Samsung 933HD stripes in image

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  • magneh
    Badcaps Veteran
    • Apr 2014
    • 595
    • Portugal

    #1

    Samsung 933HD stripes in image

    Hello,

    I have a Samsung 933HD with weird stripes in the image.
    First two pics were taken with some seconds of difference, and we can see that the stripes change.

    I've checked the voltages of the power board, they are all OK.
    I've also disconnected the screen from the mainboard, and the bulbs and inverter are OK, as the screen presents itself white and with no picture as supposed.

    The problem should be in the mainboard probably.
    Can I mesure voltages in LVDS connector to troubleshoot?
    Maybe those IC's with alu dissipators are the source of the problem...

    Any thoughts?
    Thanks!
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Samsung 933HD stripes in image

    Do the stripes move for any given image, or are they fixed?
    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

    • magneh
      Badcaps Veteran
      • Apr 2014
      • 595
      • Portugal

      #3
      Re: Samsung 933HD stripes in image

      Originally posted by tom66
      Do the stripes move for any given image, or are they fixed?
      Mostly they are fixed ... just some lines change but 90% are fixed. (depends on input, as you can see the stripes are different in this photo compared to Ext1 as in 1rst picture of 1rst post)

      Another photo added with TV tuner selected.
      Attached Files
      Last edited by magneh; 11-17-2014, 05:29 PM.

      Comment

      • magneh
        Badcaps Veteran
        • Apr 2014
        • 595
        • Portugal

        #4
        Re: Samsung 933HD stripes in image

        Hello again!

        Should I consider mainboard is bad and try to get a new one?
        Or is it a waste of time and should I scrape lcd and power supply and forget it?

        Comment

        • magneh
          Badcaps Veteran
          • Apr 2014
          • 595
          • Portugal

          #5
          Re: Samsung 933HD stripes in image

          Well, since I dont want to spend what people ask for a new mainboard,
          I removed the heatspreaders to see the IC's underneath it.

          the 2 smaller ones are samsung memory chips, and the bigger one a Samsung DNle BGA.

          Could this BGA be the issue?
          Connected the power supply with mainboard and power button, and without screen so I could mesure some points labeled.

          Dunno if it's due to the fact of the screen not being connected, the 5V panel didn't present.
          Also mesured the voltages on the points nearby , all 0V.

          The set turned on without the screen connected, but didnt turn off. Had to unplug it.

          Any thoughts?
          Attached Files

          Comment

          • magneh
            Badcaps Veteran
            • Apr 2014
            • 595
            • Portugal

            #6
            Re: Samsung 933HD stripes in image

            UPDATE:

            Now I connected the lcd to see if there was any difference, and the screen didnt light up.

            The bigger heatspreader was hard to unglue ... did I damaged something when removing it?
            Weird ... now the set doesnt power off pressing power button and the screen doesnt light up...

            All 5.1V and 15V were present on the powerboard , just checked it.
            Last edited by magneh; 11-19-2014, 04:34 PM.

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Samsung 933HD stripes in image

              My guess, LCD panel is bad.
              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

              • magneh
                Badcaps Veteran
                • Apr 2014
                • 595
                • Portugal

                #8
                Re: Samsung 933HD stripes in image

                It was "good" before removing the heatspreaders...

                At least it turned on with backlight and image with problems as in the photos...

                Figured out that it turns on on the button of the set but doesnt power off ...

                But with the remote it turns off! weird...

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK

                  #9
                  Re: Samsung 933HD stripes in image

                  What I meant is the previous symptoms with the lines. That is almost always caused by bad LCD panel if the lines are mostly static.
                  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

                  • magneh
                    Badcaps Veteran
                    • Apr 2014
                    • 595
                    • Portugal

                    #10
                    Re: Samsung 933HD stripes in image

                    Originally posted by tom66
                    What I meant is the previous symptoms with the lines. That is almost always caused by bad LCD panel if the lines are mostly static.
                    Ok.

                    But this issue now with the screen not even lighning up, is it the mainboard that gives the command to turn the bulbs on?
                    Or the power supply should do it by herself , even if main is NOK?

                    Now I even dunno if the power supply is still good...

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: Samsung 933HD stripes in image

                      The main board will send PS_ON, to turn the power rails on, and then BL_ON, to turn the backlights on. In some small monitors sometimes there is only one ON/OFF signal which turns on both backlight and power, or the power rail is always on.
                      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

                      • magneh
                        Badcaps Veteran
                        • Apr 2014
                        • 595
                        • Portugal

                        #12
                        Re: Samsung 933HD stripes in image

                        Originally posted by tom66
                        The main board will send PS_ON, to turn the power rails on, and then BL_ON, to turn the backlights on. In some small monitors sometimes there is only one ON/OFF signal which turns on both backlight and power, or the power rail is always on.
                        How can I find the BL_ON signal?
                        What I can understand is after removing heatspreaders, mainboard stopped sending BL_ON to the power board.

                        Correct?
                        Last edited by magneh; 11-19-2014, 05:27 PM.

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #13
                          Re: Samsung 933HD stripes in image

                          Yes, that would appear correct. Is there a legend on the other board? Maybe indicating what pins what supply/signal is there.
                          BL_ON can also be BK_ON, ON/OFF, BLON, BL, VBL.
                          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

                          • magneh
                            Badcaps Veteran
                            • Apr 2014
                            • 595
                            • Portugal

                            #14
                            Re: Samsung 933HD stripes in image

                            Originally posted by tom66
                            Yes, that would appear correct. Is there a legend on the other board? Maybe indicating what pins what supply/signal is there.
                            BL_ON can also be BK_ON, ON/OFF, BLON, BL, VBL.
                            It could also be BLEN?
                            Attached Files
                            Last edited by magneh; 11-19-2014, 06:11 PM.

                            Comment

                            • magneh
                              Badcaps Veteran
                              • Apr 2014
                              • 595
                              • Portugal

                              #15
                              Re: Samsung 933HD stripes in image

                              Hello!

                              Mesured BLEN and I have 0.01V ... not good.

                              Is it possible to find a schematic of this mainboard?
                              Or should I just try to follow the path of this signal ?

                              Thanks for any inputs!

                              Cheers!

                              Comment

                              • selldoor
                                Slow Learner
                                • Dec 2010
                                • 7870

                                #16
                                Re: Samsung 933HD stripes in image

                                It is not good if the BLEN is supposed to be pulled high for ON. If is pulls LOW for ON then
                                there is another problem.
                                Suggest you disconnect the main board and test again to see if it starts as high.
                                If it starts as LOW then with a 300-500 ohm resistor jumper 5v to BLEN and see if they come on. ( On some sets you also have to jumper DIM to 5v using a resistor.

                                Chances are that Tom is correct in saying the panel was bad and now you have probably
                                partly pulled the chip with the heatsink off the board.
                                Please upload pictures using attachment function when ask for help on the repair
                                http://www.badcaps.net/forum/showthread.php?t=39740

                                Comment

                                • magneh
                                  Badcaps Veteran
                                  • Apr 2014
                                  • 595
                                  • Portugal

                                  #17
                                  Re: Samsung 933HD stripes in image

                                  Ok , so I've traced down BLEN signal, and it comes from a resistor I think labeled 472 (mesured 4,71k oHm) who connects to IC1022.

                                  5V are present on IC1022, and appear on one side of resistor (?) 472, but on the other side (before pin of BLEN) I only get 0.01V.

                                  Here's a photo with these points and tensions.

                                  EDIT : Mesured values @ startup , it allways shows 0.01 from the moment power supply turns on in BLEN pin
                                  Attached Files
                                  Last edited by magneh; 11-21-2014, 01:59 PM.

                                  Comment

                                  • tom66
                                    EVs Rule
                                    • Apr 2011
                                    • 32560
                                    • UK

                                    #18
                                    Re: Samsung 933HD stripes in image

                                    That would appear to be a "pull-up" resistor. It is tied permanently to a 5V supply. Then, it is controlled by the nearby transistor Q1012. When that transistor is turned ON (base-emitter >0.6V) the BLEN signal will be pulled low, turning off the backlight. (This is an inverter circuit.) The resistor adjacent, also 472 value (4700 ohms) should be checked. Voltage on the end closest to the transistor should be ~0.6V with BLEN off (0V), and 0V with BLEN on (5V)
                                    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

                                    • Shinju
                                      Badcaps Legend
                                      • Mar 2014
                                      • 1239
                                      • USA

                                      #19
                                      Re: Samsung 933HD stripes in image

                                      Have you tried a heat reflow? not sure why one would want to remove the heat sinks from the chips but my guess is something got damaged in that process as someone has stated.

                                      Comment

                                      • magneh
                                        Badcaps Veteran
                                        • Apr 2014
                                        • 595
                                        • Portugal

                                        #20
                                        Re: Samsung 933HD stripes in image

                                        Originally posted by tom66
                                        That would appear to be a "pull-up" resistor. It is tied permanently to a 5V supply. Then, it is controlled by the nearby transistor Q1012. When that transistor is turned ON (base-emitter >0.6V) the BLEN signal will be pulled low, turning off the backlight. (This is an inverter circuit.) The resistor adjacent, also 472 value (4700 ohms) should be checked. Voltage on the end closest to the transistor should be ~0.6V with BLEN off (0V), and 0V with BLEN on (5V)
                                        Hello!

                                        Well picked up some readings.
                                        The resistor seem OK .

                                        For what I understood , I got 0.7V on the end closes to the transistor, and then it's normal to have BLEN off right?
                                        Which element would be responsible to push those 0.7V to GND, having BLEN ON?
                                        Thanks!
                                        Attached Files

                                        Comment

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