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Why is Samsung TV not displaying picture, sound only?

Model #UNHU6840FXZA KS02

Factory reset and also removed all devices...powered back on same result.

Shine flashlight on screen and can see picture.

Everything seems to operate and function, just unable to see image on screen.

Please advise how to repair, what part(s) need to be replaced to correct.


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Sometimes, my TV's display goes out so badly that I have to be within an inch or two of the screen in order to be able to see bright colors on the TV.


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Hi @jringo4u ,

Try the following:

Disconnect the power from the TV and then remove the back cover from the TV and then disconnect the cable that runs between the power board and the mainboard.

Reconnect the power to the TV and turn on the TV.

The screen’s backlighting should turn on. There will be no picture because the mainboard has been disconnected.

If the backlights turn on there may be a problem with the mainboard.

If the backlights don’t turn on then there may be a problem with the power board, the cable between the power board and the LED backlight array or the connections and / or LEDs in the array.

Measure the voltage at the LED backlight cable connection point on the power board. If it measures between 180 -250VDC then most probably the problem is in the array. It it measures between 0 - 30VDC then most probably there is a problem with the power board.

Here are a couple of videos that show how to test and fix problems in the LED array.

video 1

video 2

If it is determined that it is the power board search online using the power board “board number” only in the search term e.g. BN44-00755 A Rev xxx or similar, to get results for suppliers

If you can’t find the board number search for UN(insert the screen size)HU6840FXZA power board e.g. UN55HU6840FXZA power board (if this is the size of the screen)

If it is determined that it is a mainboard problem search for it the same way.

Be sure to insert the screen size into the model number to make certain that you get the correct board. You missed it in your post. ;-)

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My bad, did leave out 55 in UN55HU6840FXZA. Is there a way to complete process without measuring voltage with meter? Don't have meter or experience with same. Hoping to isolate to board level and replace that,


Hi @jringo4u ,

Assuming that there is no backlight as per the test above, the problem is you have to prove if it is a faulty board or faulty backlights that are the cause.

You could try changing the power board BUT unless you can find a supplier who accepts returns and refunds you with minimal cost to you, it may be an expensive gamble and still not fix the problem.

Although usually the backlights are found to be the problem, in electronics nothing is guaranteed to be the certain cause of the problem in every case of no picture sound OK.

Sorry to be so vague but testing with a meter is really the best option. Perhaps you may know someone who has a DMM (digital multimeter), knows how to use it and who would help you.



Left TV sit for over 24 hours...turned it back on...working like nothing every happened???

This is not the first time, last time it worked for about 30 days and then took a day or two "PTO" and came back from the dead!!!

Please advise what this may mean???


Hi @jringo4u ,

Did the backlights come on before when you tried the test procedure I outlined initially to turn them on, you didn't say?

Next time it fails try a power refresh and check if this allows it to work properly after the refresh

Here's the procedure:

Turn off TV, turn off wall power outlet (if it has a switch) and remove TV power cord from wall outlet.

Press and hold TV power button for 30 seconds then release.

Reconnect TV power cord to wall outlet and switch on outlet (if it has a switch)

Turn on TV and check if it operates normally.

If it works OK but then occurs again later on when TV is turned on it may be a software problem or a dry joint solder connection either on a board or the backlight array.

Early days in diagnosis though. It is easier if a problem is there all the time rather than intermittently


Hadn't been able to try test procedure, prior to TV "coming back to life"!

Had performed the power refresh, as you outlined above, prior to first posting.

The TV failed to operate normally, audio present and image on screen when flashlight shined onto it, but without flashlight...screen black.

After several days of sitting without power, turned TV back on and it functions normally.

Let me know if this gives any additional indication.

Thanks for your time and assistance!


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