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Barco LCN-42 No Power

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    #21
    Re: Barco LCN-42 No Power

    That looks like the Source resistor for the MOSFET next to it, more likely to have Source to Drain shorted out, since the voltage drop on this resistor will be use for the Overcurrent feedback for the SMPS IC, if the value is too high then it will cause the power supply to shutdown too earlier, if it is too low, then it will not go into shutdown when the current is already exceed the current limit of the MOSFET and other power component. I would think it will be about 0.20 Ohm MOX type 1W (you can calculate the Wattage if you know how much current is expected to flow through this resistor). By the way, I can see a lot of failings solder joints.
    Attached Files
    Last edited by budm; 03-18-2012, 04:28 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


      #22
      Re: Barco LCN-42 No Power

      Originally posted by Jasgriff View Post
      The middle band cant be silver according to this website.
      Yes, I figured that out in post #19, but I guess you didn't see the post before post #20?

      4th band looks brown.
      --- begin sig file ---

      If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

      We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

      Please do not post inline and offsite as they slow down the loading of pages.

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      Comment


        #23
        Re: Barco LCN-42 No Power

        Originally posted by budm View Post
        That looks like the Source resistor for the MOSFET next to it, more likely to have Source to Drain shorted out, since the voltage drop on this resistor will be use for the Overcurrent feedback for the SMPS IC, if the value is too high then it will cause the power supply to shutdown too earlier, if it is too low, then it will not go into shutdown when the current is already exceed the current limit of the MOSFET and other power component. I would think it will be about 0.20 Ohm MOX type 1W (you can calculate the Wattage if you know how much current is expected to flow through this resistor). By the way, I can see a lot of failings solder joints.
        Yes I noticed that they looked bad when I reviewed the pictures. I will go over the whole board and give them a touch up.

        Do you think that resistor is that low considering the bands that can be seen?
        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

        How to resize your pictures guide click HERE
        Retiredcaps Ideal post example click HERE

        Comment


          #24
          Re: Barco LCN-42 No Power

          Originally posted by retiredcaps View Post
          Yes, I figured that out in post #19, but I guess you didn't see the post before post #20?

          4th band looks brown.
          Long time since I was in college learning the bands off by heart lol.
          Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

          How to resize your pictures guide click HERE
          Retiredcaps Ideal post example click HERE

          Comment


            #25
            Re: Barco LCN-42 No Power

            If it is the Source resistor, I would think so since most of the power supply I worked on has Source resistor from 0.1~0.47 Ohm range. That 3rd band with silver color (it looks silver to me from the pictures)
            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


              #26
              Re: Barco LCN-42 No Power

              Originally posted by budm View Post
              If it is the Source resistor, I would think so since most of the power supply I worked on has Source resistor from 0.1~0.47 Ohm range. That 3rd band with silver color (it looks silver to me from the pictures)
              According to the calculator it cant be silver on a 5 band resistor?

              http://www.maplin.co.uk/search?criteria=resistor

              Here is where I will be going tomorrow to get a couple of fuses. There is no sign of a resistor that looks like its going to do the job. Its a poor version of radio shack.
              Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

              How to resize your pictures guide click HERE
              Retiredcaps Ideal post example click HERE

              Comment


                #27
                Re: Barco LCN-42 No Power

                I Know, I will look through my spare boards and see if they have one of these five band power resistor and see what the value should be. Does it look Gray or Silver to you? If it is gray, then that will be real odd ball value.
                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


                  #28
                  Re: Barco LCN-42 No Power

                  It definitely looks more silver than grey its got a shine to it.

                  Q203 is also shorted. One of the legs of that connects to the resistor so that could have been what caused it?
                  Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                  How to resize your pictures guide click HERE
                  Retiredcaps Ideal post example click HERE

                  Comment


                    #29
                    Re: Barco LCN-42 No Power

                    Q203 is the power MOSFET mounted on the heat sink right? The Drain voltage is probably in the 100VDC or higher, so when it shorted out that will voltage will be developed on that resistor and blow up that resistor, the current feedback circuit is connected to the Source of the MOSFET will be present at the Current feedback input pin of the SMPS IC also and could have damaged the input pin of the IC as well, I would Ohm out the SMPS IC also. Do you know what the IC number is for this section of this circuits? The Gate connection should be hooked up to some resistors and Diode back to the SMPS IC output put drive, check that pin also.
                    See some example PDF, PIN3 is the CS (CURRENT SENSE) pin.
                    Attached Files
                    Last edited by budm; 03-18-2012, 05:17 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


                      #30
                      Re: Barco LCN-42 No Power

                      Originally posted by budm View Post
                      By the way, I can see a lot of failings solder joints.
                      I noticed that too and thought I put in a post regarding that, but for some reason it didn't show up. Maybe I forgot to hit submit.
                      --- begin sig file ---

                      If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                      We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                      Please do not post inline and offsite as they slow down the loading of pages.

                      --- end sig file ---

                      Comment


                        #31
                        Re: Barco LCN-42 No Power

                        Yes its mounted directly onto the heat sink.

                        13778 pjhq it looks like it says on the IC

                        I have included another pic of the area from the Mosfet and the resistor. Take a look at Q202 that had also been damaged.
                        Attached Files
                        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                        How to resize your pictures guide click HERE
                        Retiredcaps Ideal post example click HERE

                        Comment


                          #32
                          Re: Barco LCN-42 No Power

                          It may use the Half-bridge drive circuits if there are two power MOSFET's driving the power transformer.
                          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


                            #33
                            Re: Barco LCN-42 No Power

                            There are 3 Mosfets directly connected to the heatsinks. 2 of them are together and then one of them on their own that's the blown one.

                            The others don't looks shorted.
                            Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                            How to resize your pictures guide click HERE
                            Retiredcaps Ideal post example click HERE

                            Comment


                              #34
                              Re: Barco LCN-42 No Power

                              The control IC looks like it might be 1377B

                              And the 3 SMD resistors look to have taken heat too.

                              I have attached in image to show what's going where. Excuse the flash its really dark at the moment.
                              Attached Files
                              Last edited by Jasgriff; 03-18-2012, 06:04 PM.
                              Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                              How to resize your pictures guide click HERE
                              Retiredcaps Ideal post example click HERE

                              Comment


                                #35
                                Re: Barco LCN-42 No Power

                                Some kind of conductor may have touched that B+ trace and the chassis?
                                This power supply has PFC Voltage booster circuits.
                                I would like to see pictures of each sections so I can try to trace out the PS_ON and VCC for each SMPS, PFC IC s.
                                Attached Files
                                Last edited by budm; 03-18-2012, 06:52 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


                                  #36
                                  Re: Barco LCN-42 No Power

                                  I have pulled the Power Mosfet that has shorted.

                                  11N80C3 Ordered.

                                  Fuse - FT8AH250VP - These are the nearest I can find will they be alright?

                                  http://www.ebay.co.uk/itm/8-Amp-8A-T...item35a4a11674

                                  How can I find out what value the Q202 Transistor was?
                                  Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                  How to resize your pictures guide click HERE
                                  Retiredcaps Ideal post example click HERE

                                  Comment


                                    #37
                                    Re: Barco LCN-42 No Power

                                    Controller is an NCP1377B:

                                    Check pins 4-5, 4-6 and 4-8 for short circuits - all should appear >10kohm if chip is okay.
                                    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


                                      #38
                                      Re: Barco LCN-42 No Power

                                      Originally posted by budm View Post
                                      Some kind of conductor may have touched that B+ trace and the chassis?
                                      Not sure?

                                      This is exactly as I bought it.

                                      Do you think that the Q202 Transistor popping might have saved the IC?
                                      Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                      How to resize your pictures guide click HERE
                                      Retiredcaps Ideal post example click HERE

                                      Comment


                                        #39
                                        Re: Barco LCN-42 No Power

                                        Originally posted by tom66 View Post
                                        Controller is an NCP1377B:

                                        Check pins 4-5, 4-6 and 4-8 for short circuits - all should appear >10kohm if chip is okay.
                                        They are all over 20k. It looks like the Transistor took the grunt of it.
                                        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                        How to resize your pictures guide click HERE
                                        Retiredcaps Ideal post example click HERE

                                        Comment


                                          #40
                                          Re: Barco LCN-42 No Power

                                          I still to find out the designators of those transistors you are talking about, I cannot easily see them in the pictures so I have no ideas what their functions are. Can you mark the pictures?
                                          Oh I see the Q202 now, what is the output voltage of this power supply as printed on the DC output connector of this section?
                                          Last edited by budm; 03-18-2012, 06:58 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

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