Dead A1278 (Early 2011) Macbook Pro?

[Srjh]

Hi all. I fear the worst, but hopefully some here can be of assistance or at least find me closure.

I fixed what I thought was a simple problem with the battery in a friend's A1278 (820-2936-A). Dead battery, new battery installed. Everything was working fine while I reinstalled the OS (which was corrupted), but about an hour in, the logic board died completely.

While I have the G3Hot supplies and the charging circuitry works, the other rails appear dead. What's more, there appears to be a dead short from PP1V05_S0 to GND (multimeter reads 0.5 Ohm, the same as from ground to ground). Removing the relevant inductor, it seems the short is on the CPU side, not the power side.

Furthermore, looking at the logic board there does seem to be evidence of burned out pins near the CPU (see attached).

Is there hope for recovery? Is a dead CPU more likely to show up as effectively 0 Ohms, rather than a cap? Something else in the circuit I should be looking at?

Alternatively, as this wasn't my board, is there evidence of what happened? It can't be a coincidence that the laptop died at the exact time I was testing it after a repair, but if I messed up the repair I'll make it right, but if the board was on its way out and died on my watch it would be useful to know. If it's relevant, the hidden RAM module was loose when I disassembled it further, but I didn't think this could cause a short. Do logic boards commonly burn out like this?

This one's keeping me up at night... any help would be appreciated.

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

What is the resistance with cpu removed? Probably shorted MCP

[dellxps15]

Re: Dead A1278 (Early 2011) Macbook Pro?

Hi all. I fear the worst, but hopefully some here can be of assistance or at least find me closure.

I fixed what I thought was a simple problem with the battery in a friend's A1278 (820-2936-A). Dead battery, new battery installed. Everything was working fine while I reinstalled the OS (which was corrupted), but about an hour in, the logic board died completely.

While I have the G3Hot supplies and the charging circuitry works, the other rails appear dead. What's more, there appears to be a dead short from PP1V05_S0 to GND (multimeter reads 0.5 Ohm, the same as from ground to ground). Removing the relevant inductor, it seems the short is on the CPU side, not the power side.

Furthermore, looking at the logic board there does seem to be evidence of burned out pins near the CPU (see attached).

Is there hope for recovery? Is a dead CPU more likely to show up as effectively 0 Ohms, rather than a cap? Something else in the circuit I should be looking at?

Alternatively, as this wasn't my board, is there evidence of what happened? It can't be a coincidence that the laptop died at the exact time I was testing it after a repair, but if I messed up the repair I'll make it right, but if the board was on its way out and died on my watch it would be useful to know. If it's relevant, the hidden RAM module was loose when I disassembled it further, but I didn't think this could cause a short. Do logic boards commonly burn out like this?

This one's keeping me up at night... any help would be appreciated.

make a macro picture of the burned ic. probably it's not cpu problem but only ic that is fried.

did u make the wotk with bracialet in your arms ?

did u put macbook on what place to work on ?

wood + ipa or any other liquid solution = bad thing.

when testing macbook mainboard only i use good paper completely dried.

[Srjh]

Re: Dead A1278 (Early 2011) Macbook Pro?

Haven't got access to a BGA rework station to remove the CPU, and I didn't remove the logic board until after it died... it was on a dry cloth when I was testing the laptop with the backplate off.

Could be static as I wasn't wearing a strap, but I didn't touch the board directly until after the fault, the humidity here makes ESD much less of a concern, and I grounded myself before work to a PC chassis.

Not sure what you mean by "make a macro picture of the burned ic". It appears the burned ic is the CPU, but I'm not sure how to confirm that without removing it (which I don't have the equipment for).

[dellxps15]

Re: Dead A1278 (Early 2011) Macbook Pro?

cpu that goes wrong is almost impossible. make a detailed (macro) picture of the left center part.

[Srjh]

Re: Dead A1278 (Early 2011) Macbook Pro?

Thanks for your help. Unfortunately I haven't got a good microscope or something to give a detailed image and I still can't see any burned ICs to focus on, but I've attached a few files that might help.

And strangely enough the "burned" pins near the CPU are not PP1V05, but VCORE.

I know CPUs rarely fail, but I'm not sure what else it could be. My guess is something happened to dump a higher voltage into the rail. It could be a cap, but there are a lot of caps on that rail and I didn't think failed caps tested as a dead short.

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

PP1V05_S0 is the 1.05v rail to PCH/MCP (if I am looking at the proper schematic). I 've already told you, probably shorted PCH/MCP.

[BCConnectionLLC]

Re: Dead A1278 (Early 2011) Macbook Pro?

Umm the PCH and MCP should have low resistance. Why would you want a high resistance on something like that? It will cause excessive heat.

Shorts dont just happen unless a chip fails. From the looks of your photos it looks like the board saw some liquid. Thats why you have so many red pads plus the Diagnotic pads near the fan look corroded.

So do you have a green light on charger? You said it charges so I assume yes?

Does the board attempt to power on? Fan spin? Anything?

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

Umm the PCH and MCP should have low resistance. Why would you want a high resistance on something like that? It will cause excessive heat.

Shorts dont just happen unless a chip fails.

Of course and the resistance should be low but not 0 ohm. That means, from my long experience, shorted chipset, especially when the short is from that site. (except in very rare occasions when somebody before me messed up with vrams while reflowing and caused shorts to supply rails of gpu's)

[dj_ricoh]

Re: Dead A1278 (Early 2011) Macbook Pro?

check U3815 for voltage

[dellxps15]

Re: Dead A1278 (Early 2011) Macbook Pro?

when u say burned cpu pins, can u show them ? in all of your pictures i didnt either see a picture showing that cpu (opposite pcb side) burned pins.

[BCConnectionLLC]

Re: Dead A1278 (Early 2011) Macbook Pro?

Of course and the resistance should be low but not 0 ohm. That means, from my long experience, shorted chipset, especially when the short is from that site. (except in very rare occasions when somebody before me messed up with vrams while reflowing and caused shorts to supply rails of gpu's)

He said they are .5 Ohm resistance and from what Ive seen even on working boards thats not far off.
Could it be a PCH or MCP sure but I would check other things since this board has seen liquid, before I go straight to main BGA chip replacement.

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

Half an ohm is normal on bga power rail!!!!!!

[Srjh]

Re: Dead A1278 (Early 2011) Macbook Pro?

Thank you all for the help. I think I'm getting closer to resolving this...

PP1V05_S0 is the 1.05v rail to PCH/MCP (if I am looking at the proper schematic). I 've already told you, probably shorted PCH/MCP.

Yeah, I fear it's that or the CPU (the CPU also takes 1.05V for something - I/O perhaps?). I only say that because some of the worst damage seemed to be near the CPU.

Umm the PCH and MCP should have low resistance. Why would you want a high resistance on something like that? It will cause excessive heat.

Shorts dont just happen unless a chip fails. From the looks of your photos it looks like the board saw some liquid. Thats why you have so many red pads plus the Diagnotic pads near the fan look corroded.

So do you have a green light on charger? You said it charges so I assume yes?

Does the board attempt to power on? Fan spin? Anything?

It's a low resistance to ground. And not low as in a few ohms, low as in as close to zero as I can measure with my equipment. I wasn't 100% sure this was a fault (if there are non-linearities and the CPU draws a constant current even at low voltages it would cause this), but it appears so.

Water damage is one thing I'm considering, considering the corrosion (there's also some minor rusting on the backplate). It would give me peace of mind knowing I didn't cause that, but it's still sadly an unrecoverable laptop.

Yes, it's charging. Indeed, it goes from orange to green on the charger and the lights on the side indicate the charging side of things is working fully. More support for the fact that the fault is on the low voltage S0 rails of the logic board.

No fan spin, nothing.

Of course and the resistance should be low but not 0 ohm. That means, from my long experience, shorted chipset, especially when the short is from that site. (except in very rare occasions when somebody before me messed up with vrams while reflowing and caused shorts to supply rails of gpu's)

This is what I was thinking too. The other resistances are indeed quite low - the order of tens of ohms or so, which doesn't worry me, but the dead short does. Is a shorted chipset substantially more likely than a shorted CPU? That rail goes to both chips, and I was only thinking CPU because of the corroded pads near the Vcore capacitor.

check U3815 for voltage

No voltage there. The input is the shorted rail, so 0 in and 0 out.

when u say burned cpu pins, can u show them ? in all of your pictures i didnt either see a picture showing that cpu (opposite pcb side) burned pins.

I was thinking the ones near the CPU capacitor, but I might be wrong. There just seem to be a few that are bright red/orange rather than the shiny copper of a normal pad. But I'm not too experienced with this, it could be water damage corrosion as has been suggested.

I've attached the front side before I tried cleaning it. Nothing quite as obvious in terms of damaged pins, but there was an overall dirtiness that could be the dust or water damage.

He said they are .5 Ohm resistance and from what Ive seen even on working boards thats not far off.
Could it be a PCH or MCP sure but I would check other things since this board has seen liquid, before I go straight to main BGA chip replacement.

Realistically, it's closer to 0.1 ohms as I measure about 0.4 with my meter on the same pad (wiring, contact and internal resistances, etc.). If it's indeed the case that a resistance that low is normal, I'll continue diagnostics somewhere else, but I don't think it is.

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

Just to confirm it and if you have a lab supply inject voltage to the line to check what is getting hot. Use a thermocouple and do not exceed 1.05v, start at 0.5 amps and increase if necessary. Bga's usually need more current to start getting hot.

[Srjh]

Re: Dead A1278 (Early 2011) Macbook Pro?

No lab supply, unfortunately. I'm considering jury rigging one from a PC power supply with a standard power diode for overvoltage protection, but it's at the point where without the tools (PCH or CPU, it's out of my league) it's probably not worth it.

Might see if any tech nearby do BGA rework on Macbooks, but it's over four years old so probably not worth fixing.

[BCConnectionLLC]

Re: Dead A1278 (Early 2011) Macbook Pro?

No lab supply, unfortunately. I'm considering jury rigging one from a PC power supply with a standard power diode for overvoltage protection, but it's at the point where without the tools (PCH or CPU, it's out of my league) it's probably not worth it.

Might see if any tech nearby do BGA rework on Macbooks, but it's over four years old so probably not worth fixing.

2011 Macbook sells for around 400 to 500 dollars usually working

Also that board looks absolutely horrid. As soon as you opened it you should have been like uhh this needs to go into an Ultrasonic

[alas3376]

Re: Dead A1278 (Early 2011) Macbook Pro?

the solution is to reload eeprom firmware with minipro

[BCConnectionLLC]

Re: Dead A1278 (Early 2011) Macbook Pro?

the solution is to reload eeprom firmware with minipro

what?

[atsio]

Re: Dead A1278 (Early 2011) Macbook Pro?

the solution is to reload eeprom firmware with minipro

How is this going to help on a shorted board?