Macbook A1708 / 820-00840-A / No boot

[GfilipeZ]

Hi,

With the Logic Board connected to the DC source, in the USB-C adapter it gives 19.75V and the current is mostly at zero volts and from time to time it peaks at 0.035A (for about a second).
I was able to find the source of the anomaly, that is, the PP1V_S5G rail is shorted.

I know it's not advisable to inject voltage, but that's what I did and with the help of an infrared camera I saw that the processor is the only component to heat up.
With this, is it correct to conclude that the source of the short is in the processor?

Best regards.

[mon2]

Re: Macbook A1708 / 820-00840-A / No boot

Ouch! I think so but wait on others to chime in.

What voltage did you inject?

We repaired the same logic board with the same current draw a few weeks ago - 8 hours later on the review (no microscope), found the issue was due to the ISL9239 not communicating over SMBUS. The ESD diodes caked up and caused a haul down on the SDA / SCL lines.

Do you have PPBUS_G3H ? We did not. Then replaced the ISL9239 and one of the mosfets. Neither helped. Then cried a bit and almost thought of start drinking but calmed down and logically traced all parts for the ISL.

In our case, the voltage on the SMBUS line - SCL I believe was too low. The SDA was @ 3v3. Removed the part and the board came back to life.

Arrow has the tiny tiny tiny parts for the ESD TVS function.

Fairly sure that Apple had a design weakness on this logic board where the display connector (backlight voltage to be exact) would short to the CPU rail causing this destructive event.

Review these:

https://boards.rossmanngroup.com/thr...shorted.52266/

[mon2]

Re: Macbook A1708 / 820-00840-A / No boot

Do review this excellent webpage:

https://repair.wiki/w/A1708_2016,_20...ar_MacBook_Pro

My post is the last one

[GfilipeZ]

Re: Macbook A1708 / 820-00840-A / No boot

Ouch! I think so but wait on others to chime in.

What voltage did you inject?

We repaired the same logic board with the same current draw a few weeks ago - 8 hours later on the review (no microscope), found the issue was due to the ISL9239 not communicating over SMBUS. The ESD diodes caked up and caused a haul down on the SDA / SCL lines.

Do you have PPBUS_G3H ? We did not. Then replaced the ISL9239 and one of the mosfets. Neither helped. Then cried a bit and almost thought of start drinking but calmed down and logically traced all parts for the ISL.

In our case, the voltage on the SMBUS line - SCL I believe was too low. The SDA was @ 3v3. Removed the part and the board came back to life.

Arrow has the tiny tiny tiny parts for the ESD TVS function.

Fairly sure that Apple had a design weakness on this logic board where the display connector (backlight voltage to be exact) would short to the CPU rail causing this destructive event.

Review these:

https://boards.rossmanngroup.com/thr...shorted.52266/

I injected 1.5V and 200mA. I started with 1V and 100mA, but it wasn't enough to see which component went into overload (heating) first.

First I detected that the voltage drop on L7030 was not stable at 13V. It was constantly varying between 0.4V and 1.15V.
Then I checked on the U7000, which also had various input and output voltages fluctuating.

As I couldn't find any reason for this behavior or short circuit, I went to check the behavior of the U1900. It was here that I found the PPVIOE_PCHCLK (2) line shorted (caused by the short in the PP1V_S5G voltage).

I'll review your post and the other link you shared.

As soon as possible I will give feedback.

Thank you very much.