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MacBook Air 2020 A2179 820-01958 - Water damage - clicking sound in the CPU area

S

stef4n

Member
Good evening,
I have a 820-01958 with water damage. Corrosion was especially present around Q7680 and Q7660. There was also corrosion around CC714 / CC715, CC716, CC717, CC7A0, CC8A1, R7686, R7666, CC760, CC761, CC786, CC787, C7681, CC789, CC788, C7660, C7060, CC784, CC785, R7070, R7071, D7070, CC796, Q7070, but not as bad as between Q7680 and Q7660.

I'm not familiar with the MacBook Air yet; and I'm even less familiar with the after 2015 boards. That's the first one I see. I did read the https://repair.wiki/w/A2179_2020_MacBook_Air, and the below thread:

820-01958-A / Model A2179 - Water Damage

Hi there. I have an Apple Macbook Air A2179 with water damage. It was not charging and was stuck on 5v. I removed the board, and there were corrosions on multiple spots I cleaned and resoldered using flux to make sure all disconnections connected back again. Then I connected the charging cable...
boards.rossmanngroup.com boards.rossmanngroup.com

1681341726772.jpegIMG_1813.jpg

Measurements taken in the corroded areas, which I've cleaned:
R7686 and R7666 reads 1.5 Ohms, seems okish.
R7070 and R7071 are okish too.

PPBUS_G3H: stable at 12.57V
Q7660: 12.57V on pin 2, 5.11V on pin 3 and 4, 41.9mV on pin 5, 5.08V on pin 6,7,8
Q7680: 12.58V on pin 2, 3.33V on pin 3 and 4, 3.3V pin 6, 7, 8, pin 5 83mV
L7400: 1.8V, diode mode obviously does not beep and resistance is around 187 Ohms.
L7230, L7220, L7210: 6.2mV

I ordered a USB-C ampmeter, I'm clueless regarding how much mAh/Volts it takes.

The MacBook does not boot, there is no chime, there is no sign of life and the fan does not spin. The CPU area gets warm, though.

The sound starts to be audible ~10 sec after I press on "On".

The other side of the board was perfectly clean, no corrosion.

The customer said the water came from the back of the MacBook AIr. Someone spilled a glass of water behind it.

Since the T2 chip is present on this model, I guess that if the macbook is unable to boot, data are lost? Data encryption keys being in the T2...would it be doable to unsolder both the T2 chip and the SSDs? Then what? Solder them back in another macbook ? Doesn't seem to be worth the troubles
 
2informaticos

2informaticos

Administrator
Staff member
Check R7665/85.
Replace C7669/89.

Do you get voltage at L7700 and L8100/50?

A2179 (similar to A1932) suffers a lot because of audio board corrosion.
Remove and inspect it, as audio flex too.
 
S

stef4n

Member
Good evening 2informaticos, thanks for your help!
I do have voltage on L7700, pin 1: 1.81V
I do have votage on L8100, pin 1: 1.09V, both side
On L8150, pin1: 2.64V, pin2: 0.606V, but, most of the time, it is 1.1V on both side. I would have expected 0.6V considering the boardview but I read 0.606 V only once.

On R7665 and R7685 I read 0.5 Ohm
Regarding C7669 and C7689, sorry sir but my multimeter shows 100 nF on both, which is in line with the schematics showing 0.1uF.
Unless the schematics must be considered as wrong, perhaps it is better to keep these 2caps in place.
 
2informaticos

2informaticos

Administrator
Staff member
I mentioned these resistors and caps to check, because of advanced corrosion.
Is better to have new/clean components in boost circuits.
If any fail soon, Q7660/80 wil burn.

Check U7100 and all surrounding components.
Be sure it gets power (41/42) and enable (48).
If all good there, CPU is probably dead.
 
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