Announcement

Collapse
No announcement yet.

Samsung 912N Problem

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #41
    Re: Samsung 912N Problem

    Hi all,

    A quick update on my 912N project...I replaced the dual channel mosfet on the logic card this weekend, and it is still not working properly. The problem persists in that, with no pc connected, I get a steady green indicator light, and the 'Check Signal' box moves around the screen freely and does not turn off, albeit the box does not appear uniform (see photo above) but then once I attach the pc video source, using several different cables, the video goes completely dark. The difference is now, since replacing the mosfet on the video card, I can get the Check Signal box to appear for a few seconds first.

    I'm thinking that on the inverter board, there is a mosfet hidden on the underside of a smaller circuit board. Hopefully tonight I can post photos of the inverter board, and at that time I would like to ask the group if they recommend me to remove the little attached circuit card and test the mosfet under it.

    Thanks as always.

    Comment


      #42
      Re: Samsung 912N Problem

      You may want to check the BL_ON signal line to see if it changes when you have the monitor connected to the PC, I have a feeeling that the BL_ON changes when the PC is connected.
      Attached Files
      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


        #43
        Re: Samsung 912N Problem

        Originally posted by budm View Post
        You may want to check the BL_ON signal line to see if it changes when you have the monitor connected to the PC, I have a feeeling that the BL_ON changes when the PC is connected.
        Hi Budm,

        Thank you for the schematic diagrams. I have printed them out and taken a look but was unable to find reference to BL_ON. I did, however, see BL_EN on a few of the pages.

        This is my first time reviewing schematics for this monitor; could you offer me some guidance on how to locate what I am looking for? And then I can give it a try this evening, once I'm home from work.

        On another subject, I am in the final stages of assembling my Blue ESR meter. It was a lot of fun and my seven year old was an eager helper. Maybe he will take it to science class and impress his friends.

        Thanks all once again.

        Comment


          #44
          Re: Samsung 912N Problem

          BL_EN is the one. See if you do have CN600 on the logic board, then see if the connector CN600 PIN9 has voltage reading, RED PROBE on pin 9, black probe on the chassis. Turn on the monitor without hooking up to pc so you cane see "CHECK SIGNAL" and read the DC voltage, then hook it up to PC and see the voltage again.

          Service manual: http://elektrotanya.com/samsung_510n.../download.html
          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


            #45
            Re: Samsung 912N Problem

            Originally posted by budm View Post
            BL_EN is the one. See if you do have CN600 on the logic board, then see if the connector CN600 PIN9 has voltage reading, RED PROBE on pin 9, black probe on the chassis. Turn on the monitor without hooking up to pc so you cane see "CHECK SIGNAL" and read the DC voltage, then hook it up to PC and see the voltage again.

            Service manual: http://elektrotanya.com/samsung_510n.../download.html
            Very helpful Budm. I will check this tonight, and report back shortly thereafter.

            Comment


              #46
              Re: Samsung 912N Problem

              Hi Budm,

              My logic board has no CN600...I took a look upthread at #22 where I posted a photo last week. It would have been right under the top left white multipin connector. Can BL_EN be checked some other way?

              Comment


                #47
                Re: Samsung 912N Problem

                I'll check Q600 right next to it for shorts. I missed that one while looking it over.

                Comment


                  #48
                  Re: Samsung 912N Problem

                  We are looking for the HI-LO signal on this pin, if it changes when the monitor gets the video signal from the PC, then it is not the inverter circuits problem, it is just some how being told to turn off the backlights when the monitor gets the video signal, se we want to verify if that is the case.
                  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


                    #49
                    Re: Samsung 912N Problem

                    Originally posted by LAS View Post
                    Hi Budm,

                    My logic board has no CN600...I took a look upthread at #22 where I posted a photo last week. It would have been right under the top left white multipin connector. Can BL_EN be checked some other way?
                    Looking at the schematic that budm supplied, you should be able to monitor BL_EN at the collector pin of transistor Q601. The collector pin is the side of the transistor with one leg coming out of it. Q601 is located directly below the white 9-pin connector on the logic board.

                    Comment


                      #50
                      Re: Samsung 912N Problem

                      Thank you jetadm123. I have identified Q601 on the logic board, and I will test the one leg for hi / low and I will also test across the transistor for any shorts.

                      I have also found it on the schematic.

                      Comment


                        #51
                        Re: Samsung 912N Problem

                        Budm and jetadm123,
                        When the monitor is turned on, with no video cable attached, the Q601 pin which is on a side by itself (I am thinking the is the base, not the collector, yes?) I get 3.7v. When I plug in the video cable, it goes to zero. If I unplug the cable and give it a few seconds, the backlights come back on and the pin goes back to 3.7v.

                        The transistor does not appear to be shorted out.

                        Comment


                          #52
                          Re: Samsung 912N Problem

                          I suggested the collector because it's tied directly to the 9-pin connector. However, I see what you did. You measured the BL_EN voltage at the base, which is tied directly to the output of IC200, which is acceptable. It looks like the backlight is responding to the on/off commands. Sounds almost like the logic board can't handle the load when you plug in the video cable. Looking at the wiring diagram of the 9-pin connector, each pin has a voltage or ground associated with it. 14V, 5V. BL_EN, etc. I suggest you measure the voltage on every pin before you plug in the cable and again after you plug in the cable.

                          Comment


                            #53
                            Re: Samsung 912N Problem

                            He measured at the Collector (PIN 9 of the connector) which is correct. If you have the 2 pins pointing toward you, the left pin is Base, the right pin is Emitter. The Collector has pull up resistor (R604, 10k), the transistor (NPN) is normally off which makes the Collect goes HI, when the controller send the positive signal to the Base, the transistor will turn on so the Collector voltage will go low.
                            That is, the BL_ON command output to the Base of Q601. So some how the controller chip tells the inverter to turn off when it gets the Video signal! The middle pin is Collector.
                            BL_EN HI = INVERTER OFF, Q601 turns ON, cOLLECTOR goes LO.
                            BL_EN LO = INVERTER ON, Q601 turns OFF, Collector goes HI.
                            You can force the Inverter to be on by connecting Base to Emitter.
                            See attached PDF for the transistor Q601, 2SC2412.
                            You will have to start checking the output of the voltage regulators, I see 3.3v, 2.5v, etc.
                            Attached Files
                            Last edited by budm; 04-16-2012, 09:26 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


                              #54
                              Re: Samsung 912N Problem

                              While looking at your logic board photo, I noticed it had a Novatek controller, NT68F63L, which jarred my memory. Apparently, your logic board was also used on the 913N, which also had problems similar to yours:

                              https://www.badcaps.net/forum/showth...light=nt68f63l

                              Seems like this controller goes bad over time and the fix is to replace it and reload it's firmware. From what I can see, the success for this repair was pretty low.

                              Comment


                                #55
                                Re: Samsung 912N Problem

                                Ah, that what I remember now! I know I see the symptom on other model before on this site, thanks for finding it, jetadm123.
                                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


                                  #56
                                  Re: Samsung 912N Problem

                                  Well, the good news is that the monitor was given to me, and while I did change the caps, they can always be taken out and used elsewhere. Alternatively, the day may come when I come across another 912N and I can create my own 'Frankenstein' version out of the spare parts.

                                  And the other good news is that my Blue ESR meter went together smoothly, and it's now complete. So I save these monitor parts for another day, and another monitor, and in the meantime I thank you all for your perserverence, help and extensive memories and experience.

                                  LAS.

                                  Comment


                                    #57
                                    Re: Samsung 912N Problem

                                    Originally posted by jetadm123 View Post
                                    Seems like this controller goes bad over time and the fix is to replace it and reload it's firmware. From what I can see, the success for this repair was pretty low.
                                    $4 for an empty one, but then it needs to be programmed and the soldering looks a bit intimdating.

                                    http://www.ebay.com/itm/270825016266

                                    Well, it looks like you have some spare ccfls now to use for testing.
                                    --- begin sig file ---

                                    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                                    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                                    Please do not post inline and offsite as they slow down the loading of pages.

                                    --- end sig file ---

                                    Comment


                                      #58
                                      Re: Samsung 912N Problem

                                      Retiredcaps, I'm ok with the $4 and I'm ok with the soldering, but the reprogramming - any special equipment required?

                                      LAS.

                                      Comment


                                        #59
                                        Re: Samsung 912N Problem

                                        Originally posted by LAS View Post
                                        Retiredcaps, I'm ok with the $4 and I'm ok with the soldering, but the reprogramming - any special equipment required?

                                        LAS.
                                        On the link I supplied above, check out post #56. Gonzo0815 gives a rough idea of what hardware/software to use.

                                        Comment


                                          #60
                                          Re: Samsung 912N Problem

                                          Can anyone tell me if the login card on the 712N is the same as in the 912N? If so, I may be able to aquire one for a nominal amount.

                                          Comment

                                          Working...
                                          X