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    Asus K501UX won't charge

    Hi,
    I have an issue with my laptop, Asus K501UX.
    At first, it was working properly. Then it began to try to start up but shut down after a few seconds. Now it won't do anything, no light is showing, nothing.
    I did tried to reset the BIOS.

    I have another Asus laptop, an Asus UX303L. I disassembled both laptops, and found out that the batteries are the same. When I put the UX303's battery inside the K501, it works perfectly, normal discharge time, everything is working properly. When the charger is plugged, windows tells me that it is indeed charging. But it is not the case, the battery is discharging like if the power connector wasn't plugged in. By the way, the K501's battery is working properly on my UX303.

    The laptop isn't booting up if there is no battery. And if the battery is dried, it won't boot up either.

    I made some research, and found this thread : https://www.badcaps.net/forum/showthread.php?t=54003

    I then decided with my multimeter to test some things, but I don't have the background to analyse them ... That's why I need your help !

    Here are my results :

    A) Battery unplugged, charger plugged

    - Voltage on the power connector, it is 19.32, this is normal.

    - Voltage on the connector of the battery :
    The connector looks like that : BLACK BLACK BLACK DATA CLOCK RED RED RED
    Black pins are connected together and to the ground, and red pins are connected together. I measured 0.14V between ground and red.

    - Voltage between the MOSFETS (see attachments) and the ground. On the first side of the first Mosfet, it is 19.32V. On the other side it is exactly 0 (and obviously on the second one everything is at 0V because the second ne is connected to the first one). Someone told me that this is normal, because the battery isn't plugged in.

    - I saw a video on YouTube, which suggested to test if capacitor were okay. I put one side of my multimeter (with the bip mode) on the ground, and tested both sides of every capacitors on my MB. On a lot of capacitors, I could hear a bip on both sides.

    B) Battery plugged, charger unplugged

    - Voltage on the power connector, 10.8V

    - Voltage on the connector of the battery :
    The connector looks like that : I measured -10.8V between ground and red. It is negative, I figured it was normal because the voltage comes from the battery, not from the charger which isn't connected

    - Voltage between the MOSFETS (see attachments) and the ground. On the first side of the first Mosfet, it is . On the other side it is exactly 10.8V. On the second one, I can measure 10.8V on both sides.

    - When I test every capacitor, none of them bip on both sides.

    C) Both plugged

    I got exactly the same results as when the battery is plugged and the charger isn't.

    Can you guys help and tell me what to do next ? I'd really enjoy to fix this computer which is better than mu UX303L. And I don't really want to modify the computer to add my own charging circuit.

    Feel free to ask me any information.

    Thanks !
    Attached Files

    #2
    Re: Asus K501UX won't charge

    Up please ^^

    Comment


      #3
      Re: Asus K501UX won't charge

      Use diode mode on your multimeter and check the mosfets and capacitors for shorts.

      Comment


        #4
        Re: Asus K501UX won't charge

        Hi,
        Yes that's how I tested them ^^

        Comment


          #5
          Re: Asus K501UX won't charge

          you have to find the schematics and check the 19v rail without battery.

          Comment


            #6
            Re: Asus K501UX won't charge

            Originally posted by Kashi_Haname View Post
            Hi,
            Yes that's how I tested them ^^
            in diode mode; test with no battery no charger.

            Comment


              #7
              Re: Asus K501UX won't charge

              Hi !
              I'm sorry I misunderstood what you said !
              Without the charger and without the battery, and in diode mode (please don't laugh, I didn't know that mode before I thought it was the bip mode x'D And this diode mode is very useful !) I got those results :

              First kind : Some capacitors give me a value on one side, and when I change side they give no value. I think that's normal.
              Second kind : Some other capacitors give me a (non negligible) value on both side.
              Third kind : And, some capacitors give me a steady "normal" value on one side (eg 500), and on the other side, they first go as high as 1400, and then drop to 0L. I'd say it is just the discharge, but I am not sure.

              What do you think about that ? And why, with the battery connected, every capacitor are like kind 1 ?

              Thanks you for your help.

              (and sorry for my poor English ^^")

              Comment


                #8
                Re: Asus K501UX won't charge

                Up ^^

                Comment


                  #9
                  Re: Asus K501UX won't charge

                  Your problem is probably with one of the fets or charger ic and not a capacitor. You have to check if fets are allright and if yes, that they have the right voltage on pin 4 (gate). For this is better to have a schematic and even better and a boardview. If somebody can help here with schematic and boardview.

                  Comment


                    #10
                    Re: Asus K501UX won't charge

                    Hi,
                    How do I know I got the right voltage ? Because as I said, with the battery unplugged, I have 0V on output. But when I plugg the battery in, I got about 11V.
                    I actually found a boardview on some russian website, it perfectly matches my motherboard. Here is the link from my drive : https://drive.google.com/open?id=10g...u42WXvtPLMpH64

                    I hope it will help you to help me hahah ;p

                    Thank you and happy new year !

                    Comment


                      #11
                      Re: Asus K501UX won't charge

                      Up ^^

                      Comment


                        #12
                        Re: Asus K501UX won't charge

                        Up

                        Comment


                          #13
                          Re: Asus K501UX won't charge

                          Take large resolution photos of the two sides of your board

                          Comment


                            #14
                            Re: Asus K501UX won't charge

                            check for voltages/resistance to ground on 4th pin of both mosfets. its the pin that isnt connected with others
                            Last edited by ktmmotocross; 12-05-2018, 11:10 AM.

                            Comment


                              #15
                              Re: Asus K501UX won't charge

                              Hi,

                              I'm getting back with some news. (I've switched country for a while so I couldn't get back to the motherboard).

                              So, first thing, I think the battery is dead. I let it drop to -13% for 2 years, it didn't like it x'D I tried to revive it with my iMax b6 by charging to three cells separately, but I still have 0V between Black and Red, whereas I had 10.8V before (battery on board, and I have 3.28V on both yellow and white wires). I think the battery's controller is dead and I have no idea how I could reset it. Couldn't either find schematics for the controller board. If you have no idea I'll end up buying another battery but I would like to avoid that. Moreover, maybe the issue is on the motherboard too.

                              Second thing, check on the screenshot of the boardview.

                              - The gates of the mosfets are connected together
                              - The sources are connected together

                              - Drain from Mosfet 1 is 19V (DV voltage)
                              - Everything else is 0V, even the Gates

                              When I short the first mosfet with a wire between drain et source, the laptop starts. (this is the red wire that appear on an image I wanted to "cleanly" solder a wire for security purpose).

                              So I think there is something wrong, probably related to the Gate line. What do you think ? I kinda lack a lot of experience for this (slowly learning board level repair ^^). I followed the gate line and took measures on some points which you can see on the attached picture.

                              I think maybe the MLCC (PC8905) is bad ? What do you think ? I'm open for testing what you tell me ;p.

                              A resistance (PR8934) is also going to a "charge manage IC" (PU8901). I'm waiting for your advice before going deeper.

                              Additional measurement : without the battery plugged in, on the battery connector between Black and Red I have 0.86V. I would expect it to be 0V, but I'm not sure.

                              Thank you for your help. I hope you understood me x).

                              Note : In attachment the pictures and the boardview fz file, that you can open with boardview software.

                              EDIT : I want to short the MLCC (PC8905) in order to see if this will power the mosfets and the IC, but I don't trust my knowledge to predict the consequences.
                              Attached Files
                              Last edited by Kashi_Haname; 04-04-2020, 06:57 PM.

                              Comment


                                #16
                                Re: Asus K501UX won't charge

                                Up

                                I narrowed down the issue to ACOK being 0V. The conditions to get it to HIGH are fullfilled, but the pullup resistor doesn't seem to be connected to +3V power rail. I am trying to find the issue but it's complicated x)

                                Comment


                                  #17
                                  Re: Asus K501UX won't charge

                                  I have this no charging problem also, after investigation 2 resistors are missing, PR8904 AND PR8905... And only PC8905 is left. So been thinking about REPLACING the missing caps, but don't know if I need specific ones or if any of the same size (rc0402) will work

                                  Comment


                                    #18
                                    Re: Asus K501UX won't charge

                                    Hey !
                                    How can you be sure you have two resistors missing ? Are those resistors or capacitors (you later mention caps) ?
                                    Can you clearly see on the board that caps were there and now are missing ?

                                    Be careful, for SMD components size means nothing, you can have 0805 resistors with plenty of different values so be careful.

                                    Have you check your power rails ?

                                    Comment


                                      #19
                                      Re: Asus K501UX won't charge

                                      I have the schematics and boardview, that how I knew they were missing.
                                      sorry didnt mean "caps". its definitely 2 resistors

                                      and thanks , i will order the missing resistors.

                                      I did check the power rails... its actually the pc I'm typing on now.

                                      For some weird reason, when I press my finger against where the resistors used to be, the laptop starts charging. stops shortly after.
                                      (discovered this when i was looking for shorts with my finger )
                                      Last edited by Jason13; 03-25-2021, 04:30 AM.

                                      Comment


                                        #20
                                        Re: Asus K501UX won't charge

                                        Be careful, seeing a component on the schematic doesn't necessarily means it should be there on your motherboard. On mine, there were a lot of differences.

                                        Hum, you issue is weird. I don't think your resistors are the issue. If it was the case, why would the laptop start charging when you press on the motherboard ? Check again if you can't think of anything else, maybe something is not properly soldered on and makes contact when you press with your finger ?

                                        Comment

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