phillips lcd keeps blowing fuse

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  • TimT
    Badcaps Veteran
    • Nov 2012
    • 268
    • us

    #101
    Re: phillips lcd keeps blowing fuse

    sorry Budm when you posted this I had to check... it is a 10a fuse with 24v at both ends. I was going off my memory and it's failing me...

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #102
      Re: phillips lcd keeps blowing fuse

      OK, you have all the correct signal and voltages, so check the transformer resistance will be the next test per post 96.
      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

      • TimT
        Badcaps Veteran
        • Nov 2012
        • 268
        • us

        #103
        Re: phillips lcd keeps blowing fuse

        here are my results. tested transformers with power off, meter set to 2000 ohms using the + - probes on the pins all were 958. reversed probes all same 958.

        selldoor the Mosfets are 50N04. tested powerd on - grounded to chassis. meter set to 200 dcv
        results are in picture. thanks everyone!
        Attached Files

        Comment

        • selldoor
          Slow Learner
          • Dec 2010
          • 7870

          #104
          Re: phillips lcd keeps blowing fuse

          Originally posted by TimT
          here are my results. tested transformers with power off, meter set to 2000 ohms using the + - probes on the pins all were 958. reversed probes all same 958.

          selldoor the Mosfets are 50N04. tested powerd on - grounded to chassis. meter set to 200 dcv
          results are in picture. thanks everyone!
          OK Did all the transformers test the same?

          I was expecting this test
          Mosfets

          If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

          a) black on pin 1- red on pin 2 - record ohms
          b) black on pin 1- red on pin 3 - record ohms
          c) black on pin 2- red on pin 3 - record ohms

          If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

          So I dont really know what to make of the voltages - perhaps Budm will comment.

          Can you do apicture of the full boards as he requested - I tried to piece them together but dont think they overlap.
          Please upload pictures using attachment function when ask for help on the repair
          http://www.badcaps.net/forum/showthread.php?t=39740

          Comment

          • vinceroger69
            Badcaps Legend
            • Mar 2012
            • 6714
            • uk

            #105
            Re: phillips lcd keeps blowing fuse

            good guide for testing mosets out of circuit
            http://www.4qdtec.com/mostest.html

            Comment

            • TimT
              Badcaps Veteran
              • Nov 2012
              • 268
              • us

              #106
              Re: phillips lcd keeps blowing fuse

              If I set the meter to 200 and test i get 1. only when I set meter to highest ohm setting do I get a reading.

              Comment

              • selldoor
                Slow Learner
                • Dec 2010
                • 7870

                #107
                Re: phillips lcd keeps blowing fuse

                That suggests they are ok - at least to the point of not being shorted - as I said perhaps budm will comment on the voltages - please post the picture he requested.
                Please upload pictures using attachment function when ask for help on the repair
                http://www.badcaps.net/forum/showthread.php?t=39740

                Comment

                • TimT
                  Badcaps Veteran
                  • Nov 2012
                  • 268
                  • us

                  #108
                  Re: phillips lcd keeps blowing fuse

                  I believe he wanted a full picture of the inverter board. thats in post 99

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #109
                    Re: phillips lcd keeps blowing fuse

                    OK, let's see what you get at the current sensing transformer.
                    The voltage reading on the MOSFET's indicated that they are not being driven after the backlights go out.
                    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

                    • TimT
                      Badcaps Veteran
                      • Nov 2012
                      • 268
                      • us

                      #110
                      Re: phillips lcd keeps blowing fuse

                      meter set to 2 im getting 0 in standby the only reading im getting is when the backlight flashes. reading .077 the after the flash it's back to 0. tested this several times with readings ranging from .007 to .055 im thinking the flash is to quick for my meter to read. .077 was the highest reading. thinking this is closer to the true value.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #111
                        Re: phillips lcd keeps blowing fuse

                        I expect something like 0.2~0.5v when lamps are on, and more than a volt if the lamps draw too much current.
                        I am running out of idea, I am thinking about put the jumper on the two terminals on the left side of that current sensing transformer to see if the lamps will stay on, that will tell us if the lamps shutdown due to too much current or not.
                        Last edited by budm; 12-31-2012, 10:22 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

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #112
                          Re: phillips lcd keeps blowing fuse

                          It's quite possible it's a very short transient causing the controller to shut down, if it's a "dumb" controller.
                          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

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #113
                            Re: phillips lcd keeps blowing fuse

                            This current sensing method is about the same as the SAMSUNG/SONY use on the balancer board. They save money on this one by using only one sensing transformer for all the lamps, not like SONY/SAMSUNG that detects each lamp.
                            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

                            • TimT
                              Badcaps Veteran
                              • Nov 2012
                              • 268
                              • us

                              #114
                              Re: phillips lcd keeps blowing fuse

                              I got a new multimeter today (Klein) so I retested the current senser transformer. when lamps kick in 0175. tested twice. it's Auto Ranging.

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #115
                                Re: phillips lcd keeps blowing fuse

                                Did you try jumping those two pin on the left side of the current sensing transformer yet. If it still does not stay when they are jumped then we can eliminate lamp over current as the cause of the problem and look some where else.
                                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

                                • TimT
                                  Badcaps Veteran
                                  • Nov 2012
                                  • 268
                                  • us

                                  #116
                                  Re: phillips lcd keeps blowing fuse

                                  budm you talking about these two pins?
                                  Attached Files

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #117
                                    Re: phillips lcd keeps blowing fuse

                                    Yes, that is the primary side of the current sensing transformer, the output winding on the right side feeds the Dual Diode to convert AC to DC for the current feedback.
                                    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

                                    • TimT
                                      Badcaps Veteran
                                      • Nov 2012
                                      • 268
                                      • us

                                      #118
                                      Re: phillips lcd keeps blowing fuse

                                      no luck with the jumper

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #119
                                        Re: phillips lcd keeps blowing fuse

                                        Well, that eliminate the over current shutdown problem. Need to look some where else next.
                                        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

                                        • TimT
                                          Badcaps Veteran
                                          • Nov 2012
                                          • 268
                                          • us

                                          #120
                                          Re: phillips lcd keeps blowing fuse

                                          budm do you think the problem is on the inverter board? or somewere else?

                                          Comment

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