For two years I’ve been storing a broken MacBook Pro in my closet that would no longer boot and was not worth a repair according to Apple. Wanting to charge the same amount of money it would cost to purchase a new mac for a replacment logic board, it effectively rendered the machine totaled. It seemed like a shame to simply throw away such a nice computer so I figured if I could find some time and the right schematics for the board, I might be able to save the machine from the dump.
I recently had some free time around the holidays and was able to dig up the schematics I needed to debug the problem. The Apple store did mention it was an issue with the logic board, so I at least had a starting point. Following an excellent YouTube series on the basics of logic board repair, I started probing around the voltage rails using a multimeter to check if all the power signals were good. Sure enough, after a couple of tests I was able to determine that one of the 5v power rails was not holding any voltage which most likey indicated a short on the board. I spent another hour checking various voltages on the board but was not really finding anything of value. My next move would be to inject some current into the power rail and check for “warm spots” indicating the location of the short, which I was not very excited to do. But just as I was planning to wrap up my effort, I examined the board one last time for damage and something peculiar caught my eye.
There appeared to be a component on the board without a top. When I examined it under a digital microscope, it certainly appeared to be some sort of damage to what looked like a capacitor. After looking at the schematic I was able to verify this was indeed a capacitor, part of the left speaker amplifier circuit. While this function may not be critical to the computer itself, if it was shorting a 5v rail then it could certainly be the reason the power status was not allowing the machine to boot. Using the multimeter in continuity mode, I verified the capacitor was indeed a short circuit. I was then able to order a replacement SMD capacitor from Mouser.
When it arrived, I fired up the SMD hot rework station and applied some flux to remove the old broken capacitor and replace it with the new one.
Unfortunately, during the process the hot rework station managed to blow one of the other ceramic capacitors completely off the board, never to be seen again. Luckily, I was able to reference the schematic to figure out the value and harvest one from another board I had laying around.
These components are incredibly small, I can understand why Apple is not interested in repairing these boards. To give you a sense of the scale, below is a picture of me holding one of the components with tweezers. The second and third photos were taken with a digital microscope zoomed in to around 1000x.
When I finally got the components seated back into place, I was able to check the voltage rail again and voilà, 5 volts. I reassembled the machine to power it on and heard that wonderful chime.
If you are interested in learning more about getting started with logic board repairs, be sure to check out this YouTube series on board repair basics.