Hello friends of Yoreparo! :)
I come to raise a problem that was presented to me by repairing a Samsung LED TV model UN40JU6000.
The fault is that the TV does not turn on the backlight. I proceeded to take it apart and in fact I found 3 LEDs burned. I replaced them and to my surprise, the backlight still doesn't turn on. I checked all the LEDs again, and they are perfect.
I do not understand what exactly happens, I am confused.
The voltage output of LEDs according to the silkscreen of the source, is 162v. The tv has 5 strips of 9 leds each. A total of 45 leds.
In the output I only measure 119v.
I also want to clarify that the output of the LEDs has 4 cables. Only in one of those 4 cables I have 119v reading. In the other 3 I have nothing at all.
I leave photos of the source, to see if someone can give me a hand. As always, I will value all the answers.
A hug !!! and thanks in advance! ;)
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QUESTION EXTENSION:
I tried all the strips and they work OK. I injected voltage to each strip, and they lit OK. I tried led by LED and the same, they are all OK. With that I discard the LEDs and also the contacts that bind each strip together.
In total there are 5 led strips of 9 leds each (45 leds in total). They work at 3v.
The 3 lower strips turn ON when measuring voltage with the tester. That is, if I put the negative tip on the chassis, and the positive on each of the 3 lower strips, the LEDs light dimly. Something that surprised me is that if I repeat that same procedure, but with the diode scale tester, the 3 lower strips light up to the maximum. I know it is dangerous for the tester, but on that scale by putting a negative tip on the chassis, and a positive tip on the positive of each strip, I get the lower LEDs on.
With the top LEDs, I get nothing at all.
Now, those 3 strips are powered with 119v. But in the upper strips (which are 2) there is no voltage. Nothing.
And I think that is the reason why they do not light the upper LEDs, not even repeating the previous procedure (that is, measuring voltage with the tips of the tester, I do not get them to light).
I LEAVE 2 PHOTOS GRAPHING THE BACKLIGHT and its diet:
CLEAR UP AGAIN: The lower LEDs inside the green box ONLY ON BY SUPPORTING THE POSITIVE POINT on the positive of each led strip, and the negative to chassis. If I do not do that, the lower LEDs do not light.
The upper LEDs inside the red box, have no voltage, so, despite repeating the previous procedure with the tips of the tester, I can not turn them on.
Next, a photo of the circuit that carries the voltage to the strips:
On the right in green, the power of the lower LEDs is 119v. On the left, power absent for the upper LEDs.
Conclusion:
I think the source is damaged in the LED voltage output. But I have no diagram of it and I have no idea how to solve the problem without changing the source.
I can be wrong, but I think the damage is at the source, because there is no power for the higher LEDs (LEDs that are OK)
THANK YOU ALL THE POSSIBLE HELP: (
