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Acer Nitro 5 (AN515-54) No charge No power

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    #1

    Acer Nitro 5 (AN515-54) No charge No power

    Hello all,
    I'm working on an Acer Nitro 5 (AN515-54) with motherboard EH5VF LA-501P with a short on the power rail.
    I'm just learning board level diagnostic, but here is what I've found so far.
    I injected 1.5v to one of the positive leads on the DC jack connector (PJP101) and read about 1.4a to ground.
    I felt around for heat and found the MOSFET at PQB12 is rippin hot!
    when i pulled the MOSFET from the board the short went away. In my mind it was a faulty MOSFET.
    Ordered a replacement and got it installed only to find it gets very hot again and the short returns.
    Looking around I don't see any obviously damaged caps or components. maybe the fault is in PUB1?
    Like I said I'm very new to this but I feel like I've got to be close.
    Any thoughts or suggestions would be awesome!
    Thanks
    -Earwig
    Tags: None
    #2
    With no power to the board, meter in resistance mode, measure the resistance to ground of the ACN / ACP pins on pub1. You are checking if there is a short on the main power rail that follows the 2 * dcin mosfets of which you have replaced one so far.

    Post the measurements in ohms.

    Comment

      #3
      Pardon my ignorance:
      Which pins are you referring to?
      I don't see ACP on this diagram.
      1 Photo

      Comment

        #4
        On pins 31 and 32 (CSIN and CSIP) I'm showing 3.2ohms and 2.2ohms respectively.

        Comment

          #5
          Your main rail of 19V is shorted to GND. De solder the CLR just after dc-in mosfets and inject 1V/5A on the shorted side of CLR pad and see what gets hot.

          Comment

            #6
            Originally posted by mcplslg123 View Post
            Your main rail of 19V is shorted to GND. De solder the CLR just after dc-in mosfets and inject 1V/5A on the shorted side of CLR pad and see what gets hot.
            Would you point out the CLR? I'm not exactly sure what you're referring to.

            Comment

              #7
              It´s a small value resistor on that path. Also, please link to board schematics for your board, if they are in the schematics sub-forum.

              Comment

                #8
                This motherboard is a CPU Killer

                Comment

                  #9
                  Originally posted by rogfanther View Post
                  It´s a small value resistor on that path. Also, please link to board schematics for your board, if they are in the schematics sub-forum.
                  Thanks! here's where I got the schematic I'm using:
                  https://www.badcaps.net/forum/troubl...eh5vf-la-h501p

                  Comment

                    #10
                    PRB4 is CLR. measure resistance to GND on any pads of PRB4. If its in ohms,19V rail is shorted. desolder it and recheck resistance to GND on both pads and then proceed to inject 1V/5A on the shorted pad of this CLR.
                    Hope you can understand my suggestion clearly.

                    Comment

                      #11
                      Originally posted by mcplslg123 View Post
                      PRB4 is CLR. measure resistance to GND on any pads of PRB4. If its in ohms,19V rail is shorted. desolder it and recheck resistance to GND on both pads and then proceed to inject 1V/5A on the shorted pad of this CLR.
                      Hope you can understand my suggestion clearly.
                      Got it. I will do that on Monday and report back when I can.

                      Comment

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