MacBook Pro A2251 20V on USB-C, 0.00-0.01A current draw repair

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MacBook Pro A2251 20V on USB-C, 0.00-0.01A current draw repair
Device	MacBook Pro A2251
Affects part(s)	Motherboard
Needs equipment	multimeter, soldering iron, soldering station
Difficulty	3. Hard
Type	Micro-Soldering, Soldering

Problem description

Dealing with a MacBook (820-01949) showing 20V on USB-C with a current draw of 0.00-0.01A.

U7800 (Figure 1) -- No image yet. Help expand this page by uploading it

R8050 (Figure 2) -- No image yet. Help expand this page by uploading it

Symptoms

• MacBook displaying 20V on USB-C ammeter
• Current draw registering 0.00-0.01A

Solution

Identifying the problem

Check PMU (U7800) Input:

• Verify if PMU U7800 (Figure 1) is missing 12V input (PMU_VDD_HI) caused by R8050 (Figure 2) being blown or corroded.
• Check resistance on R8050; normal value should be around 877kΩ.
• Note: R8050 is part of a voltage divider circuit, so voltage will be lower on pin 2 of the resistor.

Solving the problem

Blown R8050 with Short to Ground:

• If R8050 is blown and there's a short to ground on pin 2, replace both U7800 and R8050.

Blown R8050 without Short to Ground:

• If R8050 is blown but no short to ground is found, replace R8050.