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Samsung ue65nu7400 - Boot Loop - blinks 2-3 time, short backlight

Tv model Samsung ue65nu7400 from 2018.

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?

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Based on your description, the issue with your Samsung UE65NU7400 TV seems to involve a potential problem with the power board or the connection between the main board and the LCD panel.

Start by verifying that the power board is supplying power correctly to the main board through all cables. If that checks out, focus on inspecting the connections between the main board and the LCD panel connectors for any loose connections or issues.

If these steps don't resolve the issue, the main board itself likely needs attention.

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Hi,

thank you for the answer,

regarding the power board, from all the sources i seen they always said if i disconnect the cable between power board and main board, activate the tv and there is backlight, it means the issue is not with the power board.

i am not familiar with working a multimeter, but i can learn if you think the problem is in this area.

Regarding the connection between the main board and the lcd panel connector, no loose connection as i even disconnected and connected all of them already,

also, the fact that removing any of the connectors stops the power cycle (but still no image) makes me think the issue is not with any specific connector or long lcd boards.

da

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@peterberge78152 Sounds like a main board issue but you can never rule out the driver boards. Just because there is no visible damage, there is always the chance that this si a failed component. Explain point 8 a bit more. How did you disconnect the long boards? I do hope you mean that you disconnected the ribbon cables from the main board at the "long boards" and not the boards from the panel itself :-)

Thise maybe an issue of the processor on your main board. You could try and disconnect the heatsink and take a close look at the processor as well as the components around it. Since there are no schematics for the main board, you would most likely need to find a replacement for it. Sometimes reflowing (baking :-) the board can temporarily fix it, if it is an issue with the processor (not uncommon).

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5 Commenti:

Thank you for the answer :)

Regarding point 8 - I disconnected the cables from the long board (not the panel side :)),

i tried disconnecting each long board one by one and see the affect, any of the disconnection caused the boot loop to stop (but still no image),

there are total of 4 long boards - two sets connected from main board and daisy chained between them,

i tried disconnecting the connection between them also and it gave me same result as disconnecting a set from the main board.

Regarding the processor , i actually did taken a look at it and other than missing the heat paste, it seemed fine.

Never heard about the reflowing thing, do you think it worth a try to actually bake the main board? at what temperature?

i understand any plastic components (if exists) on board itself may be damaged by this process.

da

@peterberge78152 this "any of the disconnection caused the boot loop to stop" increases the possibility that this is a panel error. Actually it's not the panel but the long driver boards that have developed some kind of error.

As for the baking, check something like this Careful with anything that is not supposed to get hot, like plastic connector etc. and remove the heatsink Do this only at your own risk :-) Make sure everything is covered with aluminum foil and mylar tape etc. Check the voltage for the panel output on the power board. I don't think the power board is the issue but you have to make sure that it has the proper voltage going to the panel.

da

but how can it be the long drivers if no matter which one i disconnect if receive the same result? unless all of them suddenly received the same malfunction...

da

@peterberge78152 those share the power source. That is what I was going for not a failure on the individual driver boards. If you separated all four boards and tried individually and still did not work, it can be the main board or the panel itself.

da

Thank you,

i think there is a not a bad chance the issue is with the main board,

i am going to order a used board from eBay and try it,

i will update here on the results.

da

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Peter Berger Personal sarà eternamente grato.
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