how can i test individual leds without tester

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  • nubinator
    Member
    • Jan 2012
    • 34
    #1

    how can i test individual leds without tester

    Hello I have TCL 65S4 and it has no backlight, seems common problem on this tv to have bad LED's. I have no tester though I thought I could just test each LED with 2xAA batteries for 3v but it doesnt light up at all?
    I saw a vid with LED tester on this TV and it had 130v for 1 good line which is 24 LEDs does that mean it needs around 5.5v per LED?
    Tags: None
    • eccerr0r
      Solder Sloth
      • Nov 2012
      • 8694
      • USA
      #2
      Re: how can i test individual leds without tester

      I usually use 3 or 4AA with a drop resistor to limit to about 10mA, so it can only test LEDs one at a time. However this does not tell the difference between a shorted or open LED nor its ability when at full current (and full brightness).

      One simple mod is use 4AA and a red LED in series with a limiting resistor and the device you want to test, so you can definitively tell the difference between a shorted and an open LED - though in most situations it doesn't matter the failure, if it doesn't light it needs to be replaced anyway...

        Comment

        • Davi.p
          Hobbist Tech
          • Sep 2009
          • 4286
          • Italy - Milan
          #3
          Re: how can i test individual leds without tester

          you have to scratch the bars in the right points and connect the battery, but this simple test is not enough to find those half damaged leds.. you better build a self made led tester with two testing currents, one medium, one very low, with very low one you will probably find those near to full shorted, thus semishorted
          those are 6v leds
          Last edited by Davi.p; 10-26-2022, 01:33 AM.

            Comment

            • nubinator
              Member
              • Jan 2012
              • 34
              #4
              Re: how can i test individual leds without tester

              Thanks guys I added another two AAs and found one LED not lighting up at all so thats all the confirmation i need to order a backlight set for it

                Comment

                • nomoresonys
                  Badcaps Legend
                  • Jan 2013
                  • 12096
                  • U.S.
                  #5
                  Re: how can i test individual leds without tester

                  https://www.youtube.com/watch?v=1qi9QS3tRfM

                    Comment

                    • ramondo
                      Confused Member
                      • Jun 2015
                      • 39
                      • USA
                      #6
                      Re: how can i test individual leds without tester

                      add this electronic circuit to your multimeter and get an amazing option

                      https://www.youtube.com/watch?v=SJkx8HRmCTQ

                      Mextraf on youtube. I have made this and used a cheap harbor freight mm and it does work.. Try to use a lamp circuit with a transformer on board (safer maybe) I did have plenty of home depot eco smart bulbs that were flikkering of going off after 10 mins.
                      Thanks to all for being__WAR_KITTENS____!

                        Comment

                        • nubinator
                          Member
                          • Jan 2012
                          • 34
                          #7
                          Re: how can i test individual leds without tester

                          i saw a vid to just bridge the bad LED and i did that and tv all working again. ill keep backlight level low and hope others dont blow.
                          I'm surprised nothing broke I dont even have suction tools to lift panel. i copied this guys method and it worked a treat. https://youtu.be/JHvysrIbY1U?t=486
                          Last edited by nubinator; 10-26-2022, 09:18 PM.

                            Comment

                            • nomoresonys
                              Badcaps Legend
                              • Jan 2013
                              • 12096
                              • U.S.
                              #8
                              Re: how can i test individual leds without tester

                              ok, but I hope you didn't have that same long awkward trip to where he put it.

                                Comment

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