Why do backlight LEDs burn out and go blue? - Page 1
Forum section: electronics / general

author: eti
author_rank: Super Contributor
timestamp: November 05, 2021, 09:44:34 pm
content: Why do backlight LEDs burn out and go blue?12-11-21: (update) - attached, images of the faulty LEDs being tested. They have around 2.5v drop across them.I've been given an LG 4K TV, and the backlight LEDs have been left on full whack, and have gone blue... but why does this happen - phosphor diminishing?(14-11-21) Jump to this post to see macros of the bare LED die and lens type assy:https://www.eevblog.com/forum/chat/why-do-backlight-leds-burn-out-and-go-blue/msg3812753/#msg3812753Edit (added info): just found this article >>https://jestineyong.com/quick-understanding-of-led-bulb-turning-blue/https://www.circuitsonline.net/forum/view/148440For anyone doubting that this is the case, see below:

author: bdunham7
author_rank: Super Contributor
timestamp: November 05, 2021, 10:16:58 pm
content: They don't. Your TV is in blue mode.

author: eti
author_rank: Super Contributor
timestamp: November 05, 2021, 10:31:14 pm
content: Quote from: bdunham7 on November 05, 2021, 10:16:58 pm

author: amyk
author_rank: Super Contributor
timestamp: November 06, 2021, 12:28:34 am
content: That doesn't look like the backlight, but rather (two!) missing channels of video data.

author: IanB
author_rank: Super Contributor
timestamp: November 06, 2021, 12:30:56 am
content: Quote from: eti on November 05, 2021, 09:44:34 pmThey don't. You have a TV with an undiagnosed fault where the symptom is a blue screen.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 12:40:45 am
content: Quote from: IanB on November 06, 2021, 12:30:56 amI beg to differ. Google "LG TV blue picture fault" and count the endless results that show engineers replacing the backlight strips that have gone blue.I have another spare TV with led backlight (JVC) - would the LEDs be the same if I desoldered the working JVC ones and transplanted them onto the backlight strips of the LG?Thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2021, 12:44:15 am
content: There actually is a blue mode in the service menu of most TVs, but looking more closely at your picture, that might not be it. Is the white spot in the upper left a reflection or is that the sun appearing in the actual TV picture?LG has an issue with LED backlights bluing with age, but I've never seen one that bad! Unless the TV was simply left on in some function where nobody cared what it looked like, I can't imagine watching it long enough for it to get that bad--it takes years and years. Why they do it I don't know, but it is a defective part. A few minutes of disassembly will suffice to determine if this is the case.

author: IanB
author_rank: Super Contributor
timestamp: November 06, 2021, 12:45:48 am
content: Quote from: eti on November 06, 2021, 12:40:45 amIt's impossible to say, since you have an undiagnosed fault with the current TV.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 12:46:55 am
content: Quote from: IanB on November 06, 2021, 12:45:48 amDiagnosis: LEDs have turned blue and need replacing. Did you even Google it?https://jestineyong.com/quick-understanding-of-led-bulb-turning-blue/

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 12:49:59 am
content: Quote from: bdunham7 on November 06, 2021, 12:44:15 amYes, the bright spot upper left is a reflection. There seems to be a lack of understanding with others in this thread about exactly how white LEDs manage to emit white light - it's UV light which strikes a phosphor and that causes the phosphor to emit white light (I forget the physics term).Yep LG definitely have an issue, and they also had HUGE numbers of issues with their smartphones a few years ago (different faults). A brand to avoid.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2021, 12:50:22 am
content: Quote from: eti on November 06, 2021, 12:40:45 amUnless they are the same size and voltage--the LEDs are in series--no. If you really do have the worst case of blue tint imaginable, then there are places that sell replacements. What model is the TV.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 12:53:07 am
content: Quote from: bdunham7 on November 06, 2021, 12:50:22 amActually it's nowhere near that blue in reality - more like a mid purple haze (makes sense as it's UV).The TV is an LG 43uj630, and I've found the strips but would like to try the free repair first 😁Thanks mate.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2021, 12:58:30 am
content: Quote from: eti on November 06, 2021, 12:49:59 amLuminescence. And it's widely known. It's just a bit unusual to see white LEDs go that bad and still all work. Perhaps they run too hot? Was this used as some sort of static display or just someone's television?

author: IanB
author_rank: Super Contributor
timestamp: November 06, 2021, 01:00:22 am
content: Quote from: eti on November 06, 2021, 12:49:59 amNo, there is a lack of understanding by certain people in this thread about how to diagnose faults. You have a probable cause, even a very likely cause, but you have not proven it to be the case. Especially since you posted a picture of a blue screen, but now you tell us it is not actually blue, but a kind of purple-hazy.I'm seeing a pattern of you creating antagonizing threads, which means you are going into my ignore list. Goodbye.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 01:02:39 am
content: Quote from: bdunham7 on November 06, 2021, 12:58:30 amIt was in an old folks home. These questions have no answers I can give. Yes it’s widely known - you and I know that. IanB seems to think it’s “undiagnosed” when I can see the leds through the grilles in the rear of the set, glowing this purplish blue…I’m not wanting to be awkward or rude, IanB, but it’s very much diagnosed. I’m moving on from that point, not backwards to an imagined other misdiagnosis.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 01:03:32 am
content: Quote from: IanB on November 06, 2021, 01:00:22 amWow. Okkkkk then.Blue, purplish blue, purple, whatever - what’s the difference? When a WHITE LED is meant to be white, splitting hairs over the shade of purple or blue that it’s clearly not meant to exhibit, might actually show that the antagonist is someone else. Ignore me if you wish, you’ve not helped the thread and clearly just want to storm out in a temper and make a flourish. Great.I wasn’t asking IF the LEDs are the wrong colour, I asked why they go that way.🤦‍♂️🤯

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 01:18:53 am
content: Quote from: amyk on November 06, 2021, 12:28:34 amThanks for the reply. Actually one can see the LEDs glowing this bluish purple through the grilles in the back of the set. Also the camera puts a very blue cast on what is, in actuality, a more purple hazy screen.Looking past the "purple haze" one can see all the RGB data is present, as it's colour with a purple overly - it's nowhere as exaggerated as in the photo.

author: amyk
author_rank: Super Contributor
timestamp: November 06, 2021, 03:03:28 am
content: I think you're being met with incredulity because that is aninsanelyblue photo you've taken, and while a few bluish patches would be clearly phosphor degradation, they must've really messed up a whole batch of LEDs for them toallgo bad like that.If you open it up and show the backlights themselves, that would clear up a lot of the disbelief."Roses are red,violets are blueso are these LEDsbut they can't believe it's true."

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2021, 03:16:03 am
content: Here's my TV in blue mode. It has no LEDs. The picture is pretty close to the way I saw it and I've never seen an LED-backlit TV look anything remotely similar. Like the OP, the only visible light that isn't blue is a reflection.

author: eti
author_rank: Super Contributor
timestamp: November 06, 2021, 03:32:40 am
content: Quote from: amyk on November 06, 2021, 03:03:28 amI've no desire to "prove" it to one bloke who's gone off in a tantrum and blocked me. Meh.If you Google the symptoms it's EVERYWHERE and extremely widely known re LG LED backlit TVs.If that bloke can be bothered to form a pedantic reply on a forum, he can at least use those typing fingers to do a TRIVIAL bit of research for about 5 mins.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 06, 2021, 08:13:26 am
content: More likely the backlight consists of RGB LEDs and R, G have failed for a reason or another. Or, the signal chain has failed regarding R and G.Very unlikely this is due to using white LEDs with slowly failed phosphors to the point image is completely blue. But of course, that's possible, too.The fact that others have seen the same failure to the point it's a very common issue is interesting, because it should indicate someone knows the likely cause. This should make your life easier; Google further until you find an explanation from someone who actually investigated what's wrong. But obviously if you refuse to investigate and fixate into the initial idea of white LED phosphors failing like in one documented case in an LED lightbulb with external phosphors, then there is nothing we can do.Fixation is a bitch. Airplanes have crashed thanks to fixation. I feel sorry for you, but good luck.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 06, 2021, 10:14:55 am
content: Could that be that the TV uses kind of 'remote phosphor'? Some TV-Sets use blue LEDs with a bar contain the phosphor or nano-crystals (most of them contain cadmium!) to transform the blue light to the specific spectra required. If that piece fell off/moved that only the light from the LEDs enters the diffusor of the LCD?But often there are LEDs on two edges (if not spread over the background). That would rule out the idea the the remote phosphor bar is the culprit unless both fell of the same way. Unless the TV experienced any kind of stress (quick change or high temperature, vibartion...) that made fell off the phosphor?EDIT: I missed the point that you actually mentioned that it was on at full whack. So the LEDs ran hot and the phosphor might have been damaged/detached from the LEDs.I think RGB LEDs for background illumination is not commonly used anymore. From what I've heard too many problems with the uniformity of the used LEDs (brightness, aging, color...) and too expensive.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2021, 02:26:39 pm
content: Here's a photo of failed LED strip from such a TV.

author: themadhippy
author_rank: Super Contributor
timestamp: November 06, 2021, 02:50:10 pm
content: Quoteis that for viewing adult movies?

author: ealex
author_rank: Frequent Contributor
timestamp: November 06, 2021, 05:58:53 pm
content: @bdunham7: that's exactly how the leds looked like in the LG i've recently repaired.the phosphorus layer was flaking off, and most of the leds where pure blue.there where no signs of overheating.the fix was easy, but handling the huge glass pane is scary@eti - i don't think you can desolder those, they are bare dies on the pcb, with a lens glued above.the replacement led strips are cheap, just take care to get the proper ones, and maybe some good / thin double sided tape

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 06, 2021, 07:52:05 pm
content: Quote from: Twoflower on November 06, 2021, 10:14:55 amIsn't cadmium restricted by RoHS?QuoteThere are displays that use a RGB backlight and a monochrome LCD, I'm pretty sure there aren't any direct view TVs using that technology although it works on the same principle as DLP projectors. The one application I heard of for it was a tablet that could operate as a regular color tablet with the backlight on or as an eink like tablet with the backlight off. Probably the main problem is that it requires a very fast LCD to not flicker and the power use of such a fast LCD offsets the savings of not having color filters.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 06, 2021, 08:16:08 pm
content: Quote from: NiHaoMike on November 06, 2021, 07:52:05 pmYes it is but I think there is/was an exception for the Cd-based quantum dots for TV usage (e.g.https://optics.org/news/7/6/8).Quote from: NiHaoMike on November 06, 2021, 07:52:05 pmAn interesting technique replacing the filters by time multiplexing. Sounds logical, as it has also an advance in the resolution as only one single pixel is used for the three colors. But probably nothing for me as I seem to sensitive to the rainbow effect on DLP projectors.I remember some very expensive monitors had also RGB backlight with filters. They supposed to have an excellent color space in that time. But the phosphors for LEDs and filters on the LCDs got better to allow the huge color space of modern monitors/TVs.

author: amyk
author_rank: Super Contributor
timestamp: November 07, 2021, 01:39:47 am
content: Wow.That is certainly a lot worse failure than I thought it would be. Even the various generic Chinese COBs I've seen have not failed like that, despite being heavily overdriven - usually the die or the bond wire goes first. Almost looks like they were really trying to save on the phosphor application.

author: james_s
author_rank: Super Contributor
timestamp: November 07, 2021, 03:06:22 am
content: An easy way to tell if it's the backlight is to look around the back and sides of the panel, almost always there is a gap somewhere that light from the backlight will show through. If that leaking light is blue then the backlight is blue.

author: eti
author_rank: Super Contributor
timestamp: November 07, 2021, 04:42:44 am
content: Quote from: james_s on November 07, 2021, 03:06:22 amyep, and it is.

author: newbrain
author_rank: Super Contributor
timestamp: November 07, 2021, 09:02:15 am
content: Quote from: Twoflower on November 06, 2021, 08:16:08 pmExactly, my Dell 2713H display is halfway there, as it uses blue and green LEDs, with a red phosphor.The coverage is 99% of Adobe RGB colour space, with excellent linearity due to the internal programmable LUT.

author: Brumby
author_rank: Unknown
timestamp: November 07, 2021, 11:52:16 am
content: Quote from: eti on November 06, 2021, 01:18:53 amI might suggest that this would have been a useful observation to have included in the original problem description.

author: tooki
author_rank: Super Contributor
timestamp: November 07, 2021, 07:58:12 pm
content: Quote from: eti on November 06, 2021, 12:49:59 amYes but in this case it’s your understanding that is incorrect.White LEDs areblueLEDs with yellow phosphors. While white LEDs based on UV theoretically exist, I’ve been unable to find even a single example of one, despite extensive searching. (UV LEDs require appreciably higher forward voltage than blue, and every single white LED I’ve looked at has had a Vf matching the blue LEDs of the same series, not UV.)The exact spectral output of the yellow phosphors depends on the application: for general illumination a broad spectrum is desirable, whereas for LCD backlighting you’d ideally want just two sharp peaks (one green, one red) with wavelengths exactly matching the red and green filters on the respective subpixels.You can easily test this by the way: but some white, blue, and UV LEDs. Alternately shine the blue and UV light onto the phosphor of the unlit white LED. You’ll find that it lightsfarbrighter with the blue than with the UV, because it’s optimized for blue. .Quote from: eti on November 06, 2021, 12:53:07 amBut since they’renotUV at all, it’s actually because the yellow phosphors have degraded and thus the ratio of blue to red and green is out of whack.

author: eti
author_rank: Super Contributor
timestamp: November 08, 2021, 03:31:28 am
content: Quote from: Brumby on November 07, 2021, 11:52:16 amOne would think, would one not, that a thread asking "why", and not "if" the LEDs have lost their white output, would be enough to satisfy people that I've sussed pretty quickly that THE LEDS **HAVE** GONE OFF COLOUR. Instead of a thread full of pedantry and wise-acrey, we could've got to the (excruciatingly obvious) point that I've ascertained the state of the LEDs, and was enquiring from that known point onward. But then, that wouldn't allow people to brag and boast and belittle one another, to-ing and fro-ing, would it. No wonder poor Dave gets fed up of all the "have you tried X Y and BLAH?" on his YouTube comments - people are so eager to be right, they DO NOT PAY ATTENTION.I should have included it maybe, but I'm pretty sharp, being an ex TV engineer, and I think my lateral thinking circuits are granular enough to discern whether it's just "Muh TV has gone blue!" like an average person, or "The LEDs are no longer white", as you'll see is the purpose of the thread.I've even stated, a few times now, how simple it is to Google this fault and see how prevalent it is for LG TVs. A trivial Google for 5 mins can sum this up without explicit declarations from me.Wow. Just amazing.

author: bw2341
author_rank: Regular Contributor
timestamp: November 08, 2021, 03:53:57 am
content: Quote from: tooki on November 07, 2021, 07:58:12 pmhttps://www.digikey.ca/en/articles/royal-blue-leds-decoding-the-datasheetIt seems that remote phosphor products use royal blue LEDs which are shorter wavelength than regular blue LEDs. I haven't seen royal blue LEDs myself, but they apparently do look strange compared to regular blue.

author: james_s
author_rank: Super Contributor
timestamp: November 08, 2021, 04:30:50 am
content: Quote from: bw2341 on November 08, 2021, 03:53:57 amThey look pretty much like ordinary blue to me, I've removed the remote phosphor panels from some old Philips LED bulbs that were intermittent and the exposed blue LEDs are a very bright saturated deep blue. It definitely looks blue rather than violet. It's kind of pedantic to debate anyway, I don't remember where the exact cutoff between blue and UV is defined but it's a continuous spectrum, just deeper and deeper violet that your eyes are less and less sensitive to. All sorts of stuff will fluoresce across much of that span.

author: gnavigator1007
author_rank: Unknown
timestamp: November 08, 2021, 04:44:24 am
content: We have a similar issue with many of the street light leds around town

author: magic
author_rank: Super Contributor
timestamp: November 08, 2021, 08:50:33 am
content: Quote from: eti on November 08, 2021, 03:31:28 amYour original post consisted exactly of a single "muh tv has gone blue" picture and a few links to people who happened to have the same symptom and zero mention of any diagnosis performed by you on your TV.That sort of posts are the staple of Internet geniuses who did their homework by googling for 5 minutes and know exactly what the problem is and only need help with "that one final bit".The response was totally predictable.

author: Ranayna
author_rank: Super Contributor
timestamp: November 08, 2021, 10:20:41 am
content: Uhh, that should go into the pet peeve thread as wellPost as much information about the issue you want help with as you can.People cannot read minds, even hereName the device or software your question is about. If possible the exact version.Software and Hardware versions can differ greatly. With software, many known issues can be fixed with updates.Quote any error messages you get. And quote them exactly as you get them. Pro-Tip: In Windows, on many (sadly not all) error messages, hit CRTL-C on the message box to get the contents into the clipboard, ready to paste. On recent Windows 10 (i think 20H1 and higher) hit Windows-Shift-S to start the snipping tool. Or hit ALT-PrintScreen to screenshot your current window.The Error message details, if available, are importantList what you already have done or researched. If you followed any online guides, link them.If you do not want the helpers to repeat the most basic troubleshooting steps, you have to list what you have done already. It's generally fine if you have not done anything yet, but tell us.This should be included in *any* post seeking help. I have posted lists similar to this, or have seen them, in many many forums that allow help questions. This is, i my opinion, just basic decency, to not waste the time of the helpers, and your own as well.I do not know if people are afraid to post such information to protect from potential identification, or if people think that no one knows the device anyway. Or, and i am afraid that this is actually the most likely, if people are just too lazy.

author: Zero999
author_rank: Super Contributor
timestamp: November 09, 2021, 01:29:17 pm
content: Quote from: james_s on November 08, 2021, 04:30:50 amI've seen the term Royal blue used on data sheets. It is indeed a slightly shorter wavelength, than ordinary blue used for illumination, but colour perception is subjective and LEDs differ between manufacturers.Phosphors are often mixed to produce several different wavelengths to ensure a good colour rendering index. It's possible the green-yellow part of the phosphor has faded more than the red, giving a more purplish/violet colour.

author: PlainName
author_rank: Super Contributor
timestamp: November 09, 2021, 03:19:47 pm
content: QuoteNo doubt a combination, but sometimes it's not knowing what info is relevant. In some other forums, people post 100K-worth of log output, 99.99% of which is of no use and just obscures the relevant part. I suppose in some ways it is akin to quoting - IMO a succinct quote of the section being addressed is far better than the full quote and then trying to work out which is The Bit being dealt with.But we also see quite comprehensive descriptions which include fixes that can't be used for some reason (usually quite sensible) and yet at least a couple of responses will be to use those specific fixes. Sometimes you can't win.

author: PlainName
author_rank: Super Contributor
timestamp: November 09, 2021, 03:23:47 pm
content: And... it pains me to say so but eti did actually ask a generic question (why do LEDs burn out) and perhaps his only fault is to include a specific example. So with a quick reading (mea culpa) one might assume he is asking what's wrong with his TV, whereas in fact he is asking why backlight LEDsin generalgo like that.The answer would seem to be that stick-on phosphor patch, which is something I didn't know about so I am grateful for the question coming up!

author: Cerebus
author_rank: Super Contributor
timestamp: November 10, 2021, 12:33:23 am
content: Quote from: Ranayna on November 08, 2021, 10:20:41 amThe problem is that some people are quite good and do all that, even to the point of meticulousness, but then there are certain individuals who just seem congenitally incapable of actually reading it and shoot off at some tangent.For a very simple example, I just read a thread where someone says "I want to buy anupmarket-brand-namemodel XYZ scope; can anyone recommend anupmarket-brand-namedealer inmy-area". Thevery nextposter says "You should get a downmarket-brand model ABC!".Do we really need to start making people sit a reading comprehension test before they're allowed to post?I'm not saying that's what's happening here, in fact it's not, but it just goes to show that some people are so dumb, or determined to just go their way, that clearly and completely stating the problem/issue for discussion/question isn't a foolproof way of getting a sensible discussion/answer. I've noticed that quite a lot of the people who derail things in this way have self-congratulatory superlatives like 'guru', 'expert', 'master', 'wizard' and so on in their chosen user names. I think the implications are quite self-explanatory.

author: eti
author_rank: Super Contributor
timestamp: November 10, 2021, 01:58:22 am
content: Quote from: Cerebus on November 10, 2021, 12:33:23 amI shall freely admit my propensity to rocket off at tangents, it’s a lateral thinking trait of mine 😁 for which I make no apologies whatsoever; it’s a function of how my mind works. I am sorry if I’ve confused anyone, especially the “experts” <bows with great humility> 😉😉I agree regarding those using the cliched superlatives in their surnames, and will quote a phrase I once heard, regarding one naming oneself an “expert”:“An ex is a has-been, and a spurt is a drip under pressure.”😛I find humility wins every time, and I feel that maybe a great deal of personal insecurity leads some people to feel a need to establish their prowess by over-compensating, when, in fact, talent and gifting can speak for itself FAR louder than any superficial, somewhat boastful moniker.

author: station240
author_rank: Unknown
timestamp: November 10, 2021, 11:14:39 pm
content: Quote from: eti on November 06, 2021, 12:40:45 amAh there is a difference between a service technician/engineer and engineers in general.engineer: That's can't happen, (assumes customer is an idiot), spends ages on other random guesses before giving up.technician: (takes one look at the set) Yup had one of those in last month, backlight LEDs have failed and gone blue.Still you'd think engineers would know white LEDs are just blue ones with a phosphor layer added.I've got a LED backlight and PSU here, after some reverse engineering I found how to turn the LEDs on without the control board.But turns out if you drive them 100% (no PWM signal), they all turn blue after a few hours, but leave them off for a few days and they go back to white.Obviously that can't happen if the phosphor layer falls off entirely. Bad bonding material perhaps ?

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2021, 02:26:19 am
content: Quote from: station240 on November 10, 2021, 11:14:39 pmI'd assume most of them do. I had never in my life until this thread ever heard of the phosphor coming off of an LED. I've had cheap white LEDs phoshor fail such that it got really dim and gray but I've never seen it fall off. That seems like a serious design flaw, maybe class action lawsuit if it's a common problem. LED backlights should last *at least* 10 years of normal use in a TV.

author: IanB
author_rank: Super Contributor
timestamp: November 11, 2021, 02:37:38 am
content: Quote from: james_s on November 11, 2021, 02:26:19 amRight. Best Buy is full of stunning looking LG OLED TVs costing ~$1000. I'd be seriously pissed if the phosphor fell off the backlight LEDs.

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2021, 04:24:03 am
content: If they're OLED they don't have a backlight, perhaps you meant QLED? Those are just LCD, with a deliberately deceptive name clearly meant to confuse them with superior OLED displays.

author: IanB
author_rank: Super Contributor
timestamp: November 11, 2021, 05:07:36 am
content: Quote from: james_s on November 11, 2021, 04:24:03 amI didn't know that about OLED displays. If they don't have a backlight, that's good in a way, there is less to go wrong. But I suspect there is a downside. I'll have to research it.

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2021, 05:40:20 am
content: Quote from: IanB on November 11, 2021, 05:07:36 amOh yes. Every OLED display in history (so far) has been a short-lived POS. TV screens are a newer application, but since LG did so well with their backlights, I can't wait to see the screen burn on the OLED models in a few years.

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2021, 07:03:11 am
content: Quote from: bdunham7 on November 11, 2021, 05:40:20 amI know several different people with OLED TVs that are several years old and holding up well so far, they look absolutely fantastic too. They seem to hold up pretty well on the higher end smartphones too, but there are also a lot of lousy OLED displays that are notorious for failing.The old CRT rear projection TVs were prone to screen burn too but it is not normally a problem with most content. Unfortunately all of the broadcast channels have those stupid logos in the corner now and I've seen those burn into displays. Those logos are the reason I stopped watching broadcast TV.

author: eti
author_rank: Super Contributor
timestamp: November 11, 2021, 07:31:06 am
content: I have never and will never buy an OLED anything as long as I live. They exaggerate the pros and hide/deny the cons until the cows come home. I’d rather have LCD than a half-hearted stop gap technology.

author: Zero999
author_rank: Super Contributor
timestamp: November 11, 2021, 08:03:30 am
content: Quote from: eti on November 11, 2021, 07:31:06 amThat's a very close minded statement. Technology improves all the time and the day might come when OLED displays become highly reliable and better performance than LEDs. You just don't know what will happen. I'm pretty sure some electric car owners, said the same thing about EVs in the past.

author: eti
author_rank: Super Contributor
timestamp: November 11, 2021, 08:10:14 am
content: Quote from: Zero999 on November 11, 2021, 08:03:30 amThey’ve had plenty long enough to improve - decades. They’re #%#% end of. The industry is moving away from OLED, I can’t recall what to, but this is a tacit admission of how crap they are in one terrible flaw where the colours burn in and one colour dies faster than the others. Good riddance.

author: Zero999
author_rank: Super Contributor
timestamp: November 11, 2021, 08:24:37 am
content: Quote from: eti on November 11, 2021, 08:10:14 amSo what? That means nothing. Electric cars were invented well over a century ago, before the cathode ray tube. You can't predict the future.

author: PlainName
author_rank: Super Contributor
timestamp: November 11, 2021, 09:04:32 am
content: QuoteIf it takes oLED more than 100 years to get to the stage where eti stops hating them, I'd say that's beyond the entire future as far as we're concernedThe trouble is, as you say, we can't predict it. Electric cars stayed shit for maybe 95 of those years and it's only in the last few that they've become nearly a replacement for petrol/diesel. Still got a bit of a hurdle to leap, but maybe we'll end up changing to suit the technology instead. OTOH, LEDs have improved massively over a decade or so, IoT gone off like a rocket, etc.

author: Cerebus
author_rank: Super Contributor
timestamp: November 11, 2021, 12:12:54 pm
content: Quote from: Zero999 on November 11, 2021, 08:03:30 amWhat do you expect? Have you ever seen eti express an opinion that wasn't set on a 'black/white' scale?

author: Cerebus
author_rank: Super Contributor
timestamp: November 11, 2021, 12:16:54 pm
content: Quote from: Zero999 on November 11, 2021, 08:24:37 am[Fx: Peter Cook 'farty little man' voice**] "Did you know, that the electric automobile was in fact in common usebeforethe petrol automobile?"** This is, in fact, true.** For those who don't know what I'm on about:

author: wraper
author_rank: Unknown
timestamp: November 11, 2021, 12:17:36 pm
content: Quote from: eti on November 11, 2021, 08:10:14 amLOL, LG OLED TV in most cases last longer than LG LCD with failing backlight. Burn-in in most cases can be eliminated by running a compensation cycle for a few minutes. I'd say the most prominent downside is price rather than reliability.

author: Zero999
author_rank: Super Contributor
timestamp: November 11, 2021, 12:43:33 pm
content: Quote from: Cerebus on November 11, 2021, 12:16:54 pmYes I knew that, but back then automobiles weren't yet mainstream, which wouldn't have happened so soon, had it not been for the massive improvements made to the internal combustion engine.

author: IanB
author_rank: Super Contributor
timestamp: November 11, 2021, 03:30:06 pm
content: Quote from: wraper on November 11, 2021, 12:17:36 pmYes. Also, I was looking at a price sticker of nearly $1000 underneath a display TV, and realized it was not the price of the TV, but the price of a sound bar to pair up with the TV (which also cost nearly $1000).In the old days you would buy a TV with integrated sound. Now, they are decoupled and you have to buy your sound separately.

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2021, 03:34:42 pm
content: Quote from: wraper on November 11, 2021, 12:17:36 pmThat's a pretty low standard. It is certainlypossiblethat LG has perfected the OLED display and there won't be any issues, but given the track record of LG and the OLED in general, I'm not going to give them the benefit of the doubt quite yet. The few years that they have been out isn't enough to convince me to replace my 14 year old plasma TV. I like to keep things and a TV that only lasts 5 years would really irk me.

author: wraper
author_rank: Unknown
timestamp: November 11, 2021, 04:07:28 pm
content: Quote from: bdunham7 on November 11, 2021, 03:34:42 pmFailing multimeter, coffee machine and similar small displays are not an indication of OLED TV reliability. They are out way more than a few years.

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2021, 04:51:38 pm
content: Quote from: wraper on November 11, 2021, 04:07:28 pmOLED TVs have been out for 14 years, but those were rare, expensive and not very good. Modern, mainstream 4K OLED TVs have been out about 4 years or so, AFAIK. Here's an LG OLED with screen burn after about 4 years of use. Go to 2:30 to skip the lower-time ones without burn.

author: Ranayna
author_rank: Super Contributor
timestamp: November 11, 2021, 05:40:20 pm
content: Quote from: IanB on November 11, 2021, 03:30:06 pmThey do still have integrated sound. But modern TVs have to be razor thin, and since decent sound needs physical volume, the inbuild speakers are mostly bad.Well, now they can upsell their soundbars as well

author: wraper
author_rank: Unknown
timestamp: November 11, 2021, 05:59:06 pm
content: Quote from: bdunham7 on November 11, 2021, 04:51:38 pmIf he had manually ran compensation cycle, most likely those issues would be gone.

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2021, 06:08:37 pm
content: Quote from: wraper on November 11, 2021, 05:59:06 pmI've seen no success with screen-burn reduction apps in other devices--is there something special about the compensation cycle in an LG OLED? Does it know somehow which pixels are weak? Does it store calibration data?

author: wraper
author_rank: Unknown
timestamp: November 11, 2021, 06:17:59 pm
content: Quote from: bdunham7 on November 11, 2021, 06:08:37 pmAFAIK it somehow measures the voltage on individual LEDs or something like that. IIRC there are repair threads on eevblog where after running it, visible burnout effects disappeared.

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2021, 08:44:30 pm
content: Quote from: Zero999 on November 11, 2021, 08:03:30 amI have so far never paid money for a TV, but if I do ever buy one it will be OLED. The picture quality is simply stunning, no LCD can even come close. It's not like LCD TVs are some shining beacon of reliability either, right now I have two nice big LED lit LCD TVs in the back of my closet that have bad backlights. The 65" LCD that is my main TV is one I got for free because the LED backlight had failed. OLED TVs are already more reliable than a lot of LCD TVs.

author: eti
author_rank: Super Contributor
timestamp: November 12, 2021, 01:13:52 am
content: Quote from: bdunham7 on November 11, 2021, 03:34:42 pm2007 vintage Panny plasma here, given to us by a couple who were - ahem - "upgrading" - still going strong, daily use, MANY hours!

author: eti
author_rank: Super Contributor
timestamp: November 12, 2021, 02:17:31 am
content: Consumers are far too pampered and demanding, and I find people get overly obsessed with specs, display technologies etc, having swallowed and digested the marketing garbage, hook line and sinker. 😁Quit the pixel peeping and just enjoy what you’ve got. The novelty of a new toy and all the things it can do, fade away and soon are forgotten once it transitions from “MY NEW TV!” into just “My TV”. I find this carries across the entire line of consumer gadgets too. Just use the thing and enjoy it - I don’t ever remember thinking “😱 Oh no! My blacks are too bright - it’s ruined my film - how can I possibly enjoy it now?!”Reminds me of when my neighbour came back from the cinema, having watched a 3D film - he was extolling the virtues of how amazing it all was, how it jumped out at you, on and on… I said “yea that’s amazing but was the story any good?” - he was fixated on the novelty factor. In a similar vein, my Panasonic plasma isn’t even 720p, and yet it performs incredibly, and I never even think about that.

author: PlainName
author_rank: Super Contributor
timestamp: November 12, 2021, 12:59:09 pm
content: QuoteIs it colour?QuoteSo you'd be OK watching stuff in B&W? I'm betting when colour TVs first came out there was someone asking, yeah but was the story any good?

author: Cerebus
author_rank: Super Contributor
timestamp: November 12, 2021, 01:28:26 pm
content: Quote from: dunkemhigh on November 12, 2021, 12:59:09 pmI (voluntarily) carried on watching TV in B&W into the 1990s. I rarely felt I missed out on anything without colour and with analogue SD the fact that the luminance signal had over twice the bandwidth of the chrominance signal meant that B&W was considerably crisper than colour. When you've only got at most 704 pixels in a line you need all the resolution you can get.

author: PlainName
author_rank: Super Contributor
timestamp: November 12, 2021, 02:54:43 pm
content: QuoteBut eti doesn't care about resolution...I think all this shows is that different people have different appreciation of features. Resolution vs colour vs frame rate vs 3D vs power vs adverts vs ... well, there are lots of things you can trade off and we decide the balance that would suit us. Seems a bit silly to deride the choice of others when one has made one's own off-the-curve choice.

author: macboy
author_rank: Super Contributor
timestamp: November 12, 2021, 04:45:40 pm
content: Quote from: bdunham7 on November 11, 2021, 06:08:37 pmYes, it is special.LG engineers determined that the forward voltage of the individual OLED pixels changes predictably with wear. So if you can measure the forward voltage, you know the state of that pixel and compensate. The modern OLED TV panels are engineered with a substantial headroom in maximum brightness output. As the each pixel ages, the TV applies compensation to boost the output to match original specifications. Eventually of course, it will run out of headroom and won't be able to boost some pixels any further, at which time light output will decrease and burn in will begin to show up. I've read they expect this will occur after approximately 100000 hours, or around 10 hours a day for 30 years. This technology has improved over the years (and didn't exist at first) so don't be surprised to hear of burn-in issues from people with old OLED panels. It's highly likely that modern OLED TVs (just like LCDs) will be replaced due to technological obsolescence or some non-panel fault far before the panel is worn out.Even if my OLED TV only lasts 5 years, I will get another OLED to replace it. There is no other tech on the market that comes anywhere close to the picture quality. The picture uniformity is perfect; in fact, I now find it almost painful to watch any LCD TV due to the subtle non-uniformity (blotches, brighter edges, etc.) that most people don't even notice because it's so "normal"/common. The black levels and shadow detail of OLED are amazing. The best zone-lit LCDs have narrowed the gap but don't and can't match the performance.

author: james_s
author_rank: Super Contributor
timestamp: November 12, 2021, 09:32:08 pm
content: It's the contrast ratios and black levels that really sold me on OLED, they look absolutely stunning in a darkened room, and the color is also amazingly good. LCD looks washed out and bland in comparison. I think it's unfortunate that so many people don't care about picture quality and that has kept LCD going when it should have been largely obsolete by now.I don't watch TV in a traditional sense, I use my TV for movies and streaming older shows and it is only on when I'm actively sitting there watching something so the potential for screen burn is not really an issue, and picture quality is very important to me. I have an LCD TV only because I got it for free, it's not nearly as nice as the OLED sets a couple of my friends have but it's good enough for the price.

author: Zero999
author_rank: Super Contributor
timestamp: November 12, 2021, 09:50:11 pm
content: Quote from: macboy on November 12, 2021, 04:45:40 pmWouldn't it have been much easier to allocate an area of memory to store how long each pixel is illuminated for and at what brightness? Then the wear can be calculated and compensated for.

author: james_s
author_rank: Super Contributor
timestamp: November 12, 2021, 10:01:12 pm
content: Quote from: Zero999 on November 12, 2021, 09:50:11 pmThat would rely on the wear being absolutely predictable, which it may not be. If you can measure the actual condition of the pixel that is likely to produce much better results.

author: PlainName
author_rank: Super Contributor
timestamp: November 12, 2021, 11:37:30 pm
content: QuoteThat's got me puzzled. What is the 'traditional sense' for a TV? Are they used instead of, for instance, a radio (I note Freeview over here has a lot of 'FM' channels).

author: eti
author_rank: Super Contributor
timestamp: November 13, 2021, 01:45:34 am
content: Quote from: dunkemhigh on November 12, 2021, 11:37:30 pmStreaming on demand, and/or YouTube as opposed to watching broadcast tv through the air, or via cable, I should think.

author: james_s
author_rank: Super Contributor
timestamp: November 13, 2021, 04:03:03 am
content: Quote from: dunkemhigh on November 12, 2021, 11:37:30 pmLoads of people just have the TV on for many hours of the day tuned to whatever happens to be on, whether it is being actively watched or not. My dad was like that, he'd have his TV on from the time he got home from work to the time he went to bed, and on the weekends it was on from the time he got up, he liked having it as background I guess. I turn on my TV when I want to watch something, I watch the show/movie I want to see and then I turn it off. It rarely gets used more than an hour or two a day and it is never displaying anything with a logo in the corner.

author: amyk
author_rank: Super Contributor
timestamp: November 13, 2021, 04:08:59 am
content: Quote from: macboy on November 12, 2021, 04:45:40 pmDriving the worn ones harder to get the same light output just means they'll wear out even faster, so it's a very temporary solution and once the degradation starts it will quickly accelerate. It reminds me of CRT "booster" transformers that increased the filament voltage, more quickly destroying the cathode emission completely....and 30 years? They claimed the same 50-100k hours for LED lamps when they first came out... but look at what the actual lifespan in practice is

author: james_s
author_rank: Super Contributor
timestamp: November 13, 2021, 04:14:05 am
content: Quote from: amyk on November 13, 2021, 04:08:59 amWell time will tell how it actually plays out, but in theory at least they are run well below their maximum output so there is a lot of room to drive them harder without exceeding the point at which lifespan is rapidly reduced.I don't remember seeing 100k rated LED lamps but I do have some of the early ones that are 50k rated and most of those are either still going or they were replaced due to the availability of more efficient lamps. I have a Philips 8W LED bulb in my front porch light that I installed in 2011, it has been running dusk till dawn so around 12 hours a day average since then and still looks like it did the day I installed it. That's well over 40k hours so it may actually achieve the 50k rating.

author: eti
author_rank: Super Contributor
timestamp: November 13, 2021, 05:44:46 am
content: Quote from: amyk on November 13, 2021, 04:08:59 amYes, marketing people live in fairytale land.

author: wraper
author_rank: Unknown
timestamp: November 13, 2021, 08:01:28 am
content: Quote from: james_s on November 12, 2021, 10:01:12 pmAnd the amount of data and speed at which it would need to be processed are quite extreme.

author: PlainName
author_rank: Super Contributor
timestamp: November 13, 2021, 10:46:07 am
content: Quote from: james_s on November 13, 2021, 04:03:03 amOK! Kind of wallpaper.Got to admit I have a small 7" monitor hooked up to STB output which is on whenever my PC is. Reason is that when I was developing a CCTV DVR I needed a video source other than the DVD players being already used, and 24-hour news channel hit the spot. I just got used to it being there as a kind of ticker tape, keeping up with the world.

author: Cerebus
author_rank: Super Contributor
timestamp: November 13, 2021, 02:34:58 pm
content: Quote from: amyk on November 13, 2021, 04:08:59 amAre you making assumptions from what you know about the wear characteristics of 'conventional' LEDs and applying them to organic LEDs? Straight question, because if you are then there's every possibility that those assumptions are wrong (they could also be right). One type are made out of elements, one out of compounds, they may wear/age in very different ways. I just don't know because I haven't looked into OLEDs in any more systematic a fashion than reading the odd article in the trade press as they started to emerge. So I'm not saying you're right or wrong, just asking "Is this an assumption or actual knowledge"?Quote from: amyk on November 13, 2021, 04:08:59 amI have an unpleasant suspicion that the shorted life is down to value engineering and "Design it so they need to come back and buy more."

author: james_s
author_rank: Super Contributor
timestamp: November 13, 2021, 06:53:03 pm
content: Quote from: Cerebus on November 13, 2021, 02:34:58 pmUnfortunately a lot of TV manufactures have miscalculated and gone too far. The number of late model LED lit LCD TVs I have been given with bad backlights makes me very hesitant to ever recommend buying one of those brands. I come from an era when a TV was expected to last around 20 years and I still expect that. Anything less than 10 years is absolutely unacceptable.

author: Cerebus
author_rank: Super Contributor
timestamp: November 13, 2021, 08:12:02 pm
content: Quote from: james_s on November 13, 2021, 06:53:03 pmWe were talking of LED lamps, and that's where I suspect perhaps a little less good faith from their manufacturers towards the public than is properly warranted. One would hope that TV/panel manufacturers cared a bit more for their reputation. After all, youwillremember whose TV brand you bought, the brand of that £4 LED lamp that lasted a disappointing time? Probably not.

author: james_s
author_rank: Super Contributor
timestamp: November 14, 2021, 05:05:34 am
content: Quote from: Cerebus on November 13, 2021, 08:12:02 pmThe oldest LED bulbs I have are ones that cost me around $40 each back when I bought them. At the prices they were charging back then I think most of the bulbs were over-engineered because they knew a lot of early failures would risk killing the entire market, a lot of people already didn't trust them after experiences with CFLs not lasting as long as claimed. Then there was the predictable race to the bottom, although you can still get reasonably good ones. I've had good luck with Cree and Philips bulbs.

author: strawberry
author_rank: Super Contributor
timestamp: November 14, 2021, 12:44:44 pm
content: make so called old tech unappealing and degrade it and then replace it with more predictable (shorter) life product then add commercials at bootup and everyone is happyLCD block ~1/2 backlight while white is displayed

author: PlainName
author_rank: Super Contributor
timestamp: November 14, 2021, 01:44:25 pm
content: QuoteThat makes sense - white is essentially unobstructed whereas other colours reduce the intensity because R, G or B are filtered, so without artificially reducing white it would appear too bright in comparison.

author: wraper
author_rank: Unknown
timestamp: November 14, 2021, 02:02:16 pm
content: Quote from: dunkemhigh on November 14, 2021, 01:44:25 pmWhat? White is not artificially reduced. There is a light loss because subpixels have color filter behind them and pass only narrow range of wavelength. When 3 colors are combined in your eye, you see "white". There are also RGBW displays which add a subpixel without a color filter for better brightness/efficiency, but it reduces picture quality.

author: strawberry
author_rank: Super Contributor
timestamp: November 14, 2021, 03:48:23 pm
content: I think these are fancy RGB LEDs to increase efficiency and match LCD filters and some might be more fancy switching on/off at black spots

author: eti
author_rank: Super Contributor
timestamp: November 14, 2021, 09:01:18 pm
content: [1 of 3 messages with attachments]I thought you'd like to see the bare die on the backlight strip, along with the special lens type device, inside which is a conical, hollow cavity, clearly designed for maximum dispersion (I'd think)

author: eti
author_rank: Super Contributor
timestamp: November 14, 2021, 09:02:36 pm
content: [2 of 3 messages with attachments]

author: eti
author_rank: Super Contributor
timestamp: November 14, 2021, 09:03:51 pm
content: [3 of 3 messages with attachments]