Another LED Strip Head Scratcher.. Sanyo DP42D23

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  • Michale32086
    New Member
    • Nov 2011
    • 1453
    • USA
    #1

    Another LED Strip Head Scratcher.. Sanyo DP42D23

    This seems to be my month for weird LED Strip issues..

    I have this Sanyo that I broke down to the bare strips and discovered that the LED assembly is identical to some LGs and some VIZIOs I worked on..

    I used my LED tester to find the bad strips and LEDs and was able to create an array that was fully functional.. No bad LEDs at all..

    STILL wouldn't come on...

    So I cracked open a 47" LED that had a bad display panel. At least I HOPE it did..

    Anyways, long story short (too late!) I have confirmed that the following parts of the LED TV are fully function..

    Power PCB

    Main Video Board

    ALL LED Strips

    Cable that goes from the Power PCV to the Array board..

    The "array board" (green strip that all the LED Strips plug into) seems to be the culprit.. But, near as I can tell, it's just traces and I can't find any breaks...

    Voltages at the 4 pin connector on the array board are solid.. 200v at one testing....

    I am thinking I need to check the voltages at the point where the LED Strips plug into the array board but I wanted to get guidance on what voltages should be present...

    Thanx

    FURTHER INFO: Regarding the pic, the upper array board is from the Sanyo and doesn't work. The lower array board is from the LG and it works fine.. It should also be noted that, lemme see if I can explain this right, the connectors that go from the Power PCB to the array board are inverted.. On the LG, the connector tab on both ends face the same way.. On the SANYO, the connector tabs are opposite..... If that makes any sense
    Attached Files
    Last edited by Michale32086; 12-12-2017, 08:14 AM.
    Tags: None
    • Michale32086
      New Member
      • Nov 2011
      • 1453
      • USA
      #2
      Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

      Here is what I mean about the Power PCB/Array connectors...
      Attached Files

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA
          #3
          Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

          Can we see good clear pictures of the whole power supply/LED driver board?
          The SANYO one: the black wires are more likely to be the Anode of the LED string, the white wires are the Cathode returns.
          Attached Files
          Last edited by budm; 12-12-2017, 01:39 PM.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK
              #4
              Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

              I've encountered a set where every LED tests okay on a meter, but the whole setup fails for some reason. Perhaps an LED breaking down as voltage is applied or as it heats up. Odd, though.
              Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
              For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • augiedoggy
                  Senior Member
                  • Aug 2016
                  • 62
                  • united states
                  #5
                  Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                  Originally posted by tom66
                  I've encountered a set where every LED tests okay on a meter, but the whole setup fails for some reason. Perhaps an LED breaking down as voltage is applied or as it heats up. Odd, though.
                  Ive seen this too... sometimes Ive actually discovered it was just a cold solder joint on one of the leds..

                    Comment

                    • CapLeaker
                      Leaking Member
                      • Dec 2014
                      • 7964
                      • Canada
                      #6
                      Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                      LED's can work even for a while like it should and then go off. They can fail in a weird way and it is very hard to test unless you power the strip up properly on a CV/CC PSU and run it for a little while.

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA
                          #7
                          Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                          But he said "STILL wouldn't come on..." I would expect if the LED/LEDs is bad with high drive current then they should at least come on for seconds and then go off, according to the post, they did not come on.
                          Never stop learning
                          Basic LCD TV and Monitor troubleshooting guides.
                          http://www.badcaps.net/forum/showthr...956#post305956

                          Voltage Regulator (LDO) testing:
                          http://www.badcaps.net/forum/showthr...999#post300999

                          Inverter testing using old CFL:
                          http://www.badcaps.net/forum/showthr...er+testing+cfl

                          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                          http://s807.photobucket.com/user/budm/library/

                          TV Factory reset codes listing:
                          http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment

                            • CapLeaker
                              Leaking Member
                              • Dec 2014
                              • 7964
                              • Canada
                              #8
                              Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                              Then maybe measure the LED string voltages at each of the strips and see if LED power actually gets there? Gotta be an open somewhere then.

                                Comment

                                • freakaftr8
                                  Badcaps Legend
                                  • Oct 2012
                                  • 3743
                                  • USA
                                  #9
                                  Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                                  I have supplied voltage to LED strips in different TV's especially LG, What normally happens is when I supply an external voltage to test LED strips, one led may light up on that strip however powered with the power supply on a much broader voltage range causing the LED to burn brighter starts to flicker
                                  Did I leave the soldering iron on?

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA
                                      #10
                                      Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                                      That is why it is important to use CC power supply to test the LED/LED strip due to the fact the if you have a bunch of shorted out LEDs on the strip then the good LED will be forced with lots of current trying to maintain the Vf when using CV power supply.
                                      I.E. people see 4 LEDs on the strip so they figure that 4 LEDs x 3V =12V so he is going to use 12V to test the strip, but if two of the LEDs are shorted out then guess what happen when you apply 12V to the strip?
                                      Last edited by budm; 12-13-2017, 11:05 AM.
                                      Never stop learning
                                      Basic LCD TV and Monitor troubleshooting guides.
                                      http://www.badcaps.net/forum/showthr...956#post305956

                                      Voltage Regulator (LDO) testing:
                                      http://www.badcaps.net/forum/showthr...999#post300999

                                      Inverter testing using old CFL:
                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                      http://s807.photobucket.com/user/budm/library/

                                      TV Factory reset codes listing:
                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                        Comment

                                        • Michale32086
                                          New Member
                                          • Nov 2011
                                          • 1453
                                          • USA
                                          #11
                                          Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                                          Thanx for the replies, guys.. Turns out that it WAS a bad cable connector from the array board to the Power PCB...

                                          Sorry it took so long to get back on it.. GRRRRRRRR I am NOT a holiday fan.. I would be happy to go from Oct 15 to Jan 16.....

                                          Thanx again...

                                            Comment

                                            • budm
                                              Badcaps Legend
                                              • Feb 2010
                                              • 40746
                                              • USA
                                              #12
                                              Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

                                              Thanks for the follow-up.
                                              Never stop learning
                                              Basic LCD TV and Monitor troubleshooting guides.
                                              http://www.badcaps.net/forum/showthr...956#post305956

                                              Voltage Regulator (LDO) testing:
                                              http://www.badcaps.net/forum/showthr...999#post300999

                                              Inverter testing using old CFL:
                                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                              http://s807.photobucket.com/user/budm/library/

                                              TV Factory reset codes listing:
                                              http://www.badcaps.net/forum/showthread.php?t=24809

                                                Comment

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