MacBook Air 13 Retina 2018 820-01521-A

[pascable]

Logic board 820-01521-A

Dear all

When I plug in the USB tester I have 5V but I don't go to 20V so no starting.
After examining the 5V on the logic board I have short circuits on C7675, C7676, C7677. I had the L8570 burned out, replaced it and still no start.
I removed the IC U7650 and I still have the short-circuited, it seems to me that my problem is with the 5V but where?
Can someone help me please.

Looking forward to friends.

Pascal

[mon2]

Re: MacBook Air 13 Retina 2018 820-01521-A

https://www.logi.wiki/index.php/CD3215_Bootup_Sequence

[pascable]

Re: MacBook Air 13 Retina 2018 820-01521-A

I will study this carefully and thank you very much.
If necessary I come back to the forum.
See you soon

[pascable]

Re: MacBook Air 13 Retina 2018 820-01521-A

Reading this sentence and looking at the BRD I realize that the U3200 of my 820-01521-A is the master and the U3100 the slave.
But I have dismantled the U32OO, I ask for confirmation that I must buy a U3200 and weld it before continuing?
https://store.rossmanngroup.com/inde...cd3215c00.html
-----
U3200 is the master while U3100 is the slave. The master is connected directly to the TBT ROM (U2890), while the slave (U3100) reads the TBT ROM firmware through the master (U3200). As a result, if the master (U3200) is not working properly, the slave (U3100) won't work either.

[piernov]

Re: MacBook Air 13 Retina 2018 820-01521-A

Why did you remove U3200? When you have an obvious problem like a short to ground on some power rail that should be fixed first.
In any case all USB-C controllers must be present for USB-PD negotiation to work.

[pascable]

Re: MacBook Air 13 Retina 2018 820-01521-A

Since a while ago, I reballing the U3200 and I resoldered it.
It's good, I have the power supply on the U3200 and the U3100 but it remains at 5V.
I agree there is a short to earth but where is it? Where to look for it?
To smile

PS Je n'avais vu que c'était piernov. Je suis français aussi et suis fan de vos travaux.

[slava318]

Re: MacBook Air 13 Retina 2018 820-01521-A

Thank you!