820-01958-A / Model A2179 - Water Damage

zeydullak

Member
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 to USB-C Meter and it started to use 20v 0.12 amp. Amp started to go up and back to 0.12. Amp usage was going to 0.35 and then back to 0.12 and then up to 0.55 and back to 0.12, t9 0.70 and back to 0.12.

The CPU area got hot, and it felt like the mainboard booted. I connected the board to Apple Configurator to see if it is in DFU mode or not. It did not detect it. I assembled the board on a different working A2179 body and started charging and using an amp 2.6amp. The fan was silent, and the screen was black. I connected my iPhone to another USB-C port and the iPhone was taking charge from the Board.

But the board was making a ticking sound near L7400. I removed that coil and powered the board. The ticking noise is gone. I put in a new L7400 coil, but the ticking sound came back. I need your guidance to get the issue fixed.

Thank you again.

Let me know if you need anything else.

Regards
Zeyd
 

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2informaticos

Administrator
Staff member
Did you check diode mode to ground at L7400?
Stopping ticking noise doesn't necessarily mean L7400 is the culprit.
Once PCH is not powered, CPU also will not receive power.

Inspect for corrosion the audio board/flex and touch ID.
Compare diode mode readings on J6100 with good board.
 

zeydullak

Member
I put the L7400 chips back in place on good and customer boards. Did a diode mode to the ground, and they have similar ohm on both sides? 215-400 Ohms. CPU is getting warm, the board charges the iPhone, and also getting charged from the USB-C cable. Does it mean the CPU works fine?

Your comment: Inspect for corrosion the audio board/flex and touch ID. I used a working new audio board/flex and Touch ID from different computer. The result is the same.

I should do diode mode readings on all J6100. socket contacts? right? Thanks.
 

2informaticos

Administrator
Staff member
testing another audio board/flex will not discard a previous damage caused on the MLB.
That's the reason I told you to check in diode mode.
BTW, I'm very curious how can you get ohm readings in diode mode!
I saw several boards with SPKRAMP_RESET_L shorted to ground (inside T2), because of audio board corroded.
I suggested to check, because you've mentioned liquid spilled machine.

"CPU is getting warm, the board charges the iPhone, and also getting charged from the USB-C cable. Does it mean the CPU works fine?"
Don't make confusion between USB power and activity.
Check USB activity properly; already explained on the forum.
See at least if Caps Lock light reacts.
You can also test external video; w/ and w/o internal LCD connected.

Compare CPU core voltage with good board; allow 10-15s after power is applied.
 
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