Sharp LC-42SB48UT-a no standby voltage

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  • jts1957
    Member
    • Dec 2008
    • 38

    #61
    Re: Sharp LC-42SB48UT-a no standby voltage

    Originally posted by dick_barton
    Service manual attached with power supply schematic, hopefully
    Be sure to look at 42", there is also a 32".

    AcGeorgiegirl: 1st attachment wrong PS.

    Comment

    • AcGeorgiegirl
      Badcaps Veteran
      • Jun 2013
      • 202
      • USA

      #62
      Re: Sharp LC-42SB48UT-a no standby voltage

      Here are the PFC & Key Diagram, too.
      Attached Files

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #63
        Re: Sharp LC-42SB48UT-a no standby voltage

        I got it from ELEKTROTANYA and it does not match the OP diagram. See post 57
        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

        • AcGeorgiegirl
          Badcaps Veteran
          • Jun 2013
          • 202
          • USA

          #64
          Re: Sharp LC-42SB48UT-a no standby voltage

          Originally posted by budm
          You have the schematic?
          OK, I download the service manual from ELEKTROTANYA.
          My manual show TNY277, your manual shows something else.
          Please look at what is actually printed on top of the IC903.
          Where did you get the manual from?
          Yes, it is printed on the ic as TNY277. My manual, pretty sure, came from ELEKTROTANYA. I'll post the manual here, too, if that helps.
          Attached Files

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #65
            Re: Sharp LC-42SB48UT-a no standby voltage

            OK, your manual does not match your TV version.
            The one I download is the 'A' version and seem to match your power supply board picture.
            But any way, it uses TNY277 none the less, so I still suspect the parts in the feedback regulation circuit.
            Try having the main board connected to the power supply board to see if it will go up to 5V in case the circuit does not like to work without the load.
            Attached Files
            Last edited by budm; 06-22-2016, 04:53 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

            • AcGeorgiegirl
              Badcaps Veteran
              • Jun 2013
              • 202
              • USA

              #66
              Re: Sharp LC-42SB48UT-a no standby voltage

              Yes, that's it, then, BUDM! Mine didn't have the "a" after model code, but I just looked again, and it's the one that I get from my search on ELEKTROTANYA.
              Last edited by AcGeorgiegirl; 06-22-2016, 04:54 PM.

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #67
                Re: Sharp LC-42SB48UT-a no standby voltage

                Originally posted by AcGeorgiegirl
                This is weird. ELEKTROTANYA is the only site that I've found that has the manual free, and I'm pretty sure mine came from there. Don't know if it matters, but my model has "A" after the name, and the manuals don't.
                There are two manuals at ELEKTROTANYA, the one I downloaded is for the 'A'.
                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

                • AcGeorgiegirl
                  Badcaps Veteran
                  • Jun 2013
                  • 202
                  • USA

                  #68
                  Re: Sharp LC-42SB48UT-a no standby voltage

                  I am so sorry for causing all this confusion, while you guys are trying to help me. My translation app for Elektro- apparently mussed up my search, without me noticing. The "a" was left out.

                  Comment

                  • AcGeorgiegirl
                    Badcaps Veteran
                    • Jun 2013
                    • 202
                    • USA

                    #69
                    Re: Sharp LC-42SB48UT-a no standby voltage

                    Originally posted by budm
                    OK, your manual does not match your TV version.
                    The one I download is the 'A' version and seem to match your power supply board picture.
                    But any way, it uses TNY277 none the less, so I still suspect the parts in the feedback regulation circuit.
                    Try having the main board connected to the power supply board to see if it will go up to 5V in case the circuit does not like to work without the load.
                    I tested with psb connected to the main, and got a fluctuating voltage from around 2.8 to 3.8 or so.

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #70
                      Re: Sharp LC-42SB48UT-a no standby voltage

                      OK, so it cannot even maintain the regulated 5V output.
                      I would try replacing C969 in the primary side and the 4 cap in the cold side by the connector that goes to the main board.
                      Last edited by budm; 06-23-2016, 08:40 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

                      • AcGeorgiegirl
                        Badcaps Veteran
                        • Jun 2013
                        • 202
                        • USA

                        #71
                        Re: Sharp LC-42SB48UT-a no standby voltage

                        Originally posted by budm
                        So it lookds like you meter is OK.
                        There are parts that are used for regulating the output of the 5VSTBY:
                        IC913 (Vref diode xx431??, IC911 (OPTO), Voltage divider for the IC913.
                        Originally posted by budm
                        OK, your manual does not match your TV version.
                        The one I download is the 'A' version and seem to match your power supply board picture.
                        But any way, it uses TNY277 none the less, so I still suspect the parts in the feedback regulation circuit.
                        Try having the main board connected to the power supply board to see if it will go up to 5V in case the circuit does not like to work without the load.
                        The IC's you suggest I test...can you give me some guidance on how to do this, if other than removing them completely from the board?

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #72
                          Re: Sharp LC-42SB48UT-a no standby voltage

                          The IC is kind of working because you do have output Voltage, just not the right level as needed, there really no 100% test to verify that it is good or bad. You can try replacing it but I would try replacing the cap first.
                          This IC when it failed, it usually blew up badly due to shorted out internal Power MOSFET.
                          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

                          • AcGeorgiegirl
                            Badcaps Veteran
                            • Jun 2013
                            • 202
                            • USA

                            #73
                            Re: Sharp LC-42SB48UT-a no standby voltage

                            Originally posted by budm
                            The IC is kind of working because you do have output Voltage, just not the right level as needed, there really no 100% test to verify that it is good or bad. You can try replacing it but I would try replacing the cap first.
                            This IC when it failed, it usually blew up badly due to shorted out internal Power MOSFET.
                            Ok. You mention one IC....are you referring to the IC913? What about the IC911? And by "voltage divider" for the IC913, are you meaning a voltage regulator that I should find to check?

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #74
                              Re: Sharp LC-42SB48UT-a no standby voltage

                              I am referring to the TNY277 IC.
                              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

                              • CapLeaker
                                Leaking Member
                                • Dec 2014
                                • 8013
                                • Canada

                                #75
                                Re: Sharp LC-42SB48UT-a no standby voltage

                                He means IC903 (TNY277)

                                Comment

                                • AcGeorgiegirl
                                  Badcaps Veteran
                                  • Jun 2013
                                  • 202
                                  • USA

                                  #76
                                  Re: Sharp LC-42SB48UT-a no standby voltage

                                  Ok. I mistook your previous post(I quoted it above) as the area you are now referring to. So, which cap to replace? Is it c969(one closest to TNY277), or do you mean the filter cap?
                                  Last edited by AcGeorgiegirl; 06-23-2016, 09:35 AM.

                                  Comment

                                  • CapLeaker
                                    Leaking Member
                                    • Dec 2014
                                    • 8013
                                    • Canada

                                    #77
                                    Re: Sharp LC-42SB48UT-a no standby voltage

                                    change c969 first.

                                    Comment

                                    • AcGeorgiegirl
                                      Badcaps Veteran
                                      • Jun 2013
                                      • 202
                                      • USA

                                      #78
                                      Re: Sharp LC-42SB48UT-a no standby voltage

                                      Replaced C969. No change.

                                      Comment

                                      • CapLeaker
                                        Leaking Member
                                        • Dec 2014
                                        • 8013
                                        • Canada

                                        #79
                                        Re: Sharp LC-42SB48UT-a no standby voltage

                                        Did you check the ESR of C955 and C934? What DC voltages do you get on all the pins of IC903?

                                        Comment

                                        • AcGeorgiegirl
                                          Badcaps Veteran
                                          • Jun 2013
                                          • 202
                                          • USA

                                          #80
                                          Re: Sharp LC-42SB48UT-a no standby voltage

                                          I don't have an esr meter, so I can't test the caps. The IC reads .06 on pin #4(the Mosfet drain connection). All others are between .04 and .05 BUT these are a negative(-) number. My DMM is set on 20 dc volts.

                                          Comment

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