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Sylvania lc320ss2 LCD TV keeps blowing fuse

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    #41
    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

    OK, I just trace out the board. Check D611 to see if it is shorted.
    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


      #42
      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

      OK, this is the best I can do due to the white paint masking on the bottom side, I cannot trace out the Gate drive, but this will give some idea what to look for on the board. You can see that it has many Zener Diode across the output of the power supply, they need to be checked.
      Check Q601 and all the Diodes in the primary side, Q601 could have been damaged also when Q600 shorted out.
      Attached Files
      Last edited by budm; 01-19-2013, 01:58 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


        #43
        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

        Originally posted by budm View Post
        I think the short is in the primary side of the circuit. If you remove the MOSFET, will it still light up the lamp?
        I also search using all those models without luck.
        On from that - is the mosfet on the heatsink ? is it meant to be electrically isolated and if it is , is it?
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment


          #44
          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

          have you checked the inductors L600+L601 i have had shorts on other power boards with them?

          Comment


            #45
            Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

            Inductors are coils of wire. They are supposed to read short.
            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


              #46
              Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

              Not between the coils there not?

              Comment


                #47
                Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                That's a lot of work @budm, thanks for taking the time.
                Yeah I had previously checked d611 and it was alright.
                Short of maybe 2 or three I think I checked all the other diodes on the primary side.

                I'll try a few things now and report back.

                @floco, I'll check the inductors with the blue ring tester to see if it picks it up.

                Comment


                  #48
                  Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                  Oh, yeah I had checked Q601 already, it's good.

                  Comment


                    #49
                    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                    Alright @budm to answer your question, I just did that test of removing the power fet and here is what happens. The lightbulb does not light up and I get 179vdc on the filter cap. The FET is still good too.

                    I'm now going to check a bunch of those zeners on the secondary side by the output lines.

                    Comment


                      #50
                      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                      So the mosfet you have removed - that is the one on the heatsink
                      -yes? Well as I asked before is it insulated from the heatsink?
                      was the original one insulated or in a plastic casing.
                      Please upload pictures using attachment function when ask for help on the repair
                      http://www.badcaps.net/forum/showthread.php?t=39740

                      Comment


                        #51
                        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                        selldoor, sorry I didn't understand your question before.
                        No it was just screwed down onto the heatsink, the same way I have it now.

                        Comment


                          #52
                          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                          Originally posted by Beowulf View Post
                          selldoor, sorry I didn't understand your question before.
                          No it was just screwed down onto the heatsink, the same way I have it now.
                          Ok but did you check if the original was in a plastic moulded casing and is the new one in a plastic casing. Sometimes a mosfet with almost the same part number comes in an insulated type and sometimes in a type that is connected electrically to the heatsink. If you get the second type instead of the first it will short.
                          Please upload pictures using attachment function when ask for help on the repair
                          http://www.badcaps.net/forum/showthread.php?t=39740

                          Comment


                            #53
                            Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                            Oh, good to know.
                            No they look identical both the original and the replacement when it comes to the packaging and no the original was mounted on the heat sink directly without any plastic casing.

                            Comment


                              #54
                              Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                              Insulated:


                              Not insulated:
                              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


                                #55
                                Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                Cool.
                                Yeah then It's the insulated packaging on both the original and the replacement FET

                                Comment


                                  #56
                                  Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                  Here is a picture highlighting the components I've tested today and also some from before. The ones enclosed in a orange square are those I'm not sure how to test therefore I opted for removing from the circuit (one at a time) and test to see if anything changed and it did not.

                                  The ones enclosed in red are the ones i've tested and found to be good.

                                  The two big inductors checked out ok with the blue ring tester.

                                  From the bunch of diodes (orange/black) there were a few reading higher than the rest, around 700+ where most other ones would read around 500 just to point that out.

                                  Would love to learn when and when not a component could be tested in-circuit. You know just a few things I could start learning like "you can check a given component in circuit as long as it doesn't have a certain component in parallel/series etc". I currently have an analog meter, a digital meter, a capwizard and a bluering tester.

                                  Also was wondering if using a lesser watts lightbulb (currently using a 100W) could help in getting the shorted component be spotted out easier due to it getting hotter. At the moment the only components that get slightly warm are the large cement resistors and the rectifier diodes, if I remember right.
                                  Attached Files

                                  Comment


                                    #57
                                    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                    So is it still blowing fuses?

                                    Sometimes the lightbulb trick doesn't work for these designs, due to the self-oscillating nature. It'll just stay lit as the circuit oscillates.

                                    A lower power lightbulb would lead to less heat, not more.
                                    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


                                      #58
                                      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                      "Would love to learn when and when not a component could be tested in-circuit."

                                      Logging off now - I dont know if you have seen this guide written by retiredcaps, it contains lots of tests most are carried out without power to the boards.
                                      https://www.badcaps.net/forum/showthread.php?t=10419

                                      There are few updates the latest starts at post19.
                                      Please upload pictures using attachment function when ask for help on the repair
                                      http://www.badcaps.net/forum/showthread.php?t=39740

                                      Comment


                                        #59
                                        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                        I wouldn't dare try it without the lightbulb. Last time I did, I had to replace some of the new components again plus thefuse which it blew up horribly. Since it's very bright and I'm not getting the right voltage on the filter cap I'm thinking there's still something shorted. And of course this is while on stand by, and the tv wouldn't turn on so...

                                        Comment


                                          #60
                                          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                          With the lightbulb in place and a self-oscillator failing to start you'll see nothing across the primary cap.

                                          Eventually you have to, unfortunately, risk it without the bulb, unless you have a variac to slowly ramp it up.
                                          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

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