need help to test inverter transformer

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  • selldoor
    Slow Learner
    • Dec 2010
    • 7870

    #61
    Re: need help to test inverter transformer

    good - were you able to find a panel with that type of backlight connector?
    If not ,I am not sure how the Big plugs are wired -perhaps budm will suggest how you
    can best test the bulbs
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment

    • woaimi
      Senior Member
      • Sep 2005
      • 94
      • US

      #62
      Re: need help to test inverter transformer

      that is my problem right now, I couldn't find anything with that plug, my bulbs mostly came from computer LCD and the biggest size i have is 19". There are 6 plugs for this tv set and I'm assuming it represent 6 bulbs, here's what I'm thinking will I cause any damage if I only plug in 1 or 2 bulbs to the corresponding transformer and leave the other unplug? this way I can verify which transformer is working and which one is not and may be at the same time can figure out the questionable bulb/s.

      Comment

      • selldoor
        Slow Learner
        • Dec 2010
        • 7870

        #63
        Re: need help to test inverter transformer

        I am hoping all transformers will be good and we can work out which lamp or lamps is
        causing the shut down. As I said budm has more ideas on this and has a way of using
        old domestic energy saving bulbs to test so we need to hope he comes back to this thread. For testing the size of your panels doesnt matter I think you can get adapter from small to big but for now just see if you can plug a small plug in onto one pin of the big connector. If it will go on then we can consider cutting the small plug in half.
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

        • woaimi
          Senior Member
          • Sep 2005
          • 94
          • US

          #64
          Re: need help to test inverter transformer

          I measured the Vcc input to the transformers and reading 56v at all time whether the TV is on nor not, does that suggest anything?

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #65
            Re: need help to test inverter transformer

            OK, I looked at the inverter/power supply board, all three transformers are driven by the same output MOSFET's. I still think you should have replace all 3 transformers.
            You have indicated that you have 56V at all time on the inverter transformers primary side. It should have 0 Volt due to DC blocking cap, and the junction between the two inverter MOSFET's should have 0V (not 100% sure since I did not draw out the circuits in details). I would take that blue DC blocking cap out and measure for any leakage resistance using the highest Ohm scale, cap should show open circuits, you should also check its capacitance.
            Another thing you can check to see if all the lamps do at least try to light up or not by just having one set of lamp connector connected one at a time, then turn on the TV in the dark room and see if each set of the lamp will light/flash.
            I will tell you later how to use home made tester lamp.
            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

            • woaimi
              Senior Member
              • Sep 2005
              • 94
              • US

              #66
              Re: need help to test inverter transformer

              Wow, thanks for that drawing, I've learned much more since I take on this project. Thanks for all those replies.
              I checked the light bulbs one at a time and they're all flashed up in the same pattern; it flashes like twice in about 5 seconds, I think they are fine.
              The DC blocking cap were removed to test, it read opened when test with the ohm meter and the capacitance measured 0.452 nF and the caps's label said 474K (I'm guessing that 's a 0.47 nF cap)

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #67
                Re: need help to test inverter transformer

                It is 0.47uF cap not 0.47nF.
                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

                • woaimi
                  Senior Member
                  • Sep 2005
                  • 94
                  • US

                  #68
                  Re: need help to test inverter transformer

                  thanks budm for pointing it out, i will have it verify later tonight, I might have mis-read the 'u' and 'n' on the meter.

                  Comment

                  • woaimi
                    Senior Member
                    • Sep 2005
                    • 94
                    • US

                    #69
                    Re: need help to test inverter transformer

                    It was verified as 452nF, that's what happened when I tried to work on it at 2:00 am. So, going back to your drawing, if I can't measure those 2 points you mentioned how can I verify it 0 voltage? I'm feeling very close to get it working, really don't want to throw in the towel yet.

                    Comment

                    • selldoor
                      Slow Learner
                      • Dec 2010
                      • 7870

                      #70
                      Re: need help to test inverter transformer

                      Perhaps just replace it - I dont think they are v expensive? perhaps you have one on a "spares" board?
                      Please upload pictures using attachment function when ask for help on the repair
                      http://www.badcaps.net/forum/showthread.php?t=39740

                      Comment

                      • woaimi
                        Senior Member
                        • Sep 2005
                        • 94
                        • US

                        #71
                        Re: need help to test inverter transformer

                        Could you please help to id this cap? all I can tell is .47uF, don't know what the voltage rating. I probably be able to find it in my junk pile. Thanks

                        sorry for the blurry image, that's the best i can come up with with my iphone.
                        Attached Files

                        Comment

                        • selldoor
                          Slow Learner
                          • Dec 2010
                          • 7870

                          #72
                          Re: need help to test inverter transformer

                          I dont know but thought id say something to bring it back to the top.
                          Is the K relative to 1000 or is it a tolerance value - I have seen some with a J.
                          The 4 could be 400v is there a voltage on the small blue cap next to it?
                          Please upload pictures using attachment function when ask for help on the repair
                          http://www.badcaps.net/forum/showthread.php?t=39740

                          Comment

                          • woaimi
                            Senior Member
                            • Sep 2005
                            • 94
                            • US

                            #73
                            Re: need help to test inverter transformer

                            there's nothing written on the small cap either. From what I found the 3rd character is the multiplier and K is tolerance value of +-10%

                            Comment

                            • selldoor
                              Slow Learner
                              • Dec 2010
                              • 7870

                              #74
                              Re: need help to test inverter transformer

                              Yes that was what I thought - in the absence of more educated input I would try a 400v - I have looked at a few and some are just coded so 4 could be anything. Can you get a better close up of the logo in the middle of the bottom line - if anyone recognises that we might find the codes.
                              Please upload pictures using attachment function when ask for help on the repair
                              http://www.badcaps.net/forum/showthread.php?t=39740

                              Comment

                              • woaimi
                                Senior Member
                                • Sep 2005
                                • 94
                                • US

                                #75
                                Re: need help to test inverter transformer

                                I'll try with a real camera later when I get home.
                                Anyhow, I wanted to retake the voltage reading off the connector so I soldered it back on last night, plugged everything in, turned it on. I realized I was able to see the screen with a spot light. I checked the transformers in frequency mode to find out they were all run at 63 kHz (if I remember correctly) and all shut down as the screen goes dark.
                                The CN600 connector reads as follow
                                V-PWM = 0.54V/ 0.54V (on/off)
                                BL-ON = 5.15V/ 65mV
                                PS-ON = 4.7V/ 4.7V
                                GND
                                GND
                                5V = 5.2V / 5.2V
                                5V = 5.2V / 5.2V
                                5V = 5.2V / 5.2V
                                5VS = 5.2V / 5.2V
                                GND
                                GND
                                12.5V = 12.7V / 12.9V
                                12.5V = 12.7V / 12.9V

                                I also took reading at the secondary diodes (D601, D605, D607) but forgot what they were
                                I hope that would give the experienced users some more details to work with.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #76
                                  Re: need help to test inverter transformer

                                  That cap should be 630V or higher due to high voltage pulse.

                                  http://www.digikey.com/product-detai...F6474-ND/56678

                                  Bythe way:
                                  474k = 470000 pico farad(pF is x 10 to the minus 12) = .47uF (uF is x10 to the minus 6), K = 10% tolerance)
                                  Last edited by budm; 08-09-2012, 10:15 AM.
                                  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

                                  • selldoor
                                    Slow Learner
                                    • Dec 2010
                                    • 7870

                                    #77
                                    Re: need help to test inverter transformer

                                    Right - that is the blue cap sorted then. I think we need to have a look at the Tcon board it is under a metal panel in one of your pics. Can you get to it and take some pictures - I think there will be fuses on it to test.
                                    Have you tried unplugging the lead to the Tcon from the main board to see if that allows the backlights to stay on?
                                    Please upload pictures using attachment function when ask for help on the repair
                                    http://www.badcaps.net/forum/showthread.php?t=39740

                                    Comment

                                    • woaimi
                                      Senior Member
                                      • Sep 2005
                                      • 94
                                      • US

                                      #78
                                      Re: need help to test inverter transformer

                                      whew! my 2 little boys are really know how to keep daddy busy, finally able to break away from them to work on this tv set

                                      that is the blue cap sorted
                                      I couldn't find 1 similar from my pile of electronic junk so I guess I will have to order the replacement.
                                      I think there will be fuses on it to test
                                      I scanned through the t-con board and couldn't find any fuse, may be someone can help me spot it. I hope the photo is clear enough
                                      Have you tried unplugging the lead to the Tcon from the main board to see if that allows the backlights to stay on?
                                      I have not tried this because I currently have couple mosfet off the pcb for testing.
                                      As I mentioned, I de-soldered these 2 mostfet U603 & U600 of the board to test (using retiredcaps instruction). The part numbers are P65NF06 & FQP17P06. The test (setting @ 200 ohm)result are "1" on every pair of leads. Isn't that suggested the mosfet are bad?

                                      EDIT: i found the fuse on t-com board, so obvious can't believe I missed it. It labeled on board as F1 and has letter K on the fuse itself. It measured 0.4 ohm, i think that meas it's good.
                                      Attached Files
                                      Last edited by woaimi; 08-11-2012, 06:00 PM. Reason: update

                                      Comment

                                      • selldoor
                                        Slow Learner
                                        • Dec 2010
                                        • 7870

                                        #79
                                        Re: need help to test inverter transformer

                                        Originally posted by woaimi

                                        As I mentioned, I de-soldered these 2 mostfet U603 & U600 of the board to test (using retiredcaps instruction). The part numbers are P65NF06 & FQP17P06. The test (setting @ 200 ohm)result are "1" on every pair of leads. Isn't that suggested the mosfet are bad?
                                        Yes - just check that the "1" is one ohms and not "1" meaning "out of range"
                                        would would mean they are likely ok.

                                        EDIT: i found the fuse on t-com board, so obvious can't believe I missed it. It labeled on board as F1 and has letter K on the fuse itself. It measured 0.4
                                        ohm, i think that means it's good.
                                        Yes fuse is good- There are at least 2 voltage regulators on that board
                                        They will need checking if new mosfets and blue cap doesnt fix it.
                                        Please upload pictures using attachment function when ask for help on the repair
                                        http://www.badcaps.net/forum/showthread.php?t=39740

                                        Comment

                                        • woaimi
                                          Senior Member
                                          • Sep 2005
                                          • 94
                                          • US

                                          #80
                                          Re: need help to test inverter transformer

                                          that was the "1" on the left, so it's out of range
                                          I'm waiting for the blue cap in order, I'll update with result later. Thanks

                                          Comment

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