Samsung UA50F5500 No Power to Some LEDs

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • brodymc
    New Member
    • Mar 2019
    • 3
    • New Zealand

    #1

    Samsung UA50F5500 No Power to Some LEDs

    I've managed to pick up this TV from a relative for nothing.
    However, it's got some issues: some of the LED strips don't light up.

    I've done a little bit of testing and found that pins 10 (2+) and 12 (1+) on CNL802 have no power. Pins 6 (3+) and 4 (4+) have power.

    According to the stats on the PSU board, it should be 274V (I think), but when reading the 2 pins that work (6 & 4), it reads between 350V and 360V (a lot higher than it should be). This testing was done with the LED strips disconnected. I also noticed that out of all the dead LED strips, the very bottom strip dimly flickers every couple seconds.

    I'm pretty sure all the LEDs are good however, as I tested each individual one with my multimeter set to diode and they all lit up, so I'm fairly certain the issue is the PSU (just not what part specifically).

    Full album of photos (with descriptions): https://imgur.com/a/Mc79u6S

    Any help would be appreciated!

    PSU Board: BN44-00612D / L55S1V DSM (equivalent BN44-00612B)
  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8061
    • Canada

    #2
    Re: Samsung UA50F5500 No Power to Some LEDs

    Yes, LED's can fail like that. They don't necessarily have to burn out like a light bulb. They can fail in a matter that they are not only to go out when they are failed short or open, but also if they get hot! If you have a backlight issue, first thing to always to do is to turn the backlight's waay down and see if the backlights stay on longer.
    The 350V tell me that there is an open LED in one string or generally an open. That is because LED's are current controlled, not voltage controlled. Don't test LED's with your DMM in diode mode, you'd have to actually put power and current to them with a variable constant current / constant voltage PSU.
    So all jammed together, it's not the PSU, it's the LED's!
    Please use the attachment function to upload pictures.

    Comment

    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada

      #3
      Re: Samsung UA50F5500 No Power to Some LEDs

      I have found that connector going to the LEDs in that model can be a bit flakey.

      https://www.badcaps.net/forum/showthread.php?t=72299

      Comment

      • brodymc
        New Member
        • Mar 2019
        • 3
        • New Zealand

        #4
        Re: Samsung UA50F5500 No Power to Some LEDs

        Originally posted by CapLeaker
        Yes, LED's can fail like that. They don't necessarily have to burn out like a light bulb. They can fail in a matter that they are not only to go out when they are failed short or open, but also if they get hot! If you have a backlight issue, first thing to always to do is to turn the backlight's waay down and see if the backlights stay on longer.
        The 350V tell me that there is an open LED in one string or generally an open. That is because LED's are current controlled, not voltage controlled. Don't test LED's with your DMM in diode mode, you'd have to actually put power and current to them with a variable constant current / constant voltage PSU.
        So all jammed together, it's not the PSU, it's the LED's!
        Please use the attachment function to upload pictures.
        Originally posted by neilc6
        I have found that connector going to the LEDs in that model can be a bit flakey.
        I managed to get a hold of a power supply to test the strips. All of the strips tested OK.

        Thanks Neil for the suggestion but I found that the connector had perfect continuity so that's not the issue either it seems. I can't seem to find a schematic or anything for this board either so it's fairing to be a bit of a head-scratcher.

        Comment

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 8061
          • Canada

          #5
          Re: Samsung UA50F5500 No Power to Some LEDs

          oops, I've read your first post again. You stated that you did the testing with the LED's disconnected? That is wrong. Connect the LED's and measure the voltage on each string.

          Comment

          • nomoresonys
            Badcaps Legend
            • Jan 2013
            • 12093
            • U.S.

            #6
            Re: Samsung UA50F5500 No Power to Some LEDs

            Looking like bad leds, replace all of them, BE VERY CAREFUL, screens are very delicate and break very easily, check some youtube videos if unsure about the process.

            Comment

            Related Topics

            Collapse

            • Document Archive
              Samsung Galaxy Book 2 Notebook Specification for Upgrade or Repair
              by Document Archive
              This specification for the Samsung Galaxy Book 2 Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Galaxy Book 2 boardview and Galaxy Book 2 schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification, datasheet, or download...
              09-07-2024, 05:50 AM
            • Kingfreddie
              LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every second.
              by Kingfreddie
              Ok.. this is the story:
              Have an old Samsung LED 3D TV (UE55F6475). First it started to lose light on the lower 40% of the screen now and then. Like for 10-60 mins and then it would work again. Then a bit later it just got stuck in that position. The lower 40% of the screen is dark, and it gets progressively darker the lower u go so it's obviously that LED strips where not working. I also looked for similar errors online and saw an exact copy and on that one it was faulty LED strips.

              This is kinda how it looked, just that mine were at the bottom of the screen:

              ...
              09-11-2021, 01:57 AM
            • Document Archive
              Samsung Galaxy Book Ion NP950XCJ Notebook Specification for Upgrade or Repair
              by Document Archive
              This specification for the Samsung Galaxy Book Ion NP950XCJ Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the NP950XCJ boardview and NP950XCJ schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification, datasheet, or download...
              09-06-2024, 11:40 PM
            • Document Archive
              Samsung Galaxy Book Ion NP930XCJ Notebook Specification for Upgrade or Repair
              by Document Archive
              This specification for the Samsung Galaxy Book Ion NP930XCJ Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the NP930XCJ boardview and NP930XCJ schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification, datasheet, or download...
              09-06-2024, 11:40 PM
            • Document Archive
              Samsung Galaxy Book Ion NP950XCJ Notebook Specification for Upgrade or Repair
              by Document Archive
              This specification for the Samsung Galaxy Book Ion NP950XCJ Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the NP950XCJ boardview and NP950XCJ schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification, datasheet, or download...
              09-06-2024, 08:40 PM
            • Loading...
            • No more items.
            Working...