⟐ Answered 五月 23, 2026 at 13:08 GMT-7

It suddenly the screen went black during normal activation, When i turn it on it seems it tries to start and shuts down in a loop (i can see it changing from complete black to little bit lighter in a loop --> backlight).

I can see the red led indictor flashing one long and two short times when in a loop during power up.

Tried the following:

1. Changed the power cable and socket and removing all connected devices and it didn't help.
2. Unplugging and turning off and pressing on control button to try reset capacitors and leaving it for the night -> didnt help.
3. Looking closely with a flashlight i cant see anything and no sound is heard at any time or when pressing on remote,
4. Opened the tv and visually inspected the boards for any brown or bloated capacitators --> nothing found.
5. Visually inspected the long boards connected to the panel --> nothing weird.
6. Disconnect the main board from the power board and power on the TV. The backlight works fine -- > this probably means power board is fine.
7. When I reconnect the main board and remove either of the LVDS cables and then supply power, i can see backlight, but no picture, pressing buttons on remote produces sound.
8. Disconnecting any of the long boards connected to the panel results in the same result as disconnecting any of the LVDS cables (point 7).
9. Tried using tape (as suggested by various Youtube videos) --> this produced the same result as disconnecting any of the LVDS cables (point 7).

#

I suspect the issue to be with the main board or panel, what do you think?

⟐ Commented 五月 23, 2026 at 3:52 GMT-7

I have tried unplugging it, holding the power button for 10 seconds and plugging it back in. I tried switching picture settings to vivid. But did not help. Sound works fine.

What else can I try.

⟐ Commented 五月 22, 2026 at 21:44 GMT-7

Got the tv second hand a month ago and accidentally pushed the right tv stand in too hard, which seemed to push apart the screen a little and cased some damage in back. Tv has been working fine since but two days ago a thick black vertical bar appeared right above the right tv stand insert. It flickered a few times that day and now is constant. I’ve done the picture test, reset tv settings, restarted tv etc but no change. Could the tv stand be pinching the ribbon and it could be fixed?

⟐ Edited 五月 22, 2026 at 18:10 GMT-7

One of the COF tabs somehow did begin to split away, so I know that one horizontal section might not be working unless I figure out how to fix it.

Even so, I couldn't see (even during disassembly) what the tabs on the left and right of the screen are meant to connect to. They seem to must be pushed up against bits of black papery duct tape, which are only taped onto the inner plastic bezel.

On the bottom of the screen, it's clear that the tabs are connected to the two long PCBs, but on the left and right, I can't figure what they go to. There's a little metal nub inside each one, about the size of 1/4 a toothpick, but there's nothing electronic that they seem to connect to, and nothing changes when I try touching them directly to the metal chassis.

⟐ Commented 五月 21, 2026 at 17:34 GMT-7

⟐ Answered 五月 19, 2026 at 18:44 GMT-7

⟐ Commented 五月 19, 2026 at 17:24 GMT-7

model 40 LV665D green power light comes on but screen remains black with no sound

⟐ Commented 五月 18, 2026 at 2:26 GMT-7

⟐ Answered 五月 17, 2026 at 20:34 GMT-7

⟐ Answered 五月 17, 2026 at 15:19 GMT-7

⟐ Commented 五月 17, 2026 at 9:07 GMT-7

⟐ Answered 五月 17, 2026 at 6:51 GMT-7

A few days ago I started experiencing Samsung UN75NU800DF rebooting issue and I am hoping someone can help.

This 75" UN75NU800DF is 5 years old and started to reboot itself, like turning on then off with a relay click sound. After some google and youtube I tried some troubleshooting.

I removed the back panel and checked the power board for any irregularity, and the capacitors and solder joins look fine. I then disconnected the ribbon cable between the power and main boards and powered on the tv. Clicking stop and backlight stayed on.

I then tested each pin out for the ribbon cable with a digital meter and the output voltages match to the pinout diagram on the power board (13v but tested to be around 12.8V). At this point I am thinking the power board is working OK.

Next I tried removing each of the two ribbon cables between the main and the LCD boards (labeled 1 & 2 in the photo below) in turn to test if it's LCD problem. First the top cable is removed (the bottom is still connected to the main board) and powered on the TV. The TV turned on, sound is on, remote is working, backlight is on, but no picture. Then I did the same for the bottom ribbon cable while leaving the top cable connected, same thing happened. Finally I disconnected both the ribbon cables and again, sound, backlight, remote are all working but no picture.

Finally, I reconnected everything back to original and sure enough, the TV went back to rebooting and clicking.

My question is what can be the issue? The power board seems to be working, backlight stays on if not connecting to the main board. Can main board be the problem? Or is LCD driver board the issue and I nees to try the tape off method?

Thank you very much.

The connection where the ribbon cables terminate is shown below:

It's showing the area of the incoming power cable connector and first ribbon cable to the LCD board

⟐ Commented 五月 16, 2026 at 10:54 GMT-7

⟐ Commented 五月 16, 2026 at 8:13 GMT-7

⟐ Commented 五月 16, 2026 at 1:46 GMT-7

⟐ Answered 五月 15, 2026 at 20:47 GMT-7

⟐ Commented 五月 15, 2026 at 11:01 GMT-7

⟐ Answered 五月 15, 2026 at 7:58 GMT-7