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Apple A2251 820-01949

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    #1

    Apple A2251 820-01949

    Hi everyone. Looking for a few pointers. Above mentioned machine. There was corrosion around the U6300 area, basically from C2842_r to U4910.
    The corrosion was not heavy. I have cleaned the effected area, replaced the L6302 as the pads were damaged, so cleaned the pads and replaced the component ( L6200 from a 820-4924-A). Tested all cap's in the area for shorts ( none found)
    The machine will only BOOT if the adapter is plugged in. Automatically BOOT's. If the machine is powered down, it will not boot up unless the adapter is disconnected and reconnected. The adapter is detected OK and the battery is fully charged.
    The only thing that jumps out to me ( an this could be a red herring) when the machine powers down with the adapter connected and an ampmeter still in line, the voltage drops to 5.1v. Does not return to the 20v. If I disconnect the adapter and reconnect it, it negotiates correctly from the 5.1v to the 20v and the machine will power on.

    One thing I have also noticed, although there was/ is absolutly no corrosion around the power button or any tears in the ribbon, the power button does not seem to respond to pressing and holding to turn the machine off, but if I am quick enough, when the machine powers down the 20v is present on the ampmeter for approx 3-5 secs, and pressing the power button will start the machine back up.

    There is just no start/ BOOT once the ampmeter shows 5.1v.
    Same issue is present on all 4 usb-c ports.


    EDIT:- tested a couple more things, doing a restart does allow the machine to reboot with no issue. Finger print sensor also functions correctly.
    Am I looking at failed CD3217's or ILS9240?
    Any help is greatfully received.
    Last edited by pc1staid; 12-28-2022, 06:56 AM.
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    #2
    Re: Apple A2251 820-01949

    1) what is the voltage output of the isl9240?

    2) is the logic board able to boot with only a charged battery?

    3) if not at 20v, check the LDO rails of each cd3217. Confirm each ldo rail is matching the schematic values.

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      #3
      Re: Apple A2251 820-01949

      Originally posted by mon2 View Post
      1) what is the voltage output of the isl9240?

      Gonna sound really dense here.... where do I measure the voltage output of the isl9240 please? I have read the schematic and it makes little sense to me. Please understand I do have reading difficulties ( dyslexic) and i find a schematic hard to follow.

      2) is the logic board able to boot with only a charged battery?

      Nope, will only power on when the adapter is connected automatically. If I power down, with or without the adapter connected I can not power back up. If I restart it will power on as normal. The only thing I can see at the moment is when powered down and the adapter is connected with the ampmeter, the voltage drops to 5.1v

      3) if not at 20v, check the LDO rails of each cd3217. Confirm each ldo rail is matching the schematic values.
      It does negotiate to 20v and will power on once it hits 20v.
      Once booted the machine works as normal, adapter is detected. If i let it run down to 80% and connect the charger it does charge back to 100%

      I am leaning towards a power button now as it seams to do nothing. I have tried to replicate the process of when it powers down and before the voltage drops to 5.1v I press it to power back on but to no avail. Is there a way of powering on without connecting the adapter, like it was with the earlier macbook's by shorting 2 pads???

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        #4
        Re: Apple A2251 820-01949

        Review the use of the pushbutton @ RE031 - see attached.
        Attached Files

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          #5
          Re: Apple A2251 820-01949

          Originally posted by mon2 View Post
          Review the use of the pushbutton @ RE031 - see attached.
          That's what I was thinking... jus was not sure. I am back in the workshop tomorrow so will try then.just for informational purposes... Reading the schematic is like reading a map for me. It's the abrievations.. I get letters and numbers mixed up so things don't make sense... but I do get there... eventually...lol

          Comment

            #6
            Re: Apple A2251 820-01949

            Originally posted by mon2 View Post
            Review the use of the pushbutton @ RE031 - see attached.
            Thank you Mon2, your advise was spot on. I can clarify the power button has failed.
            I used RE030 as it was on the bottom side of the board so it could be tested in situ. I found that RE030 and RE031 are connected using FexBV .

            Once again, thanks for your help and assistance.
            Wish you a happy new year

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