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T-Con board V315B1-C01 shorted SMD capacitor

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    T-Con board V315B1-C01 shorted SMD capacitor

    Hey Guys,

    I am encountering a problem with this LCD TV T-con board above which I am hoping the experts here can advise me. Please excuse the flash in the photo/s below. I was taking them when there is not much sun shining here. Ok here goes…

    T-con board model : V315B1-C01 found in Samsung (mine is LA32S81B) and if I am not mistaken, some of Chimei LCD TV models.

    Symptom/Fault of the TV: I plugged in the TV to the Mains and Power LED standby light up. I switched on the TV, Power LED blinks 4 times (normal) but no chime was heard (abnormal). The backlight lights up but the screen is black with some vertical lines and a buzzing sound on the speaker. I decided to leave it on for a few more seconds & I could smell burnt on the back of the panel near the top (middle) of the TV. I disassemble the back panel & remove the metal cover of the T-con. Indeed a burnt SMD capacitor (CP15) can be found on the T-con. Using my multimeter, I measured shorted across it. I removed it & measured again & it is no longer shorted. I decided to leave CP15 empty & fix it to the back of the TV again. This time when I switched on the TV, Power LED blinks 4 times & a chime sound is heard (normal). Pictures appear on the screen but are washed out (negative mode). After a while, the image was better but the color especially black, contrast, gamma was off, not as a normal TV (Sorry I could not take a image of it as I have now already removed the T-con). Black image/background do have colored, fuzzy lines on them. The lines will go away if I increase the brightness though. Hope I am describing it correctly.

    I have also confirmed that the other SMDs capacitors lining up above & bottom of the burnt one (CP26, CP21, CP23, CP20) are inter-connected together (parallel?). 1 point on them is connected to the VDA point (below the label C46) while the other point is grounded. VDA is measure 13.65V to Gnd. I did experiment by wiring up the 2 point of the burnt SMD capacitor & placing a Electrolyte capacitor (ranging from 1uf to 47uf) across it but still the image is not normal. I do not have a capacitance meter.

    So what do you guys think? Should I just buy the whole T-con board set which I think will cost me around US$40 (including shipping from China)? TRY to replace the burnt SMD capacitor? But if I do that, I do not have the information what is the capacitance of the original burnt SMD capacitor or if there is other components failure on the T-con board. Many thanks in advance for all the feedback/s provided.
    Attached Files

    #2
    Re: T-Con board V315B1-C01 shorted SMD capacitor

    Originally posted by newbie1 View Post
    So what do you guys think? Should I just buy the whole T-con board set which I think will cost me around US$40 (including shipping from China)? TRY to replace the burnt SMD capacitor?
    Depends on how much your time is worth.

    Personally, I would try replacing the burned ceramic capacitor. You don't really need to know the info on it - just grab another ceramic capacitor that has the same size. Junk motherboards and video cards should have plenty of these.

    If that doesn't fix the problem, check the voltage on test points VDD, VGL, and VGH. VGL should be negative (typically -5 to -15V depending on the t-con design), and VGH is typically 15-35V. Post what results you get.

    Comment


      #3
      Re: T-Con board V315B1-C01 shorted SMD capacitor

      Thanks momaka.

      I managed to find an SMD capacitor from graphics card. Same length but it is thinner. Replaced it and the image was initially dark (negative) but slowly producing a much proper image. However, the black areas are having colored lines on them (See first photo). I then realized that the picture is in ‘Dynamic' mode setting. I changed to ‘Standard' mode and the image is better (See second photo). However, in ‘Standard' mode the white area of the display is more yellowish than white.

      Measurements taken from the T-con board are:
      VDD = 3.3V
      VGH = 18.7V
      VGL = -5.5v
      VDA = 13.6V

      Do you guys think that the T-con is causing the description above or is the logic board faulty? If it is the logic board, then i guess I have to live with it as I am not sure I can get a used one for cheap.
      Attached Files

      Comment


        #4
        Re: T-Con board V315B1-C01 shorted SMD capacitor

        Originally posted by newbie1 View Post
        Measurements taken from the T-con board are:
        VDD = 3.3V
        VGH = 18.7V
        VGL = -5.5v
        VDA = 13.6V
        I can't confirm that VGH and VGL are 100% correct since I don't have the service manual for this TV, but they still seem okay. The other voltages are fine.

        Originally posted by newbie1 View Post
        Do you guys think that the T-con is causing the description above or is the logic board faulty?
        Not sure. Check the TV's menus - do they appear to have the same problem as the picture or is the color there fine. If the color in the menus is fine, then it's most likely a faulty logic board. If the menus have the same problem as the picture, then it's most likely the t-con.

        Comment


          #5
          Re: T-Con board V315B1-C01 shorted SMD capacitor

          Originally posted by momaka View Post
          Not sure. Check the TV's menus - do they appear to have the same problem as the picture or is the color there fine. If the color in the menus is fine, then it's most likely a faulty logic board. If the menus have the same problem as the picture, then it's most likely the t-con.
          Thank you momaka for the tips/hint. I will check it out but if i recalled correctly, seems like the TV menu is having the same problem as well. Will try to source for a spare t-con to test it.

          Comment


            #6
            Re: T-Con board V315B1-C01 shorted SMD capacitor

            j'ai presque la même problème je pense que le t-con

            Comment


              #7
              Re: T-Con board V315B1-C01 shorted SMD capacitor

              Merci pour vos commentaires. Avez-vous acheté un nouveau t-con et at-il résoudre le problème?

              Comment


                #8
                Re: T-Con board V315B1-C01 shorted SMD capacitor

                Hi Guys,

                Just an update. Replacing the whole T-Con board solve the problem. Thank you guys for all your input/s..

                Comment


                  #9
                  Re: T-Con board V315B1-C01 shorted SMD capacitor

                  You can figure out the value of the shorted out cap bu remove the other one that is in parallel with the bad one then use the C meter to read the value, they use them in parallel to get large enough capacitance so they will low profile instead of large electrolytic cap with high profile.
                  See my pictures here:
                  http://s807.photobucket.com/albums/y...NS-LCD37HD-09/
                  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


                    #10
                    Re: T-Con board V315B1-C01 shorted SMD capacitor

                    i have samsung lcd model la32s81b
                    problame

                    pictures negative and menu

                    Comment


                      #11
                      Re: T-Con board V315B1-C01 shorted SMD capacitor

                      hi friends i have 32bx350 sony lcd tv 3.3v and 12v are ok from ps front red led not glowing any help

                      Comment


                        #12
                        Re: T-Con board V315B1-C01 shorted SMD capacitor

                        Originally posted by malik4 View Post
                        i have samsung lcd model la32s81b
                        problame

                        pictures negative and menu
                        If you have the same t-con replace the as15 chip that controls gamma.
                        I assume no responsibility for any stupid suggestions I might post.

                        Comment


                          #13
                          Re: T-Con board V315B1-C01 shorted SMD capacitor

                          Good day. Can you advise me what the part according to the attachment was - it was burned and I circled the empty space and the place where there are probably identical components. The designation is S1Ac and I can't find what it is and the equivalent. Maybe it's a mosfet or a double diode. There are no diagrams anywhere. well thank you
                          This T-CON V315B1-C05
                          Attached Files
                          Last edited by peterkos2; 01-07-2021, 06:11 AM.

                          Comment


                            #14
                            Re: T-Con board V315B1-C01 shorted SMD capacitor

                            The PCB designator for that component shows "QP1", so it must be a transistor of some sort. If I had to guess, it's most likely a MOSFET as I don't see any Base resistors. But it's hard to say. Infineon has a MMBT3904 transistor (NPN BJT) in SOT-23 case that is marked with "s1A" rather than "S1Ac".

                            Post the part number found on that square IC chip above it (UP1.) If we can get a datasheet for that, we can see what pin the missing QP1 transistor goes to, and then try to determine that from the app circuit in the datasheet for UP1.

                            Another approach is to see to what rails the pins of QP1 connect to. We can see the left-most pin (when the single pin on the SOT-23 device is at the top) should be the Gate/Base connection, given the thiner wire. So if we can figure out to what rails the other pins connect to (i.e. ground, 5V, 3.3V, etc.), then we can see what function this transistor has in the circuit and then we may be able to guess if it's a MOSFET or BJT.
                            Last edited by momaka; 01-09-2021, 08:52 PM.

                            Comment


                              #15
                              Re: T-Con board V315B1-C01 shorted SMD capacitor

                              Thank you for your response. I'm just a beginner. Here's a photo
                              Attached Files

                              Comment


                                #16
                                Re: T-Con board V315B1-C01 shorted SMD capacitor

                                Thank you for helping me. So far, I have found that PIN 27 from MAXIM is marked as GATE and goes to the missing part. So it should be a MOSFET. But according to that table, it should be an NPN transistor. So I don't really know what part was there at all.
                                Attached Files
                                Last edited by peterkos2; 01-10-2021, 08:39 AM.

                                Comment


                                  #17
                                  Re: T-Con board V315B1-C01 shorted SMD capacitor

                                  According to the pictures on the internet, it is not the same part as I thought that the missing one is the same as the circled ones. There are no photos where you can read the code on the part. There are no schemes either.

                                  Comment


                                    #18
                                    Re: T-Con board V315B1-C01 shorted SMD capacitor

                                    According to the pictures on the internet, it is not the same part as I thought that the missing one is the same as the circled ones. There are no photos where you can read the code on the part. There are no schemes either.

                                    Comment


                                      #19
                                      Re: T-Con board V315B1-C01 shorted SMD capacitor

                                      According to MAX8728 datasheet, pin 27 has the following description:
                                      "Input MOSFET Gate-Driver Output. GATE controls an external p-channel MOSFET between the input voltage and the step-up regulator’s inductor. The switch is off when the step-up regulator is turned off, so that the regulator’s output discharges to ground. During startup, the step-up regulator’s soft-start begins when VGATE falls below the GATE done threshold"

                                      So you just need a P-ch MOSFET there.
                                      As for what MOSFET to use, that you'll have to search what is available to you. I think a MOSFET rated for 25-40V V_sd and 750 mA to 1 Amp should work, but maybe get a small variety, just in case. And make sure to get P-channel type. N-channel will NOT work.

                                      Also, you don't really need to get a matching SOT-23 case size. If all you can find is bigger cases like TO-252 or SOT-223, you can just solder these MOSFETs with a bunch of wires to the board - at least for a test, if nothing else.

                                      Lastly, was QP1 chipped from physical damage or from overload? If from overload, check for shorted ceramic caps on the AVDD rail (i.e. check resistance between ground and the Cathode of SMD diode DP6 - you should probably get a few hundred Ohms there or more.) If you get less than 50 Ohms, there may be a shorted ceramic cap somewhere, and that may cause your new MOSFET to blow again.
                                      Last edited by momaka; 01-10-2021, 11:48 PM.

                                      Comment

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