Just picked up a 55 inch LG 4k OLED for $50!

[freakaftr8]

Owner States that screen just went out no picture no lighting period. of course this is OLED so pixel fires light by each diode cell. Apparently Best Buy and in LG certified technician both started replacing all the boards inside this TV in found out that the picture will not come on.

My 1st question is why would an LG tech Start board swapping if the tests were apparently showing panel failure? What happens is when I picked it up the guy showed me when he turned it on by remote the LG emblem light would light up brightly in and start flashing in 1 second intervals consistently. When I brought it home the LG standby light is dim when I press power I get quick Flash of power led back to standby. I haven't opened it up yet. This is of course an entirely different beast than I am used to working on.

I'm just knowledgeable of OLED screens that when they get A-line or crack the whole screen will go out. I do not see any cracks on this panel. Of.course this Pertains to Cellphone screens but nonetheless similar beast.

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

1st order of action is the typical removal of ribbon cables driving the panel and see if the TV will come up.

Model 55EG9600

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Well after realizing that mainboard will not send ps on, I decided to jump the gun figuring this is some firmware related issue with previous board swaps by LG and Best Buy geek squad, I jumped PS_ON, DRV_ON, and 12v_ON, and got this with funky sound coming from tcon. Frequency reset sounds. Panel is shorted.

Probably a roasted COF there. I tried the usual panel ribbon disconnect method and got a few horizontal striped lines on the left side but with LVDS disconnected I can tell tcon is trying.to show test patterns by the frequency sounds it's making, but.no picture. If I disconnect power and reconnect I can get a quick flash of one pixel line wide at the very top of the panel.

If I look closely I can see a dull black raster filling the screen except the 3 inches in the area where the vertical lines are present telling me that the area is not receiving VCOM, but DVDD has to be there or I wouldn't see the lines I believe.

[Davi.p]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Just for curiosity, are there any testpoints on the tcon and which one? Have you tried the same method i suggested you in the other thread? Supply externally the panel...

[budwich]

Re: Just picked up a 55 inch LG 4k OLED for $50!

freakaftr8... based on your other "fun experience" with shorted capacitors at the edge board... have you wandered over there yet? Of course, when I refer to "shorted", I mean "weakened" as opposed to totally shorted.... or even possibly opened.

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

The bottom panel boards look like a pain in the ass to get to as the plastic back is literally fused to the bonding of the back side of the panel. The capacitors that I see where the ribbons go into the panel boards I have tested in a read equal but I do read shorts on the outermost capacitors. I'm not sure if it's literally a short but I'm getting 8 Ω between both of them on each side

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

freakaftr8... based on your other "fun experience" with shorted capacitors at the edge board... have you wandered over there yet? Of course, when I refer to "shorted", I mean "weakened" as opposed to totally shorted.... or even possibly opened.

Yes I have I just successfully removed the short on a 75" Sony XBR panel dealing with the bottom drive boards. I have yet to score on a tcon that will power the panel yet however I supplied voltage to HVDD and realized That I have equal vertical stripes on both sides of the panel without shorting the capacitor out that was running off of one of the Gate drivers.

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Just for curiosity, are there any testpoints on the tcon and which one? Have you tried the same method i suggested you in the other thread? Supply externally the panel...

I have not pulled off the metal heatsink from the T con yet but I'm pretty sure I'm going to find test points in that will be the 1st thing I will look at. Trying to find voltages letter in cpec are going to be interesting due to the difference between OLED vs LCD. However my understanding is there is still is VCOM, HVDD and all the other drive controls there

[Davi.p]

Re: Just picked up a 55 inch LG 4k OLED for $50!

"I have yet to score on a tcon that will power the panel yet however I supplied voltage to HVDD and realized That I have equal vertical stripes on both sides of the panel without shorting the capacitor out that was running off of one of the Gate drivers."
Please can you clarify this? Are you talking about the other tv (sony)? Which voltage you supplied? You know HVDD (or probably HAVDD) means Half AVDD=15v/2=7,5v??

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

"I have yet to score on a tcon that will power the panel yet however I supplied voltage to HVDD and realized That I have equal vertical stripes on both sides of the panel without shorting the capacitor out that was running off of one of the Gate drivers."
Please can you clarify this? Are you talking about the other tv (sony)? Which voltage you supplied? You know HVDD (or probably HAVDD) means Half AVDD=15v/2=7,5v??

Yes, on that tv I supplied 6v to those rails. I used a resistor to cut the 12v down on my supply feed.

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Here is something interesting. On panel driver board left side which is the side with the issue these small for M LCC capacitors are reading dead short on the opposite side you can see the for M LCC capacitors read about 1K ohm.

If you look close enough the 3 capacitors on the inner side look darker then the first.

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

C8001, c8427,c8425 and c8002 are shorted as opposed to right side there these caps in dsame locations are 1kohm

[budwich]

Re: Just picked up a 55 inch LG 4k OLED for $50!

I think you got it!!!! Hopefully, those replaced will get you further down the road to happiness... :-)

[budm]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Can we see some pictures of the boards and how they are connected together?

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Pretty simple setup really. It's got two power supplies one the main filter with 4 bridge rectifiers thou! Pretty beefy primary side!

[budm]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Lots of heavy power buss to drive the OLEDs.
It looks like there are another circuits on that board with the shorted out MLCC.
Is there panel model number some where?

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Looks like LC550LQD

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

There's Tape over the the label Holding down a cable that I had to carefully peel away I can still see the model of the panel but it wore the letters off a little

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Here's a good closeup of tcon

[freakaftr8]

Re: Just picked up a 55 inch LG 4k OLED for $50!

Well those capacitors are ok. Board still shows a short with them removed. Looks like it has deeper issues.