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LG 3D 4K TV repair - UB980 range 65UB980 79UB980 84UB980

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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 TVs

Fortunately, there is a good amount of service information available online for these TVs.

The LG Service manual for the 79UB980T is available here:

The T-CON board is missing from the above service manual, but fortunately it is summarised on page 123 of this document:

However, 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?

I found a datasheet (42 page PDF) for the LCD & backlight module used in the LG 84UB980T (LC840EQD-SEM1):
But unfortunately, there's still no circuit diagram for the circuit boards in this module, or identity of the mystery "J516T" component.

I did a video on almost exactly this:

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.

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".
The first ESD SOT-23-5 that I looked up could be a winner.
The 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!


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