Macbook Pro A1708 820-00840 20v 0a

[andersonamr]

Hi guys, let's start the journey....

Costumer brought in this Macbook Pro 1708 Non-Touchbar that was stuck at 20v 0a.
Measured F7000 and found PPBUS_G3H shorted to groud.
Pulled out F7000 to confirm the shorted line, it was indeed PPBUS_G3H.
Injected 1.8v, and found U7420 shorted by using a thermal camera.
U7420 out of the board, PPBUS_G3H comes back to live, giving 0.400 Diode Mode.
Replaced him with a U7420 from an A1706 board.
Until this moment, all good, went to testing phase

Now, when connecting the charger, with battery unplugged, i have 20v 0.80a, fan spins (but stops after 15s) but no boot at all.

Some readings:

PPBUS_G3H 13v
L7210/20 0.8v
L7410/20/30 0.68v

Any suggestions?

 

[2informaticos]

Probably dead CPU.
PPBUS_G3H speaks into iGPU core.
Also 2.8V injected by was a very bad idea; went to same iGPU core.
iGPU core should be 0V, until high load graphics is detected.

 

[andersonamr]

Injected 1.8v, also worth mentioning CPU gets mildly hot while cable connected.

Is there any chance to measure igpu?

 

[andersonamr]

On a side note, the power outlet should be over 75w to start this macbook?

 

[2informaticos]

61W is OK for this model.
Don't waste more time with it.

1.8V is also more than iGPU nominal voltage.
We discussed many-many times about how NOT to inject voltage on the forum.

However, the problem came from the burnt U7420.

 

[andersonamr]

Alright, i'll not waste more time, thanks buddy! Already told the costumer his board is dead forever.