820-3437 fan 5 sec and shutdown

raainxx

Member
Hi
i have this macbook air where i find a liquid spill on R7611,R7612 & C7615 on P1V05_S0_VREF, i change all this component but the problem is same, fan start 5 sec & shutdown
P1V05_S0_VREF fall 1,043V to 0V when the mac shutdown.
I don't find where P1V05_S0_VREF is generate, do you know?
thanks
 

smiba

New member
i have this macbook air where i find a liquid spill on R7611,R7612 & C7615 on P1V05_S0_VREF, i change all this component but the problem is same, fan start 5 sec & shutdown
P1V05_S0_VREF has at most likely nothing to do with the reason its shutting down. The system is simply going back into a earlier power stage (S5) so the voltage simply does not get generated anymore.

Issues like this can be a pain in the butt.
How does the U6100 area look like (No corrosion)?

I feel like duke might know better on how to solve this
 
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raainxx

Member
ok thanks.
I look near the smc no corrosion, i resolder U6100 nothing better.
PP3V3_SUS=3,34V
I try with a new magsafe board and new cable 820-1722, same issue.
all the board seems clean
 

raainxx

Member
I check tomorow for the Vcore but no shutdown and stay off, but when i short power pad, he start again.
 

raainxx

Member
ALL_SYS_PWRGD climb to 3,34 and fall at 0V.
i disconnect keyboard, only magsafe board with cable left board and power adapter.
 

raainxx

Member
I inspect all the board under microscope, i put the board in ultrasound cleaner, the board is clean, no corrosion on the board.
i check with scope the signal Y1905 ok i have SYSCLK_CLK25M_X2 at 25mhz but nothing in output of U1900, all PP3V42_G3H=PP3V3_S5=PP3V3_S5RS3RS0_SYSCLKGEN=3,34V during my board is ON.
is it U1900 bad?
thanks
 

dukefawks

Administrator
U1900 is fine as the only output needed to work is 32kHz on pin 12. Without that the board would not even power on.

Does it stay on for 5 seconds then off and then repeat forever?
 

raainxx

Member
i have in fact the clock in pin 12 32Khz and always on but the board start and shutdown.
i can't find where is the problem?
 
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