EEVblog #725 - LG Plasma TV Teardown

[JoeN]

1. When Dave saw the plasma TV in the dumpster, why did he go through all the trouble of bringing the 50 kg beast into the lab? He obviously doesn't want it because he has no space for it and it consumes too much power, and he doesn't show much interest in repairing it either. So why did he take it then? It doesn't make any sense.

I was thinking that myself. I think George Mallory can provide the answer.

Maybe he is actually going to do what he said he might do - part it out.  I think those heatsinks are the very least are worth the effort, and probably all the parts he mentioned except maybe I would leave the capacitors.

[calin]

Think you got me wrong .. i was not referring @ 4K resolution .. but at more than 4000$ back in 2005.  Even by 2005 standards the price I paid was up to the roof ... the Pioneer was second most expensive thing that was in the store  . The guy that sold it was asking me what kind of business I have 


Quote from: JoeN on Today at 08:43:19 PM

>Quote from: calin on Today at 07:56:55 PM

yeah I paid more than 4K on it back in 05

Doesn't matter until there really is 4K.  4K monitors are one thing.  4K content is another.  I expect real general availability of 4K content is still 5 years away.  Who cares what the monitor can do until I can watch Raiders of the lost Ark on it .

[JoeN]

Yeah, someone else was talking 4K resolution and somehow I glossed over that. 

Anyway, if you like your set and it still works, good for you.  I love my 42" plasma.

[DanielS]

I wouldn't be surprised if that is the case. Planned obsolescence; it's still happening today.

Electrolytic capacitors have the most predictable failure characteristics.

How many other components are explicitly rated for service lifetime based on voltage, temperature and current with some parameters allowed to degrade by 20-200% along the way? Semiconductors, inductors, resistors and most other components are stable within a few percent from nominal over 10+ years unless they are exposed to extreme conditions.

[RetroGameModz]

Maybe he is actually going to do what he said he might do - part it out.

Yep, it sounds like he has that in mind, and I do agree that there are a lot of parts in there that could be salvaged. But I mean, if you're only looking for junk parts for your lab, then why go for the heaviest, biggest and beefiest piece of equipment you can ever find in the dumpster? Why go through the trouble when you could just as well stick to other things being thrown away there, like computers, smaller TV sets, printers, CD players etc etc? Things like that are much easier to handle, yet still contain a lot of parts. I would personally not go for a big-ass 50 kg 50 inch plasma TV if I was only looking for parts and had no interest in the device itself whatsoever. A few parts in exchange for a broken back doesn't sound too tempting to me. But each to his own.

[coppice]

I took a look at the Samwha website looking for a datasheet for their caps, but I couldn't find anything.  These things fail so regularly that I wonder if they have a guaranteed maximum lifetime?  Maybe they have a lifetime chart with time on one axis and temperature on the other.  Companies like LG and Samsung use these caps to ensure that the electronics they sell will only last a bit past the warranty period.

The Asian TV makers I've worked with all seem to use the same baseline for how long their TVs should run without problems - 8 years of typical domestic use. However, they can be a bit vague about the average hours per day they rate as "typical domestic use".

[vlad777]

Your digital PSU capacitors are all dead. You should replace them.

You got a working unit and you are going to scrap it? Are you shitting me?

Please don't do it.  At least replace those caps and test it , show us it works , and then scrap it.

[tom66]

...

I'm glad to see someone on here with respect for older technology. Plasmas were killed off in part because consumers found it hard to judge the improvement in picture quality in a bright storeroom. Ask almost any home theatre professional, LCD vs Plasma, and they'll say plasma any day (or OLED, a true successor - just need to get price down & more sizes) The main issue plasma had is the light output is capped to keep power requirements sane, and the screens are extremely reflective. Most people have the ability to control the light in their room (curtains, blinds, or position of the TV) but it didn't help show the TVs for what they were.

Interesting post. However, the TV is not dead. Look at 18:49 in the video. There you can clearly see that the TV powers up and is even showing something on screen. That is not what most people would refer to as being "dead".
If you are referring to the plasma display panel itself... well, there is no evidence of the plasma panel in that TV being dead. On the contrary, it looks like there is nothing wrong with it at all.

The panel is, sadly, dead (for any reasonable TV-viewing purpose) as the pixel-wide pink lines are caused by failure of the address drivers. These are bonded to the display panel and are non-serviceable. LG had a lot of issues with this on their 2007-2009 model TVs (both LCD and plasma) due to poor bonding quality (possibly solder failure.) The failure is the same as on Dave's Panasonic TV (though that Panasonic was due to the actual IC failing, rather than a solder failure.)

Part of the problem is the drivers dissipate a lot of heat in a tiny area (1" x 0.2" max, 5W or so) and most manufacturers don't heatsink them well.

Perhaps it will be good enough for someone who just wants to use it as a TV but I certainly would struggle to use it...

[Grapsus]

Not all problems in the world are due to bad capacitors. So many things can we wrong with this TV, including damaged panel or those high-voltage hybrids in which case there's nothing that can be done.

By the way many very big capacitors are not totally flat from the beginning. The only real way to tell is to ESR test all of them, if it's even possible to do in-circuit.

[Rasz]

.

LOVE your YT channel 

[DanielS]

Your digital PSU capacitors are all dead. You should replace them.

You got a working unit and you are going to scrap it? Are you shitting me?

While bad caps on the low-voltage supply may explain some of the artifacts, the flickering which is Dave's biggest reason to decide to not bother fixing it (in addition to the weight and power draw issues) is a problem either with the HV stuff or the panel itself. The flicker could be a bad panel, worn electrodes, gas leakage, current leakage, sputtering, dying hybrids, etc., all non-fixable issues. The HV caps are plentiful and look fine, so they are unlikely to be the source of flicker. You also need to keep in mind that Dave said the flicker looks much worse in person than it did on camera and from what he has shown on camera, I would expect it to translate to the screen being unbearable to look at for any sort of normal use.

Would you bother attempting to fix a 400W power-hogging TV (at least the bits that you might be able to) when you are pretty much certain beforehand that the most painful issue with it is most likely hopeless?

[NiHaoMike]

Doesn't matter until there really is 4K.  4K monitors are one thing.  4K content is another.  I expect real general availability of 4K content is still 5 years away.  Who cares what the monitor can do until I can watch Raiders of the lost Ark on it .

All you need to get 4K content is a GPU. If you're not a gamer, a $100 750 will do the trick. See all that work area once and you won't want to go back. It's like having 4 1080p monitors in a 2x2 grid, just without the borders...

If you haven't already figured it out, 4K is an integral multiple of not only 1080p but also 720p.

[JoeN]

Doesn't matter until there really is 4K.  4K monitors are one thing.  4K content is another.  I expect real general availability of 4K content is still 5 years away.  Who cares what the monitor can do until I can watch Raiders of the lost Ark on it .

All you need to get 4K content is a GPU. If you're not a gamer, a $100 750 will do the trick. See all that work area once and you won't want to go back. It's like having 4 1080p monitors in a 2x2 grid, just without the borders...

If you haven't already figured it out, 4K is an integral multiple of not only 1080p but also 720p.

Do you mean as a computer monitor, displaying games, Excel spreadsheets, possible your photo collection?  The content I am talking about are Hollywood movies and television shows and live TV/sports content.  I get it that I could run my computer on such a TV and play Skyrim, but that isn't good enough for me, at least.   You're right, though, I will probably get a 4K monitor before a 4K TV because that makes more sense.

[Ed.Kloonk]

Once I looked in an old dumpster and I found an old wino. He was annoyed that I woke him up.

[Fungus]

All you need to get 4K content is a GPU.

Nope, that's not "content".

If you're not a gamer, a $100 750 will do the trick.

I'm a gamer and I have a 750...

[Fungus]

1. When Dave saw the plasma TV in the dumpster, why did he go through all the trouble of bringing the 50 kg beast into the lab? He obviously doesn't want it because he has no space for it and it consumes too much power, and he doesn't show much interest in repairing it either. So why did he take it then? It doesn't make any sense.

I was thinking that myself. I think George Mallory can provide the answer.

Well ... Dave is a fitness instructor so 50kg is nothing to him.

Why did he do it? Maybe he was interested in salvage (he says so several times in the video).

[RetroGameModz]

The panel is, sadly, dead (for any reasonable TV-viewing purpose) as the pixel-wide pink lines are caused by failure of the address drivers.

I was first wondering which pink lines you were talking about when I read your post, so I had to go back to Dave's video to have a look. And sure enough, I could clearly see the lines now when looking at the video in 1080p on a larger display. I watched the video on a smartphone the first time, that's probably why I missed it. 

I think you might be right. Those vertical lines certainly doesn't look good, and one common cause would be a problem with the either the flat flex cable(s) which are bonded to the X electrodes in the plasma panel (they could be ruptured), or the COF on these flat flex cables (could be faulty), or poor bonding of the flat flex to the plasma panel which makes them lose contact with age. There isn't much to do in any of these cases as repairing a flat flex cable or a COF is nearly impossible.
However, a lot of people have reported fixing X address problems by simply locating which flat flex cable that corresponds to the affected area, then releasing the flat flex cable from the connector at the X address board, cleaning the flat flex cable end with a bit of alcohol as well as the connector, and then reseating the flat flex into the connector again. I would certainly have tried that if I were Dave since I definitely think it's worth a shot.

It looks like the vertical lines are happening only on either the upper half or the lower half of the picture. Some of the lines, for example, are present only at the upper left portion of the screen. This suggests to me that this is a dual scan plasma TV and not a single scan one.
Hold on...
Ok, I just checked the video again. Yes, it's a dual scan system, because you can clearly see the X address boards at the top of the TV as well, not only at the bottom. (Around 3 mins into the video.)
The lines going vertically through the screen would then have something to do with the X address bus corresponding to that portion of the screen.
For example, the lines at the upper left of the screen, those lines would correspond to the upper right flat flex cables going into the plasma panel, looking at the TV from the back as can be seen at around 3 minutes in.
There is a metal bar going at the top of the TV from left to right. This bar is partly covering the two X address boards. If this bar is removed, the flat flex cables for the X address electrodes can then be accessed. It's then possible to clean them and reseat them in an attempt to repair the TV. Definitely worth a try, I would say.
Of course, the same goes for any vertical lines at the bottom half of the screen. The cause would then likely be the corresponding flat flex cables at the bottom of the screen instead.

And the flickering is most likely because of the bad capacitors. It might be a bit unnecessary to replace the capacitors if the flat flex issue cannot be fixed anyway, so I would have a look at the flat flex cables at first and try to clean them to see if that fixes the vertical lines to start with. If it does, I would then go for the capacitors in an attempt to get rid of the flickering.

These are bonded to the display panel and are non-serviceable.

Actually, you can service them, but you would need to have access to a special bonding machine used for that very purpose, and this is not something you would often find in the ordinary workshop. So indeed, they are non-serviceable for most people.

Part of the problem is the drivers dissipate a lot of heat in a tiny area (1" x 0.2" max, 5W or so) and most manufacturers don't heatsink them well.

In the case of a COF sitting on the flat flex for the X address electrodes, it seems to be common to heatsink these chips by using the metal bar covering the X address boards as a big heat sink. These COF are then pressed against this metal bar with thermal paste in between, heatsinking the COF driver ICs.

I don't know the reason why many plasma TVs are designed like this. Wouldn't it be better to have the driver ICs mounted directly on the X address boards (with heat sinks, of course), and just have a plain flat flex cable going to the X electrodes in the plasma display panel? It would certainly be a lot easier to service these TV sets if that was the case, but there might be some design complications involved there which I don't fully understand, perhaps...

Perhaps it will be good enough for someone who just wants to use it as a TV but I certainly would struggle to use it...

Same here. I didn't notice the lines first time watching the video (sorry about that), which made me believe that the lines that Dave was talking about was the type of line fault that only shows up every once in a while. I could live with that if it's not too serious, but I wouldn't want to use a TV that has stationary lines or some other kind of continuous line failure, which is the case with the set in Dave's video.
But on the other hand, I would certainly not mind taking on the challenge of repairing it.

LOVE your YT channel 

Haha. Love you too man. 

[RetroGameModz]

Would you bother attempting to fix a 400W power-hogging TV (at least the bits that you might be able to) when you are pretty much certain beforehand that the most painful issue with it is most likely hopeless?

I certainly would, and I was kind of hoping Dave would too.

1. Because experience can be gained from every repair attempt, whether or not you succeed in repairing the device you're working on. Dave is running a video blog, so his repairs (successful or not) are shared with a lot of people worldwide. That means a lot of people, not only Dave himself, will gain more knowledge from his repairs.

2. Because you can never be completely sure about what is causing the problem before you have troubleshooted the device and verified the cause. And as long as you haven't done that, there is always the chance that the cause of the problem is something that is very much serviceable.
I personally don't like to assume things. I like to verify.

3. Because if Dave does manage to fix the TV, then not only will it be saved from going to the landfill, but Dave can also sell it on eBay (local pickup only, of course) and earn some money on it. There are still people out there who are big fans of the plasma TV technology, and a 50" plasma could sell for quite a bit of money. The new owner of the TV will be happy as well, so it's a win-win situation.

4. Because there is nothing to lose, only to win.
TV turns out to be unrepairable; troubleshooting experience gained.
TV turns out to be repairable; troubleshooting experience gained and money earned since TV can then be sold.

But I do realize that Dave is a very busy man, and I can somehow understand his decision considering he's not interested in the TV. And I'm sure there will be other repair episodes on his channel in the future anyway.

[Zbig]

Cut the guy some slack. It seems Dave's mind was already at building his new, double Xeon monster machine - see Twitter. It indeed seems a bit rushed, like he just wanted to be done with it already, but I bet, my inner child and the urge to get to something much cooler, rather than to deal with some old appliance, would win, too. I think most of us have been there as well ;-)

[VK3DRB]

Anyone notice the triangular pin 1 designators on the LG PCB's? Good engineering ! Round pin 1 designators are second class citizens compared to triangular pin one designators because triangular pin 1 designators are more easily discernible and they point to the device of interest.

[DanielS]

3. Because if Dave does manage to fix the TV, then not only will it be saved from going to the landfill, but Dave can also sell it on eBay (local pickup only, of course) and earn some money on it. There are still people out there who are big fans of the plasma TV technology, and a 50" plasma could sell for quite a bit of money. The new owner of the TV will be happy as well, so it's a win-win situation.

A quality plasma TV in perfect working order might be worth some decent money. A plasma display with unknown ownership history salvaged from a commercial dumpster room and horrible flicker and line/column glitches is mostly worthless. If it is not something obvious like ripple on the voltage rails which Dave had a quick look at with a multimeter, then the other possibilities are either busted/flaky digital chips which involves replacing a board since the chips are likely not available as loose parts, or the hybrids, which are also not available as parts (or even if they were, they are potted) so that's another set of board-swapping.

Dave's lack of enthusiasm about this potential repair is quite understandable. There is not much that can be repaired in it that would make economical sense. If he sold it as parts though, he might be able to earn $150-200, which is more than what he would likely get for the whole unit even after a successful repair without the expense of throwing parts at it and the risk of doing so for nothing.

[Wim_L]

Is it only the light beeing reflected or do those caps look bulged? There seems to be even some black stuff leaking at the top of each cap or are the caps deliberately beeing marked?

Those are definitely bad caps even though the black stuff is just a marker. (quite common on those caps, probably marked after testing) I was screaming at my monitor when Dave was talking about the caps in the high-voltage supply and didn't notice the horde of bad caps in the logic power supply.

Remember Dave usually sees the item he's filming through the screen on his camera, which would be quite small and low resolution compared to what ends up on Youtube.

[VK3DRB]

Is it really worth salvaging anything from this plasma TV?

I used to hoard electronics and when I moved house in 1986, I took 6 trailer loads of TV's and VCR's and other electronic junk to the local garbage tip. Next time I moved house in 1999, I took 8 trailer loads of TVs, VCR's, computer chassis, useless test equipment and boards to the tip, vowing never to hoard again.

Eventually I learnt it is better to buy new parts than to take up so much valuable real estate with electronic junk box stuff. The economics actually makes sense NOT to hoard just in case you might need something one day. High voltage capacitors are the exception, because they are generally hard to get.

[aveekbh]

Remember Dave usually sees the item he's filming through the screen on his camera, which would be quite small and low resolution compared to what ends up on Youtube.

Although, to Dave's credit, he usually puts in annotations in post-production (in the video itself) or even in YouTube once he spots something that he missed while filming.

I totally understand Dave's reluctance to try a repair. Like he said, some of the boards are worth salvaging for components. I hope once he's removed the boards, I hope he will dispose of the panel et al responsibly. Dave is ecologically minded, after all.

[Fungus]

I totally understand Dave's reluctance to try a repair. Like he said, some of the boards are worth salvaging for components. I hope once he's removed the boards, I hope he will dispose of the panel et al responsibly. Dave is ecologically minded, after all.

If it *is* the column drivers as some people have suggested then it's probably not fixable (without spending a lot of money).

OTOH I think he should have tried swapping those caps just to see what happens. Where's the sense of curiosity?

If it starts working perfectly then... I dunno. Put it in the lobby with a sign on it saying "fixed! working!" and see what happens (leave a GoPro filming it or something). Have some fun! Maybe somebody will use it.

One time I replaced the ugly bathroom cupboard/mirror that came with the house for a new one and I left the old one downstairs with a sign saying - "Haunted mirror - we saw dead people in it! Do not take to your house!!" to see what would happen

(Answer: We got bored and went home after watching it for 20 minutes, I guess I'm not cut out to be a PI).