Doesn't power on, flickers on and off

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Samsung Television

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Gabe @crk1918

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Posted: Sep 5, 2023

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Doesn't power on, flickers on and off

I got a UN70NU6900F TV, it has the same problem. I got it to temporary fix if I unplug a display cable on top while the TV power is on (flickers) and plug it in again. I got the picture (but if I restart again, the same problem repeats). For reference, I also found a video: https://youtu.be/zGAVbMQrSek , at about 8:40 timeline, that is the cable I unplugged and plugged in. This temporary fix it I tested and got everything working and the picture shows up nicely. Only when I turn the TV off and turn the back on again, the screen start to flicker again, not sure what is the issue with that? Is it a bad connection, the motherboard problem, or the screen panel problem?

update:

one pin:

tape more than one pin:

Answered! View the answer I have this problem too

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My 70 inch has the same problem too.

Aug 4, 2024 by Brenda G.

@brendag84361 same model? what have you checked? 70" is a beast to work on because of its size. Just taking the back off seems to require more workspace :-) Anyhow, give us more details about what is going on with it and what you have tried. Maybe we can resurrect this TV as well.

Aug 4, 2024 by oldturkey03

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oldturkey03 @oldturkey03

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Posted: Sep 5, 2023

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@crk1918 that cable is the power cable. TRy this. Unplug the power cable. Disconnect the main board from the power board. Plug the power cable back into the power board. your back lights should come on. you can see those through the hole sin the sheet metal on the back of the display. If they do come on, your power board is okay. Unplug the power cable, reconnect the main board to the power board. Now you got to measure the voltages on the connector CNM801 where the mainboard plugs into the power board. You will have to do that while you turn your TV on. So keep your hands of the power board since it will be live and will zap you pretty good if you touch the components with your bare hands.

This model is known to have issues with the panel. Let's try to at least rule out the mainboard. Post some pictures of your boards etc. with your question so we can see what you see. Adding images to an existing question

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@oldturkey03

I just tested the power supply it was okay, I got the LED light on when disconnected CNM801, and CNM801 4 pins got 13V.

When I put a piece of tape on the upper display ribbon cable, it will turn on okay. But the color is not great even though I try to put anyone or two of the clock lines, it could be a piece of clock broken. it seems like it does not matter which spot I put the tape on, if I put it in the general area it will turn on.

So it seems like if I catch the right moment in that second when the TV turns on, I unplug the upper display ribbon cable and plug it back in it will work again, but it doesn't work if you do a power cycle, maybe when the TV it will detect certain area have an error when the power is turned on? so that is why I can bypass that after that stage? So I can keep my full color.

I also wonder which command or signal cable to turn on and off when in the power on stage... or maybe it's not possible？

And also thank you so much for helping me with the issue

Sep 6, 2023 by Gabe

@crk1918 this is called a tape-off you should always try 3 pins at a time and just keep moving along the connectors until your get the right picture. It'll take time and practice to get it done.

Sep 6, 2023 by oldturkey03

@oldturkey03 Sounds good, thanks for your help!

Sep 7, 2023 by Gabe

Just a update, see my picture, I come down to that pin is cause it. when I tape it, it got a many line on top. And then I end up to tape more than one pin with no line, but color is off.

Sep 7, 2023 by Gabe

@crk1918 try a couple of pins. I have seen people having had to tape off multiple different lines

Sep 8, 2023 by oldturkey03

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@brendag84361 same model? what have you checked? 70" is a beast to work on because of its size. Just taking the back off seems to require more workspace :-) Anyhow, give us more details about what is going on with it and what you have tried. Maybe we can resurrect this TV as well. — oldturkey03
@oldturkey03

I just tested the power supply it was okay, I got the LED light on when disconnected CNM801, and CNM801 4 pins got 13V.

When I put a piece of tape on the upper display ribbon cable, it will turn on okay. But the color is not great even though I try to put anyone or two of the clock lines, it could be a piece of clock broken. it seems like it does not matter which spot I put the tape on, if I put it in the general area it will turn on.

So it seems like if I catch the right moment in that second when the TV turns on, I unplug the upper display ribbon cable and plug it back in it will work again, but it doesn't work if you do a power cycle, maybe when the TV it will detect certain area have an error when the power is turned on? so that is why I can bypass that after that stage? So I can keep my full color.

I also wonder which command or signal cable to turn on and off when in the power on stage... or maybe it's not possible？

And also thank you so much for helping me with the issue — Gabe
@crk1918 this is called a tape-off you should always try 3 pins at a time and just keep moving along the connectors until your get the right picture. It'll take time and practice to get it done. — oldturkey03
Just a update, see my picture, I come down to that pin is cause it. when I tape it, it got a many line on top. And then I end up to tape more than one pin with no line, but color is off. — Gabe
@crk1918 try a couple of pins. I have seen people having had to tape off multiple different lines — oldturkey03

Samsung Television

Doesn't power on, flickers on and off

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