Samsung UN55NU7100 Backlights

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  • m4a2t0t
    Badcaps Veteran
    • Mar 2013
    • 276
    • USA
    #1

    Samsung UN55NU7100 Backlights

    I replaced the backlights in this unit and only half of them are now working. The strips were bad, I could see a few LEDs that blew up. The power supply outputs 190V to the LEDs in the working strip (1-2 and 3-4) and the non working LEDs (5-6 and 7-8) have 120V on + and 65V on -.. Using chassis as ground point. Any suggestions
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    • ResetReality
      New Member
      • Jul 2024
      • 3
      • Malaysia
      #2
      Was the connector for the led backlights disconnected before you replaced? Also do you own an led light tester? Where strips new? Or used? These are edgelit leds and alot more fragile than direct array

        Comment

        • m4a2t0t
          Badcaps Veteran
          • Mar 2013
          • 276
          • USA
          #3
          The strips were new and I tested them with my backlight tester and both strips lit up. I disconnected the connector before I replaced the strips

            Comment

            • EazyBone
              Badcaps Legend
              • Jun 2023
              • 1340
              • United states
              #4
              Is the TV already put back together?

              Generally this is what you should do, leave all boards on tv when changing backlights, disconnect PSU from main board. Change the lights, don't put anything back together and the plug in the PSU. When you do all the lights will turn on, if they don't you can diagnose while it's all still apart. That's likely where you need to be. Basically all the way broken down again and then plug it in to see. You probably just didn't connect it back in.

              Or one time (won't do it again) I stuck my led tester into the plastic bracket to test the LEDs (at PSU while PSU was removed) because of a odd occurrence. In doing so I pushed a little too hard and the metal contacts spread apart which are supposed to connect to the PSU. When it was fixed the lights wouldn't turn on anymore even though they all tested fine. I thought it was PSU but then I realized I spread the contacts apart by sticking the probe too hard into them. So I had to bend it all back into shape and then the PSU made contact again and voila back to working

              This second part probably isn't the case but if I was dumb enough to do that lol maybe someone else did also.

              So break it back down again is likely what needs to happen!

                Comment

                • m4a2t0t
                  Badcaps Veteran
                  • Mar 2013
                  • 276
                  • USA
                  #5
                  I removed the panel and connected the cable that was in the working strip and plugged it into the strip that wasnt working and the LEDs light up.

                    Comment

                    • EazyBone
                      Badcaps Legend
                      • Jun 2023
                      • 1340
                      • United states
                      #6
                      Definitely good to know, so now it's either the connector or the PSU. You can use continuity mode and test that cable from one end to the PSU connection point. See if it isn't broken some how. Whenever I change backlights on these tvs the connector into the lights get very brittle and break sometimes. Luckily I've been able to still use them all. Let us know what you find the problem is

                        Comment

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