problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

[randaz81]

I have an LG OLED 55EC930V.
The problem started a couple of days ago: tv working, but no video, only audio.

I opened the tv and I checked the parts. The mainboard has the red led on, which means that it working correctly. The power board supplies 24V correctly.

I focused my attention on the t-con board, LC550LUD-LGP1, I disconnected it to observe it carefully, no signs of damage. Then I mounted it again and I reconnected to the tv.

After this, the tv started to show a different behavior: it turns on and then, after few seconds, it turns off. I cnanot hear the audio anymore.

This happens in all the following different cases:
1- t-con board is connected to the motherboard and the power supply, but all the four ribbon cables to the panel are not connected.
2- t-con board is disconnected from the 24V power supply
3- t-con board is disconnected from the 24V power supply and the main board.

So my question are:
A- do you think that this behavior is normal? i.e. on a working tv if I disconnect the oled panel from the t-con board, does the tv stays on, or it turns off automatically? Does the t-con board have a system to detect if the planel is connected?

B- Can I safely assume that the only broken part is the t-con board? I'd be happy to replace it, but only if I am pretty sure that is the only broken part.

Thank you for the help.

Btw, can you recommend to me where I can find the replacement, besides eBay?

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Make one or two very sharp photos of the tcon possibly at sun light with readable serigraphs.

[TeslaMichael]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

The LVDS cable will check for panel. if you disconnect it, TV should turn on, but only with sound.

[William1967]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

With OLED TVs you can throw overboard all the tricks you use with an LED TV. The t-con has a protect circuit onboard that comes in quickly so that there is no image. Disconnecting cables between the panel and the t-con will always result in a shut down of the tv. The same goes for disconnecting the power to the t-con.
There is a way to check whether the display or the t-con is the cause and that is to start the device in p-only mode, for this you need a service remote.
If the t-con needs to be replaced remember that the t-con is programmed on that panel, the MURA clouding settings are in the t-con and need to be transferred to the replacement t-con. LG has a service tool for that. First the data must be loaded from the old t-con and than loaded into the new t-con.

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

is it available that LG tool?
I've seen a detailed LG tcon photo, the power circuitry is almost the same as LCD tcon, same tensions, plus a bunch of new control signals..

[William1967]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

The tool is available (RAD33387801) but it's not cheap. The t-con from a Oled looks very similar like the "normal" t-con but it works a bit different.

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

@William1967
> There is a way to check whether the display or the t-con is the cause and that is to start the device in p-only mode, for this you need a service remote.

I'm waiting to receive a service remote. Then, after starting the tv in p-only mode, how can I distinguish if the problem comes from the panel or from the t-con?

Do you have any idea why before I was able to listen to the audio from the tv (with no video), while now I cannot anymore turn on the tv at all?

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

have you ruined the flat cables? Why don't you publish photos? are you able to repair at component level? Are there too the 24v? If you don't put pictures i cannot say you the points to measure, it is possible that supply converters that feeds the fpga doesn't work and without serial comm the software goes in protection..

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

>have you ruined the flat cables?
Hopefully no, I tried to be very gentle with them... (Btw, this is just my curiosity: there are four flat cables from the t-con to the panel. Does it mean that the panel is divided into four independent sections?")

>Why don't you publish photos
I attached some pics of the power supply board and the t-con board

>are you able to repair at component level?
I have good soldering skills, but I have no clue about what to replace... By visual inspection, I was not able to see anything damaged.

The only thing that I'm wondering about is one of the two large vertical heatsinks in the exact center of the power supply board. The one on the right is ~50degrees, while the one on the left is at room temperature (observed with a borrowed thermal camera). Anyway, the 24v lamp seems to turn on correctly, so I don't think I have a power supply issue...

>Are there too the 24v?
Yes, there are. I found here in the forum a link describing a test with a small car lamp. I did it, attaching the lamp to the power supply and putting a jumper on the 24v enable pin, and I can confirm that the car lamp turns on.
About the voltages for the logic... I have no idea about which voltages should I check. Do you have any info on that?

Thank you a lot!!

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Just a silly question, since I have never seen this type of flat cables. Can you confirm that the closed position is correct? I just placed the cable in position and closed the slot, without trying to force the cable inside any further.

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

i have asked only tcon photo with READABLE serigraps... only component side.

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

ok, sorry... I'm having bad times trying to make a clear single photo of the whole board with my phone.

So I did several pics, from left to right. Please tell me if it is ok... I can eventually try to use photoshop to assemble all the pics together but I'm not very familiar with it and it will take a while...

Thank you a lot

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Next time= horizontal board> Horizontal cellular...
test in volt these points respect to GND: 2.5v, 1.15v, 1.8v burk, Vpred, L8, VDD, C1528, C1554, F3 (both terminals), C1516, VGH, D44...

The questions:
1) I think No.. from what i see, each half of tcon: 1 conn. for video data , sync, etc... 1 conn. for power supply, gamma lines or clock lines, i don't see..
2) the flat cables and connectors seem right in place..

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Hi! Here the results:
1.15v, ok
2.5v, missing!!!!!!!!!! (0v)
L8, 3.2V
Vpred, 6.56V
1.8v ok
1.8v burk, ok
C1554, 23v
C1516, 11.34v
VGH 23v
C1528, 16v
D44, 6.56v
VDD, 16v
F3 (both terminals), 11.33v

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Is there a VGL test point? i can't see..
Near 2.5v test point (6.jpg) measure C1606, then measure EVSS_Con_out

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

hi again, last week I was traveling. Here are the measurements:

C1606 = on one side I measured GND, the other side seems to be 0v/floating (maybe like the 2.5V test point?)

about VGL, I found a test point called VGL_SENSING at 1.9V, and a test point called EN_VGL which seems to be 0V/floating.

On EVSS_Con_out I measured GND.

Thank you

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

about 2,5v the U772 must be a linear voltage regulator for the near emmc supply, but on C1606 i think there must be the input voltage and i don't know why it is not present, i think that 2,5v is built probably by a 3,3v, you have 3,3v on L8 but i don't see the capacitors connected to it, so maybe there a switch transistor between 3,3v and U772, or it comes from another place, try to test in volt C1615 on top of 7.jpg, near L9... For the VGL the points you found are not the right points but probably is L9 or i don't know where it is..

[randaz81]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

I measured C1615, it is 1.509V. The other side of L9 has a similar value, 1.52V.
U772 seems to be powered through R7590, one of its sides is also connected to C1608, where I can measure 5.1V.

The very bad news is that I bought a T-CON board from ebay and this does not work either. I also tried to test the 2.5V and also in this case I cannot measure anything.

Therefore there is a chance that maybe the 2.5V is enabled by something that is somewhere else and it is not working, I don't know :-(

[Davi.p]

Re: problems with LG OLED 55EC930V, t-con board LC550LUD-LGP1

Don't consider 100% spare parts are good, better to investigate, there are 2 ways, with multimeter check C1606 where it is connected to in the board, or input a 2,5v externally.., before doing this check in ohms the 2,5v to gnd for possible short..