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Device and repair information for the 60" LED HD TV by Samsung released in 2013, model number UN60FH6003FXZA.

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Intermittent Backlight Failure. Please help

So, I have been having an intermittent black screen for about a year now. It’s a tv in the basement, so we don’t use it much (mainly because it doesn’t work at times).

Sometimes I will turn the tv on and the picture will come up and other times it won’t come on. When the tv is on black screen, obviously I can see a picture with a flashlight and the sound still works because the picture comes back on, eventually. I usually have to keep the tv on for a few days before the picture comes back. It’s almost like the tv has to warm up before the backlights fire on.

it usually will turn on the next day after I have used it the night before, but if I were to wait a few days in between turning it back on I will normally have a black screen. Once again, I have sound and I do see a picture when the screen does go black.


Any ideas where I should start?

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Hi @sammyhagar ,

As a start, disconnect the power from the TV, remove the back cover from the TV and then disconnect the cable that runs between the power board and the mainboard.

Reconnect and switch on the power to the TV and check if the TV backlights come on and stay on. Obviously there will be no picture as the mainboard is disconnected.

If the backlights come on and stay on then there is a problem with the mainboard or the connection between the mainboard and the power board.

if the backlights don’t come on or if they come on and then turn off and then turn on again or come on, turn off and then stay off then there is either a problem with the power board or the LED backlight strips, cable connections etc.

If you have a DMM and know how to use it, you can measure the voltage being supplied to the backlights at the LED connector on the power board.

It should be a very high DC voltage (possibly 200-300VDC) if the backlights are off as there is no current flowing through the LEDs.

If the backlights are off and you are not measuring voltage in this range but a lot less if any, then there is a problem with the power board.

If you do measure voltage this high with the backlights off then there is a problem in the circuit from the power board to the LED strips. You will have to gain access to where the cable from the power board to the LED strips disappears behind the back of the screen and then use an Ohmmeter (power totally disconnected from the TV) to test for continuity in the wires from the power board through the LED power cable to most probably a distribution board where the LED strips are connected to and then on to the LED strips, looking for loose connections and dry solder joints.

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Hi @mountainyooper ,

What are the voltage readings on CNL802connector (LED power connector) with the cable removed from the power board?

Depending on the TV model type 2D or 3D, the voltages are shown in an "Output rating" table on the opposite side of the board.

If the voltages are the same as what you measured, with the cable disconnected, then there is a problem with the LED strips or the connection to the LED strips.

The power board is driving up the power trying to turn the LEDs on but there is no current flowing through the circuit

You'll never guess what happened, during the process of getting these readings I had apparently not screwed down the power board when I put it on the backplane of the TV and forgotten that I had not screwed it down. So then I plugged it in to take these readings, I noticed the ribbon cable going to the mainboard wasn't plugged in so I pushed it towards the power board which moved the power board and one of the legs to the little fuse hit the backplane, YIKES, SPARKS. Quickly I disconnected the power, had to resolder the fuse down and jump a trace that burned off. Screwed it back down, plugged it in, turned it on, and everything works. It did this once before and ran for a few days but eventually would not come back on when power was disconnected so I am waiting for that scenario to repeat before I take the readings you suggested (unless you think I should do it now?). Thank you for your help! Tom

@mountainyooper

Intermittent faults are a nuisance. It is a lot easier to find a problem when it is there all the time, rather than having to look for something when it is working OK

All what you've done may now have rectified the problem.

Maybe just handle the TV as per normal usage i.e. move it, touch it to clean etc as you would normally and then check if the problem is there or not.

If not then leave well enough alone.

If it is there it will come back soon enough and then hopefully it will stay long enough for you to find it.

Cheers

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