Fixing a Retina MacBook Pro that doesn't turn on

October 8, 2019

What's wrong with this MacBook?

This MacBook was sent to us for our MacBook Logic Board Repair Service in Austin because it didn't turn on.

How can we fix the issue?

Initial diagnosis

First, we start off by observing that it pulls 200mA from the charger. This indicates that it has either a short on PPBUS_G3H, or the CPU VCORE rail is not present. Next, we check the power rails required for the machine to turn on. PPBUS_G3H, PP5V_S5, PP5V_S4, and PP5V_S0 are all present. However, CPU VCore and ALL_SYS_PWRGD are not present.

Next, we check the schematic to see what creates ALL_SYS_PWRGD, as that is required before VCore can be present. We find all rails normal except PP1V35_S3, which instead of 1.35v is measuring at 2.7V. After checking the area around the chip responsible for that rail, we find that its pins are corroded.

Repairing the Board

This board came in with what we thought was no liquid damage. However, upon inspection of U7400, we found some corrosion around the pins. This chip is on the PP1v35_S3 rail, which is measuring the incorrect voltage. This means that this chip is likely the culprit here. After replacing the chip, we see that the machine now has a green light on the charger and has fanspin, and fanspin means the computer is now functional again.

I can't fix this myself. How do I get it fixed?

Rossmann Repair Group repairs MacBooks in New York City. Our MacBook Repair is not limited to Austin though, we accept mail-in repairs from virtually anywhere! Visit https://sendyourmacbook.com to start your MacBook repair.