MacBook Air a1466 820-3437 no CPU VCOR

[ACS-Repair]

Hello,
I have an 820-3437 board that I've been working on for a while. I resolved a problem with the ALL_SYS_PWRGD and the board comes alive with all the normal S0 rails. There is no PPVCC_S0_CPU (actually 0.06v). The CPU doesn't appear to be shorted and there re no cracks on the surface.
Other threads speak of PTL_RESET_L, which in my case is 0v. This signal comes from the processor and I don't understand what could be missing to stop it.
I did an SMC reset and the LED on the adapter changed from orange to green to orange again which confirms it responded.
I would appreciate it if anyone has any experience with a problem like this.

[reassor]

Re: MacBook Air a1466 820-3437 no CPU VCOR

https://www.badcaps.net/forum/showthread.php?t=89867

[ACS-Repair]

Re: MacBook Air a1466 820-3437 no CPU VCOR

Thanks, I looked at this prior to posting. My case is different where I don't have the CPU VCORE.
About an hour after I posted I realized that the PTL_RESET_L should not be present if the CPU is not powered. I'll need to look elsewhere I think.

[ACS-Repair]

Re: MacBook Air a1466 820-3437 no CPU VCOR

I see that there is no CPU_VR_EN. Will require further investigation.

[ACS-Repair]

Re: MacBook Air a1466 820-3437 no CPU VCOR

Just an update to this... I finally got this board working, although I thought I never would.
In the end I found that CPU_VCCST_PWRGD was at 0.04v. The inputs on U1930 were correct and I could not understand why the signal was low. By accident I touched the probe while measuring pin 4 and the voltage jumped to 0.9v. This was a water damaged board so I decided to touch up the solder joints on R1931 an C1930. That solved the problem.
I now have the signals and the computer is up and running. Thanks to all of those that viewed and contributed.

[cruiser_]

Re: MacBook Air a1466 820-3437 no CPU VCOR

wow, @ACS-Repair, kudos for persistence! Does that not fell great when a 'goner' is brought back to life

[ACS-Repair]

Re: MacBook Air a1466 820-3437 no CPU VCOR

Yes, cruiser it does, although lately it doesn't alway start up to S0 state (a new problem). With the corrosion I'm going to go back and look at ALL_SYS_PWRGD at the point where it doesn't start. lucky for me this is a personal board and challenge. The learning experience has been great.

[ACS-Repair]

Re: MacBook Air a1466 820-3437 no CPU VCOR

Sorry @cruiser for not prefixing the '@' to your name.
I believe I was able to resolve the latest problem after discovering intermittant connectivity between R8165(2) and R8167(2). Everything looked clean but I went ahead and placed a jumper between these points. the computer has been running flawlessly for the last couple of days since doing this. It just shows that you need to check everything. Hopefully this experience can help someone.