X450ubr main power rail missing after first mosfet!

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • mr-marlan
    New Member
    • Jul 2024
    • 4
    • Iran
    #1

    X450ubr main power rail missing after first mosfet!

    Hi this is my first topic, im new here and learning
    Laptop model: x450ubr rev2
    main issue: no power after 1st mosfet
    After bypassing 1st mosfet laptop runs! Picture+fan even winfows boots up
    but after a few minutes (2-3m) it shuts down.
    things i noticed:
    -charger led blinks 4 times and stops and repeats.
    -No overheated components found everything seems normal.
    -​​​ 19v 5v 3.3v are present and stable
    the original charg ic have been replaced by someone (i think) new ic is bq780

    thats all i could figure out, im stuck
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14985
      • Canada
      #2
      Test the first mosfet. Remove all power. Meter in resistance mode.

      Measure:

      Source / drain
      source / gate
      gate / drain

      Post each measurement. Each must be hundreds of k ohms or more else the mosfet may be defective.

        Comment

        • mr-marlan
          New Member
          • Jul 2024
          • 4
          • Iran
          #3
          Hey 👋
          tnx for ur reply!
          Originally posted by mon2
          Measure:

          Source / drain
          source / gate
          gate / drain

          Post each measurement. Each must be hundreds of k ohms or more else the mosfet may be defective.
          Source/drain 255k
          Source/gate 6k
          Gate/drain 255k

          there is a 6kohm resistor connecting the source to gate, removed it and i now get almost 3.8Mohm
          should the resistor i removed be a higher value?


          Edit: checked the schematic, the risistor value should be 4.7Mohm!

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14985
              • Canada
              #4
              Do not have this schematic in my database. Can you post / link inside the schematic forum?

              Yes, if this resistor is of the wrong value, do replace it.

              The source/drain values look low as well.

              What about gate / drain measurement? Most likely this mosfet is defective and must be replaced.

                Comment

                • mr-marlan
                  New Member
                  • Jul 2024
                  • 4
                  • Iran
                  #5
                  i made a mistake, the board is actually x540ubr not x450ubr...
                  i massaged you check it plz
                  the measurement between gate/drain is 255k, same as source/drain
                  i will update you when i find a replacement for the mosfet and resistor.

                    Comment

                    • mon2
                      Badcaps Legend
                      • Dec 2019
                      • 14985
                      • Canada
                      #6
                      No worries. Yes, have this schematic. Do replace as noted and update this thread.

                        Comment

                        • mr-marlan
                          New Member
                          • Jul 2024
                          • 4
                          • Iran
                          #7
                          hi there,
                          Please remove this post. The customer has requested their laptop back, and I was unable to locate the resistor needed for the repair

                            Comment

                            Previous template Next

                            Related Topics

                            Collapse
                            • mkdj
                              Acer TravelMate P214 - N19Q7 main power rail shorted to ground
                              by mkdj
                              Dear all,

                              I have taken out the motherboard of a Acer TravelMate P214. There is a short to ground on the main power rail (19V). I don't have the schematics or boardview for this board (DAZ8IMB1AA0 REVA). But I have found 4 MOSFETS close to the main power rail : 2 N-Channel and 2 P-Channel.

                              I have checked resistance across each of the 4 MOSFETS. I have the following readings:
                              Both N-Channel Mosfets: nothing odd

                              P-Channel MOSFET number 1:
                              source - drain : 117 kOhm
                              source - gate: 96 Ohm
                              gate - drain: 117 kOhm

                              P-Channel MOSFET...
                              08-20-2025, 06:08 AM
                            • joshAU
                              Acer AN515-55-528T FH52M LA-J891P - Short ciruit after PQW1 MOSFET on +1.35VSDGPU rail.
                              by joshAU
                              Hi all.
                              This notebook was showing no signs of life.

                              I removed the FH52M LA-J891P mainboard and found that there was 19V at the DC jack.
                              However there was zero volts on the two PRB2 and PRB46 resistors immediately after the two polarity protection MOSFETs (PQB11 & PQB12).

                              If I remove the PQW1 MOSFET, the 19V rail starts working, and I can turn on the unit - at least I get the fans, and the power light comes on, when I simulate the power button being pressed. No display.

                              I tried replacing the MOSFET with a new one, but again no voltage on the...
                              05-29-2024, 12:33 AM
                            • W3rtl0s
                              RX 5700 XT 1.8V rail missing.
                              by W3rtl0s
                              Hi, first of all im a complete newbie. I bought two non working gpus (or so the seller said) one is a 1660 super, the other is a 5700xt. He mentioned on the 5700 xt that the fans would spin, led would light up and it would show a picture for a split second and then it would turn off or something, but when i tested it i only saw the first two symptoms and no picture. Now when i started probing around i saw that A- the gpu was not shorted B- the 12, 5, 3.3V rails were present but vcore, vram and others were completely missing. I then stumbled upon one coil that had 1v present on it which was strange,...
                              12-05-2025, 08:47 AM
                            • prototypedoc
                              Lenovo Legion 5 15IAH7 NM-E241
                              by prototypedoc
                              Hello guys,

                              Got my hands on this laptop and started troubleshooting. The only thing I know is it turned off and never came on. No lights and not coming on.

                              Started doing some checks and found the main rail present everywhere. Something weird though as the gate of the first input mosfet is 3.7V and the output is 20.3V.
                              Tried to trace the gate and it looks like it's connected to pin 61 on the io. Is the IO supposed to monitor the gate voltage?

                              5V and 3.3V are missing from the coils. Found by lifting PL6202(on the 5V rail) the clicking fet sound goes...
                              2 Photos
                              04-24-2024, 02:32 PM
                            • FrozenHaxor
                              Lenovo Ideapad 3 15IIL05 NM-D031 +3VALW missing
                              by FrozenHaxor
                              Hello,

                              Having an issue troubleshooting this board, it takes no current. PQ100 MOSFET gets 0V on the gate and does not open, when I short it out the laptop powers up. There is 0V on ACDRV from BQ24780, 0V on ACOK.

                              Now for the fun part, ACOK is pulled up to 3VALW rail, when I short out the PQ100 and power up the laptop, ACOK jumps up to correct 3.3V, as soon as I remove the short across the MOSFET it goes fully dead again. Now my issue is that according to schematic this is a circular logic, I can't have +3VALW without getting power to the PU1101 SY8386BRHC, but I can't...
                              10-16-2025, 05:58 AM
                            • Loading...
                            • No more items.
                            Working...