MacBook Pro Retina 820-00138 CPU chirping clicking

[ACS-Repair]

Hello All,
I received a return from a sale I made a couple of months ago on a 2015 A1398 MacBook Pro. The report from the customer is that the computer does not startup.
What I found is that if I start it from cold, it comes up fine. If I then shut it off, wait 10 seconds, then try to start it up, it doesn't start. What I do hear is a couple of chirps coming from what I believe to be the CPU. At this point, I get all the main rails (PPBUS, 3.3, 5.0, 1.36, 3.42, 1.51, 1.05), but not CPU VCORE. This is whether the board is in or out of the shell.
CPU resistance is 29 ohms. I don't see a short anywhere on the board so this has me stumped. The strange part about this is the chirping. anyone have experience with something like this?

[reformatt]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

Clicking etc will be switching noise from the inductors. I'd be casting an eye over the controller U7200 and the each CPU phases drivers U7310~U7330. Have the drivers been replaced? FDMF6808 drivers are a common issue with A1398 and AFAIK these were only made for Apple. Some have had mixed success with replacement FDMF6708/FDMF3030 chips.

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

Hi @reformatt. The VRMs were all changed to FDMF6708 when I first got the board last year. U7200 has not been changed but it looks clean. Not sure why this would happen but a good suggestion, thank you. The strange thing is that it comes up OK when cold and the VRMs don't run hotter than they should.

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

I replaced the FDMF6708 VRMs with FDMF3030 and the computer will now start up from cold every time. Unfortunately the computer will hang on reboot and shut down. I always have trouble putting these VRMs on so I'm going to take another shot at it.

[reformatt]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

Review this thread on Rossman. Mixed success with this repair.

I would probably consider a board pre-heater when replacing these due to the amount of heat involved in the vicinity of the CPU. Less heat required with your air then. I'd also put a thermal pad on the CPU too.

[reformatt]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

https://boards.rossmanngroup.com/thr...n-chips.48121/

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

Thank you for that info @reformatt. I haven't touched the board in a while but I plan to go back to it soon. In my case, the computer does startup and run with no issue until I restart or shut it down. I have done a few of these and all the others were fine. I'm sure this is me, and I'll let you know how it goes.

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

So this is a twist... I think the CPU VRMs are probably OK.
I can run MEMTEST or load a Linux USB flash drive, and both run OK without any trouble. I ran linux for almost 1/2 hour and was able to restart it again.
The reason this logic board failed is still mainly a mystery. What doesn't make sense is that the computer hangs only when I load MacOS. This is the case either from the internal SSD or an external flash drive. It hangs if I load MacOS in safe mode as well.

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

I decided to load a new EFI onto the computer. I used one available here with a clean ME and inserted my serial number. The computer still came up but now crashes soon after I login. On another post @piernov suggested that a PRAM reset and a MacOS install from the internet should be done. I completed the PRAM reset then loaded Yosemite from the internet. The process must have take 20-25 minutes and the computer was stable all during this time. Once the install was complete and the OS started to load, it once again crashed. Very strange...

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

More testing done today...
I can now load MacOS Yosemite or any other MacOS in safe mode. I read a post about boot looping from @mon2 and he suggested testing the SMBus. I compared the values between the pairs of each in diode mode and it looks like they match as they should.

[ACS-Repair]

Re: MacBook Pro Retina 820-00138 CPU chirping clicking

I decided to replace the 820-00138 logic board as this was going nowhere. the first board I received was a parts board with a shorted PCH. I replaced that one with an 820-00426, which works great.
I decided to do some resistance measurements between the two 820-00138 boards and found that the CPU resistance was 49 ohms on the shorted PCH board, but only 31 ohms on the board that would work only in safe mode. These are both Haswell i7 2.2GHz CPUs. The only thing that makes sense is that there is a partial short on the CPU of the board that crashes. I haven't been able to find any other reference to what the resistance should be.