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[SOLVED]a1278 2012 820-3115 only runs with charger plugged in ,quarter fan spins with battery

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  • [SOLVED]a1278 2012 820-3115 only runs with charger plugged in ,quarter fan spins with battery

    Hi guys,
    I have a liquid spilled 820-3115 board. the area around SMC got some spills, not severe though. ultrasonic cleaned then replace the cracking looking components.
    Machine can power on now and everything runs.

    Here is the probelm:
    The machine only power on with charger is plugged in, it can't turn on when charger is disconnected. with battery fully charge and connected, when you try to turn on,it will be quarter fan spin.
    the system can detect the battery and charges it.R5280 ,R5281 both have 3.3v on 2 pins of theirs.
    Ran ADT got one error:4SNS/1/40000000:VC0C-3.196
    Did some research and say's it's CPU voltage sensor.

    not sure if the CPU is related so I just point my finger to other signals. I checked SMC_BATLOW_L, when only battery plugged in, SMC_BATLOW_L is 0,so PM_BATLOW_L is 0 too.SMC_BATLOW_L comes from the SMC. and that means the SMC is bad? (I did a reflow on it but no change)
    when I press power button, both of the signal jumps to 3.3v then back to 0 along with the quarter fan

    my thought is just kind of massive now and dont know where to go.any advice would be appreciaited!

  • #2
    My vote is on SMC, I would still check resistance on pins 17/18 of U7000 with no power just to see - should be 2-3.3 ohms on the meter just to make sure, but then go to SMC.

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    • #3
      check 17 18 of 7000,unfortunately,they are all good. damn, it's the POS SMC again, really a nightmare.
      the thing is that all these SMC takes long time to replace and have no clues if the replacement IC is good until the whole process. 5 out of 10 of the donor boards won't work....that gotta be hours of works..

      is there any way we can modify the circuit and "lie" to the PCH and let it think there is battery plugged in? let's say jump a 3.3v from s5 rail to PM_BATLOW_L? so the PCH thinks it has battery plugged in?
      then cut off the original SMC_BATLOW_L to PM_BATLOW_L trace?

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      • #4
        since i know all other functions of the SMC is good,it's just this signal is not outputting and make the whole thing not able to turn on

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        • #5
          where do you guys get the SMC btw?any good sources? hate getting those donor boards and don't know if they were already having bad SMC when arrived.

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          • #6
            First check voltage on R5014 should be 3.4V.
            If that is ok I would first reflow the SMC there is probably just crap under it. Flux and not too much heat, do NOT melt the solder!

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            • #7
              solved! reballed 2 SMC from dead boards..finally got it to work!! thanks guys

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