Macbook Pro 15" A1398. Turn off randomy

[Eleways]

Hi guys.

I've aMacbook pro 15" model A1398 2014, logic board 820-3662-a

With the battery it turn off after few minutes. The fan run to max.
Same problem with battery and power supply connected.
If i remove the battery, it works normally.

I think about battery problem, so i've changed battery 2 times with different brand.

The computer find the battery, recharge the battery and work for some minutes before turn off.

I realized that the battery heats up a lot while it is charging.

Can you help me on this?

Thanks!

Luca

[piernov]

Re: Macbook Pro 15" A1398. Turn off randomy

Probably the usual problem with CPU VCore VRM ICs on these boards. Gotta replace them with new FDMF6708N from Mouser and hope for the best.

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

I have one of these 820-3662A with the same issues as Eleways.
I replaced the CPU FETs with FDMF6708 thinking that was the issue. I have used these FETs on a 820-00138 without any trouble. I have swapped in a newer top plate with battery, keyboard and trackpad. The computer works well without the battery connected for as long as I like. It will run only a couple of minutes on a fully charged battery, or on charger if the battery is connected. I replaced the 3v3_S3 FET because it had a hole in it. It didn't change anything and the 3v3_S3 is present. The computer will shut down if I put it into sleep mode. This is still a mystery but I'm looking into what is different between being on adapter or being on battery.

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

I've done a bit more digging and I've found that the PHASE-3 VRM is not as stable as the other two phases when on battery alone. Measuring on pin 1 of each coil, the output voltage of each is stable at 1.77v, but PHASE-3 will be stable for a while, then will randomly jump around as high as 1.87v, then float back to 1.77, and it will continue to do this while powered. This is not the case for the other phases, which are quite stable at 1.77v. On adapter only, PHASE-3 remains fairly stable but did float around for the first 15-20 seconds. This computer would crash like this before the VRM FETs were changed. Investigating U7200 now. I'm curious if anyone has experience like this.

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

At this point, I don't believe that there is any problem with the driver because I had a voltage before I removed the unstable FET. I've replaced that FET a few times now and can't get better than 1.10v out of the combined VRMs. The Phase 3 FET got very hot so I replaced it. The replacement now also gets very hot.
What I found on another board that I was successful with is that if one of the FETs is working the combined output is 0.7v. With 2 FETs working the output is 1.10v. With all 3 on my working board the output is 1.77v. The Phase 3 FET is hot, the Phase 2 FET is cold and the Phase 1 FET is warm. What I may do is replace the Phase 2 FET as it appears to be not contributing. I'm interested in what experience others have with changing these FETs.

[raajkumar]

Re: Macbook Pro 15" A1398. Turn off randomy

What is the CPU temperature ? Is it higher than Usual ?

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

I remember it getting warm, not hot, given the VCORE is only 1.1v. There is some heat though. Unfortunately with these all in parallel, I can't determine which one(s) are not working. I'm putting this down to the FETs not being seated properly. Some FDMF3030 FETs have arrived and I may look at replacing all of them again to see I get any further. I'm going to poke at this a little further first because I believe these FETs are good. I went through a similar situation with a 2015 A1398 and had similar results until I got all the FETs to sit down flat.

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

I've replaced the 3 FETS with the new FDMF3030 that arrived from Mouser the other day. The output voltage is now 1.35v and the PHASE 3 FET is still getting quite hot while the others are not. I don't understand this at a all. This should have been a simple swap. There is little in the schematic that would explain the heavier load. It looks like I need to spend some time looking more closely at the surrounding components.

[ejaboz]

Re: Macbook Pro 15" A1398. Turn off randomy

CPU Mosfets get the 6708N and replace all 3 with this one and you wont have a issue.

[ACS-Repair]

Re: Macbook Pro 15" A1398. Turn off randomy

Thanks ejaboz,
I believe that the FDMF6708 FETs have come to end of life and people are now recommending the FDMF3030. I may have an issue with the controller now so I'll need to look at it now.