820-02918 A2992 No Power Repair – SN2012024 USB-C Controller and Digital Mic Fault

Fault Description

This 14-inch MacBook Pro 2024 with logic board 820-02918 came in with water damage and no power.

Initial USB-C meter readings were:

USB-C port 1: 5V / 0.4A stable
USB-C port 2: 5V / 0.23A repeat rebooting

The board was not completely dead because PPBUS_G3H was present at 12V, but the MacBook still could not complete a normal startup.

This meant the charger input and main power rail were partly alive, but one of the USB-C controller support circuits was still pulling the board into an abnormal state.

Initial Symptom

The two USB-C ports behaved differently.

Port 1: 5V / 0.4A stable
Port 2: 5V / 0.23A repeat rebooting

This difference was important. One side was drawing stable current but not moving forward, while the other side was repeatedly trying to start and falling back.

Because PPBUS_G3H = 12V, the main power path was not missing completely. That changed the diagnosis direction. Instead of starting from a totally dead PPBUS fault, the focus moved to USB-C controller support rails and local shorts around the affected controller area.

Measurements Table

Test Point / Observation	Reading	Result
USB-C port 1	5V / 0.4A stable	Abnormal
USB-C port 2	5V / 0.23A repeat rebooting	Abnormal
PPBUS_G3H	12V	Present
CF508 pin 1 diode mode	0.003	Shorted
After CF508 removed	0.472	Short cleared
Port 1 after CF508 removal	5V / 0.4A stable	Still abnormal
Donor SN2012024 transferred	Same board position	Boot restored
JR940 pin 3 / PP1V8_DMIC	0V	Mic rail missing
LR940	Open	Fault found
PP1V8_DMIC after LR940 replacement	0.9V	Still dragged low
Final repair	Mic flex replaced	Fully fixed

Why CF508 Was Checked First

The board had water damage near the USB-C controller area. With one port stuck at 5V / 0.4A stable and the other port repeat rebooting, the first step was to check the local USB-C support rails around the suspected controller.

At CF508 pin 1, the diode-mode reading was:

0.003

That is effectively a short to ground.

After removing CF508, the diode-mode reading became:

0.472

That confirmed CF508 or the local circuit around it was involved in the short. However, removing the short did not fully restore normal USB-C behaviour:

USB-C port 1 still 5V / 0.4A stable

So the repair had moved past the obvious short, but the controller circuit itself still was not working correctly.

Why the SN2012024 Chip Was Transferred From the Same Position

The next suspect was the SN2012024 USB-C / USB-PD controller in the affected area. The schematic identifies SN2012024 as an ACE3 USBPD controller used in this board family.

For this type of chip, using a donor chip from the same board position is the safest approach because:

it has the same package and pinout;
it belongs to the same controller circuit position;
it avoids mixing a similar-looking chip from a different port or different option area;
it reduces the risk of using a different variant or configuration;
water damage may have damaged the original controller internally even after the external short was removed.

In this case, after transferring the SN2012024 from the same position on a donor board, the MacBook could boot into macOS.

That proved the no-power / no-boot fault was in the USB-C controller circuit, not just CF508.

Why the Microphone Fault Was Diagnosed Separately

After the MacBook booted, the remaining issue was:

Microphone not working

The microphone circuit was then checked at JR940 pin 3:

PP1V8_DMIC = 0V

The schematic includes the Digital Mic Flex Connector area with JR940 and LR940, which matches this diagnosis path.

The next component in the rail path was LR940, which was found open. After replacing LR940, the rail came up only to:

PP1V8_DMIC = 0.9V

Since this rail should not be dragged down like that, the microphone load side was still suspicious. The likely explanation was that the digital microphone assembly was partially shorted or leaking, pulling the rail down.

After replacing the microphone flex, the MacBook became fully functional.

Circuit Logic

This repair had two separate stages.

Stage 1: No power / no boot

Water damage near USB-C controller area
↓
Port 1 = 5V / 0.4A stable
Port 2 = 5V / 0.23A repeat rebooting
↓
PPBUS_G3H = 12V present
↓
CF508 pin 1 diode mode = 0.003 shorted
↓
CF508 removed, diode mode improves to 0.472
↓
USB-C behaviour still abnormal
↓
SN2012024 controller suspected
↓
Donor SN2012024 from same position transferred
↓
Mac boots to macOS

Stage 2: Microphone fault after boot

Mac boots but microphone does not work
↓
JR940 pin 3 / PP1V8_DMIC = 0V
↓
LR940 found open
↓
LR940 replaced
↓
PP1V8_DMIC only rises to 0.9V
↓
Microphone flex suspected partially shorted
↓
Mic flex replaced
↓
Mac fully functional

The important point is that the first repair restored boot, but the job was not complete until the remaining functional fault was tested and fixed.

Repair Timeline

Step	Result
Customer reported water damage and no power	Confirmed
Tested USB-C port 1	5V / 0.4A stable
Tested USB-C port 2	5V / 0.23A repeat rebooting
Checked PPBUS_G3H	12V present
Checked CF508 pin 1 diode mode	0.003, shorted to ground
Removed CF508	Diode mode improved to 0.472
Retested USB-C port 1	Still 5V / 0.4A stable
Donor board used	Same-position SN2012024 selected
Transferred SN2012024	Mac booted to macOS
Tested remaining issue	Microphone not working
Checked JR940 pin 3	PP1V8_DMIC = 0V
Checked LR940	Open
Replaced LR940	PP1V8_DMIC = 0.9V only
Suspected microphone flex	Partially shorted / leaking
Replaced microphone flex	Mac fully functional

Key Lesson

Water damage can cause more than one fault on the same MacBook.

In this case, the first fault stopped the MacBook from booting:

CF508 short + faulty SN2012024 USB-C controller

After the Mac booted, the second fault became visible:

Microphone not working
PP1V8_DMIC missing
LR940 open
Mic flex partially shorted

The key lesson is to continue testing after a successful boot. A water-damaged board may power on after the first repair, but related parts such as microphones, flexes, sensors or small power rails may still be damaged.

Final Fix

The final repair was:

confirmed water damage and no power;
tested both USB-C ports;
confirmed PPBUS_G3H was present at 12V;
found CF508 pin 1 shorted to ground;
removed CF508 and confirmed diode reading recovered;
transferred same-position SN2012024 from a donor board;
confirmed the MacBook booted to macOS;
found microphone not working;
measured PP1V8_DMIC = 0V at JR940 pin 3;
found LR940 open;
replaced LR940;
found PP1V8_DMIC still dragged low at 0.9V;
replaced the digital microphone flex;
confirmed the MacBook fully functional.

Case Summary

Item	Details
Device	MacBook Pro 14-inch 2024
Model	A2992 — please verify against A2992 before publishing
Logic board	820-02918
Customer fault	Water damage, no power
USB-C port 1	5V / 0.4A stable
USB-C port 2	5V / 0.23A repeat rebooting
PPBUS_G3H	12V
CF508 pin 1 diode mode	0.003 — shorted to ground
After removing CF508	0.472 — short removed
After CF508 removal	Port 1 still 5V / 0.4A stable
USB-C controller repair	SN2012024 transferred from donor board, same position
Result after controller repair	Mac booted to macOS
Remaining fault	Microphone not working
JR940 pin 3 / PP1V8_DMIC	0V
LR940	Open
After LR940 replacement	PP1V8_DMIC only 0.9V
Final fault	Digital mic partially shorted
Final repair	Replaced microphone flex
Final result	MacBook fully functional

If you are interested in the deeper diagnostic side of Mac repair, we have more real logic board fault cases documented here:
Mac Logic Board Repair Case Studies

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