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Dell Latitude 5480 - No 3v & 5v

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    #1

    Dell Latitude 5480 - No 3v & 5v

    I have a Dell Latitude 5480 which has power going in (charger stays lit) but no indication of life from the switch or the switch LED.

    On inspection I can see that I am getting 12.5v to the power 3v and 5v IC's, PU100 and PU102, however I am seeing nothing coming out. I believe these IC's are where the 3v and 5v rails are meant to start?
    Is there another pin on these IC's which should be toggled to trigger these IC's to start feeding power? Any help / pointers will be appreciated.

    PQ9
    Pin 4 - 9v
    Pin 5 - 20v

    PQ4
    Pin 1,2,3 - 19.86v
    Pin 4 - 19.86v

    PU901 (ISL88738)
    Pin 3 - 12.5v (VSYS)

    PU100 (SY8288BRAC)
    Pin 2,3,4,5 - 12.5v (+PWR_SRC)
    Pin 17 - 0v (+3.3V_ALW2)
    Pin 19 - 0v (+3.3V_ALWP)
    Pin 20 - 0v (+3.3V_ALWP)

    PU102 (SY8288CRAC)
    Pin 2,3,4,5 - 12.5v (+PWR_SRC)
    Pin 15 - 0v (+5V_ALW2)
    Pin 19 - 0v (+5V_ALWP)
    Pin 20 - 0v (+5V_ALWP)
    Last edited by SMDFlea; 10-27-2023, 05:50 AM.
    Tags: None
    #2
    Re: Dell Latitude 5480 - No 3v & 5v

    Hello
    I mean +PWR_SRC must be 19v with charger

    Comment

      #3
      Re: Dell Latitude 5480 - No 3v & 5v

      Okay, what was throwing me off was another post (https://www.badcaps.net/forum/showthread.php?p=978407) which mentioned that 13v should be okay on the +PWR_SRC - I may have misinterpreted this. Let me check back at PU901 (ISL88738) to see if I can spot something there.

      Comment

        #4
        Re: Dell Latitude 5480 - No 3v & 5v

        Looking at all the pins on PU901 (ISL88738), I can see that PIN 20 (OTGEN/CMIN) is shorted to ground. PIN 18 is NOT shorted. Which makes me think (being a novice) would it not be best / less intrusive to first take off PR960, as it is either this resistor or PU901 which is shorted?
        Trouble is that I have no idea where PR960 is on the board... anyone with a boardview who can help?
        Alternatively, i am sure others may just say go straight for the charger IC and replace PU901?
        Attached Files
        Last edited by elfelvin; 06-22-2021, 02:20 AM. Reason: attaching image

        Comment

          #5
          Re: Dell Latitude 5480 - No 3v & 5v

          see attached.

          Also from my understanding, either PR960 OR PR919 will be stuffed.

          PR960 (0 ohm, 0402) shunts this logic line to ground.

          PR919 (0 ohm, 0402) shunts this logic line to Vdd (+V).

          So both of these parts should not be stuffed on your PCBA. Please confirm.
          Attached Files
          Last edited by mon2; 06-22-2021, 06:55 AM.

          Comment

            #6
            Re: Dell Latitude 5480 - No 3v & 5v

            I dont have any physical resistors in these locations, all I have are tracks.
            I have highlighted the "test points" which are grounded.

            This surely means that PU901 is at fault, as there is no PR960 / PR919?
            Attached Files
            Last edited by elfelvin; 06-22-2021, 08:15 AM.

            Comment

              #7
              Re: Dell Latitude 5480 - No 3v & 5v

              It can be rezerve for different use. How many volts do you see on the PR901 resistor? Is there AC_OK 3.3v on the 3 pins of the pu901 IC? In order to output ALW voltage in Pu100, there should be 3.3V at 12 pins (from IO)
              Last edited by Sametbey; 06-22-2021, 10:55 AM.
              I'm not happy to be so strong. because it's not humanly

              Comment

                #8
                Re: Dell Latitude 5480 - No 3v & 5v

                PR901 - 19.8v

                Below are the pins i managed to find voltages on. Which 3 pins should have 3.3v?

                PU901
                Pin 1 - 12.6v (CSON)
                Pin 2 - 12.6v (CSOP)
                Pin 4 - 5.2v (BOOT2)
                Pin 7 - 5.1v (LGATE2)
                Pin 8 - 5.2v (VDDP)
                Pin 9 - 5.1v (LGATE1)
                Pin 12 - 5.2v (BOOT1)
                Pin 13 - 9.1v (ASGATE)
                Pin 14 - 19.8v (CSIN)
                Pin 15 - 19.8v (CSIP)
                Pin 16 - 19.8v (ADP)
                Pin 17 - 19.7v (DCIN)
                Pin 18 - 5.2v (VDD)
                Pin 19 - 3.6v (ACIN)
                Pin 24 - 3.1v (ACOK)
                Pin 28 - 1.4v (COMP)
                Pin 31 - 12.4v (VBAT)
                Pin 32 - 12.6v (BGATE)

                Comment

                  #9
                  Re: Dell Latitude 5480 - No 3v & 5v

                  PU100
                  Pin 12 - 2.7v (which should be the logic coming from MEC1501)? Not quite 3.3v though!

                  Comment

                    #10
                    Re: Dell Latitude 5480 - No 3v & 5v

                    Originally posted by mielta View Post
                    Hello
                    I mean +PWR_SRC must be 19v with charger
                    Dont you think its NVDC technology used here?? In that case PWR_SRC will be +13V. Whats your opinion friend??

                    Comment

                      #11
                      Re: Dell Latitude 5480 - No 3v & 5v

                      I believe the issue is with PR102.
                      When i measure continuity between pin 2 on PR102 and PWR_SRC, I get nothing. There seems to be a dry joint between pin2 and the board. I will confirm the outcome once this has been fixed.

                      Comment

                        #12
                        Re: Dell Latitude 5480 - No 3v & 5v

                        I replaced PR102 with a 499K and now both 3v and 5v rails are working. The laptop powers on and peace has been restored in the world.
                        Thank you to all that commented, hopefully the diag helps someone in the future!

                        Comment

                          #13
                          Re: Dell Latitude 5480 - No 3v & 5v

                          Originally posted by elfelvin View Post
                          I replaced PR102 with a 499K and now both 3v and 5v rails are working. The laptop powers on and peace has been restored in the world.
                          Thank you to all that commented, hopefully the diag helps someone in the future!
                          Thanks a lot, I just got the same with LAT 5490. Seems to be a common problem on these models.

                          Comment

                            #14
                            Originally posted by mon2 View Post
                            Re: Dell Latitude 5480 - No 3v & 5v

                            see attached.

                            Also from my understanding, either PR960 OR PR919 will be stuffed.

                            PR960 (0 ohm, 0402) shunts this logic line to ground.

                            PR919 (0 ohm, 0402) shunts this logic line to Vdd (+V).

                            So both of these parts should not be stuffed on your PCBA. Please confirm.
                            Hello,
                            I have similar problem, laptop was water damaged.
                            After cleaning it woks from battery/not charging, but only until battery died.
                            I replaced some rotten resistors, now its recognized by USB-C charger, but it's stils dead.
                            I got 3,3V, but not 5V ALW.
                            On PU901 PIN3 i got 0V. I can't find PR929 on that board.

                            What can cause such problem?
                            What program you use for opening .cad BDV files?

                            Thanks.

                            Comment

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