LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980 - Page 1
Forum section: electronics / repair

author: 3DMovieList
author_rank: Contributor
timestamp: October 22, 2022, 03:46:09 pm
content: Recently I've been working on the repair of (IMHO) three of the best 3D TVs ever manufactured - the "UB980" range of LG passive 3D 4K TVsFortunately, there is a good amount of service information available online for these TVs.The LG Service manual for the 79UB980T is available here:https://www.manualslib.com/manual/1293719/Lg-79ub980t-Ta.htmlThe T-CON board is missing from the above service manual, but fortunately it is summarised on page 123 of this document:https://pdfcoffee.com/collection-of-lg-t-con-board-testing-points-amp-voltages-pdf-free.htmlHowever, there is one more board (or actually 8 small long boards) still not described and it's the boards connected directly to the LCD panel.I've included a photo of two of those boards here:Unfortunately, one of those boards experienced some water damage, as pictured here:I guess some water or other liquid was spilt on the TV.Fortunately, these boards are fairly simple, mainly consisting of some capacitors and resistors.After cleaning off the corrosion, I've found three capacitors had gone short circuit and I've been able to replace those.However, there is also a 5-legged SMD IC labelled "J516T" which is performing unusually.Unfortunately, I have not been able to find a datasheet or other information about this IC.Does anyone have any ideas?Another item I have to contribute and summarise here is that many of the LG TVs have a problem that the main chip gets very hot and causes dry joints in the solder joints.Reheating the chip using a hot air solder station can help bring TVs back to life (I have repaired three LG 3D TVs (LW6500 models) this way).Here is a video which illustrates the technique of reflowing the solder on the main chip and overcoming the dry joints:So... who else is repairing these LG passive 3D 4K TVs?I have looked at the service manuals for other TVs, including other brands, to see if there is a hint as to what this chip might be, but no luck.Anyone have any ideas?Thanks!

author: 3DMovieList
author_rank: Contributor
timestamp: October 23, 2022, 10:41:16 am
content: I found a datasheet (42 page PDF) for the LCD & backlight module used in the LG 84UB980T (LC840EQD-SEM1):https://datasheetspdf.com/pdf-file/907195/LG/LC840EQD-SEM1/1But unfortunately, there's still no circuit diagram for the circuit boards in this module, or identity of the mystery "J516T" component.

author: EEVblog
author_rank: Unknown
timestamp: October 24, 2022, 01:57:39 am
content: I did a video on almost exactly this:

author: sinewave
author_rank: Unknown
timestamp: October 24, 2022, 02:42:38 am
content: If you could remove the chip that would help and also post photos of the underside to better understand where signals/voltages are going. Doing a quick search I see that part number: R1154N001C matches quite well in terms of pinout if the middle pin on the side with three pins connects to the copper fill, looking at the application in the datasheet, I see that the VOUT pin is connected to a resistor, with an accompanying footprint for the resistor between the VOUT/ADJ and GND.

author: 3DMovieList
author_rank: Contributor
timestamp: October 24, 2022, 03:50:38 am
content: G'day Dave and Sinewave,Thanks for the pointers.Attached are photos of the board (front and back) with the chip removed.Unfortunately, the board looks like it is a multi-layer so not quite so easy to trace out visually.U1 is the chip in question.Pin 2 is definitely ground.Pins 3,4,5 immediately disappear off to vias. I would need to do some poking around with the multimeter to see where they go.Pin 1 connects to a via _and_ a resistor. I could measure the value of this resistor but not sure it would reveal anything definitive.I was wondering whether the chip was a linear regulator, BUT the lack of any caps immediately nearby is a counter-indicator.Looking up "_J51_6T" on the SMD marking code database suggests it might be a linear regulator, or an "ElectroStatic Discharge Protection diode".https://smd.yooneed.one/code4a35.htmlThe first ESD SOT-23-5 that I looked up could be a winner.https://au.mouser.com/datasheet/2/240/Littelfuse_TVS_Diode_Array_SP05_Datasheet_pdf-777043.pdfThe SP0504BAHTG has pin 2 GND, with a single diode going to each of the other four pins.This looks to me to be the most likely bet - I'll check the chip with a semiconductor tester to see if this confirms anything.Thanks again for the hints!

author: sinewave
author_rank: Unknown
timestamp: October 24, 2022, 04:19:02 am
content: I doubt it is the ESD diode as in the datasheet it says the package will be marked 504B which it is not and wouldn't seem needed, as there is a VCC silkscreen and a bank of 4 capacitors nearby makes me believe it is a regulator, I'd suggest you check if R_93 is continuous to pin 4 if it is I'd say with a bit more certainty that it is a regulator, most of the time with these components it's pretty hard to find a match anyway.

author: projectgus
author_rank: Newbie
timestamp: October 24, 2022, 09:49:47 pm
content: (Moving here from our twitter discussion.)I had a similar guess to you, sinewave, ofR1154N051B. J516T marking matches (J51 prefix and then a two digit date code, which for that family seems to be number+letter). But pin 4 would be NC for that fixed voltage variant so I'm not very confident about it, unless the part is dual-sourced with an adjustable voltage version and pin 4 runs off to some unpopulated pads.3DMovieList, you said on twitter that there are a few J516T chips on the PCB and the others all probe differently with your multimeter. FWIW, this is what I'd be focusing on next - can you post any photos of how the other J516Ts are connected on the board, and also can you give any details about what you've measured between the various pins? Bear in mind that probing in-circuit you may be measuring a lot of other things as well as that chip, but it still could be a good clue.If you haven't already, another thing you could try doing is test continuity between the pins and the marked test points or bulk capacitors nearby on the board.

author: sinewave
author_rank: Unknown
timestamp: October 24, 2022, 11:48:37 pm
content: There is indeed an adjustable version according to the datasheet,https://www.n-redc.co.jp/en/pdf/datasheet/r1154-ea.pdfR1154N001C is the adjustable version whereas R1154NxxxB is the fixed version, I do agree on you with it being dual-sourced as it seems to have the correct circuitry for an adjustable LDO.

author: EEVblog
author_rank: Unknown
timestamp: October 25, 2022, 01:35:44 am
content: On twitter I speculated a dual mosfet.A regulator without any caps doesn't make any sense.

author: EEVblog
author_rank: Unknown
timestamp: October 25, 2022, 01:41:44 am
content: Maybe a load switch, but again, lack of caps.https://www.farnell.com/datasheets/2304069.pdf

author: sinewave
author_rank: Unknown
timestamp: October 25, 2022, 01:53:32 am
content: I do agree with it more than likely being not an LDO, due to the lack of caps around, figuring out the actual package would help as there are 4 or so footprints with a similar layout (2 pins on one side and 3 on the other)

author: 3DMovieList
author_rank: Contributor
timestamp: October 25, 2022, 01:56:08 am
content: A few folks have mentioned the Twitter thread. For those following this discussion, the Twitter thread is here:https://twitter.com/3DMovieList/status/1583982843344326656?s=20&t=qZjoL39L_oq3PdYxA8_C-wBUT let's keep the detailed discussion here. ;-)

author: sinewave
author_rank: Unknown
timestamp: October 25, 2022, 02:06:56 am
content: 3DMovieList, can you measure the height/width/length of the package?

author: 3DMovieList
author_rank: Contributor
timestamp: October 25, 2022, 02:17:16 am
content: I don't have my notes with me at the moment, but when I originally tested the "good" J516T, it looked more like a diode package with several 0.6V diode drops identified using the multimeter. But I didn't test thoroughly, and it was in-circuit, so at the time, I was just noticing a difference between the "good" and the "bad".Hopefully I'll have time today to desolder a good J516T chip to allow some more detailed testing to check what the chip might be.Thanks for all the good suggestions everyone.

author: EEVblog
author_rank: Unknown
timestamp: October 25, 2022, 03:05:06 am
content: Quote from: sinewave on October 25, 2022, 02:06:56 amI overlaid a SOT23-5 package on it visually and it matched.

author: 3DMovieList
author_rank: Contributor
timestamp: October 25, 2022, 03:16:02 pm
content: So I was able to desolder a good version of the "J516T" chip and do some tests.Buzzing out the chip with a PEAK diode/transistor/semiconductor tester indicated that the chip contains 4 diodes, as indicated in the diagram below.The configuration is (to me) unusual and the forward voltage of the diodes falls into two groups (two are 0.65V and two are 2.8V) as indicated in the diagram.For the bad "J516T" chip, the diode on pin 1 was open circuit, but otherwise the same as the good chip.I also tried testing various combinations of the SMD legs to see if there was a transistor or FET present, but nothing came up - just independent diodes.So... the plot thickens.I didn't spot any SOT-23-5 devices with two sets of different diodes in the package when I was looking around.Any ideas?

author: 3DMovieList
author_rank: Contributor
timestamp: October 26, 2022, 02:22:26 pm
content: I just had a look through a range of 4 diode SOT-23-5 packages available on Mouser and couldn't find anything remotely similar to the diode configuration measured on the good J516T.The two different forward voltages, and the alternating directions of the diodes I found seems very unusual.I did test for transistor and FET modes too using the semiconductor tester, but the device always identified just four separately diodes.I did some quick tracing of connections to the chip today and found just bypass capacitors so nothing special to suggest this chip is anything other than ESD protection.

author: projectgus
author_rank: Newbie
timestamp: October 30, 2022, 03:45:52 am
content: Is it possible you're measuring pin protection circuitry here?Bit of a wild guess, but could it make sense for a differential line driver or receiver? Something likeDS90LV011A(but not that exact one). Many SOT-23-5 all with the same basic pinout for driver or receiver.Pins 3 & 4 are the differential pins so you may be measuring overvoltage for an LVDS pin relative to GND (pin 2)? (The LVDS maximum voltage is not referenced to VCC in these chips, although I don't know how they are actually implemented.)However if this was the case then you'd also expect to be able to measure some protection circuitry directly between pin 1 (VCC) and pin 5 (the LVTTL single-ended pin), and probably also undervoltage protection between 3 & 4 and GND. Also, I have no idea why these boards might need this.The only similar (equally wild guess) option there would be an op amp, which are available in similar SOT-23-5 standard pinouts and pins 3 & 4 are typically the op amp inputs.

author: 3DMovieList
author_rank: Contributor
timestamp: October 30, 2022, 04:23:39 am
content: Thanks for the suggestion projectgus. At this point anything is possible. ;-)I did some further testing on the board yesterday to check the chips connections to other points on the board.Pin 1 and pin 4 of the J516T chip are connected together, and together connect to a zero ohm resistor (R394) (I think effectively a fuse), but it doesn't seem to connect to anything else on the board, which is really weird. The only thing they might connect to is a connection on the thin ribbon cables that run to the LCD panel, but I'm unable to probe those.Pin 3 goes to one pin on the input connector CN2 (pin 3) (which I think is a power supply pin, but I'm yet to confirm) on the other end of the board and there is one bypass capacitor (C305) on the line near the input connector.Pin 5 goes to three sequential pins on the input connector CN2 (pins 68,69,70) on the other end of the board and it also connected to 8 bypass capacitors (C304,C316,C323,C326,C333,C336,C343,C346) going to ground along the way.Pin 2 is ground.I've captured a high-resolution image of the board, which helps understand the configuration. The J516T chip is removed in this image.Unfortunately, it seems the board is multi-layer, so this top view doesn't tell the full story.But... given it seems there are only bypass capacitors connected to the J516T chip, to me it seems likely to me that this is a Transient Voltage Suppression (TVS) chip.Given it's only one of the diodes (pin 1) that is malfunctioning on the bad J516T chip (which should have a forward voltage of 0.7V) I might just solder the chip back with pin 1 disconnected, and see if this allows the LCD panel to behave correctly. I could solder a small external signal diode between pins 1 and 2 to replace the missing diode in J516T, but I wonder if that is absolutely necessary. I was thinking of drawing up a simple schematic to illustrate what the circuit looks like.But as you can see from the circuit board image, the J516T chip is the only chip on the board. Everything else is just capacitors and resistors.All comments, ideas and theories very welcome! Thanks for reading this far!

author: 3DMovieList
author_rank: Contributor
timestamp: October 30, 2022, 04:25:25 am
content: Quote from: sinewave on October 25, 2022, 02:06:56 amI've measured the J516T chip with a vernier and the measurements are:3.0mm (L) x 1.6mm (W) x 0.75mm (H)

author: 3DMovieList
author_rank: Contributor
timestamp: November 17, 2022, 02:08:17 am
content: Good news! There is LIFE in the TV!!!I borrowed a "J516T" chip from another 65UB980T that I am repairing and that has brought the 84UB980T TV to life!More details to follow, but replacing three SMD caps, and the "J516T" chip has brought the TV to life.

author: 3DMovieList
author_rank: Contributor
timestamp: November 24, 2022, 07:02:31 am
content: So the 84" TV is alive, but actually there is one remaining problem with the TV that I need to solve to get it fully operational.The mainboard also has a problem. The image you saw earlier is with a borrowed mainboard from another TV.So, the TV had four problems, of which I've solved three so far: (a) blown fuse on the T-CON board, (b) broken and twisted trace on one of the T-CON board flex cables, (c) the three caps and J516T chip on the LCD driver board, and finally (d) a mainboard problem (yet to be solved).I'll report more as things progress!

author: 3DMovieList
author_rank: Contributor
timestamp: December 24, 2022, 04:21:29 pm
content: I've found another two useful reference documents that can hopefully help solve faults on the UB980 range of LG 4K 3D TVs:1. Full service manual for the LG 98UB980 (98" 4K 3D TV)https://www.manualslib.com/download/1163299/Lg-98ub9800.htmlThis document is very similar to the 79UB980T service manual mentioned earlier in this thread.2. "Novacom Collection of OLED/LED/LCD TV Repair Tips V5.0"https://lcdledsolutions.com/circuitpdf/pdf/V5%20OLED.LCD.pdfFrom page 76, there are further debugging information for the LG 84UB9800 TV.Firstly, the interconnect diagram, and then in following pages a series of Main Board Component Voltage measurements for chips all over the main board.Unfortunately, this information hasn't helped solve the UB980 mainboard problems as yet.

author: 3DMovieList
author_rank: Contributor
timestamp: December 26, 2022, 04:52:40 pm
content: Some more useful information for debugging/repairing LG TVs.The following document is titled: "LG - OWNER’S MANUAL - EXTERNAL CONTROL DEVICE SETUP"http://www.proaudioinc.com/Dealer_Area/RS232.pdfIt contains the IR remote control codes, including the elusive code for the "ADJ" (adjust) button on the LG Service Remote Control, which isn't generally available for purchase.This page on Reddit suggests how to generate this code using ESPhome:https://www.reddit.com/r/OLED_Gaming/comments/vuphk0/does_anyone_have_the_ir_codes_for_lg_service/

author: 3DMovieList
author_rank: Contributor
timestamp: April 10, 2023, 12:15:50 pm
content: I found another interesting repair resource for the UB980 range of LG 4K TVs.This video shows a repairer reflowing the CPU which returned the TV to life.(the reflow occurs at 5:20)Prior to this process, the repairer checks various voltages to confirm correct operation of the various power supply sections.In his case, the voltages were all OK, which led to the CPU reflow option, which was successful.In my case the voltages are all OK as well, however reflow has not worked. There's one more thing I want to try...

author: flangefrog
author_rank: Newbie
timestamp: April 29, 2024, 12:36:29 pm
content: I found the error codes for the power supply led

author: 3DMovieList
author_rank: Contributor
timestamp: April 29, 2024, 04:04:00 pm
content: Nice work! Thanks for posting!Now, what does "Driver On Signal error" mean?

author: flangefrog
author_rank: Newbie
timestamp: April 29, 2024, 05:51:56 pm
content: Quote from: 3DMovieList on April 29, 2024, 04:04:00 pmNo DRV_ON aka INV_CTL (LED backlight enable) in a certain time period after PWR_ON signal received

author: flangefrog
author_rank: Newbie
timestamp: May 22, 2024, 04:09:20 pm
content: I've done a bit of work on my 65UB980T. Figured the issue is bad BGA ICs - Either the XD image processor, or the main CPU. I ruined the motherboard by attempting to reflow it as a last ditch effort without all my equipment (just moved into a new house). But I did a lot of research on V-by-One connections and bought a 4k 60Hz to 4k 120Hz V-by-One frequency doubling board which duplicates frames and takes an 8 lane input with a 51p connector and provides 16 lane output over a 51p and 41p connector. I used an android TV motherboard from another broken 4k TV I'm playing with and managed to get the TV to work. There's also lots of 4k 60Hz 8 lane V-by-one display driver boards which could be used, or even a few native 4k 120Hz 16 lane V-by-one display driver boards which can take displayport 1.4 or HDMI 2.1. There's a few 4k 120Hz smart TV boards out there but they're pretty rare, and only the most recent can actually take a 4k 120Hz input via DisplayPort or HDMI.Getting the inbuilt speakers running should be fairly easy by using a little amplifier (something like a TPA3116 or more recent model would work well) and the camera seems to be USB so it should be possible to get that working as well. The inbuilt power board should be able to be used with any third party motherboard or display driver board as well as for powering the amplifier etc.I put some of my instagram updates together into a YouTube video:One of the 4k 120Hz display driver boards:https://www.aliexpress.com/item/1005006163848433.htmlThey're cheaper over at TaoBao:https://item.taobao.com/item.htm?_u=t2dmg8j26111&id=715145782611&skuId=5310061734568&spm=a1z0k.7628869.0.0.32b437deSJlcmmhttps://item.taobao.com/item.htm?id=775355498771&spm=pc_detail.27183998/evo401271b517998.202208.6.5ba77dd6LLOuh6The 4k 60Hz to 4k 120Hz V-by-One adapter board I used:https://www.aliexpress.com/item/1005003730360591.htmlNote they come in many different models including 60Hz to 60Hz, 120Hz to 120Hz (changing partition modes) as well as LVDS 1080p 60Hz to 4k 120Hz etc.You may need adapters depending on which motherboard or display driver board you use.https://www.aliexpress.com/item/1005004244737281.htmlOr you can use a cable with a JAE FI-X connector on one end, and an appropriately shaped plain FPC at the other.https://www.aliexpress.com/item/1005004383279204.htmlI actually ended up using the original LG motherboard cable, and removed the FI-X connector then cut down the FPC to 26mm with scissors.Here is the pinout of the LG motherboard 51p connector overlaid on the 51p output connector of the 120Hz adapter board. I had to choose 10 bit mode, using 0 for both data input format lines let me have all the dip switches set to off. The local dimming can be switched on or off at any time and seems to be fully controlled by the TCON (which sends data to the power supply).See page 8 of the LC840EQD panel datasheet or page 63 of the 65UB980T service manual for more info on pinouts. My panel is actually an LC650EQF-FGF1 but it seems pretty similar to the LC840EQD

author: 3DMovieList
author_rank: Contributor
timestamp: May 26, 2024, 01:25:57 pm
content: Hi Flangefrog,Thanks for posting here!And thanks for including the video and all the extra details.That's amazing work - especially given the limitations of the equipment you've been using.It's unfortunate that mistakes happened to your original board.The use of a mainboard from another 4K TV and an interface board is fascinating and I'm glad you were able to get the TV back to life that way.In my case, it's important to retain the original 3D capability so I am needing to resurrect the original LG mainboard.I have tried reflowing the XD processor on the dead 84" mainboard I have here without a successful outcome so far, but I haven't tried reflowing the CPU.I have previously been successful reflowing the main processor on several LG ##LW6500 TV mainboards.For your reference, I found some LG XD processor chips (LGE7411) online and bought a couple - they were pre-balled.https://www.aliexpress.com/item/1005004641223187.html?spm=a2g0o.order_detail.order_detail_item.3.271cf19cj5Ga7EI have recently acquired a functioning mainboard from an LG 65UH950T (which has similar specs to the UB980T range) so I should try doing a swap with that board. I hadn't thought of doing that! ;-)Thanks again for posting your journey!Collectively we can hopefully solve this seemingly common problem!Please keep us updated with your progress.Cheers!

author: flangefrog
author_rank: Newbie
timestamp: May 28, 2024, 01:35:10 am
content: Interesting to see the XD ICs are available on AliExpress, I hadn't thought to look. I think my main board is probably too far gone though.I think 3D should be possible using any computer as the input. As far as I can tell it's just simple passive 3D with row interleaved polarisation for L/R. So most good media players should be able to output row interleaved 3d stereo.The TCON has a 3D_EN_LGD_120Hz pin, otherwise known as PCID enable/disable. Not sure exactly what that pin does, or what PCID stands for. The TV is marketed with 200/240Hz capability - although it has a 120Hz panel. I think maybe it's something to do with how it manages the odd/even gate drivers for the panel (VGH_Odd/VGH_Even) - maybe switching them twice per frame so it can output interleaved 240Hz with a progressive 120Hz input? Since the pin is just a simple high/low input it should be possible to test.I'd assume the 3D playback is something that should work with a lot of other mainboards, even 60Hz ones, assuming they were from a TV that also had line interleaved polarisation (passive 3d).

author: 3DMovieList
author_rank: Contributor
timestamp: May 29, 2024, 04:02:50 pm
content: Indeed these TVs are row-interleaved passive 3D, so the display can be driven directly with a 4K row-interleaved 3D signal (e.g. from a PC) to achieve 3D display - but... in order to support Blu-ray 3D playback (using HDMI 1.4 frame-packed 3D), a 4K passive 3D compatible motherboard would be required.I compared the UB980 and the UH950 motherboards I have, and unfortunately the TCON ribbon connector is a different pitch, so unfortunately it's not an easy swap.BTW: I found the service manual for the 65UH950 here:https://www.manualslib.com/manual/1990825/Lg-65uh950v.html

author: boz
author_rank: Regular Contributor
timestamp: June 02, 2024, 11:31:29 pm
content: Just repaired a 75" LG LED 4k TV (75UK65 model) had backlight and sound but nothing else. It was the second similar LG 4K model I fixed, both had the same fault, so I am guessing it is quite common.For this particular fault the gate driver high (+16V) or low (-8V) voltage is being pulled down by a shorted smoothing cap.Easy to check with just a DMM and without getting all technical with scopes or circuit diagrams, firstly pull out one of the two ribbon cables from the TCON board to the TFT to see if half the screen goes white. If it does, then one side is shorting the supply. in both my faults it was just a case of going through the ceramic caps on the long PCB at the bottom of the screen which the faulty ribbon cable came from with a continuity tester to find the shorted one.Might help someone save a good TV from landfill.

author: 3DMovieList
author_rank: Contributor
timestamp: August 04, 2024, 01:18:55 pm
content: Thanks for posting boz. @boz Much appreciated.> Just repaired a 75" LG LED 4k TV (75UK65 model) had backlight and sound but nothing else.> It was the second similar LG 4K model I fixed, both had the same fault, so I am guessing it is quite common.>> For this particular fault the gate driver high (+16V) or low (-8V) voltage is being pulled down by a shorted smoothing cap.Shorted ceramic capacitors are a common fault across many electronics systems.I had the same problem on the 84UB980 mentioned in the very first post of this thread.Shorted ceramic capacitors are a much easier fault to identify and correct than some of the other faults present on these TVs.See my text post.

author: 3DMovieList
author_rank: Contributor
timestamp: August 04, 2024, 01:45:33 pm
content: I've just purchased another sick LG 79" 4K 3D TV - a 79UB980.The owner said that the screen was black but sound was OK.That could be a few things, but some quick testing has narrowed it down to the mainboard, as is often the case on these TVs.On first powerup, there was no image, no backlight, and the LED on the power board flashed 5 times.I swapped the mainboard out with another good mainboard I have, and the TV sprung to life, confirming the fault lies with the mainboard.I haven't delved deeper into what the problem might be on this mainboard yet, however, dry joints on the two main BGA chips are my main suspects.I really wish there was a way to do some testing to work out *which* BGA chip was the problem, but there just isn't enough information available to work this out.