Not turning on. Fan spinning. A1708 ECM3154 820-00840-A

[Manuel]

Hello there, I’m new on the forum and got this MacBook Pro a1708 EMC 3164 schematics.
The customer dropped it here saying that was liquid damage.
It’s Not turning on, the fan spinning when connected to the charger and it stops after a while.

I checked :
R1530 3V is ok. ( PP3V1_RTC )
R1401 3V is OK. ( PCH_INTRODER_L )
R1408 3V3 OK
R1407 3V3 OK
R1405 3V3 OK
L7690 3V3 OK
R1403 3V3 OK

Q7900:
PIN 6;7 AND 8 1V
PIN 5, 1V
PIN 2, 13V
PIN 4, 1V
PMIC_EN_P3V3S5 OK
PM_EN_P3V3S5G OK

I checked R766 ( P5VS4_EN )
It was supposed to be 5 according to the schematics, but it's present only 3.3V.
PM_EN_P1V8S3 3.3 present and it's weird
The charge also works one way. If I flip it won’t charge or doesn’t appear any signal
Can you help me, please? Any suggestion.

 

[2informaticos]

First of all, welcome to the forum!

"I checked R766 ( P5VS4_EN )
It was supposed to be 5 according to the schematics, but it's present only 3.3V."
Do NOT make wrong assumptions.
That is an enable signal, not the 5V power rail.

"PM_EN_P1V8S3 3.3 present and it's weird"
Again just an enable signal.

When you post voltage, use corresponding rail name, not a component!

"The charge also works one way. If I flip it won’t charge or doesn’t appear any signal"
That means a problem into USB-C areas.
Both ports have the same behavior?
Inspect for corrosion around CD3215 chips.

 

[Manuel]

Hi there, Thank you so much for the feedback. I inspected if any corrosion around that chip ( CD3215 CHIPS), and I didn't see any corrosion around it.
But I found a spot blocking the signal around the chip U7100 pin 41. The path was broken ( corroded ) as you can see in the pictures.
I am just delighted because I just recovered that path and the MacBook is working perfectly.
Thank you so much for the tip!

BDW, next time I will use rail name, not component. I didn't know that. I'm studying it yet.

So, for example, P5VS4_EN Shouln't measure with a multimeter, but oscilloscope right.

Yes, both ports had the same behavior.

Regards
Manuel

 

[2informaticos]

You don't need o-scope to check DC signals.
Only in case of fast pulse, where the multimeter cannot catch the peak pulse, but o-scope is fast enough.