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Lenovo Y50-70 (not touch) - Screen LED Backlight

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    Lenovo Y50-70 (not touch) - Screen LED Backlight

    Hi all,

    I need a little help with my second Lenovo y50. Board schematic is attached.

    Little explanation, the 40 pin connector for the LCD was broken, I made the replacement and it looks fine. I can see the screen showing some images.

    Problem here is that the screen backlight doesn't turn on (tried also the FN + ...). Screen is working fine on my other y50 laptop (cable also).

    Could you help me to identify what is wrong on the board? I think about something wrong with pin 28 of the LCD connector but that it...

    Thanks a lot !
    Attached Files

    #2
    Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

    Please post a picture of the area you worked on.
    Also, what voltage do you get on pin 28, 29 and 40 of LCD connector?
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment


      #3
      Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

      Hello Piernov,

      Thanks for the answer, here is the picture.

      Regarding voltage, i get 0V for the 3 pins (28 -29 -40)

      Thanks !
      Attached Files

      Comment


        #4
        Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

        There you should have 19V in order to get backlight.
        Check R375 and measure voltage at both sides at R375.
        R375 is 0 ohms and acts as a fuse.
        If it is burned no voltage could pass through to drive the backlight.

        Comment


          #5
          Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

          Not so pretty but it should do the job. Not sure about the 4th and 5th pins from the left though.

          Could you mesure all the voltages on PU1203 pins?
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

          Comment


            #6
            Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

            The 4th and the 5th from the left, there was a scratch, I verified, and both pin join to the ground, so it should be fine.

            To solder the connector, I've used my smd rework station with soldering paste, as this is really small, it is really difficult to make it really clean.

            I'll measure voltage right now ! Thanks !

            Comment


              #7
              Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

              Is that normal that there is no chip on the pu1203? I will do measures tomorrow as it is quite difficult to access (under the heatsink)

              Comment


                #8
                Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                yes it's normal, you get 19V via R375, R205 doesn't exist [it has @ sign] and schematic has is as it's an option but not used
                [pu1203 is a boost converter for 12V]

                Comment


                  #9
                  Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                  Ok, so the pu1203 has 12 pins

                  1 - 0v
                  2 - 0v
                  3 - 0v
                  4 - 5.17v
                  5 - 0v
                  6 - 0v
                  7 - 0v
                  8 - 0v
                  9 - 0v
                  10 - 0v
                  11 - 0v
                  12 - 0v

                  This 5v is strange.. sometimes it drops to 3.5v and then go back to 5.17v...

                  Comment


                    #10
                    Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                    Originally posted by Kashi1712 View Post
                    Ok, so the pu1203 has 12 pins

                    1 - 0v
                    2 - 0v
                    3 - 0v
                    4 - 5.17v
                    5 - 0v
                    6 - 0v
                    7 - 0v
                    8 - 0v
                    9 - 0v
                    10 - 0v
                    11 - 0v
                    12 - 0v

                    This 5v is strange.. sometimes it drops to 3.5v and then go back to 5.17v...
                    From the schematic, I think pins are not really the same... I guess that the 4th pin is actually pin 8 (so the 5v input is correct)

                    Comment


                      #11
                      Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                      have you measured voltage at R375 ?

                      Comment


                        #12
                        Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                        I've tried to find that one, but don't know where it is located on the board. Any clue?

                        Comment


                          #13
                          Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                          you can follow the trace from the pins of the lvds if that is possible
                          a boardview can help you to find it at the moment if you can find one for this board

                          Comment


                            #14
                            Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                            Didn't find the boardview, I will check if it is visible or not.... Looks difficult

                            Comment


                              #15
                              Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                              Last option is to run a cable from 19V [B+ or CPU_B+ or anything that suits for you] and solder it at lvds pins 38-40.
                              A better option is to use a zero ohm resistor as a fuse or a use of 2,5- 3A between the cable and the pins.
                              With the 19V you'll get your backlight.
                              Last edited by rookieme; 04-18-2017, 05:18 AM.

                              Comment


                                #16
                                Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                                the 19v wire is not too risky? I can see on the schematic that there a some resistor/capa.

                                I would not take the risk to damage the LCD that is working... But if I can rewire 38-40 pin in another way that is not risky, i'm ok with that.

                                Comment


                                  #17
                                  Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                                  R375 should be the component circled in red in the following picture. Maybe yours is blown too.

                                  (Source: http://www.elektroda.pl/rtvforum/topic3228153.html )
                                  Attached Files
                                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                                  Comment


                                    #18
                                    Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                                    nice photo, this should do the job

                                    Comment


                                      #19
                                      Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                                      Ok from the point next to pu1101, I get 7.8v. on the other one, 1.30v

                                      I've tried to put 19v from the 16th pin on the pu1101 but laptop shuts down immediately. Still doesn't work

                                      Comment


                                        #20
                                        Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

                                        I will post a picture of it, mine looks just fine

                                        Comment

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