Apple MacBook A1398 820-00138-A missing 5V

[mferna14]

HI all, I am working on Apple MacBook A1398 logic board # 820-00138-A. The problem is that it does not turn on & no fan spin. Board is very clean & no sign of liquid spill. Upon checking the initial troubleshooting power rails, I found that its missing 5V (Absolute 0V on the Coil L7720, no pulsing at all, it's just 0V). 3.3V is PERFECT & across all points on the logic board. Checked the IC U7501 pin 4, this pin should have the ENABLE volts to turn on the 5v rail, & P5VS4_EN is missing. This signal generated from U8170 pin 4. PM_SLP_S5_L is also not present & ALL_SYS_PWRGD is missing too. Any tips what portion should I be checking next for the voltages. Thanks in advance.

[reformatt]

Re: Apple MacBook A1398 820-00138-A missing 5V

PM_SLP_S5 is right at the beginning of the power sequence, so any S4 or later rails are irrelevant. Troubleshoot with the sequence on LogiWiki

https://logi.wiki/index.php/G3_to_S3..._and_Broadwell

Check all coils for shorts, especially the 1.05V rail for the PCH.

[mferna14]

Re: Apple MacBook A1398 820-00138-A missing 5V

Thanks "reformatt", appreciate your reply. I did some deep troubleshooting, hopefully today might get some answers. Thanks for the tips & will surely go through this sequence.

[mferna14]

Re: Apple MacBook A1398 820-00138-A missing 5V

@reformatt, Sequencely trouble shooted & found that PP3V3_SUS is not present at all. Zero Volts out here. But PPDCIN_G3H 20V is perfect & present. Now I have to see from where is PP3V3_SUS generated, should be 3.3v on this rail. Any tips will be greatly apprecaited. Thanks

[reformatt]

Re: Apple MacBook A1398 820-00138-A missing 5V

PP3V3_SUS is switched by Q8020 and enabled by PM_SLP_SUS_L. Check the resistance of that rail to ground, and at L7630 as well. PM_SLP_SUS_L is derived from the PCH, and these have a tendency to die in the A1398.

[mferna14]

Re: Apple MacBook A1398 820-00138-A missing 5V

I was checking with a know good Logic Board & observed that PM_SLP_SUS_L on the defective one is missing. Q8002 pin 5 should be 3.3v in order to enble Q8020 & then PP3V3_SUS will be present, I think PCH is defective as this signal is directly coming from the PCH. Hopefully I have one to replace. First, I will just re-flow it, many of times it happens, & due to heat solder goes dry. Will let you know. Thanks

[reformatt]

Re: Apple MacBook A1398 820-00138-A missing 5V

Reflowing the PCH is a bit drastic, and would be my last avenue, not the first. Check the pre-requisites for PM_SLP_S5_L from the power seqeunce.

My main thought re the PCH is they are usually shorted and it saves time to rule it out.

[mferna14]

Re: Apple MacBook A1398 820-00138-A missing 5V

You are 100% RIGHT @reformatt!!! Before I could do any re-flow on any chip, what I did was I totally removed Q8020 & then checked PM_SLP_SUS_L on Q8002 pin 5. & guess what, it started to appear from nowhere??? Now I knew something was wrong between Q8002 pins 3 & 4 & Q8020 pin 3 & 4/7. Q8020 pin 4/7 was getting the PP3V3_S5 volts normally. So I knew 100% that this logic board has a defective Q8020 SIA413DJ. I got a donor for an older 820-2915-A board. Replaced it & all is working like charms & PP3V3_SUS came back. Once again thanks for all the help you offered & we together were able to revive the smiley Mac Logo once again. Pls. inform me once thing more, is the BIOS different on all these models? Because I put in this board's BIOS in another working logic board & it did not give any dsplay though it turned on. Even though I did change the serial # & in UEFI Tool program all was valid & then I did an Intel CleanMe, but this did not work on a 100% working logic board. Then I put back all the Originals ones in the respective boards & the logic board worked 100% fine. Did you ever see this???

[reformatt]

Re: Apple MacBook A1398 820-00138-A missing 5V

Good stuff. A rule I was taught years ago is that the likelihood of a component causing a fault is inversely proportional to the number of legs (or pads now) it has. The more legs/pads, the less likely it is to be the fault. Although BGA's have altered that a bit these days.

Have to use a donor BIOS from the same board number (i.e. another 820-00138). There are many variants of the A1398 so you can't just go off that. A board will still boot with a dirty ME, just albeit much slower.

[mferna14]

Re: Apple MacBook A1398 820-00138-A missing 5V

Do you know the variants of the A1398 that have to be replaced or changed?? might as well learn this too if you can pass on this knowledge. Thanks