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    Dell 5480 no power

    Hi Everyone.

    A Dell lattitude 5480 just come from my friend. That has no sign of life even when plugged in or power button pressed.
    Found a schematic see attached.

    - Charger is on and fine when connected 19.9volt is presents
    - CPU is slowly heating up when connected to the charger
    - Checked the voltages on main rails and found that 3.3_ALWP on PL100 is 0.8 Ohm.
    I'm tempted to go straight to voltage injection but I wanted to do this the right way.
    Tomorrow I make some more measurements on PU100 pins and post the readings.
    Attached Files

    #2
    Re: Dell 5480 no power

    Try the following:

    1) lift up one leg on PL100. Check the resistance to ground again on the PL100 pads. Which side is showing the very low resistance to ground ?

    Is it the producer ? (PU100)

    Is it the consumer ? (PL100, pad # 2)

    2) Locate the solder block PJP102. If present, remove the solder blob.

    Check the resistance to ground again.

    3) Suspecting that you have a bad cap in the block shown as per attached.

    Consider the above steps and even to remove the few caps mated with PL100 to find the bad (Apple? - oh the irony if this was an Apple product) seed.
    Attached Files

    Comment


      #3
      Re: Dell 5480 no power

      Cpu is heating when charger connected-is it the smaller die on soc?? If so very likely shorted pch part of soc. Check resistance on 3.3v rail

      Comment


        #4
        Re: Dell 5480 no power

        in the meantime I found a boardview to make this faster
        Attached Files

        Comment


          #5
          Re: Dell 5480 no power

          Originally posted by mon2 View Post
          Try the following:

          2) Locate the solder block PJP102. If present, remove the solder blob.

          Check the resistance to ground again.

          3) Suspecting that you have a bad cap in the block shown as per attached.

          Consider the above steps and even to remove the few caps mated with PL100 to find the bad (Apple? - oh the irony if this was an Apple product) seed.
          Removed JPJ102 and pin #2 has 0.8Ohm resistance to ground.
          I have tried to check the components that is connects to but it just too many. Any more ideas before voltage injection?

          Comment


            #6
            Re: Dell 5480 no power

            Keep track of these mods:

            Remove blob @ PJP501. Test the resistance again after this removal. Do not power up.

            My guess is that one of the load switches that make use of this always on rail (ie. EM5209) is damaged.

            I think it is safe to try voltage injection at this time but consider to use 0v8 for starters. The risk is that some short downstream may not like higher voltages and cause some serious damage to the CPU, etc. The load switches are handling some heavy currents so my bet is on one of them being the bad boy.

            Sheet # 4 of the schematics show the location of the EM5209 devices.

            You could throw some alcohol onto the EM5209 devices and then perform the injection and look for the misting of the alcohol.

            If you do proceed, update this thread for future readers with your feedback and repair status.

            Comment


              #7
              Re: Dell 5480 no power

              It's easy to kill CPU, as now 1,2V is DDR4 and CPU line, so as friend above suggested - be careful with voltage.

              Comment


                #8
                Re: Dell 5480 no power

                Originally posted by mon2 View Post
                Keep track of these mods:

                Remove blob @ PJP501. Test the resistance again after this removal. Do not power up.

                My guess is that one of the load switches that make use of this always on rail (ie. EM5209) is damaged.

                I think it is safe to try voltage injection at this time but consider to use 0v8 for starters. The risk is that some short downstream may not like higher voltages and cause some serious damage to the CPU, etc. The load switches are handling some heavy currents so my bet is on one of them being the bad boy.

                Sheet # 4 of the schematics show the location of the EM5209 devices.

                You could throw some alcohol onto the EM5209 devices and then perform the injection and look for the misting of the alcohol.

                If you do proceed, update this thread for future readers with your feedback and repair status.

                injected 0.8 volts and the motherboard draws 0.7Amps.
                The only thing that is heated up but not much is PHC part of the CPU.

                After this checked some things and found that PJP38 has 0.6 Ohms resistance to ground.
                Although I have a bad feeling about this is ending as the rest of my projects ...
                My guess is the next step that I remove PJP38 to see if the short is coming from the PCH or UZ3. Please confirm or suggest else if I am wrong.

                coming from the PCH or UZ3. Please confirm or suggest else if I am wrong.
                Last edited by questore; 01-18-2022, 12:59 PM.

                Comment


                  #9
                  Re: Dell 5480 no power

                  Some unsolder coil near CPU and check both sides resistance.
                  I didn't look into schematic, but if this PJP allow you to do the same, then check it.

                  Comment


                    #10
                    Re: Dell 5480 no power

                    - removed PJP38
                    - 0.3 Ohm reistance on Pin #2 (+3.3V_ALW_PCH)
                    I think I attempt to inject voltage on PJP38 and see what heats up

                    Comment


                      #11
                      Re: Dell 5480 no power

                      Originally posted by questore View Post
                      - removed PJP38
                      - 0.3 Ohm reistance on Pin #2 (+3.3V_ALW_PCH)
                      I think I attempt to inject voltage on PJP38 and see what heats up
                      CZ112 was burning hot so I removed it.
                      Still 0,9 Ohm resistance to ground.

                      Comment


                        #12
                        Re: Dell 5480 no power

                        PJP38 unsoldered, so PCH 3,3V is disconnected.
                        So UZ3 could be faulty.
                        What resistance it shows on PJP39?
                        Maybe you can "borrow" UZ2 for test.. no LAN and WLAN for now will be OK

                        Check resistance of UZ2 pin 1 to CZ 112 and to CZ115.
                        Last edited by rbvndonh; 01-20-2022, 05:22 PM.

                        Comment


                          #13
                          Re: Dell 5480 no power

                          Originally posted by rbvndonh View Post
                          PJP38 unsoldered, so PCH 3,3V is disconnected.
                          So UZ3 could be faulty.
                          What resistance it shows on PJP39?
                          Maybe you can "borrow" UZ2 for test.. no LAN and WLAN for now will be OK

                          Check resistance of UZ2 pin 1 to CZ 112 and to CZ115.
                          - PJP39 Resistance: 379 Ohms
                          - UZ2 Pin #1 is 0.9 Ohm
                          - CZ112 is 3Mohms
                          - CZ115 connects to PJP39 so its 0.9 Ohms

                          Comment


                            #14
                            Re: Dell 5480 no power

                            More info... if I now plug power adapter then 3.3v rail is now present with 2.6v instead of before it was 0v. So the capacitor that i removed was indeed bad.
                            CPU still heating up slowly so i disconnected.
                            - Removed PJP502 and PJP402 - 0.9 Ohm is gone.

                            I'll investigate further tomorrow.
                            Last edited by questore; 01-21-2022, 01:23 AM.

                            Comment


                              #15
                              Re: Dell 5480 no power

                              Ok So I managed to isolate 3 problems:
                              - PJP38 Pin#2 (3.3v_ALW_PCH) = 0,5 Ohms
                              - PJP505 Pin #1 (3.3v_ALW) = 1.0 Ohms
                              - PJP402 Pin #2 (+1.0V_PRIM_CORE) = 0.5 Ohms

                              Tried to investigate - 3.3v_ALW_PCH so injected 0.8v on PJP38 Pin#2... it raised up drawing 3.9 Amps, BUT NOTHINGS GETTING HOT.
                              (Thermal camera shows 29.5Celsius max on board.)
                              Help needed
                              Any suggestions that makes sense?
                              Last edited by questore; 01-22-2022, 02:20 PM.

                              Comment


                                #16
                                Re: Dell 5480 no power

                                PJP38, pin #2 is linked to the PCH which is not good as this often means the CPU is damaged.

                                Do you have a heatsink on the CPU ?

                                Check if the CPU is heating up without the heatsink during the injection testing. Do not raise the voltage about 0v8.

                                Comment


                                  #17
                                  Re: Dell 5480 no power

                                  Originally posted by mon2 View Post
                                  PJP38, pin #2 is linked to the PCH which is not good as this often means the CPU is damaged.

                                  Do you have a heatsink on the CPU ?

                                  Check if the CPU is heating up without the heatsink during the injection testing. Do not raise the voltage about 0v8.
                                  Yes heatsink is on the cpu. I try to remove it and see if it heats up.

                                  Comment


                                    #18
                                    Re: Dell 5480 no power

                                    SOC is a large bga chip with cpu & pch integrated on single chio-so it wont heat up strongly. Only a mild heating can be felt with naked hand and that too after injecting 1V/5A for atleast 5 mins or more.

                                    Comment


                                      #19
                                      Re: Dell 5480 no power

                                      Originally posted by mcplslg123 View Post
                                      SOC is a large bga chip with cpu & pch integrated on single chio-so it wont heat up strongly. Only a mild heating can be felt with naked hand and that too after injecting 1V/5A for atleast 5 mins or more.
                                      I Will try it but since all shorts seems to lead to CPU chip I think this is a Dead CPU/PCH so I have to burry this guy.

                                      Comment


                                        #20
                                        Re: Dell 5480 no power

                                        I stated that at post#3. its shorted PCh part of SOC.

                                        Comment

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