Sharp Aquos LC-46A77M Power Problem

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  • DjKrish
    Badcaps Veteran
    • Oct 2012
    • 354
    • SG

    #1

    Sharp Aquos LC-46A77M Power Problem

    This tv is having some power problem that's seriously a bit weird. It turns on when plug in power cable, from red turns to green then after few seconds, the relay cuts off and nothing there after. When led was green, the picture was ok and sound was ok for few seconds till the relay clicks off and nothing at all form there. Have to unplug and plug it in after 10 to 20 minutes and it repeats the same process.

    Any kind human able to help me on this? Anyone has the service diagram? Already re-solder all the cold joints with flux. Still no luck. Any help will be highly appreciated.

    Last edited by DjKrish; 07-26-2013, 05:52 AM.
  • DjKrish
    Badcaps Veteran
    • Oct 2012
    • 354
    • SG

    #2
    Re: Sharp Aquos LC-46A77M Power Problem

    Somehow i think the 5v standby is failing as it comes and then it dies off.

    Comment

    • ben7
      Capaholic
      • Jan 2011
      • 4059
      • USA

      #3
      Re: Sharp Aquos LC-46A77M Power Problem

      Check for any out of spec capacitors in the 5v standby circuit then
      Muh-soggy-knee

      Comment

      • DjKrish
        Badcaps Veteran
        • Oct 2012
        • 354
        • SG

        #4
        Re: Sharp Aquos LC-46A77M Power Problem

        Originally posted by ben7
        Check for any out of spec capacitors in the 5v standby circuit then
        Already replaced the bad caps Still no go. I think the switching IC could be the culprit though.

        Comment

        • DjKrish
          Badcaps Veteran
          • Oct 2012
          • 354
          • SG

          #5
          Re: Sharp Aquos LC-46A77M Power Problem

          Manage to replace the tny264pn IC, power came back, from red turn to green but no picture, and then red and green started changing lights and a few relay clicks and then no power again as usual. Looks like the IC is blown again. Replaced the caps around and still no go. Any idea anyone can help?

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: Sharp Aquos LC-46A77M Power Problem

            The power relay which is turn on by the main board, so if you monitor the 5V STBY, is it always there and steady when the relay clicking?
            I cannot read the labeling around the connectors to see what they are, can you provide close up pictures?
            Last edited by budm; 07-27-2013, 12:38 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

            • DjKrish
              Badcaps Veteran
              • Oct 2012
              • 354
              • SG

              #7
              Re: Sharp Aquos LC-46A77M Power Problem

              Originally posted by budm
              The power relay which is turn on by the main board, so if you monitor the 5V STBY, is it always there and steady when the relay clicking?
              I'm sorry I do not have a service manual for this model so I couldn't trace where to measure the 5v. I used my multimeter and measure the switching ic legs and it only showing 2v.

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: Sharp Aquos LC-46A77M Power Problem

                Then we will need good closed up pictures of the board, whole both sides, then in small section so we can see the traces and able to read the component designators and any labeling of the connectors.
                For example:
                http://s807.photobucket.com/user/bud...?sort=3&page=1
                Last edited by budm; 07-27-2013, 12:48 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

                • DjKrish
                  Badcaps Veteran
                  • Oct 2012
                  • 354
                  • SG

                  #9
                  Re: Sharp Aquos LC-46A77M Power Problem














                  Last edited by DjKrish; 07-27-2013, 01:34 AM.

                  Comment

                  • DjKrish
                    Badcaps Veteran
                    • Oct 2012
                    • 354
                    • SG

                    #10
                    Re: Sharp Aquos LC-46A77M Power Problem

                    Originally posted by budm
                    Then we will need good closed up pictures of the board, whole both sides, then in small section so we can see the traces and able to read the component designators and any labeling of the connectors.
                    For example:
                    http://s807.photobucket.com/user/bud...?sort=3&page=1
                    Have attached the pictures, pls have a look

                    Comment

                    • DjKrish
                      Badcaps Veteran
                      • Oct 2012
                      • 354
                      • SG

                      #11
                      Re: Sharp Aquos LC-46A77M Power Problem

                      Updates, 470VAC present at the big caps

                      Comment

                      • DjKrish
                        Badcaps Veteran
                        • Oct 2012
                        • 354
                        • SG

                        #12
                        Re: Sharp Aquos LC-46A77M Power Problem

                        Kept the unit cool for many hours then turned it on, it works fine with the picture and sound which only lasted for like 15 seconds then the relay clicks off and everything blackout there after. Cant turn on, cant switch on, nothing. Does this means that the power board is faulty? All caps replaced brand new, check all resistors, re solder all cold joints. Still no go. Can anyone help?

                        Comment

                        • DjKrish
                          Badcaps Veteran
                          • Oct 2012
                          • 354
                          • SG

                          #13
                          Re: Sharp Aquos LC-46A77M Power Problem

                          Theres 4 units of K3569 Field Effect Transistor Silicon N Channel MOS Type and 1 unit of PQ30RV31 Variable Output Low Power-Loss Voltage Regulator on this board. Checked the k3569 for fault and all 4 of them reads perfectly fine on my meter. Unable to check the PQ30RV31 regulator though.

                          Comment

                          • ben7
                            Capaholic
                            • Jan 2011
                            • 4059
                            • USA

                            #14
                            Re: Sharp Aquos LC-46A77M Power Problem

                            Originally posted by DjKrish
                            Theres 4 units of K3569 Field Effect Transistor Silicon N Channel MOS Type and 1 unit of PQ30RV31 Variable Output Low Power-Loss Voltage Regulator on this board. Checked the k3569 for fault and all 4 of them reads perfectly fine on my meter. Unable to check the PQ30RV31 regulator though.
                            We still haven't checked the 5v standby smps circuit yet!

                            What is the part number of IC7905? It is the chip by that small transformer. This will be the 5v standby control chip. Once you tell me the part number, I can direct you to which pins you should test.
                            Muh-soggy-knee

                            Comment

                            • DjKrish
                              Badcaps Veteran
                              • Oct 2012
                              • 354
                              • SG

                              #15
                              Re: Sharp Aquos LC-46A77M Power Problem

                              Originally posted by ben7
                              We still haven't checked the 5v standby smps circuit yet!

                              What is the part number of IC7905? It is the chip by that small transformer. This will be the 5v standby control chip. Once you tell me the part number, I can direct you to which pins you should test.
                              The part number is TNY264PN

                              Enhanced, Energy Efficient, Low Power Off-line Switcher

                              Comment

                              • ben7
                                Capaholic
                                • Jan 2011
                                • 4059
                                • USA

                                #16
                                Re: Sharp Aquos LC-46A77M Power Problem

                                Originally posted by DjKrish
                                The part number is TNY264PN

                                Enhanced, Energy Efficient, Low Power Off-line Switcher
                                What is the voltage across pins 1 and 2?
                                Muh-soggy-knee

                                Comment

                                • DjKrish
                                  Badcaps Veteran
                                  • Oct 2012
                                  • 354
                                  • SG

                                  #17
                                  Re: Sharp Aquos LC-46A77M Power Problem

                                  Originally posted by ben7
                                  What is the voltage across pins 1 and 2?
                                  It measures 6v ac across pin 1 and 2 after turning on the power. Pls note i measured this without plugging any of the sockets to the tv. Just the board only with power and the best part, the relay clicks on immediately upon turning on power without even being plugged to the tv. It clicks off when turn off power. I put the black probe on pin 2 and red probe on pin 1.

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #18
                                    Re: Sharp Aquos LC-46A77M Power Problem

                                    See the STBY power supply output as indicated, monitor that Voltage and report the reading when the TV acts up and when it is working.
                                    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

                                    • DjKrish
                                      Badcaps Veteran
                                      • Oct 2012
                                      • 354
                                      • SG

                                      #19
                                      Re: Sharp Aquos LC-46A77M Power Problem

                                      Originally posted by budm
                                      See the STBY power supply output as indicated, monitor that Voltage and report the reading when the TV acts up and when it is working.
                                      When the relay clicks, 4.86v present.

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #20
                                        Re: Sharp Aquos LC-46A77M Power Problem

                                        How about when the TV is turn off (since this is STBY power supply, it is always running the minute you plug the TV into the AC outet)?
                                        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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