A2179 Watered

[Vonevoe]

The MacBook received liquid damage on the motherboard, causing damage to various chips. It's the 2020 model A2179 with motherboard 820-01958. Upon inspection, the CD3217 (U3100) was corroded but functional. I re-balled it to ensure its functionality. The C6962 chip was also corroded, so I replaced it. The SMC was also corroded in one corner of the chip. I desoldered it and re-balled it. The Q7880 chip was also corroded, so I re-did it. The U7650 chip was also corroded, so I desoldered and resoldered it on the motherboard.

The motherboard connected via USB-C reaches 19V on both ports with an amperage of 0.130A and a resistance of 140ohm.

The PP3V3_G3H_RTC is present with a voltage of 3.3V. The PPBUS_G3H is also present with a voltage of 12V.

My problem is that:

On the capacitors and resistors (C7030, R7030, R7040, C7040) around the U7000 chip, voltages fluctuate, ranging from 11V to 0.2V to 3V, and this repeats. These components have the power rail: CHGR_LX1, CHGR_BOOT1, CHGR_BOOT2, CHGR_LX2.

I replaced the U7000 chip thinking the problem was there, but the issue persists.

I checked the voltages of the U7000 chip:

• P_in = 20V
• Aux_det = 5.13V
• PPCHGR_VDDA = 5.17V
• PPCHGR_VDDP = 5.17V
• CHGR_EN_MVR = 5.17V
• CHGR_BMON = 0V
• CHGR_AMON = 0V

I also noticed that the coil (L7810) near the SMC chip has a voltage fluctuation from 0.8V to 0V.

If you have any ideas where the problem might be coming from, I suspect the SMC is damaged, but unfortunately, I don't have any chips in stock, so I'll have to order some. Thank you.

 

[2informaticos]

First, tell us what you name SMC there.
SMC functions are emmbeded into T2!

Check if T2 gets stable SLPS2R and AWAKE voltages.
BTW, post EXACT PPBUS_G3H voltage (12.3V?).

Test the board disconnecting audio flex.
Audio board gets damaged many times by liquid on this model.

 

[Vonevoe]

I refer to the SMC as the chip labeled U7800.


The voltages measured on the coils around the U7800 chip for the "SLPS2R" and "awake" power rails are all unstable. Here are their values:

• L7813: 1.8V to 0V
• L7814: 1.1V to 0V
• L7815: 1.1V to 0V
• L7806, L7807, L7808, L7809: 0.760V to 0V
• L7811: 0.830V to 0V
• L7812: 0.830V to 0V
• L7810: 0.801V to 0V
• C7905: 0.803V to 0V

 

[2informaticos]

U7800 is known as PMIC, or PMU, not SMC.

What about the other tests?

 

[Vonevoe]

Alright, I didn't know. Thanks for this information.

PPBUS_G3H: 12.3V

I performed all my tests without the audio flex connected.

Unfortunately, I'm not sure where to look now. I believe I have checked all the chips that were affected by oxidation.

Edit:
I noticed something abnormal on the thermal camera. The temperature of the T2 is pulsing at a regular rhythm.

 

[2informaticos]

T2 voltages are not stable; that's explain thermal image behavior.

Check U7800's LDOs; SYM 1 OF 4, page 63.

 

[Vonevoe]

PP3V3_G3H_PMU_VIN_RTC_R: fluctuates between 3.277V to 3.296V

PP3V3_G3H fluctuates between 2.2V and 3.3V

LDO_CORE: 1.5V

LDO0: 0.800V and drops to 0V

LDO1: 3V sometimes drops to 0V

LDO2: 1.2V sometimes drops to 0V

LDO3: 1.8V no drop

LDO_RTC: 1.505V no drop

After testing, all drops occur at the same time.

I assumed that it was the 3.3V dropping to 2.2V occasionally that was causing the issue, so I investigated further. Changing the U7650 fixed the problem.

Thank you.