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LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980
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flangefrog:
I found the error codes for the power supply led
3DMovieList:
Nice work!  Thanks for posting!
Now, what does "Driver On Signal error" mean?
flangefrog:

--- Quote from: 3DMovieList on April 29, 2024, 04:04:00 pm ---Nice work!  Thanks for posting!
Now, what does "Driver On Signal error" mean?

--- End quote ---
No DRV_ON aka INV_CTL (LED backlight enable) in a certain time period after PWR_ON signal received
flangefrog:
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


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).


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
3DMovieList:
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!
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