A weird voltage drop on a 2018 MacBook Pro cost me an entire weekend

Honestly, I got this MacBook in with a dead board, no power at all. I found a short on the main rail, replaced the usual suspect IC, and boom, it powered on. I thought I was done in maybe two hours. Ngl, I closed it up, but then it would randomly shut off after about 15 minutes of running. I spent the next two days chasing a tiny voltage drop on a line I never even checked the first time. It was a filter cap that looked perfect but was failing under load. I must have reflowed a dozen parts before I found it. Has anyone else had a MacBook play hide and seek with a bad cap like that?

4 comments

4 Comments

hannah_craig1mo ago

Ugh, that sounds like a total nightmare. I read a forum post once where a guy had the same thing on an older model, but it was a tiny resistor that would only open up when the machine got to a certain temp. It took him forever to find because it tested fine cold. Those hidden load problems are the absolute worst kind of repair.

wendym871mo ago

My old car had a sensor that only failed on rainy Tuesdays, drove me nuts.

michael_williams1mo ago

Man, that hidden load-dependent failure is the worst. Makes you wonder how many "no fault found" boards just have a part that only acts up when it's warm.

juliaa6510d ago

Oh man, that's the worst kind of ghost in the machine. I read a whole article about how modern boards are so dense that parts can fail only under a very specific load or heat, just like @hannah_craig said. It makes testing a total guess sometimes. Your story about the filter cap is a perfect example. It probably tested fine with a meter but couldn't handle the real current. Those repairs feel more like luck than skill by the end.