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sharp lc32d42u power supply - DPS-178APA

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    sharp lc32d42u power supply - DPS-178APA

    last 2 times I had an issue with this supply, it was a 5wt zener in the stand by circuit.
    That zener tests good and the 5vt stand by (bu) supply tests good.
    Any idea what I could check next?

    It's a cheap enough supply on the "pulled" market place, but I might just be inheriting someone elses future problem.

    https://flic.kr/s/aHsmKXfqpn
    Last edited by metropical; 01-24-2020, 12:35 PM.

    #2
    Re: sharp lc32d42u power supply - DPS-178APA

    What do you get with test #3 below.

    Comment


      #3
      Re: sharp lc32d42u power supply - DPS-178APA

      https://flic.kr/s/aHsmKXfqpn

      that is a link to snaps of the plugs in case res isn't high enough.

      the 2nd pic with 2 plugs; plugs are shown out just so I could get a clear pic. The plugs were in when tested.

      bottom plug of 2nd pict.
      Pin3 to ground stayed at 0v off and on.
      Pin2 stayed at 5v off and on.

      the 1st pic is the only other plug on the powerboard.

      Thanks for your help, nomoresonys.
      Attached Files

      Comment


        #4
        Re: sharp lc32d42u power supply - DPS-178APA

        The only two pins you checked were on PD pins 2 and 3 ? (pin 3 IS ground)
        What about pin #1 which is the PS_ON (power supply ON)?

        Comment


          #5
          Re: sharp lc32d42u power supply - DPS-178APA

          lemme clarify
          top to bottom

          p1 - gnd
          p2 - bu5v
          p3 - pnl power
          p4 - gnd
          p5 - AC detect
          p6 - PS on

          I'll go back and check the others.
          Last edited by metropical; 01-25-2020, 03:03 PM.

          Comment


            #6
            Re: sharp lc32d42u power supply - DPS-178APA

            You count the PD connector pin wrong:
            Pin 1 = PS-ON
            Pin 2 = AC_DET
            Pin 3 = GND
            Pin 4 = PNL POWER
            Pin 5 = BU 5V
            Pin 6 = GND
            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


              #7
              Re: sharp lc32d42u power supply - DPS-178APA

              OFF ON

              Pin 1 = PS-ON - 3v 3v
              Pin 2 = AC_DET - 3v 3v
              Pin 3 = GND -
              Pin 4 = PNL POWER - 0v 0v
              Pin 5 = BU 5V - 5v 5v
              Pin 6 = GND-

              In other words, voltages didn't change off to on.
              Last edited by metropical; 01-25-2020, 05:24 PM.

              Comment


                #8
                Re: sharp lc32d42u power supply - DPS-178APA

                I forgot to mention that the front "stand by" LED has been cycling since the failure.
                ~.5 sec off/~5 sec on.

                The service book I have shows a "power board" on p 10-39 to 10-42.
                PDF page 100-103.
                On page 102 there is a representation of the plug and voltages of which I've been testing.

                1 - PS_ON 2.8v - I get 3.025
                2 - AC_DET 3.2v - 3.08
                3 - G
                4 - PNL_POW 3.3v - 0v
                5 - BU5V 5v - 5v
                6 - G

                So it appears P4 is missing it's voltage.

                Though I don't think this is an exact representation of the components on the actual pcb I have.
                Last edited by metropical; 01-26-2020, 02:34 PM.

                Comment


                  #9
                  Re: sharp lc32d42u power supply - DPS-178APA

                  I think that P4 PNL_POW is a return voltage, not a source from the PS.
                  But what am I looking for and where.?
                  .
                  My time with board level stuff was on recording studio gear 30 years ago.
                  Not so familiar with this.

                  Comment


                    #10
                    Re: sharp lc32d42u power supply - DPS-178APA

                    The pnl_pow voltage comes from IC2007 (AND gate). It requires ~3v from both the cpu and mcu to send the pnl_pow voltage. See pages 72 and 102 in the SM.
                    Attached Files

                    Comment


                      #11
                      Re: sharp lc32d42u power supply - DPS-178APA

                      Originally posted by metropical View Post
                      I think that P4 PNL_POW is a return voltage, not a source from the PS.
                      But what am I looking for and where.?
                      .
                      My time with board level stuff was on recording studio gear 30 years ago.
                      Not so familiar with this.
                      PNL_POW is the "control voltage for the panel 5v" All it does is switch the PNL5V ON or OFF that's it, nothing else
                      A high or low logic (3.3v - 0v) on the PNL_POW pin turns Q7907 on or off which tells Q7905 to connect the BU5V to the PNL5V
                      You have confirmed that PNL_POW is changing from 3.3v to 0v, all you need to do is check plug PE pins 3or4 (or use J7915) PNL5V and see if it changes from 0 to 5v when PNL_POW changes.
                      Last edited by R_J; 01-30-2020, 12:03 PM.

                      Comment


                        #12
                        Re: sharp lc32d42u power supply - DPS-178APA

                        I know this is odd, but I think I may have a different board. I don't see IC2007 on the actual board, despite what the SM shows.
                        Unless it under this heat sink, pic attached.
                        .
                        But still, when I swapped the PS, the tv worked.
                        So I don't understand why I'd be looking outside the PS.
                        Attached Files

                        Comment


                          #13
                          Re: sharp lc32d42u power supply - DPS-178APA

                          So are you saying that with old power supply board the PNL_POW of PD connector shows 0V, but with new power supply it shows 3.3V?
                          Last edited by budm; 01-30-2020, 03:46 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


                            #14
                            Re: sharp lc32d42u power supply - DPS-178APA

                            sorry, my post is poorly formatted.
                            P4 is 0v on the bad PS.
                            3.3v is what is stated in the SM.
                            .
                            I swapped the PS with another one of these TVs we had that failed.
                            So I now have the failed supply.
                            When I put the known good PS in the bum TV, it lit up NP.
                            .

                            That post was suppose to look columnar, but alas...

                            Comment


                              #15
                              Re: sharp lc32d42u power supply - DPS-178APA

                              Originally posted by metropical View Post
                              sorry, my post is poorly formatted.
                              P4 is 0v on the bad PS.
                              3.3v is what is stated in the SM.
                              .
                              I swapped the PS with another one of these TVs we had that failed.
                              So I now have the failed supply.
                              When I put the known good PS in the bum TV, it lit up NP.
                              .

                              That post was suppose to look columnar, but alas...
                              I do not understand, you said TV works with new board, so PNL_POW of PD connector shows 3.3V then when using the new power supply board?
                              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


                                #16
                                Re: sharp lc32d42u power supply - DPS-178APA

                                I assume so. But that TV isn't here.
                                What I'm saying is the other TV failed. I put the other PS in it and it works fine.
                                But that TV is in a different location. I now have it's failed supply.
                                It is 0v on P4.

                                Comment


                                  #17
                                  Re: sharp lc32d42u power supply - DPS-178APA

                                  Originally posted by metropical View Post
                                  I assume so. But that TV isn't here.
                                  What I'm saying is the other TV failed. I put the other PS in it and it works fine.
                                  But that TV is in a different location. I now have it's failed supply.
                                  It is 0v on P4.
                                  What is P4? I see plug PE and plug PD

                                  Comment


                                    #18
                                    Re: sharp lc32d42u power supply - DPS-178APA

                                    yes, Pin 4 on plug PD. aka PNL_POW 3.3v. I have 0v on this supply.

                                    Comment


                                      #19
                                      Re: sharp lc32d42u power supply - DPS-178APA

                                      Originally posted by metropical View Post
                                      yes, Pin 4 on plug PD. aka PNL_POW 3.3v. I have 0v on this supply.
                                      That is because it is NOT A SUPPLY, please re-read post 11

                                      Here: Red is the BU5V volts, Blue is the panel power 5 VOLT OUTPUT, Yellow is the PNL_POW Control line.
                                      Attached Files
                                      Last edited by R_J; 01-30-2020, 04:37 PM.

                                      Comment


                                        #20
                                        Re: sharp lc32d42u power supply - DPS-178APA

                                        Originally posted by r_j View Post
                                        that is because it is not a supply, please re-read post 11
                                        +10
                                        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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