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    Missing 3.3va on Acer 14

    Good day everyone. I have an Acer One 14 (Z1401-C9JN) with board model NCBT411 ver 2.0, that's missing 3.3va. It has a 5v to 3.3v converter which is supplied by 5va.

    As you can see in the image, 5va is present on red circle c171, c197 and c164. But no output on L7 coil. Found out that output rail is shorted to ground. I removed c179, c199 and c169 cirlced in yellow but short still remain. components circled in light blue is not present (na). It's still shorted even after I removed ic u7.

    Does that mean I need to check all components that is supplied by 3.3va to find short? For the start I removed ic u20. Short still there.

    I have attached schematic here. Hope to hear some advice. Thanks
    Attached Files

    #2
    Re: Missing 3.3va on Acer 14

    locate shorted component by injecting 3V 2A and check for heating component by hand and if u locate area pour some IPA to locate burning component

    if u cannot locate area go higher with current because if u have shorted big IC it can dissipate a lot of heat

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      #3
      Re: Missing 3.3va on Acer 14

      Last edited by Duranitron; 08-19-2020, 04:53 AM.
      Never stop LEARNING because life never stops TEACHING!

      Comment


        #4
        Re: Missing 3.3va on Acer 14

        Originally posted by lezsimply View Post
        Good day everyone. I have an Acer One 14 (Z1401-C9JN) with board model NCBT411 ver 2.0, that's missing 3.3va. It has a 5v to 3.3v converter which is supplied by 5va.

        As you can see in the image, 5va is present on red circle c171, c197 and c164. But no output on L7 coil. Found out that output rail is shorted to ground. I removed c179, c199 and c169 cirlced in yellow but short still remain. components circled in light blue is not present (na). It's still shorted even after I removed ic u7.

        Does that mean I need to check all components that is supplied by 3.3va to find short? For the start I removed ic u20. Short still there.

        I have attached schematic here. Hope to hear some advice. Thanks


        in my opinion for short circuit i started first with 1v 1A oncrease the wattage as you progress too much wattage can burn off small pcb tracks .. trace all the circuit that uses 3.3v
        Attached Files
        Never stop LEARNING because life never stops TEACHING!

        Comment


          #5
          Re: Missing 3.3va on Acer 14

          Originally posted by Duranitron View Post
          in my opinion for short circuit i started first with 1v 1A oncrease the wattage as you progress too much wattage can burn off small pcb tracks .. trace all the circuit that uses 3.3v
          not needed to start with 1V on 3.3V rail. this voltage u r using only on main 19V rail when u dont know if u have shorted highside mosfet so u need to start on 1V because of CPU and GPU

          1Vx1A= 1W that is way too small heat to feel it
          Last edited by ktmmotocross; 08-19-2020, 07:28 AM.

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            #6
            Re: Missing 3.3va on Acer 14

            Sorry guys for very late reply. Tried injecting 1v to 3v, there's no component heating up. But when I use charger the only component getting hot is the cpu. No luck on finding any.

            Comment


              #7
              Re: Missing 3.3va on Acer 14

              Originally posted by lezsimply View Post
              Sorry guys for very late reply. Tried injecting 1v to 3v, there's no component heating up. But when I use charger the only component getting hot is the cpu. No luck on finding any.
              what was current consumption when inect 3,3V?

              Comment


                #8
                Re: Missing 3.3va on Acer 14

                unstable 0.06 amps. Sometimes it goes 1.16 then goes low again. weird

                Comment


                  #9
                  Re: Missing 3.3va on Acer 14

                  u r searching for short, why u use charger?

                  Comment


                    #10
                    Re: Missing 3.3va on Acer 14

                    I used both bench supply and charger. So far processor is the only one heating up. On charger it can easily heat up but on bench supply it takes about 15v.

                    Comment


                      #11
                      Re: Missing 3.3va on Acer 14

                      Is SoC itself getting hot or something near it? If it is the SoC, which part is getting hot? The PCH side (small square) or the CPU side (rectangle shape)?

                      Comment


                        #12
                        Re: Missing 3.3va on Acer 14

                        Only the processor is installed on this motherboard. Please check image.

                        I got new development. I cleaned motherboard with 90% isoprophyl. Now 5v and 3.3v are present. When I press power button laptop turns on but turns off after 10 to 12 seconds initially.

                        I'm checking diagram for power sequence to see if any voltage missing. I'll get back soon. Thanks. Spider.
                        Attached Files

                        Comment


                          #13
                          Re: Missing 3.3va on Acer 14

                          Your board is NCBT411 and schematic is for NCBT419, are they similar?

                          Glad to hear you have 3.3V again though. Any history of the laptop? Was it water damaged, etc?
                          Last edited by Spider1211; 09-23-2020, 03:17 PM.

                          Comment


                            #14
                            Re: Missing 3.3va on Acer 14

                            So far everything looks similar and also I found this pdf here but its difficult to navigate as it redirects to some page.

                            Owner told me they use laptops usb port for charging most of the time. When laptop is on, they close lid then charge tablet or phone on usb and leave it. Then one day it didn't work.

                            That's the first thing I checked, no short on usb port supply.
                            Attached Files

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