A1932 no power

[madjid911]

Hello, I have a MacBook A1932 (820-01521-02) that won't start up at all. The trackpad clicks fine, but the keyboard is unresponsive and there is no display. There is no oxidation—the motherboard is very clean—and I haven't found any shorts. DFU mode works, and I was able to restart the T2 chip without issue (I don't want to restore it because the client needs their data).

Here are the measurements:

PPDCIN_G3H 19V80
PPBUS_HS_CPU 12V63
PP2V7_NAND 2V49
CHGR_VBAT 12V62 - 0V163 cycle
PPBUS_G3H 12V62
PP5V_S5_LDO 5V
PP3V3_G3H_RTC 3V27
PP3V3_UPC_XB_LDO 3V23
PP1V2_S3 1V19
PP3V3_G3H 3V31
PP5V_G3S 5V12
PP1V8_G3S 1V8
PP1v8_S5 1V8
PP3V3_AWAKE 3V3
PP3V3_S5 3V3
PP1V1_SLPS2R 1V1

R7061 R7062 R7063 are good

The bare motherboard's current draw is 0.20 A at 19.9 V.

The CHGR_VBAT / PPVBAT_G3H_CONN voltage drops to 0V163, returns to 12.62V, then repeatedly drops back down

Can you help me find the source of the problem, please?

Schematic & Board View :
https://www.badcaps.net/forum/docume...tic-board-view

[mon2]

Remove all power. Meter in lowest resistance scale.

Measure the resistance across capacitor C7020. Next, touch your meter probes together and this is your 0R ohms baseline on your meter.

Subtract this baseline value from the measured resistance across C7020. What is the value?

[madjid911]

C7020 : 2,7 ohms

[mon2]

This is ok.

Do you have a battery attached? Disconnect it if it is connected. Any difference on the power on cycle?

Measure the voltage to ground of:

SMBUS_3V3_BATT_SCL
SMBUS_3V3_BATT_SDA

at the battery connector.

[madjid911]

No change with the battery and audio ribbon cable disconnected.

SMBUS_3V3_BATT_SCL : 3V22 3V31
SMBUS_3V3_BATT_SDA : the same

another measure:
SWE010 3V27
PCH_PWRBTN_L 3V31

[mon2]

These are ok. The nand voltage may be lower than normal. What is the voltage of the power good signal for this rail? This is P2V7NAND_PGOOD.

[madjid911]

P2V7NAND_PGOOD : 2V46

[mon2]

PP2V7_NAND 2V49
P2V7NAND_PGOOD : 2V46

Can you confirm with another multimeter or test with fresh batteries?

On the A1932 MacBook Air logic board, a reading of 2.49 V on the PP2V7_NAND rail is critically low and indicates a fault. This power rail must measure exactly 2.7 V to supply the T2-managed NAND flash storage chips.
Because PP2V7_NAND is missing its full voltage, the SSD cannot initialize, preventing the Mac from turning on or booting.

Why the Rail is Low

• Short Circuit to Ground: A failing capacitor on the PP2V7_NAND line or a damaged NAND chip itself is pulling the voltage down.
• Failing SSD Power Controller: The buck regulator IC (U9000, typically ISL95870B) responsible for creating this rail is damaged or lacks proper feedback.
• Corrupted T2 Firmware: The T2 security chip may not be enabling the rail cleanly, requiring a DFU restore. [1]

How to Diagnose the Issue

1. Check for Shorts to Ground
   • Disconnect all power from the logic board.
   • Switch your multimeter to Diode Mode.
   • Place the red probe on ground and the black probe on a PP2V7_NAND testing point.
   • A reading close to 0.000 V indicates a dead short, usually caused by a bad capacitor. [1]
2. Inspect the Regulator Enable Signal
   • Measure NAND_P2V7_EN while power is applied.
   • This signal must be a clean 1.8 V logic high coming from the T2 chip to tell the buck regulator to turn on.
3. Check the Buck Regulator Inputs
   • Confirm the chip generating this rail is receiving its main input voltage, PP5V_G3S.

[madjid911]

Yes, I confirm that P2V7NAND_PGOOD is 2.46 V.

Does ISL95870 correspond to U8110 here? I don't have a U9000 on my board.

I measured 0V49 on U8110 PVCCIOS0_SREF. Is that normal?

U9060 :
P2V7SSD0_EN and P2V7NAND_EN : 1V8, R9060 it's ok O,1 hom, which manages P2V7NAND_EN ? it's U7800 ?
P2V7SSD0_FB : 0V79
P2V7SSD0_VOS : 2V46

Diode mode reading PP2V7_NAND : 0.327

[madjid911]

I replaced the CHIP U7800, but the result is the same: P2V7NAND_EN is still at 1.8V, P2V7NAND_PGOOD 2V49


.

[madjid911]

I removed L9060 and injected 2.7V into P2V7NAND to try to boot the MacBook and recover the data, but it didn't work; I replaced U9060, but the result is the same. Do you have any ideas?

[mon2]

What is the voltage to ground of ALL_SYS_PWRGD?

[mon2]

Attached power sequence.

[madjid911]

ALL_SYS_PWRGD 0v
mode diode 0.433

[mon2]

ALL_SYS_PWRGD 0v

Confirm the pull-up resistor on this open-drain circuit has a voltage. This is R8005 - test both sides of this pull-up resistor for a voltage.

Also, U1910 for the PP1V8_S5 rail.

[madjid911]

R8005 it's ok 1koms, PP1V8_S5 0V, I had it before, but I don't anymore since I replaced U7800 U9060 U8100

[mon2]

Confirm the resistance to ground of the missing PP1V8_S5 rail.

If the resistance is high, then the PP1V8_S5 rail is not shorted. [1]

The problem is either a missing enabling signal, a blown current sensing resistor, or a faulty PMIC (Power Management IC). Because this rail must turn on before the board can reach higher power states, its absence will freeze the boot sequence. [1]

Key Troubleshooting Steps

1. Verify Input Power: Check if the PMIC is receiving its primary input voltage on the PP3V3_G3H_RTC rail.
2. Measure the Enable Signal: Locate the PMIC (U7800). Check if it receives the enable signal for this specific 1.8V rail from the T2 chip.
3. Inspect Output Components: Check the series inductors and current-sense resistors directly connected to the output of the 1.8V buck regulator circuit for physical damage or cracks.
4. Test the PMIC Outputs: If the input power and enables are present but the rail measures 0V, the U7800 PMIC itself is likely defective and requires replacement.