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Early 2011 model, A1278 / 2.3 GHz i5 or 2.7 GHz i7 processor.

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no power to MacBook, new parts, other odd behavior

I just received this A1278 EMC2419, MLB# 820-2936. I have very little history on it other than: MacBook stopped powering on, previous owner said they replaced:

  • Battery
  • MagSafe charger
  • DC-in board

I can confirm the Chinese battery is new, the charger was still in plastic, but the DC-in board showed corrosion despite looking otherwise brand new and having a 2015 date stamp.

The MacBook doesn't respond to the power button, or to shorting the power pads. the MagSafe illuminates green with or without battery connected, and the battery level indicator is non-responsive *unless* the MagSafe is connected. I have attempted SMC reset, though I cannot be sure it has completed. I've shorted the pads at R5001 (omitted) which according to the internet will pull SMC_RESET low. That didn't have any apparent effect.

I set my SPI programmer with SOIC8 clip on the EFIROM, to attempt a reflash there, and strangely enough, the MagSafe turns orange when my programmer is connected and powered on. I'm unsure if that means the battery is charging, or that the SPI programmer is drawing current and tricking the MagSafe. Due to the precarious nature of equipment and connections, I've not yet attempted an SMC reset while the MagSafe was orange.

I have the schematic and the board view, though i'm not electrical engineer. I've followed V+ lines from both the battery and the DC in. all resistors test ok, all fuses are good. I'm showing 11.99VDC at each rail from the battery, at the connector.

Can anybody point me in a direction?

PP3V3_S5 points:

Block Image

PP5V_S5 points:

Block Image

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I hope you didnt pay much as it seems like the board might be fried. Although i dont know much @mayer and @danj know more than i do


i assume the logic board is fried on any non-working mac i acquire. i pay less than the sum of the parts are worth, or i don't buy (-;


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Sounds like you have the schematic and board view for this. Check out the power aliases page, check all G3H and S5 power rails whilst just the charger is plugged in (battery is probably bad if it looks really cheap). If any rails are missing, not steady or not what they should be according to the schematic, look into it.

If DC in voltages are reading at 16V or over and is lighting up, the DC jack is fine. You can't get these new anymore, so it usually has flux on the PCB where a new charger port has been soldered on (probably not corrosion).

Leave the SPI ROM alone for the moment, this will be fine unless it has been damaged, reprogrammed or replaced by someone else. Usually if this is bad, the fan will spin but it won't chime, very rare for it to be dead from a bad SPI ROM (also, they rarely corrupt without cause).

Check out main power rails and look into this further.

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great thanks! i've got three new DC-in boards arriving by 9pm tonight just to rule that out, but i doubt that's the problem. i already scrubbed the gunk off of the "new" DC-in, but you're right it could've been dusty flux. it was localized to the solder mount on the south side of the board.

i've swapped the battery with a known-good (also chinese) battery. i have two other OEM A1278 machines i can pull the battery from, but i don't expect that to be the issue either and would prefer to avoid removing them right now.

i do a LOT of work in reprogramming apple EFI, and i've seen corrupted firmware and bad flashes result in no power at all, no display and 100% fan, or even just terrible performance. but you're right it was a reach. i did observe an EFI password's presence in the EFIROM.

anyway, thanks for the tip. i will dive in to the power aliases. you say G3H and S5 rails are the primary suspects?

i appreciate your guidance


Don't worry about the battery for the moment, this model will turn on when the charger is plugged in with no battery (if it is working fine, of course).

Yes, check G3H and S5 rails. If any are missing or low, check for a short to ground and go from there.


so... confirmed DC in is ok, replaced with new unit.

have tested all PPVBAT and PPBUS G3H rails... 12.62VDC, same reading as battery terminals. couldn't confirm voltage at Q4276, but that appears to be an IC on the firewire circuitry... and the leg on the IC is so small i can't be confident my probe was making contact.

i am going to run through the S5 rails now


U5805, 18.5VDC booster, is also tiny IC with little exposed leg. i'm almost certain i'm making contact, but i can't see well enough down there to be absolutely certain. it's a similar chip to the firewire IC on the G3H rail. all PPDCIN lines are >12VDC.

0.0VDC at U5805 on the PP18V5S5_FB

0.0VDC at Q4276 on the PP3V3_FW_FWPHY

0.0VDC at D5802 and L5801 on the PP5v_S3_P18V5S5

0.0VDC at Q7220 on P3V3S5_DRVH and DRVL

nothing on S5PGOOD_DLY

i have no idea if all of these rails are intended to have voltage while off. everything else tested ok with the exception of a few places i couldn't probe.


Firewire is irrelevent at this point. What do you get on PP3V3_S5 and PP5V_S5? If nothing, check for a short, and feel U7200 to see if it gets hot


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