SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

[samsug]

Hey there, I happen to have the about same symptoms. Plug in the TV, it starts, shows me a very crisp picture for about 20s, then first goes black with lit backlight and then reboots and with each reboot the on time decreases rapidly. Unplug it for 10s and rins and repeat.
When I unplug the ribbon between the two LCD boards, it stops cycling, but does not show a picture.
I glued of everything besides pin 1 and 46 as somebody noted. This caused the TV to only show a picture one third of the screen and quite a bit more distorted than usually, and still shuts down after a few seconds. Maybe even a few seconds later.
I glued up only the clock pins, and it showed a distorted image and shut down anyway.
The voltages over the caps on the second board seem to be “normal” at about 15.6-7 V.
Since I don't have a FLIR, I can only use my lips to find warmer components on the board. The only component I found with this so far is the AAT7212, but since it appears to be a voltage regulator, this seems to be ok to me.

Is there any hope for me / any other trick / measurement left or am I just cooked

Thanks so much in advance, and I just want to say how incredible your work here in this thread is!

[nomoresonys]

Rubbing a candle on those components is another little thing you can do to try and isolate a heat related issue. See where the wax melts first.

[kostas22]

I have the same problem,with UA50BU8000W, but i noticed something different?
When I unplug the ribbon between the two LCD boards, it stops cycling, and does not show a picture like everyone else.
But when i plug the ribbon back while the TV is still on!, The TV works normaly every time? with perfect picture and no tape on ribbon needed,
Its not a fix, when i turn the TV off i have to repeat, but i can see the TV functions normaly if you bypass the booting process?..

[federuo32]

Hello, I have a very similar problem with this tv: UE50TU8070U(XZT).
As you described, the tv continued to reboot about every ten seconds. I opened the back and disconnected the ribbon cable between the two panel boards and the tv started.
I could hear the starting melody but no picture on screen, which was backlit but black, like the panel remains undriven. The tv responds to IR inputs.
After some time i managed to understand that the cause of the rebooting was a short circuit between pin 1 and pin 46 of the mentioned ribbon cable caused by an internal short circuit between the pins on the second panel board (left side from the front of the screen). I used a thin piece of tape to cover one of the two pins but the tv still shows no picture. None of the main voltage rails of the panel boards can be detected, just few random voltages like 1.8v, 0.11v and ecc like OP already detected. If I let the tv in the reboot state, instead, those voltages can be measured for a short period of time (as already reported).
Also cannot find the AVDD line to verify a possible short circuit between AVDD and VCOM as described in post n.86
Taping the clock lines does not help since I didn't manage to get picture.
Do you have any other possible solution? It would be a shame to throw away the tv

[nomoresonys]

I have the same problem,with UA50BU8000W, but i noticed something different?
When I unplug the ribbon between the two LCD boards, it stops cycling, and does not show a picture like everyone else.
But when i plug the ribbon back while the TV is still on!, The TV works normaly every time? with perfect picture and no tape on ribbon needed,
Its not a fix, when i turn the TV off i have to repeat, but i can see the TV functions normaly if you bypass the booting process?..

Seems like they may have been having similar issues in this thread, solved by using a larger ohm resistor, check it out: https://www.badcaps.net/forum/troubl...digging-deeper

[federuo32]

Update: FIXED

After two days of attempts and many headaches i managed to get the tv running with (almost) no problems at all.
No taping solution worked for me, even though I tried different tape positions and lenght on both the main and the intercom ribbon cable.
After I simply swapped the two ends of the main ribbon cable (the one from mb to panel boards) the tv started. I then tried to put the cable back in the correct order and it worked as well.
My explanation is that, after some time, the heat coming from the chassis damages the bend in the middle of the ribbon cable. In fact, in order to put it backwards I had to use a hairdryer to soften the glue on the bend and straighten.
Otherwise no other explanation seems possible to me.
The only problem is that tiny dark horizontal lines appeared in the upper half of the screen, and they fade from right to the left (which makes me think this is not a panel damage but a problem with the tcon). In addition some of those lines are permanent, others appear and disappear every few seconds, alternating. Also, those lines change color depending on the background (way more noticeable when the background is reddish).
Hope this can help.

[nomoresonys]

The ends may just be dirty, try cleaning them with a pencil eraser or isopropyl alc.

[x_orange90_x]

Update: FIXED

After two days of attempts and many headaches i managed to get the tv running with (almost) no problems at all.
No taping solution worked for me, even though I tried different tape positions and lenght on both the main and the intercom ribbon cable.
After I simply swapped the two ends of the main ribbon cable (the one from mb to panel boards) the tv started. I then tried to put the cable back in the correct order and it worked as well.
My explanation is that, after some time, the heat coming from the chassis damages the bend in the middle of the ribbon cable. In fact, in order to put it backwards I had to use a hairdryer to soften the glue on the bend and straighten.
Otherwise no other explanation seems possible to me.
The only problem is that tiny dark horizontal lines appeared in the upper half of the screen, and they fade from right to the left (which makes me think this is not a panel damage but a problem with the tcon). In addition some of those lines are permanent, others appear and disappear every few seconds, alternating. Also, those lines change color depending on the background (way more noticeable when the background is reddish).
Hope this can help.

I just picked up a UN50TU8000FXZA yesterday that is doing this exact same thing. Turns on and goes to the Home Screen then reboots after about 10 seconds. Mine however responds very slowly. I tried to get to the settings menu and it freezes for a couple seconds before it moves within menus or even changes the selection. I also noticed right before it was about to reboot it dimmed and had distorted colors and faint horizontal bars. When its on the image is perfect. I am led to believe it's a main board issue from what I seen. I believe I have another one of this model with a cracked screen, and if so I'll definitely do some part swapping to see what happens. Given the inconsistency regarding successful "tape fixes" that people are reporting, I don't think there's nearly as many "bad panels" as believed.

What is the proper way to disassemble these? There's no screws and I've seen this before but I cracked one trying to open it and another was already cracked and I just ripped it open to get the parts out. Sometimes there's weird metal bars running through the frame on these tvs. Is that the case here?

[nomoresonys]

Notice how the bottom isn't protected, so just do the sides and top with the tool, don't stick it thru the bottom part of tv, the bottom will pop off once the rest is done: https://www.youtube.com/watch?v=kGxnt9Lhy7s

[x_orange90_x]

Notice how the bottom isn't protected, so just do the sides and top with the tool, don't stick it thru the bottom part of tv, the bottom will pop off once the rest is done: https://www.youtube.com/watch?v=kGxnt9Lhy7s

Thank you! I will do this. It never goes as smoothly as in those repair videos tho. I think they've opened up the TV's a couple times BEFORE making the video so they don't embarrass themselves struggling for 20 minutes 😂

[x_orange90_x]

I looked yesterday for my spare and I guess during a bout of cleaning I threw it away, without removing the boards from it 😔. I have a similar one but it's a TU7000 and they have completely different main boards. I will still play around with the ribbons and such to see if I can make something change. I keep the parts and ribbons from almost all of the junk ones I toss. Maybe I'll get lucky and only need a new ribbon. 🤷🏼

[x_orange90_x]

I looked yesterday for my spare and I guess during a bout of cleaning I threw it away, without removing the boards from it 😔. I have a similar one but it's a TU7000 and they have completely different main boards. I will still play around with the ribbons and such to see if I can make something change. I keep the parts and ribbons from almost all of the junk ones I toss. Maybe I'll get lucky and only need a new ribbon. 🤷🏼

Upon closer inspection I see it has faint lines on the right half of the screen. I played with the ribbons and cleaned then but it made no difference. I pulled the boards out and I'm gonna toss the rest