Barco LCN-42 No Power

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  • retiredcaps
    Badcaps Legend
    • Apr 2010
    • 9271

    #161
    Re: Barco LCN-42 No Power

    Originally posted by budm
    I am not sure what the AC frequency bandwidth of your 175 is.
    45Hz to 500Hz for 600mV to 600V according to manual page 12. For range 1000V it is 500Hz to 1kHz.

    Not as wide as your Fluke 87 which goes from 50Hz to 20kHz.
    Last edited by retiredcaps; 04-12-2012, 04:04 PM. Reason: typo
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    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #162
      Re: Barco LCN-42 No Power

      That is too low, that why I keep my 87 for poor man scope (I do have 4 scopes).
      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

      • Jasgriff
        Badcaps Veteran
        • Feb 2012
        • 578
        • UK

        #163
        Re: Barco LCN-42 No Power

        I thought retiredcaps would get to the answer quicker than me. I bet you didnt even have to look it up!

        Here is the setting that I would have though was right.
        Attached Files
        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

        How to resize your pictures guide click HERE
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        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #164
          Re: Barco LCN-42 No Power

          You meter AC frequency bandwidth is too lo for it to measure any AC in the 30~50KHz range.
          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

          • retiredcaps
            Badcaps Legend
            • Apr 2010
            • 9271

            #165
            Re: Barco LCN-42 No Power

            Originally posted by budm
            You meter AC frequency bandwidth is too lo for it to measure any AC in the 30~50KHz range.
            I think I saw a Uni-T multimeter in one of Jasgriff's pictures as well. If correct, does that Uni-T have a bar graph?
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            Comment

            • Jasgriff
              Badcaps Veteran
              • Feb 2012
              • 578
              • UK

              #166
              Re: Barco LCN-42 No Power

              The UNI-T one is a cheap one. I think it has probes and an on off switch and that's about it
              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

              • Jasgriff
                Badcaps Veteran
                • Feb 2012
                • 578
                • UK

                #167
                Re: Barco LCN-42 No Power

                Just done a little more testing to try and work out whats going on.

                It seems when I turn it on some power is supplied to the mosfet that I have marked with the letter A. This starts off at 75v or so but then quickly drops down to nothing. The same happened to the transistor which I think might be driving it? That transistor starts off at just short of 6v but then slowly drops down under 1 vault.
                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

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #168
                  Re: Barco LCN-42 No Power

                  I would like to try this to see if the 18v power supply section is loading down the 13VCC LINE, there is jumper wire in the middle of the picture shown with red line, lift one end up and see if the 13vdc comes back.
                  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

                  • retiredcaps
                    Badcaps Legend
                    • Apr 2010
                    • 9271

                    #169
                    Re: Barco LCN-42 No Power

                    Originally posted by Jasgriff
                    The UNI-T one is a cheap one.
                    Geez, 250V AC is barely enough to meet 220-240V AC regions.

                    And there is no way it can measure the PFC DC voltage of any modern electronic device with a limit of 250V DC.
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                    • Jasgriff
                      Badcaps Veteran
                      • Feb 2012
                      • 578
                      • UK

                      #170
                      Re: Barco LCN-42 No Power

                      Originally posted by budm
                      I would like to try this to see if the 18v power supply section is loading down the 13VCC LINE, there is jumper wire in the middle of the picture shown with red line, lift one end up and see if the 13vdc comes back.
                      I will try it now.
                      Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                      How to resize your pictures guide click HERE
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                      Comment

                      • Jasgriff
                        Badcaps Veteran
                        • Feb 2012
                        • 578
                        • UK

                        #171
                        Re: Barco LCN-42 No Power

                        Originally posted by retiredcaps
                        Geez, 250V AC is barely enough to meet 220-240V AC regions.

                        And there is no way it can measure the PFC DC voltage of any modern electronic device with a limit of 250V DC.
                        At the moment it cant read anything as I blew the fuse by touching the wrong connection
                        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

                        • Jasgriff
                          Badcaps Veteran
                          • Feb 2012
                          • 578
                          • UK

                          #172
                          Re: Barco LCN-42 No Power

                          Originally posted by budm
                          I would like to try this to see if the 18v power supply section is loading down the 13VCC LINE, there is jumper wire in the middle of the picture shown with red line, lift one end up and see if the 13vdc comes back.
                          Its done the opposite.

                          I have disconnected the left hand side of the jumper and now I have 0v on the left hand track that goes back to the sub board but 6.2v on the right hand side that leads back to the replaced chip?

                          Maybe the vcc comes from somewhere else and that feeds back up to the sub board?
                          Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                          How to resize your pictures guide click HERE
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                          Comment

                          • Jasgriff
                            Badcaps Veteran
                            • Feb 2012
                            • 578
                            • UK

                            #173
                            Re: Barco LCN-42 No Power

                            I have attached a pic to show the jumper that I removed and the black line shows where the vcc is coming from im getting about 8v over the black line.

                            If you can see C304 at the bottom there is 12v there so it seems that this is where the 13v should be coming from.
                            Attached Files
                            Last edited by Jasgriff; 04-12-2012, 07:31 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

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #174
                              Re: Barco LCN-42 No Power

                              Boy that is strange, you may be right that the VCC is coming from somewhere else. It is usually generated by the winding of the always on power supply then it will be fed to switched transistor to be turn on when it receives the PS_ON signal.
                              Right now we know that the 18v, 24v are not working so it can not be generated by those two transformer. You may have to trace the line, it should end at the Cathode of the Diode and DC filter cap some where.
                              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

                              • Jasgriff
                                Badcaps Veteran
                                • Feb 2012
                                • 578
                                • UK

                                #175
                                Re: Barco LCN-42 No Power

                                Right trying to trace back where this 13v should be coming from. I cannot work out from the number what IC3 is or what it does. There doesn't seem to be any significant voltage going into it to give 12.55v out on the marked pin?

                                Does anybody know what it is so I can continue to trace?
                                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

                                • Jasgriff
                                  Badcaps Veteran
                                  • Feb 2012
                                  • 578
                                  • UK

                                  #176
                                  Re: Barco LCN-42 No Power

                                  Right,

                                  I found out what it was!

                                  The new IC that I replaced became shorted on the DRV pin and the VCC pin one I disconnected that part of the circuit I get 14 volts back and then the 24v line was up and running!

                                  I have now replaced the IC but left out the mosfet so I am going to test the IC to see what voltages I have going across it then I might throw in another mosfet to see how we get on.

                                  P.s I have replaced the CS resistor that was previously blown. I am thinking that did not help with the operation of the IC and I am really hoping that by replacing that the IC will do its job and drive the mosfet.
                                  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

                                  • Jasgriff
                                    Badcaps Veteran
                                    • Feb 2012
                                    • 578
                                    • UK

                                    #177
                                    Re: Barco LCN-42 No Power

                                    New IC fitted and Mosfet back in.

                                    I am getting just short of 14v on the VCC pin now but nothing on DRV.

                                    I also noticed that there is less than 0.5V on the HV line? I am sure that this isnt correct according to the Datasheet.
                                    Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                    How to resize your pictures guide click HERE
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                                    • retiredcaps
                                      Badcaps Legend
                                      • Apr 2010
                                      • 9271

                                      #178
                                      Re: Barco LCN-42 No Power

                                      Originally posted by Jasgriff
                                      I also noticed that there is less than 0.5V on the HV line?
                                      Is the resistor that is in series with HV pin 8 open? According to page 12 of the NCP1377 datasheet, it is typically a 6.8k/0.5W resistor.
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                                      • Jasgriff
                                        Badcaps Veteran
                                        • Feb 2012
                                        • 578
                                        • UK

                                        #179
                                        Re: Barco LCN-42 No Power

                                        I am struggling to find where the HIV pin is attached too. I remember when I took the chip off it looked like it wasn't connected to anywhere. Do you think looking at the diagram that it definitely should be connected up?
                                        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                        How to resize your pictures guide click HERE
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                                        • retiredcaps
                                          Badcaps Legend
                                          • Apr 2010
                                          • 9271

                                          #180
                                          Re: Barco LCN-42 No Power

                                          Originally posted by Jasgriff
                                          I am struggling to find where the HIV pin is attached too. I remember when I took the chip off it looked like it wasn't connected to anywhere. Do you think looking at the diagram that it definitely should be connected up?
                                          Well, I wrote the post after desoldering a single capacitor so I could be high on solder fumes because I didn't use a fan for one capacitor, but figure 1 on page 2, shows a resistor in series with pin 8. That resistor looks like it is connected to the positive leg of the big filter capacitor.

                                          If you can't find a resistor, then you should have direct continuity from the HV pin to the large capacitor then.

                                          Note to self. Always use the fan regardless how long I'm soldering.
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                                          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.

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