This MacBook A2251 was so new that no schematics were available which allow us to map the logic board and find values of components.
The MacBook has been liquid damaged on the left hand size, it looks like a drink had run down the charger lead and into the USBc Socket where it then pooled on the logic board.
It has just come back from Apple who quoted for a very expensive logic board replacement.
All 4 x USBc Sockets were only at 5v which immediately points us towards a USBc charging issue. There are 4 x CD3217 Chips in these MacBooks which each control their own USBc Port. Great, so if one fails you have the redundancy or 3 x others you think? No, Apple designed this so that if one CD3217 chip has an issue none of them will work. They all communicate with each other on an I2C Data line.
As we can see, this one CD3217 is corroded with liquid. Usually capacitors corrode and short, resistors loose their connections and balls under the IC can become corroded and loose their contacts.
No Schematics are available, we have good experience of the CD3215 chips on the older MacBooks so we had to apply this knowledge to diagnose this logic board.
All corroded resistors and capacitors were removed and had their values manually read using our multimeter.
We could then clean up the corroded solder pads and fit new components to the correct value.
The CD3217 was floated to remove any corrosion which may have been underneath.
Looking much better. All of the data lines are now reconnected and the LDO voltages are now present.
The USB Charger is now switching to 20v which means that all of the CD3217 Chips are communicating with each other. The chip then requests more voltage from the charger and the MacBook can then turn on.
The Logic board is ultrasonically cleaned, dried in a PCB Oven. Brand New USBc Ports were fitted as the originals were badly corroded. The Logic board was then refitted into the customers MacBook.
The MacBook is pulling nearly 3Amps which means that the battery is charging and the MacBook is turning on.
All parts of the MacBook were then fully tested including WebCam, Sound, Keyboard etc.
We saved this customer hundreds of pounds on the repair of their MacBook. Fixing a logic board is also much better for the environment.