In this case study, we have a MacBook Pro 13" Retina 2019 A2159 model (board number 820-01598) which is not turning on and is showing no signs of life at all. The customer reported the device had previously suffered liquid damage, and had the logic board, along with other parts, replaced through Apple direct to resolve the issue. Roughly half a year later, the MacBook is dead again, with the customer saying nothing had been done to cause this issue.
Checking the MacBook with a USB C ammeter, this is pulling 5V and is power cycling; PPBUS_G3H is not stable and jumps up, then steadily falls before spiking up again. This behaviour usually indicates a short to ground on a power rail further up the boot sequence, and indicates the MacBook is trying to boot, but shuts off when it tries to power this shorted rail.
Disassembling the device, we could see no signs of liquid damage, and no signs of physical damage to the device itself, but we can see liquid staining on shields from previous damage.
In situations like this, the first thing we do is check the logic board under our thermal camera, which will point out any shorted components. In this case, we were in luck! The camera had pointed out a single capacitor (C7804) which was getting hot, and this was even heating up PP3V3_G3H_PMU_VDDMAIN connecting to the PMIC on the other side of the logic board, as you can see in the video below.
Inspecting this capacitor we can see the solder joints are very slightly burnt, although barely noticeable under a microscope. Replacing this resolves the issue and the MacBook is fixed! We are not sure what caused the problem in this case, but suspect it was either caused by a minor knock, or was a completely random failure.
If your MacBook Pro 13" A2159 is not turning on, it very likely has a problem with the logic board, like this customer's device. Feel free to book it for our free diagnostic service and we can find out what is causing the issue, and offer the relevant repair.
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