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Mid 2012 model, A1278 / 2.5 GHz i5 or 2.9 GHz i7 processor.

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Green Light & Nothing More

2012 A1278 MBP 13" 2.5GHz (820-3115) ?

I am getting only a green light on the charger, no fan spin, no boot,zero activity. I have swapped out multiple I/O boards and batteries and convinced the problem is not with them. so, It seems then that there is a problem with the board which has no visible damage or blown chips that I can see under the Michael. From what I understand G3H must be active as I have a green light, so where should I look to check next? I do have a new SMC chip laying around if that maybe needed. Calling on @oldturkey03 & @rashmikand95190 for some tips.

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I'm getting 3.46V on here (All 3 of them).

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C7040 13.35V / C7030/1 16.67V

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I cannot seem to flip the board in FlexBV....

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Here is my board (820-3115)

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I don't know where they are on this 2012, There are 3 near R36 chips, but not 4. :(

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Michael = Microscope🤦🏻‍♂️

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@livfe - If Michael was a Scotsman he wouldn't look kindly you looking under him!

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Sorry had to reply to this one. Hahaha! Oh my

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@dan0 One way to get a friendly 'Glasgow handshake' I guess :D

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@livfe Hahaha. I guess so! Won't be a nice smile I guess :P.

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@livfe I understand but you are chasing the wrong parts. You are looking for the MOSFETS like Q7055, Q7080, Q7085, Q7030 and Q7035 which are all part of your PBus Supply & Battery Charger circuit

BTW did you notice that your inductor L7030 looks like it got cooked :-) Sure looks like it's toast. That would mean you would not have the ~8.4V on F7040 and thus no power to PPBUS_G3H, which gives you a green light but nothing else ¯\_(ツ)_/¯

Replace the inductor L7030 (IHLP4040DZ) and check again :-)

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Brilliant detective work, we will update ASAP on this !

L7030 is just a bit rusty looking for sure but 13.35V reading..

F7040 (Small dot under the component 0.000 / Chip above 13.34V

Q7080 gives 15V top 4 connections, lower 4 0.000 :)

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@oldturkey03 We replaced the L7030 & the tech said everything else checks out OK, but still no fan spin here :(

He also noticed some corrosion in a few places so maybe to much to repair even if possible, but there is still hope.

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@livfe did you check PPBUS_G3H? F7040 is a fuse. Check for continuity as well. No power on the fuse means you are having issuse with your PBus Supply & Battery Charger circuit

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@oldturkey03 Not sure if the tech guy went over these things, We will go over it again ASAP.

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Green light usually confirms G3H is present. Next, check PPBUS_G3H and SMC_RESET_L to ensure the SMC is actually waking the board. Verify clock and power rails around the SMC before replacing it. Also inspect corrosion near the charger IC and power MOSFETs.

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@rashmikandhil Added image to question.

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If there is a green charger light then G3H is present. You can check S5 rails, SMC power/clock signals, and the power-on sequence. If those are missing, the SMC or its surrounding circuitry can be the problem.

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Everything is checking out with voltages, it is a difficult one this.

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