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Samsung S24D390HL flashing on and off - wrong power supply ?

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    #1

    Samsung S24D390HL flashing on and off - wrong power supply ?

    Hi,

    I just got this nice screen to repair, the first symptom was no backlight, but I could see the image with a light on it. After digging, it appeared the backlight connector was broken at the LED board, the solder failed (it doesn't seem to have been previously disassembled and it needs to be to access this connector).
    After carefully pulling the back panel of the screen to access the led board, I was able to solder back the connector.

    But now there is another issue, the backlight turns on and off a bit irregularly, then there's a hissing sound (coil whine?) and it remains black. The adapter makes a weird noise as well.
    I figure this might be due to the power supply, I'm using a 12V 2A adapter instead of the factory 14V 1.78A PSU, as I don't have it. Could this be the source of the issue ?
    I can hear a light ticking noise on the logic board everytime it turns on.
    I tried unplugging the control board, and the LCD, no difference.

    This is what it looks like inside (sorry, not there now, can't do better).




    Thanks
    Tags: None
    #2
    Re: Samsung S24D390HL flashing on and off - wrong power supply ?

    These units do suffer from firmware issues which are fixed by flashing them over the VGA port using a Samsung-provided utility.
    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

      #3
      Re: Samsung S24D390HL flashing on and off - wrong power supply ?

      I can't find anything on the subject, are you sure it's the same units ?

      Comment

        #4
        Re: Samsung S24D390HL flashing on and off - wrong power supply ?

        I doubt the erroneous behavior the monitor is showing is actually caused by firmware corruption. The phenomena the firmware error causes are described in these threads:

        https://www.badcaps.net/forum/showthread.php?t=26922

        https://www.badcaps.net/forum/showthread.php?t=29242

        and

        https://www.badcaps.net/forum/showthread.php?t=29307

        Reading the TS post I'd say there's something not right with the LED backlight. Maybe there's a short in there. The connector came loose with a reason. If the monitor's case wasn't opened until now, that cannot have been caused by 'human interference'.
        Maybe the monitor really needs 14V instead of 12V from the PSU. I'd try to get hold of the factory PSU, if only to exclude it from the suspect list.

        Error checking with more than 1 variable at the same time is not easy.

        re-atari

        Comment

          #5
          Re: Samsung S24D390HL flashing on and off - wrong power supply ?

          If you disconnect the plug going to the backlight, the monitor should come on as before and you should see the image with a flashlight, If that works, recheck your work on the plug you repaired.
          Is the plug you repaired, in the panel or the one on the logic board?
          Last edited by R_J; 09-13-2018, 11:07 AM.

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            #6
            Re: Samsung S24D390HL flashing on and off - wrong power supply ?

            The plug I repaired is on the led strip in the panel, I had to carefully disassemble the panel to access it. It's the connector on this exact part : https://www.ebay.com/itm/For-Samsung...IAAOSw24RbES7N

            The behavior seems to be located on the board. When I measure the voltages in various places, it drops whether or not I plug the screen backlight, lcd or controls.
            So it's either a power issue from the PSU, or something on the board.

            Oddly enough, at one point, the backlight did stay on until I unplugged it, butonly part of the LEDs lit up as the top and bottom of the screen were darker.
            But it usually just flickers and everything is lit up.

            Also the Samsung Magicolor chip gets hot when there is power, so I suspect a short somewhere as well. I measured the diodes and mosets but couldn't find something obviously wrong.

            But then again, with the proper power supply, that would be something less to think about.
            Last edited by SuperDuty; 09-13-2018, 02:46 PM.

            Comment

              #7
              Re: Samsung S24D390HL flashing on and off - wrong power supply ?

              I have had the same problem with the original 14V 1.78A power supply. Lowering the brightness of the monitor below 60 the problem disappeared, but if I turn on "game mode" the monitor crash. I also thought it was a problem with the power supply and I bought a new 12V 3A and it has not helped.

              Comment

                #8
                Re: Samsung S24D390HL flashing on and off - wrong power supply ?

                I think your case is a failing back lights problem.

                Comment

                  #9
                  Re: Samsung S24D390HL flashing on and off - wrong power supply ?

                  I'm here a little late, but I hope this works for the future people.
                  I have the same issue with the same monitor, I fully opened it and looks like the problem are the backlights. One of them don't turns on and maybe this makes that the main board detect and incorrect current and protect itself.
                  I bought a replacement, when I have it in my hands I will change and tell all you if it worked.
                  Attached Files

                  Comment

                    #10
                    Originally posted by Manu.ATG View Post
                    Re: Samsung S24D390HL flashing on and off - wrong power supply ?

                    I'm here a little late, but I hope this works for the future people.
                    I have the same issue with the same monitor, I fully opened it and looks like the problem are the backlights. One of them don't turns on and maybe this makes that the main board detect and incorrect current and protect itself.
                    I bought a replacement, when I have it in my hands I will change and tell all you if it worked.
                    Can you share the status of the replacement ?
                    I'm having the same problem. 1 set of 12 LED turning off, It cycle for 3 times and protection mode shuts down the other 2 set of 24 LEDs but the picture stays ON (checked with flash light)

                    Comment

                      #11
                      Originally posted by mugunthans View Post

                      Can you share the status of the replacement ?
                      I'm having the same problem. 1 set of 12 LED turning off, It cycle for 3 times and protection mode shuts down the other 2 set of 24 LEDs but the picture stays ON (checked with flash light)
                      I have the exactly same issue. Have you found a solution? (Sorry to see that Manu did not reply)

                      Comment

                        #12
                        If you got a bad backlight strip, either replace the whole strip, replace the bad LED's
                        or substitute bad LEDs with zener diodes.
                        You also can turn the backlight down to 50% and the monitor may function for a while longer. Sooner or later it will fail again… unfortunately.

                        Comment

                          #13
                          Yep. So I gambled on it being a broken backlight strip.
                          Ordered a new strip for $10.
                          Replaced and the monitor is working again.

                          Comment

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