Macbook Pro A1708 13'' 2017 Partial Short on PPBUS_G3H

[platinumsteel]

Hi guys i have a 820-00840-A that was water damaged in the wrong places with a shorted PPBUS_G3H drawing 120 milliamps at 1V on my PSU. I removed F7000 and it's partially shorted on the system side.Am scared to inject more than 1V volt . Can you guys help me determine if maybe the CPU was killed. There was some corrosion around the CPU Mosfets. I measured resistance on PPBUS_G3H to the large coils around the CPU and and am seeing 120 ohms on my multimeter. Attached 2 pictures of the corrosion around the CPU there.Any help will be greatly appreciated thanks

[mon2]

Re: Macbook Pro A1708 13'' 2017 Partial Short on PPBUS_G3H

Hi.

1) to check if the cpu is shorted, remove all power. Meter in lowest resistance mode. Check the resistance to ground on the cpu power rail. If you have a very low resistance then yes, cpu could be dead. Post the measurements.

2) the pics show damaged traces. Using boardview, you will have to locate where each trace belongs and the connection for each will need to be repaired with wire.

3) with the removed fuse and no power, meter in lowest resistance scale -> check the resistance to ground of the provider side of F7000 fuse. Then check the resistance to ground of the consumer side.

Post each resistance value.

4) with the fuse removed, what is the voltage of the f7000 fuse provider side? Do you have a valid ppbus_g3h value when adapter is attached?

[platinumsteel]

Re: Macbook Pro A1708 13'' 2017 Partial Short on PPBUS_G3H

Ok mon2 thanks for the tips. Resistance to ground on the CPU Power Rails was 18.8 ohms.
After i removed F7000 for PPBUS_G3H the low resistance was on the system side. It measured 120 ohms.
I now just solved the issue. I looked back at the pictures i took before starting to work on the board. And between U7650 and Q7680 had a good bit of corrosion. I decided to remove Q7680 and a capacitor on it's input that looked weird. After i removed both off the board I checked for short.And short on PPBUS_G3H was gone with the wind.I am not sure if it was the weird looking cracked cap which was cracked underneath didn't notice it.Not sure if the capacitor was the issue or the Q7680 went bad.But i am changing both of them anyway.I have posted pictures i circled in red the mosfet and the cap that was bad on the line.I am not out of the woods yet.I am going to town to purchase a charger hopefully if all is well i will post back if successful. Hope this might be able to help anyone. To be honest this is the first USB Type C mac i am working on.I bought it on ebay for cheap and dead not powering on.Water damaged. Took the risk just so that i can up my game from the 2015 and prior models.And learn to repair these.It didn't come with a charger. So i used multimeter to check main rails for short. and cleaned up and replace corroded components. So not sure when i get the charger and power on what will happen.Thanks for the help mon2 as always.

[platinumsteel]

Re: Macbook Pro A1708 13'' 2017 Partial Short on PPBUS_G3H

ok guys just wanted to report back. And it is sort of confirmed the CPU must of gotten 12v to it instead of 3v. The mosfet Q7680 that had corrosion around it in the red circle in the picture has PPBUS_G3H on 1 pin and next to it the other pin is P3V3_S5 which goes tru the coil straight to the CPU. P3V3_S5 has a dead short 6.9 ohms .So i think i got my first 2017 donor board I guess. Thanks everyone learnt a good bit of new things.