Mac air a1465 fan spin but no boot

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  • smic717394
    Senior Member
    • Jun 2017
    • 93
    • Spain

    #1

    Mac air a1465 fan spin but no boot

    Hi guys, I have a Mac air 1465 2015, fan spin but no image. After inspecting the main board, I found no corrosion even the test points are nice and shiny.The boards its so clean looks new. Anyways PPBUS_G3H is present 8.6V, PP3V42 is present 3.42V, the CPUVR is present 1.8V and the cpu gets warm, 3V present, 5V present. Since its start fine all the s5, s4,... must be present. I checked the s0 power rails at some points and they there.

    I also programed the flash rom U6100 with few firmware I found on the web, but the same result. Checking with the thermal camera there are 2 heath spots more than the rest, nothing over the limit about 40 degrees , one is the U7400 that is a TPS51916 that is a ram powersuply. checking the voltage near the ram and there is the 1.3v. I also reflow all the chips, with no improvements.

    The other chip that gets hot is the U3900 that is a BCM15700 IC, I think this is the camera memory ic. Now this hets warm but on one side only towards one edge.

    So basically the laptop comes on, at start I get the green then orange light on the charger, the fan spins but normally not at full speed, the battery charges fine, the light get green after the batter is fully charged, and it can start from the battery as well. Apparently everything ok, but no chime or image.

    I tried to reset the PRAM but it doesn't react. If I power it from the PSU 18.5V I see it takes about 0.441amp and if I connect the ssd goes to about 0.500 or something like this.

    The only thing I see wrong on the visual inspection is the stud where the m2 drive should be screwed is been rip of the board, but I don't see major damage.

    I'm starting to think that is a bad cpu. Any thought will be appreciated.
  • dellxps15
    Badcaps Legend
    • Feb 2014
    • 1588
    • italy

    #2
    Re: Mac air a1465 fan spin but no boot

    report resistance on cpu vcore. on air should be around 22 omh.
    also it could be bad u1950 when u have cpu voltage but no boot.

    Comment

    • smic717394
      Senior Member
      • Jun 2017
      • 93
      • Spain

      #3
      Re: Mac air a1465 fan spin but no boot

      Originally posted by dellxps15
      report resistance on cpu vcore. on air should be around 22 omh.
      also it could be bad u1950 when u have cpu voltage but no boot.

      To measure the vcore, is on sny of the 2 coils, the cpu side?

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 14020
        • Canada

        #4
        Re: Mac air a1465 fan spin but no boot

        Either side is ok. A coil is essentially a long run of wire.

        Comment

        • smic717394
          Senior Member
          • Jun 2017
          • 93
          • Spain

          #5
          Re: Mac air a1465 fan spin but no boot

          Originally posted by dellxps15
          report resistance on cpu vcore. on air should be around 22 omh.
          also it could be bad u1950 when u have cpu voltage but no boot.
          Vcore is 7.85 ohm
          U1950 has.

          Pin 1: 3.337
          Pin2: 3.337
          Pin3: 3.429
          Pin5: 3 429
          Pin6: 3.429
          Pin7: 3.429
          Pin8: 3.429

          Comment

          • smic717394
            Senior Member
            • Jun 2017
            • 93
            • Spain

            #6
            Re: Mac air a1465 fan spin but no boot

            Originally posted by dellxps15
            report resistance on cpu vcore. on air should be around 22 omh.
            also it could be bad u1950 when u have cpu voltage but no boot.
            Vcore is 10.71 ohm
            U1950 has.

            Pin 1: 3.337
            Pin2: 3.337
            Pin3: 3.429
            Pin5: 3 429
            Pin6: 3.429
            Pin7: 3.429
            Pin8: 3.429

            Comment

            • dellxps15
              Badcaps Legend
              • Feb 2014
              • 1588
              • italy

              #7
              Re: Mac air a1465 fan spin but no boot

              remove heatsink. check if pch get hot, but dont stay without heatsink and power on more then 5 -6 seconds. just check quickly if pch get hot then remove power.

              ps: i5 or i7 cpu ?
              Last edited by dellxps15; 06-05-2023, 06:30 AM.

              Comment

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