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Samsung U32D970Q works after slapping it

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    Samsung U32D970Q works after slapping it

    Hello I have a Samsung U32D970Q and it has an error I’m not able to track down any further.
    The error pattern looks like this: The Background light is off and also the standby LED. But it is possible to see the monitor recognized in the laptop settings.

    The weird thing is, when the monitor is in this state and I slap hard on the back of the monitor for several times it jumps on and also stays on. It is working correctly then (during a workday) and switches into the error state a while after my workday or after two.

    I also have opened the monitor and measured the voltages around the power supply. When the monitor is in the error state, the voltages to the mainboard are around a 1 V level. When it’s working correct, they are about 12,9 V. I can see a DC voltage about 210 V behind the DC/DC

    All Fuses and diodes are ok, I’m not sure which part gets triggered by the slapping.

    EDIT: When I bridge the PS_On/Off Pin to GND, the voltages for the 13 V Pins are around 10,3 V. So I guess there might be some bad caps. I don't have a multimeter for cap testing, do you have a guess how to check this systematically?

    EDIT2: After removing the bridge PS_On/Off - GND The voltage for the 13 V Pins git to 12,9 V. Maybe PS_On/Off to GND wasn't the supposed switch on signal. But the question is why did the voltage is now 12,9 V instead the 1 V in the error state with everythin off
    Last edited by Timex; 03-13-2021, 06:53 AM.

    #2
    Re: Samsung U32D970Q works after slapping it

    By slapping the monitor and it starts to work almost confirms a bad connection and likely a bad solder connection on the power supply board. Post some pictures so we can see what we are dealing with.
    By connecting PS_On/Off Pin to GND you are placing it in standby mode, so of course the voltage drops.
    Check, or re-solder the connections on all components attached to heatsinks, and also the transformer pins, then closly inspect the board for other poor solder connections.
    Last edited by R_J; 03-13-2021, 12:29 PM.

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      #3
      Re: Samsung U32D970Q works after slapping it

      Hi, thanks for your answer. I've had the monitor open for several times now and was inspecting the solder joints and tipping on pins. I've resoldered the mainboard<->psu connectors so far. I think it might be a last try to resolder the pins you mentioned. I didn't take pictures today, but in this video the guy is dealing with the same monitor but an obvious error: https://www.youtube.com/watch?v=tbWrSu_ESDs.

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        #4
        Re: Samsung U32D970Q works after slapping it

        I've desoldered the transformer, is it normal after manufacturing that the connections look a little bit burned?
        Edit: added board photos
        Attached Files
        Last edited by Timex; 03-14-2021, 09:32 AM.

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          #5
          Re: Samsung U32D970Q works after slapping it

          There is no need to remove these parts, that is likely varnish or glue on the transformer pins, It is not the problem. If there were any defective parts, the power supply would not operate at all! Slapping the back of the monitor would have had no effect.... but it did, so there is a intermittent connection somewhere.
          Re-install the transformer, you may have already fixed the problem if the transformer's connections were poorly soldered.
          Re-solder any of the connections that use those rivets, start from the a/c inlet and the input filter chokes including the bridge rectifier.
          Last edited by R_J; 03-14-2021, 11:33 AM.

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            #6
            Re: Samsung U32D970Q works after slapping it

            I think I heated the transformer too much, the Display startet shortly with backlight blinking in strange patterns, after that the backlight was off and the standby LED was on.
            I can only measure about 7,8 V on the PSU mainboard output. The Transformer Input is ok but there is no output. I think I might have grilled the thermal fuse within the transformer?
            Is there any store where I can order the transformer? I didn't find any so far.
            Otherwise I will buy a new display this week.
            Last edited by Timex; 03-14-2021, 11:53 AM.

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              #7
              Re: Samsung U32D970Q works after slapping it

              There is no thermal fuse in these transformers, How do you know the transformer "input" is ok?
              How can you have NO OUTPUT from the transformer, and have 7.8V going to the main board, when that voltage comes from the transformer?
              Last edited by R_J; 03-14-2021, 12:11 PM.

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                #8
                Re: Samsung U32D970Q works after slapping it

                Ok, you were right, I must have had the multimeter in the wrong mode. I'm a little bit exhausted about this display.
                Now I must have broken something else, the Displayed elements when the screen is switched on are now (like HDMI Channel Symbol Box) streched over the screen from top to bottom and only slightly visible as a silhouette. Is it maybe the T-Con Board? One thing I did was fixing the LCD matrix controlboard tight to the screen with a folded insulation tape between the metal cover and the board.. I thougt it shouldn't be so loose.. I feel so dumb today

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                  #9
                  Re: Samsung U32D970Q works after slapping it

                  Okay, I found an issue, that might cause the lines on the screen. The Panel wiring snipped on the bottom left and right get untouchable hot.
                  Is there anything I can do or is the panel dying?
                  Attached Files

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                    #10
                    Re: Samsung U32D970Q works after slapping it

                    Does anyone have a datasheet for the COF lh163y12 by sharp?
                    I would like to check if there is any line grounded of these
                    Attached Files

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