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Sharp LC-42D69U - New Main Board - No Display Troubleshooting

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    #1

    Sharp LC-42D69U - New Main Board - No Display Troubleshooting

    Hi all,

    I'm asking for some ideas/guidance on where to go next with my troubleshooting efforts.

    A history of events so far:
    • TV was dead. No signs of life, no standby light. Nothing.
    • Replaced power board. No results. Same issue (oops)
    • Replaced main board. Local supplier only had a variant board in stock. As far as I can tell, this board is used for the TV's smaller cousin (LC-32D59U). It has the same printed part number, but different sticker numbers.
    • I had to buy a new pin header, and solder to the new board to connect the display signal cable.
    • TV now enters standby (red light on power plug)! When I press the power button, the back light comes on, but I get no display information. Just a lightly glowing screen with nothing else. Red light is replaced by no led indicators. Green light does not turn on.


    So I'm wondering:
    • Perhaps this main board is incompatible with my TV? I am playing loose with the part numbers.
    • Perhaps I botched the desoldering/resoldering job? I checked pin continuity and there doesn't appear to be any shorts (with exception of 3 pins that are clearly sharing a plane).
    • Interesting note: I disconnected the signal cable, and the TV responds identically (red light standby on plug in, power button turns on backlight, no signal, no other light indicators).
    • Perhaps I need to load new firmware? The service manual has a software update procedure, but I need to interact with menus on the TV Plus I haven't had any luck finding the firmware (yet).


    Any other ideas/direction is appreciated. Thanks for reading!
    Attached Files
    Tags: None
    #2
    Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

    Need to start from the start, put the original powerboard in tv, leave unplugged the cable from powerboard to mainboard, plug power cord into powerboard, check the standby pin on the connector for the standby voltage, if its not there check the new powerboard for the standby voltage if it's not there then I would say you need to fix the standby circuit first.

    Comment

      #3
      Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

      Ok, I miss-read it a bit, I think the new mainboard is compatible, an update might do the trick, question is can it be done without the display working or remote interaction.
      Last edited by nomoresonys; 04-23-2021, 03:07 PM.

      Comment

        #4
        Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

        Depending on what was wrong with the original mainboard, meaning if the eeprom U3102 is ok then maybe you can transfer that chip from old to new board, not exactly sure. Maybe see what Diah has to say, he knows his firmware.
        Last edited by nomoresonys; 04-23-2021, 03:22 PM.

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          #5
          Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

          i think yours MB layout are sandwich boards. not easy to add sockets and no guarantee yours work 100% correct.

          as suggested by nomoresonys start trouble shooting yours original MB its much easy as you have now the cousin boards for references & Parts.

          start with upload photo on the back side of the boards and measure voltage if you have 3.3V on the SPI flash.

          Comment

            #6
            Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

            nomoresonys, Diah, thank you kindly for the replies.

            I found the U3012 chip on the front of the board. Tested both boards and got the 3.3V.

            I'm tempted to simply trying swapping the U3012 chip from my original board to the new board (crossing my fingers the socket soldering is good). Any reason I should avoid this approach?

            Attached are the pics.
            Attached Files

            Comment

              #7
              Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

              I'd say try it, don't think it would hurt any and might just do the trick.

              Comment

                #8
                Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

                Check some youtube videos on eeprom replacement and maybe practice de-soldering on a junk board if needed, never force it, when it's de-soldered it will move easily.

                Comment

                  #9
                  Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

                  inspect the point remarked on yours photo.. i guess this is the original boards ... right?

                  some spark near SPI Flash. if this correct, take the Flash and dump it first. you can use the other boards IC to flash it with yours original dump.
                  Attached Files

                  Comment

                    #10
                    Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

                    Diah, the board in that photo is actually the new board. I inspected both boards, and it looks to me like the mark is on both. But it's covered by silkscreen on the original board. It's probably a via.

                    Good news gentlemen. Removing the flash chip from the original board soldering onto the new board did the trick. We're back up and running.

                    Many thanks for your support and guidance
                    Attached Files

                    Comment

                      #11
                      Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

                      good work.. this is approve too you are master at soldering LOL

                      Comment

                        #12
                        Re: Sharp LC-42D69U - New Main Board - No Display Troubleshooting

                        Glad to hear it.

                        Comment

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