Author Topic: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980  (Read 5644 times)

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Offline flangefrog

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #25 on: April 29, 2024, 12:36:29 pm »
I found the error codes for the power supply led
 

Offline 3DMovieListTopic starter

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #26 on: April 29, 2024, 04:04:00 pm »
Nice work!  Thanks for posting!
Now, what does "Driver On Signal error" mean?
 

Offline flangefrog

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #27 on: April 29, 2024, 05:51:56 pm »
Nice work!  Thanks for posting!
Now, what does "Driver On Signal error" mean?
No DRV_ON aka INV_CTL (LED backlight enable) in a certain time period after PWR_ON signal received
 
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Offline flangefrog

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #28 on: May 22, 2024, 04:09:20 pm »
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.html

They're cheaper over at TaoBao:
https://item.taobao.com/item.htm?_u=t2dmg8j26111&id=715145782611&skuId=5310061734568&spm=a1z0k.7628869.0.0.32b437deSJlcmm
https://item.taobao.com/item.htm?id=775355498771&spm=pc_detail.27183998/evo401271b517998.202208.6.5ba77dd6LLOuh6

The 4k 60Hz to 4k 120Hz V-by-One adapter board I used:
https://www.aliexpress.com/item/1005003730360591.html
Note 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.html
2233912-0

Or 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.html
I 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).
2233888-1

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
2233894-22233900-3
« Last Edit: May 23, 2024, 12:44:58 am by flangefrog »
 

Offline 3DMovieListTopic starter

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #29 on: May 26, 2024, 01:25:57 pm »
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.3.271cf19cj5Ga7E

I 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!
 

Offline flangefrog

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #30 on: May 28, 2024, 01:35:10 am »
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).
 

Offline 3DMovieListTopic starter

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #31 on: May 29, 2024, 04:02:50 pm »
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
 

Offline boz

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Re: LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
« Reply #32 on: June 02, 2024, 11:31:29 pm »
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.

Fearless diver and computer genius
 


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