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Backlights but no picture - No 12v to Tcon board

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    #21
    Re: Backlights but no picture - No 12v to Tcon board

    Originally posted by Stuckster View Post
    Tcon fuse is good. I believe the 12v is sent to the Tcon via the 51pin LVDS cable. So I would presume that there will still be no 12v with the LVDS unplugged, but I will test it anyway.
    LOL, I meant is there voltage at the spot on mainboard where you expect it without the lvds cable hooked up.

    Comment


      #22
      Re: Backlights but no picture - No 12v to Tcon board

      Sorry, my mistake. Posted the wrong picture. Can you give the numbers on the two IC's in the red boxes. The yellow boxes have voltage regulators. Can you measure the voltage on the 3 pins of each.
      Attached Files
      Willing to help but I'm no expert.

      Comment


        #23
        Re: Backlights but no picture - No 12v to Tcon board

        Originally posted by dick_barton View Post
        Sorry, my mistake. Posted the wrong picture. Can you give the numbers on the two IC's in the red boxes.
        No problem. It's tricky to read but I think they are
        Top IC
        P3056LS
        15 10

        Middle IC
        4832
        GA5614

        Bottom IC
        4832
        GA5614

        Comment


          #24
          Re: Backlights but no picture - No 12v to Tcon board

          Originally posted by dick_barton View Post
          The yellow boxes have voltage regulators. Can you measure the voltage on the 3 pins of each.
          Top VR
          Top pin = 0.0v
          Middle pin = 3.3v
          Bottom pin = 5.1v

          Bottom VR
          Top pin = 5.1v
          Middle pin = 3.3v
          Bottom pin = 0.0v

          Thanks

          Comment


            #25
            Re: Backlights but no picture - No 12v to Tcon board

            Can you give the voltages on the IC pins. I suspect one of them may have the 12V but is not switching through to the Tcon.
            Attached Files
            Willing to help but I'm no expert.

            Comment


              #26
              Re: Backlights but no picture - No 12v to Tcon board

              Originally posted by Stuckster View Post
              Top VR
              Top pin = 0.0v
              Middle pin = 3.3v
              Bottom pin = 5.1v

              Bottom VR
              Top pin = 5.1v
              Middle pin = 3.3v
              Bottom pin = 0.0v

              Thanks
              They look fine and provides the 3V3 supply to other IC's
              Willing to help but I'm no expert.

              Comment


                #27
                Re: Backlights but no picture - No 12v to Tcon board

                Originally posted by dick_barton View Post
                Can you give the voltages on the IC pins. I suspect one of them may have the 12V but is not switching through to the Tcon.
                Top IC
                11.9 --- 0.0
                11.9 --- 0.0
                11.9 --- 0.0
                11.5 --- 0.0

                Middle IC
                1.1 --- 3.5
                1.1 --- 0.0
                23.6 --- 3.2
                23.6 --- 1.4

                Bottom IC
                9.9 --- 2.3
                9.9 --- 0.0
                23.6 --- 12.7
                23.6 --- 9.9

                Top one looks like it might be the culprit? It's also the closest to the LVDS cable connection point.

                Comment


                  #28
                  Re: Backlights but no picture - No 12v to Tcon board

                  Originally posted by nomoresonys View Post
                  LOL, I meant is there voltage at the spot on mainboard where you expect it without the lvds cable hooked up.
                  No voltage on the LVDS connector pins (with cable unplugged).

                  Comment


                    #29
                    Re: Backlights but no picture - No 12v to Tcon board

                    Originally posted by Stuckster View Post
                    Top IC
                    11.9 --- 0.0
                    11.9 --- 0.0
                    11.9 --- 0.0
                    11.5 --- 0.0

                    Middle IC
                    1.1 --- 3.5
                    1.1 --- 0.0
                    23.6 --- 3.2
                    23.6 --- 1.4

                    Bottom IC
                    9.9 --- 2.3
                    9.9 --- 0.0
                    23.6 --- 12.7
                    23.6 --- 9.9

                    Top one looks like it might be the culprit? It's also the closest to the LVDS cable connection point.
                    Can you give the IC name and pin numbers 1 to 8 as shown in the images which makes reading easier.
                    Last edited by dick_barton; 10-23-2019, 05:43 AM.
                    Willing to help but I'm no expert.

                    Comment


                      #30
                      Re: Backlights but no picture - No 12v to Tcon board

                      Originally posted by dick_barton View Post
                      Can you give the IC name and pin numbers 1 to 8 as shown in the images which makes reading easier.
                      Sure.

                      SOP-8L (top)
                      1. S - 11.9
                      2. S - 11.9
                      3. S - 11.9
                      4. G - 11.9
                      5. D - 0.0
                      6. D - 0.0
                      7. D - 0.0
                      8. D - 0.0

                      SOIC-8 (middle)
                      1. S2 - 1.4
                      2. G2 - 3.2
                      3. S1 - 0.0
                      4. G1 - 3.5
                      5. D1 - 1.1
                      6. D1 - 1.1
                      7. D2 - 23.7
                      8. D2 - 23.6

                      SOIC-8 (bottom)
                      1. S2 - 9.9
                      2. G2 - 12.7
                      3. S1 - 0.0
                      4. G1 - 2.3
                      5. D1 - 9.9
                      6. D1 - 9.9
                      7. D2 - 23.7
                      8. D2 - 23.7

                      Hope I've got them right.
                      Last edited by Stuckster; 10-23-2019, 06:04 AM.

                      Comment


                        #31
                        Re: Backlights but no picture - No 12v to Tcon board

                        I believe the gate voltage should be at least 1.5V lower than the Source voltage so it looks as though the IC is not being switched on to allow the 12V through to the Drain which is probably the 12V supply for the tcon. You can check this out. With the set switched off check the resistance between the fuse on the Tcon and the Drain of the P3056LS
                        Could you also check the resistance between the Gate and Sourse and Gate and Drain.
                        Willing to help but I'm no expert.

                        Comment


                          #32
                          Re: Backlights but no picture - No 12v to Tcon board

                          Originally posted by dick_barton View Post
                          I believe the gate voltage should be at least 1.5V lower than the Source voltage so it looks as though the IC is not being switched on to allow the 12V through to the Drain which is probably the 12V supply for the tcon. You can check this out. With the set switched off check the resistance between the fuse on the Tcon and the Drain of the P3056LS
                          Could you also check the resistance between the Gate and Sourse and Gate and Drain.
                          Just realised I made a small typo. Gate should be 11.5 (not 11.9)
                          P3056LS
                          1. S - 11.9
                          2. S - 11.9
                          3. S - 11.9
                          4. G - 11.5
                          5. D - 0.0
                          6. D - 0.0
                          7. D - 0.0
                          8. D - 0.0

                          Comment


                            #33
                            Re: Backlights but no picture - No 12v to Tcon board

                            Originally posted by dick_barton View Post
                            With the set switched off check the resistance between the fuse on the Tcon and the Drain of the P3056LS
                            Could you also check the resistance between the Gate and Source and Gate and Drain.
                            Ok. Resistance between Tcon fuse and drain on P3056LS is .001 (just the resistance of my leads). So no resistance.

                            Resistance between Gate and Source is 33 (meter set to 200k Ohms)
                            Resistance between Gate and Drain is 90 (meter set to 200k Ohms)

                            I'm only a novice when it comes to this stuff. So thanks for your patience.

                            Comment


                              #34
                              Re: Backlights but no picture - No 12v to Tcon board

                              The resistance from the Tcon fuse to Drain being 0.001 means that P3056LS should be providing the 12V Tcon supply.
                              The other resistance readings, 200K ohms means there is no internal short circuit from gate to the source

                              The problem is that the IC is not being switched on.

                              Can you take a really sharp photo around that IC to try and see what the Gate track is connected to.
                              Willing to help but I'm no expert.

                              Comment


                                #35
                                Re: Backlights but no picture - No 12v to Tcon board

                                Originally posted by dick_barton View Post
                                The resistance from the Tcon fuse to Drain being 0.001 means that P3056LS should be providing the 12V Tcon supply.
                                The other resistance readings, 200K ohms means there is no internal short circuit from gate to the source

                                The problem is that the IC is not being switched on.

                                Can you take a really sharp photo around that IC to try and see what the Gate track is connected to.
                                Sure. Try this.
                                Now the first thing you're going to say is, that's a different IC! Which is true.

                                I should explain that I currently have two mainboards (same model). Lets call them A and B. Board A is the original board that came with the set. It failed and has too much wrong with it to resurrect. Board B is a replacement board that I bought "in used working condition". It is the board that I have been talking about in this thread. All the voltage and resistance readings have come from board B.

                                When you asked for the IC numbers I assumed (wrongly) that the parts on each board would be identical. It was easier to give you the part numbers from board A since I had it on the desk and could easily take the heat sink off etc. Apologies. Nevertheless having looked up the specs for the PMK50XP IC on board B (the one in the close up photo) they appear to have the same specs and function.
                                Attached Files
                                Last edited by Stuckster; 10-23-2019, 06:00 PM.

                                Comment


                                  #36
                                  Re: Backlights but no picture - No 12v to Tcon board

                                  https://www.badcaps.net/forum/attach...2&d=1571874353
                                  SOP-8L (top)
                                  1. S - 11.9
                                  2. S - 11.9
                                  3. S - 11.9
                                  4. G - 11.9
                                  5. D - 0.0
                                  6. D - 0.0
                                  7. D - 0.0
                                  8. D - 0.0

                                  So if you check the resistance between the T-CON fuse and D pin of Q1, it shows about the same resistance of the meter's probes resistance?
                                  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


                                    #37
                                    Re: Backlights but no picture - No 12v to Tcon board

                                    Originally posted by budm View Post
                                    https://www.badcaps.net/forum/attach...2&d=1571874353
                                    So if you check the resistance between the T-CON fuse and D pin of Q1, it shows about the same resistance of the meter's probes resistance?
                                    Yes. Correct. I just measured it again.
                                    With the meter set on 2k Ohms it 's reading 0.001 Ohms to all D pins.
                                    With the meter set on 200 Ohms it 's reading 1.5 Ohms to all D pins.

                                    Comment


                                      #38
                                      Re: Backlights but no picture - No 12v to Tcon board

                                      https://www.badcaps.net/forum/attach...2&d=1571874353
                                      Put DC Volt meter black lead on the chassis, Red lead to the Base pin of Q2 then turn the TV ON and OFF (wait 5 seconds between toggling) to see if the Voltage on the Base pin of Q2 changed state when you toggle the TV ON and OFF.
                                      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


                                        #39
                                        Re: Backlights but no picture - No 12v to Tcon board

                                        Originally posted by budm View Post
                                        https://www.badcaps.net/forum/attach...2&d=1571874353
                                        Put DC Volt meter black lead on the chassis, Red lead to the Base pin of Q2 then turn the TV ON and OFF (wait 5 seconds between toggling) to see if the Voltage on the Base pin of Q2 changed state when you toggle the TV ON and OFF.
                                        Sure. Is the base pin the one on it's own? Sorry I'm a bit of a noob with pcbs.

                                        Comment


                                          #40
                                          Re: Backlights but no picture - No 12v to Tcon board

                                          https://www.badcaps.net/forum/attach...2&d=1571874353

                                          Emitter pin (Top) is connected to R125/C181
                                          Collector pin (Middle pin) is connected to R126
                                          Base is the bottom pin.
                                          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

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