820-00850 water damage fan work but dead

2informaticos

Administrator
Staff member
Not always (very) low ohm value is short.
Please, try to understand the difference.

CPU coils have very low values normally; however, not bellow 1 ohm.
Compare with similar CPU.

PPBUS_G3H looping???
 

2informaticos

Administrator
Staff member
Why do you bother with L7030???
It is not directly connected to PPBUS_G3H like in old boards.
If PPBUS_G3H is stable, there is no problem on U7000 area.
The problem is that SMC (inside T2) does NOT properly communicate with U7000.
 

2informaticos

Administrator
Staff member
You cannot replace SMC; it is part of T2 now.

I suppose board still has problems caused by corrosion.
This could be the reason is not listed on the other MacBook for DFU restore.
 

2informaticos

Administrator
Staff member
Could be just one corroded resistor, or accumulated crap under some BGA chip.
Is not an easy case; may be waste of time...
 

2informaticos

Administrator
Staff member
Do not check DC voltage on L7030.
It is not directly connected with PPBUS_G3H; didn't see Q7040?
And STOP to check Gate MOSFETs for voltage, is irrelevant.
 

yair37

Member
can it be U7650? i was take it from older board (old TPS51980 and the original is TPS51980A)
I was compare with good board.. before i was checking voltage there i want to know if is this to TPS are the same.
 

yair37

Member
dont think so..before fan works but the mac was dead and NO voltage at 5v rail and G3S 3v/5v rail at all, after replace U7560 the V was appear but with pulsing now change U7650 again(from old board (macbook 2015) but the same
 

2informaticos

Administrator
Staff member
The heat applied to the board changed the behaviour.
Something else reacted at heat.
There should be more things affected by corrosion.
Try heating BGA chips with quality flux and pass to board trough ultrasonic cleaner at the end.
 
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