Y-Sus were close enough to the panel sticker but a little low. VZB was almost spot-on at 109.8V (should have been 110). Well, after resoldering the inductors, VZB came up as 120 volts! I had to turn the trimpot down quite a bit to get it back to 110. It looks like the solder cracks on those inductors have not developed over time, they were bad since it was new, and the board got calibrated like that!

Did all other voltages too as per the panel sticker, will tweak for black level later, because now i've got another issue on my hands...

The picture doesn't start bouncing anymore (which is good), however, after a while of running, I start getting a lot of green and magenta snow in near-whites and the colors get washed out. Have reseated cables and resoldered more connections to no avail. It is definitely heat related so i'll go and get myself a can of freeze spray to troubleshoot this further.

It does so a lot later if the back panel's on, guess it helps spread the heat somehow.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Went to the hardware store, sadly they did not carry any freeze spray or duster... Picked up a can of contact cleaner though. I also found all the screws needed to assemble the stand (the former owner had lost them) Put it onto the stand and placed a room fan behind it on lowest setting. Laid it down so it blows in the area where the control board is.

5 hours later, the sides where the sustain boards are, are still getting hot. The control board area is really cool since it has the fan blowing on it. Picture noise did not show up at all, it is still perfectly clear after running this long. So I guess i found my problem. The BGA on the control board does not have a heatsink on it, and I remember it almost burning my finger yesterday when i touched it after i had just unplugged the set. There's plenty of room for a nice heatsink there, guess i have to go thru my stack of dead boards.

We have been watching a 3D movie and it goes out of 3D mode by itself every now and then, the 3D processor also has no heatsink. Full mods ahead!

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Here's some photos of the boards and the resoldering work i've done on them. Especially on the Z-Sus, that's some horrible wave soldering there, LG. Shame on you.

[Th3_uN1Qu3]

Re: Getting a LG 60PZ850 tomorrow - anything to watch for?

Ok, i might have cracked this. Not the panel, of course.

Freeze spray showed that the issue is not in the main or the control boards.

I have noticed that the color noise only occurs on white and light colors, when the brightness limiter kicks in, so it only happens when it's drawing a lot of power. It is easily reproduced by taking a white window and resizing it. When i get to the point when the panel does not get any brighter anymore by shrinking the window, the picture is perfect. As I enlarge it, the noise comes back.

The issue sounds a lot like this: https://www.badcaps.net/forum/showthread.php?t=52008 so maybe the inductors are cooked to the point where they develop shorted turns as they heat up, this would explain the slow time constant (I have to leave it off for at least 2-3 minutes for it to recover, unless it has a fan blowing on it) and also how fast the issue comes back after it's had very little cooling time.

I'll try spreading the turns just a bit, or maybe I can make some new inductors. I don't think I have wire that thick, but I doubt it would mind them being done with litz wire.