Announcement

Collapse
No announcement yet.

Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #21
    Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

    Since the battery was manufactured in 2021, I'll probably have to get the BIOS updated to the 2021 version.
    No. The battery manufacturing date is not linked to the BIOS version. In general practice, do update your motherboard BIOS to the latest version as the latest version likely fixed some bug reports.

    If the battery is reporting 0% then the communication between the BMS (circuit board that is buried inside the battery pack) has failed to function with the logic board bus master.

    Battery packs use a 2 wire communication = I2C / SMBUS (basically the same interface) - using this 2 wire interface, the host (aka bus master) can ping the battery using a special I2C address. Then it can extract out the serial #, charge level, etc.

    Using an Arduino you can dump out the same details as has been proven by another tech on this forum.

    If you are able to charge the battery then the charger IC is putting out the high enough voltage onto the battery pack leads to allow for this battery to charge.

    At least we know that the chemistry of the battery cells is OK but we do not know if the # of charge cycles is high / low / count. If there is an option, return this battery pack under the premise that the battery is not being detected.

    Or at least test with another (ideally fresh) battery. Amazon is great for this form of testing and perhaps that is the only fault with this laptop.

    Comment


      #22
      Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

      Originally posted by mon2 View Post
      If the battery is reporting 0% then the communication between the BMS (circuit board that is buried inside the battery pack) has failed to function with the logic board bus master.
      Do you think it's at all possible that there is still a problem with the system board? If so, where could it be?

      Comment


        #23
        Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

        I think you have multiple problems.

        Forget the battery - just remove it from the box.

        Does the laptop power up and function properly with only the adapter ?

        Comment


          #24
          Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

          Originally posted by mon2 View Post
          I think you have multiple problems.
          Why do you think this? Asking to learn.

          Yes it works with just the ac adapter.

          Comment


            #25
            Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

            Also, do you know specifically what IC on the board the battery communicates with? I have a donor board available so I could pull it from there.

            I know I'm getting specific but I'd like to learn as much about this as I can.

            Comment


              #26
              Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

              Powers on then powers off after 4-6 seconds
              Do you still have this fault with ONLY the AC adapter ?

              In general, it is best to stabilize the laptop with only the AC adapter. The charging / battery faults can be reviewed after the AC adapter is known to be ok with the logic board.

              Comment


                #27
                Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                Originally posted by mon2 View Post
                Do you still have this fault with ONLY the AC adapter?
                No that problem and everything previous was with what is now a donor board.

                The replacement (current one being discussed) that I got for ~$90 works with BOTH AC adapter and battery, or solely one.
                Last edited by ResoluteHawk; 07-07-2022, 11:26 AM.

                Comment


                  #28
                  Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                  Ok. To be clear, the new working board has only the fault of the battery not showing the correct battery status ? That is, it works to charge but is reporting 0% in the battery status ?

                  Technically you should have 2 batteries now ? Do they both act the same in the new working board ? Just to rule out that one battery is defective.

                  Comment


                    #29
                    Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                    Originally posted by mon2 View Post
                    Ok. To be clear, the new working board has only the fault of the battery not showing the correct battery status ? That is, it works to charge but is reporting 0% in the battery status ?

                    Technically you should have 2 batteries now ? Do they both act the same in the new working board ? Just to rule out that one battery is defective.
                    Yes the new working board only has the battery problem.
                    I do have 2 batteries but the old one is completely dead to the point where the BIOS is telling me to replace it.

                    Also there are times when I'm inside Windows and I disconnect the charger and plug it back in and the charger will sometimes shut off. This is indicative of protection mode but there are no shorts on the motherboard that I can find, unless I missed something.

                    Comment


                      #30
                      Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                      Also there are times when I'm inside Windows and I disconnect the charger and plug it back in and the charger will sometimes shut off.
                      Is the adapter the original ?

                      Inspect the first 2 / 3 mosfets linked to the AC adapter that power your logic board.

                      These are mosfets shown in the attachment.

                      Remove all power / NO battery. Meter in resistance mode.

                      Check the resistance between the mosfet pins as follows:

                      source (1-2-3) & drain (5-6-7)
                      source (1-2-3) & gate (4)
                      gate (4) & drain (5-6-7-8)


                      Post each reading & meter scale that is used. If you see '0.L.' or '1' -> switch to a higher meter scale.

                      Repeat for each mosfet in the attached.
                      Attached Files

                      Comment


                        #31
                        Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                        No power (Battery nor AC)

                        PQ701
                        Source to Drain => 0.2 Ohms
                        Source to Gate => 107 Ohms
                        Gate to Drain => 107 Ohms

                        PQ702
                        Source to Drain => >40K Ohms
                        Source to Gate => 111.8 Ohms
                        Gate to Drain => >40K Ohms

                        PQ707
                        Source to Drain => 0.3 Ohms
                        Source to Gate => 116.3 Ohms
                        Gate to Drain => 116.3 Ohms

                        Comment


                          #32
                          Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                          Each of these mosfets are too low in the resistance. They need to be replaced. These mosfets are very inexpensive and usually < $1 USD each (Aliexpress).

                          If in a rush, you can order from Digikey / Mouser / Arrow. There are many equivalent mosfets available.

                          Since you have a donor board - check the mosfet readings there for each.

                          Comment


                            #33
                            Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                            Originally posted by mon2 View Post
                            Each of these mosfets are too low in the resistance. They need to be replaced.
                            I can pull some from the back of the donor board that are measuring healthy.
                            They should be somewhere in the x10K or x100K Ohms range yeah?

                            Lol shoot how did I miss this.
                            Last edited by ResoluteHawk; 07-07-2022, 12:09 PM.

                            Comment


                              #34
                              Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                              Yes, the resistance, while being futile, is required to be high - much higher than your readings.

                              See here for more details with the resistance check chart:

                              http://electronicsbeliever.com/how-t...0good%20MOSFET.

                              Comment


                                #35
                                Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                                So I took 5 of the 6426 MOSFETs from the donor Alienware board as practice and out of the MOSFETs I took off (PQ701, PQ702, PQ703, PQ704, PQ707), only 1 of them was bad and measuring 0 Ohms between Drain and Source.

                                It was PQ707 which is the first power MOSFET. The other 4 are good as they measure 3.3M Ohms between Drain and Source.

                                On the working board, PQ701 was the one measuring 0.3 Ohms between Drain and Source, and after taking off PQ707 and PQ701, the resistance of the contact points on the board for those MOSFETs are now up into the M Ohms range.

                                So I really only had to replace one of them since measurements are now normal.

                                Comment


                                  #36
                                  Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                                  OK, and ??? (biting my nails in anticipation of what is the status)

                                  Comment


                                    #37
                                    Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                                    Resoldered the functional MOSFETs onto the board and tested resistances of PQ701 and PQ707. They're now up into the 10k Ohms after replacing PQ701.

                                    The board works. Laptop powers on still.

                                    BATTERY APPEARS TO BE CHARGING!!!

                                    BattInfoView shows 70,000 mw of charge.

                                    That...was also my first real board repair. Capacitors vs MOSFETs; two different beasts.

                                    Comment


                                      #38
                                      Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                                      Well done! I thought you were whisked away by a Moussad agent already...thanks for the update.

                                      Post #14 had the secret clue all along.

                                      Comment


                                        #39
                                        Re: Alienware 17 R3 (LA-C912P) Powers on then powers off after 4-6 seconds

                                        I actually learned a lot from this repair. This board previously had a shorted capacitor under the CPU VCORE DRMOS but I fixed that with diode mode and some voltage injection. I thought everything was working correctly because it turned on and seemed to get power to the battery.

                                        I didn't expect 1 MOSFET to cause the battery to not charge.

                                        Thanks for the help everyone! We fixed the board.
                                        Last edited by ResoluteHawk; 07-07-2022, 03:22 PM.

                                        Comment

                                        Working...
                                        X