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Dell Latitude 7420, 7320 voltage changed

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    Dell Latitude 7420, 7320 voltage changed

    Hi there,

    I got 2 Dell laptops with a locked bios (dell management protection).
    When I sent the dumps to this forum I got unlocked .bin files.

    The issue I am getting the voltage on the bios chip pins has changed once I soldered the chip back (with the unlocked even original bios file) and doesn't turn on anymore.

    Before I started to re-program the chip the voltage on the pins were 3.3V almost on each pin. Once I soldered the chip, voltage changed to 1.9V or 1.3V on few pins. No 3.3V anymore.

    I appreciate any help to get me this laptops back to life and return to customers.
    THANKS.

    #2
    Re: Dell Latitude 7420, 7320 voltage changed

    remove the bios chip and measure voltage on the remaining pads again to see if 3.3v is there.
    Last edited by caspian; 07-18-2022, 02:23 AM.

    Comment


      #3
      Re: Dell Latitude 7420, 7320 voltage changed

      Yes. The 3.3V is present on the pins when no chip is present.

      Comment


        #4
        Re: Dell Latitude 7420, 7320 voltage changed

        Are you soldering the bios chip in correctly or is it upside down?

        Post a clear pic of the soldered bios chip.

        Confirm that pin #1 on the IC matches pin #1 of the logic board.

        Comment


          #5
          Re: Dell Latitude 7420, 7320 voltage changed

          So the Bios chip is probably defective. Use another Bios chip.

          Comment


            #6
            Re: Dell Latitude 7420, 7320 voltage changed

            I can confirm the bios is in right position with pin 1. I am working on 2 identical motherboards and both failed. I am able to read and write to the bios. Not sure if it's faulty. I found out the verification of the written data fail in one of the programming software. Other one is not complaining about verification.
            Can not properly programmed chip cause the voltage change?
            If I burned both chips or their are faulty where I can get empty chips?
            Sending a screenshot attached.
            Attached Files

            Comment


              #7
              Re: Dell Latitude 7420, 7320 voltage changed

              US $4.16 | New Original W25R256JVEQ 25R256JVEQ 25R256JVEN W25R256JVEIN In Stock
              https://a.aliexpress.com/_mKbb3Ru

              You should have a bios image of 32MB for this device.

              Is this correct?

              Comment


                #8
                Re: Dell Latitude 7420, 7320 voltage changed

                Thank you for the link.
                Yes I have 32MB bios image. Just can't believe it's faulty because I can still program it.

                Comment


                  #9
                  Re: Dell Latitude 7420, 7320 voltage changed

                  The Vcc (power rail) of this flash should not be lower after soldering in correctly.

                  I think the issue is that you are using a meter to measure?

                  The pins are toggling high and low so the meter is unable to measure quick enough due to the toggle rate. Then you will read a lower voltage on pins that are not static.

                  Post the voltage of each pin.

                  You may not have a fault here.

                  Comment


                    #10
                    Re: Dell Latitude 7420, 7320 voltage changed

                    Does the verification of the written data succeed for both the two chips you have?

                    Comment


                      #11
                      Re: Dell Latitude 7420, 7320 voltage changed

                      I am able to post the measurements within 3h as will work from home.
                      As a reference I took the 3.3V measurements from a working board with a password locked bios. I had no issues to measure which pin is 3.3V and which not. Once I re-programmed it and soldered back to the same board the voltage has changed.
                      Anyway I am so happy you guys are helping me as I am such a lonely wolf while repairing electronics. Mostly getting experience from YouTube and from my failures. Really appreciate your help, comments and opportunity to get information on this forum.

                      Comment


                        #12
                        Re: Dell Latitude 7420, 7320 voltage changed

                        Just wondering why one software verification fail (SiberiaProg) and other doesn't complain (AsProgrammer). I use a USB flash programmer CH341A.

                        Comment


                          #13
                          Re: Dell Latitude 7420, 7320 voltage changed

                          I guess your programmer is not reliable enough. However, the programmer may be fine. If you can, ask a friend to test your chip using another programmer.
                          However, the chip is the main suspect now. It is possible that you applied too much heat on the chip while desoldering, so that you burned it.

                          Comment


                            #14
                            Re: Dell Latitude 7420, 7320 voltage changed

                            I tried a different one EZ2019+ and all went OK. The same results (attached). Without chip higher voltage, with chip lower voltage and laptop won't turn on or show any light.
                            Attached Files

                            Comment


                              #15
                              Re: Dell Latitude 7420, 7320 voltage changed

                              Can you reflash the same chips with the original contents again and test on your logic board ? This is only to confirm the flash IC is ok and the programmer is able to program the component properly.

                              Comment


                                #16
                                Re: Dell Latitude 7420, 7320 voltage changed

                                I programmed the chip with an original dump but no luck. Still the same measurements.

                                Comment


                                  #17
                                  Re: Dell Latitude 7420, 7320 voltage changed

                                  You have to buy a new Bios chip.

                                  Comment


                                    #18
                                    Re: Dell Latitude 7420, 7320 voltage changed

                                    Chances of 2 bios chip failing at the same time is bit doubtful. Make sure no resistor is lost around the bios chip while soldering/desoldering bios chips.

                                    Comment


                                      #19
                                      Re: Dell Latitude 7420, 7320 voltage changed

                                      I ordered not programmed bios chips just in case I burned the current ones. Also checked the resistors and capacitor, all is at the same position as before.

                                      Comment

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