Lenovo L450 no display , but only VGA

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  • Rofix
    Senior Member
    • Jul 2023
    • 73
    • Italia

    #1

    Lenovo L450 no display , but only VGA

    Hello everyone I have a problem with my Lenovo L450 there is no image on the display, but on an external monitor connected via VGA it works.

    Motheboard is : AIVL1 NM-A351 Rev .1 . . LCFC FRU:00HT673

    Laptop has no picture and no backlight,but ,the display tested on another PC works

    the main voltages are all present on the motherboard connector except the +3VALW which varies as follows:

    +3VALW: if the PC is off I find 3.3V when I turn it on they drop to 1.8V

    Thanks in advance for all the advice and help
    Attached Files
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14027
    • Canada

    #2
    Review the voltage to ground of the EN1 / EN2 pins on PU8. PU8 creates this +3VALW power rail. If working correctly, the schematic states it can output 8A of current.

    Test without the display to see if this same power rail drops the voltage when powered on.

    Comment

    • Rofix
      Senior Member
      • Jul 2023
      • 73
      • Italia

      #3
      hello thank you
      the EN1 / EN2 pins on PU8.
      Sorry but which one are you referring to? on the PU8?​

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 14027
        • Canada

        #4
        See attached.

        Click image for larger version

Name:	PU8.png
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ID:	3170896

        Comment

        • Rofix
          Senior Member
          • Jul 2023
          • 73
          • Italia

          #5
          Hi, thank you, I couldn't find the PU8 on the diagram I downloaded, I probably downloaded a version that wasn't very compatible

          Comment

          • Rofix
            Senior Member
            • Jul 2023
            • 73
            • Italia

            #6
            Hello everyone, I noticed something strange, by disconnecting the display the voltage always remains at 1.8 V, however, by disconnecting the cable from the motherboard the voltage stabilizes at 3.3 V, possible cable problem?

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14027
              • Canada

              #7
              The same display with the same cable works on another laptop that is the same model?

              Comment

              • Rofix
                Senior Member
                • Jul 2023
                • 73
                • Italia

                #8
                Hi, thank you for the advice. Unfortunately I can't carry out this test, it was nice so at least I could rule out that it was actually the cable but unfortunately I can't.

                Comment

                • Rofix
                  Senior Member
                  • Jul 2023
                  • 73
                  • Italia

                  #9
                  Good morning. Do you know where I can find this cable or one that is compatible


                  Click image for larger version

Name:	IMG_20231210_145350882_HDR.jpg
Views:	195
Size:	621.3 KB
ID:	3172101

                  Comment

                  • mon2
                    Badcaps Legend
                    • Dec 2019
                    • 14027
                    • Canada

                    #10
                    Just found this amazing item on AliExpress. Check it out! US $21.69 | New Original For Lenovo ThinkPad L450 Laptop Camera Cable FHD HD LCD Video Screen Cable 00HT981 DC02001V410 00HT816 DC02001V320
                    https://a.aliexpress.com/_mMEOHr2​

                    share your pic of your cable and the laptop with this vendor before purchasing.

                    Comment

                    • Rofix
                      Senior Member
                      • Jul 2023
                      • 73
                      • Italia

                      #11
                      hello ok thank you

                      Comment

                      • Rofix
                        Senior Member
                        • Jul 2023
                        • 73
                        • Italia

                        #12
                        Hi, I ordered the cable, I tried to mount it but the problem persists,

                        Comment

                        • Rofix
                          Senior Member
                          • Jul 2023
                          • 73
                          • Italia

                          #13
                          while I was measuring the voltages on EN1 / EN2 on PU8 unfortunately I think that with the multimeter I must have touched some other component and this damage happened to me, the PD23 component blew which should be a diode in theory, sometimes I do this type of check in the evening when you are tired it is better to avoid. Thanks in advance for any advice

                          Comment

                          • mon2
                            Badcaps Legend
                            • Dec 2019
                            • 14027
                            • Canada

                            #14
                            https://www.digikey.ca/en/products/d...7-H3F/10259887

                            it is a generic diode used to power the nearby IC. See the partial schematic above to review the operation. Diodes will pass the voltage from anode to cathode but block in reverse. Often used to permit multiple outputs or power rails to share the line safely. The highest power rail of this cluster will power the target.

                            The size of this part is a key criteria; the peak voltage is next and peak current.

                            Comment

                            • Rofix
                              Senior Member
                              • Jul 2023
                              • 73
                              • Italia

                              #15
                              Thank you, I was checking the input voltages on the diode, it shows 0 volts, moreover on PIN 8 of the PU8 I find the ground.


                              Click image for larger versionName:	FOTO 2.pngViews:	0Size:	7.28 MBID:	3210223
                              Last edited by Vesko356; 02-04-2024, 05:35 AM. Reason: Image scaled

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