SMBus "Battery A" (battery/charger) issue. MacBook will only turn on with a/c

Discussion in 'MacBook' started by Mac,Duh, Jul 5, 2013.

  1. Mac,Duh macrumors newbie

    Jul 4, 2013
    Hello everyone!

    I repair water damaged MacBook motherboards for a hobby and have several boards (A1342 models, 2.26 (2009) and 2.4Ghz (2010)) exibiting this symptom. The symptom is that the motherboard will not power on from battery alone, but will power on if the a/c adapter is connected. Investigation reveals that the SMC "Battery A" SMBus for the battery/charger is not working. The clock is generated, but the data line just stays high. Apparently, the SMC will not allow a power on unless it can communicate on this bus to the charger IC (U7000). However, it appears to allow a power on under this condition if there is also a/c connected. Upon trying to power on, all I see on the SMBus are a series of 9-12 clock pulses, but with nothing on the data line. When powering on and booting via this method, Apple ASD passes all the sensor checks, so apparently, it doesn't check this SMBus. But it also doesn't detect the (known working) battery, so I just get an X for that.

    So, naturally, you'd suspect that there is something wrong with the ISL6258 U7000 charger chip but I have changed it with no improvement. That appears to leave only one problem area, and that is the SMBus data line on the SMC is shot. Does anyone on this forum have any experience with this problem? All symptoms seem to point to a bad SMBus data line on the SMC, but given that everything else on the SMC (including the SMBus clock line) seems to work, I can't help feeling I am missing something. Changing the SMC really isn't an option as a) I don't have the tools to do that kind of BGA work, and b) Even if I could get the chip, I don't have the Apple firmware for it.

    So, would appreciate any feedback from folks familiar with this issue. Am I missing anything or do I have a bunch of boards with a bad SMBus data line on the SMC? That would be a killer as everything else appears to work on these boards!
  2. agencik macrumors newbie

    Apr 23, 2013
    battery issue

    Hi there, I don't know if you still here, but I think we have the same issue with MacBooks. Have you try to replace the SMC? thanks

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