Released June 2012, Model A1278. Intel processor with Turbo Boost, Up to 512 MB DDR5 Video RAM

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Liquid damage - replacing INA214

I had an accident with my MacBook, someone spilled a tiny amount of liquid in it (just around the circuitry of high side current sense U5410). It has now been cleaned up with rubbing alcohol, but at the time of the spill the user kept using the machine. When I plug in the charger, the fan runs full speed (without having to press the power button), but no picture on either LCD or external monitor. Battery was completely drained (and will not charge). Tried with a fresh battery, but the computer won't start when pressing the power button. Also tried SMC and PRAM reset, no luck. No chime when powering.

I've identified a damaged component and maybe a trace. Pins 4 and 5 in the U5410 (INA214 current sense) is completely missing (burned up), so the INA214 must be replaced. Also, when testing for continuity between the pads of pin 4 and 5 it is open. I figured it should read 0.003 (R sense). Am I mistaken with the continuity?

Also, based on my description (fans full blast when charger inserted, dead with only battery), will replacing the INA214 and the trace fix the problem, or does it sound like some other components must be replaced too?

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Hello,

I may have misunderstood. Did you say you cleaned up the spilled liquid with rubbing alcohol? Please let me know soon.

Thanks,

Keegan

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Actually it dried up before I was give notice of the spill. Then I cleaned it with

CRC QD-Contact Cleaner (2-propanol) and acetone.

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Is this a liquid? Because using a liquid cleaner could and probably would cause more damage. Thats why I said I may have misunderstood.

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@okwestern ... you used acetone on a pcb...?

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Yes. I know it can be bad for some plastics, silkscreens and solder mask :)

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Are you measuring continuity on U5410 with the damaged component still there? If so, remove the component first, then check continuity, since it could be bringing these pins to ground. I haven't got a working board in front of me at the moment, but the donor board had an open line between these pins too (I have taken loads of components from this though).

High side sensing can prevent it from booting, from what I have seen it can cause the mouse to lag if U5400/U5410 is bad. Replace U5410, run a wire for the damaged trace (if necessary) then check it out. I guess high side current sensing could prevent it from booting from battery, but I'm not entirely sure to be honest, so it's best to replace it first.

It's an easy job, good luck! If the component has a marking on it, make sure the new one is in the same orientation as the original as well!

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Thanks for the quick answer. The INA214 is still in place, but both pin 4 and 5 is completely burned off the chip, so I doubt there would be a short to ground. If by any chance 4 and/or 5 is shorted to ground, it would still give continuity between 4 and 5, but now also to ground. I also measure no continuity between any of the pins of INA214 to ground, except GND pin 2. I suspect trace between 4 and/or 5 to Rsense is burned off. I will replace it once I can borrow a hot air gun.

Furthermore, there is no continuity between +VCC of INA214 pin 3 and MX25L6406E (BIOS?) pin 8. I don't have schematics for my particular MacBook and the MX25L6406E is missing in my schematics, so I'm not sure if they are on the same power rail, but I strongly suspect it. Should give continuity.

I also see there are two versions of INA214; INA214BIDCKT and INA214BIDCKT. Input Bias Current 35uA (A-version) vs 28uA (B-version). Would this have any significant affect on the battery charging, and which should I choose?

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Checked a 2nd dead board (with the component still present) and get continuity between pin 4 and 5, so you should be good.

Not sure what MX25L6406E is, get a board view program and file for your board, along with the schematic, to find out which component this is and whether it should have continuity. The bios doesn't have a path to this component (PP3V3_S0 is power for U5410, bios uses PP3V3_SUS).

Not sure with the last question, I just pull the components from dead boards since it's easier and quicker. I would pick the 35uA component, both should work fine, I am not an engineer though, so I wouldn't be 100% sure.

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Update: I replaced U5410 (INA214). Trace from pin 4 and 5 was burned off the PCB so I had to create new traces. Hooked pin 4 of U5410 to pin 1 of C3890 and pin 5 of U5410 to pin 1 to C7272. Correct me if I'm wrong(?).

After this, when pressing power the fan turns on. Fan starts out slow, but increases steadily until full speed after approx. 15 sec. It does not power up, just fans are running. Have to manually turn off the computer (holding down power button for 5 sec). Plugging in AC charger turns on the fan immediately without pressing power button. Pressing and holding power button turn the fan off again.

Measuring 7.16V over C3890. Should be 12.8V.

Measuring 12.2V over C7272. Should be 12.8V. So OK.

Any ideas?

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No, C3890 is for the T29 boost circuit, you should not be running that there. You just need to run U5410 pin 4 to pin 2/4 R5410 and U5410 pin 5 to pin 1/3 of R5410.

Pin 4 and 5 use the signal ISNS_HS_OTHER_P and ISNS_HS_OTHER_N. The Thunderbolt circuit does not use this signal.

Check page 50 of the schematic to see the U5410 circuit

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I changed to U5410 pin4 to R5410 pin 2/4 and U5410 pin5 to R5410 pin 1/3. It did not solve it. I am only getting only 2.5V over C3890. Should be 12.8V.

But ISNS_HS_OTHER_P is on the same trace as PPVIN_S5_HS_OTHER_ISNS_R, which also is on the same trace as PPVIN_SW_T29BST (amongst others, see page 8 of 109, in document 051-9058)?

I figured all of these rails just have different aliases, to ensure components like capacitors etc are placed near their associated circuits.

Or am I wrong about these rails?

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