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[SOLVED]Macbook air 820-3476 can't power on from keyboard(not keyboard)

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roy.ruan

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hi Guys,
I'm having a 820-3476 that is having strange problem. everything of the machine works when it powers on EXCEPT it can't power on from keyboard.
it only can turn on when you connect the charger( the automatic turn on thing) . and yes I checked the keyboard, and tried with another known good one already. sure it's not the issue with the keyboard.

so far I checked
1.smc_on/off_l 3.4v ,when power button is pressed, it drops and back to 3.4,which should be normal
2. checked PM_PWRBTN_L, same story as smc_on/off_l

and like to mention, when the machine powers on, after you click shut down in the OS, it shuts down. then there is no way you can press power button to turn on again. only way to power on again is to disconnect the charger and battery, then reconnect the charger to let it power on automatically.

checked around the board, can't see spill or anything, just one single point with a bit green stuff that can tell what it is, but i did solder it to good condition again already,it's pin 1 on r1905, after that i checked the conductivity and it's good. so it probably has nothing to do with the problem.but still like to mention.

any advice would be appreciated!
 
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roy.ruan

New member
SMC_ADAPTER_EN is low, i think that's the cause?
when standby and no power on, the voltage would change from 1.0-1.7,it's changing when you mesure
when it's on, it's 0.2-0.5

It looks like it only goes to two place ,the CPU and the SMC. can you explain a bit what does the signal does and can we modify the circuit to make it work rather than replacing the SMC?
from what it says,it should be a signal to enable the adapter? but we have 3v42 and one wire is all good ,why we need that to "enable" the adapter?

thanks!
 
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roy.ruan

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Duke! you are the man!

lol I was just being an idiot, I actually know there is a difference between different W chargers long time ago, just didn't think it can be the charger since I WASN'T USING A CHARGER TO SUPPLY POWER.
I modified a cable from a mac charger and connect to the DC power supply unit to supply power so i know the AMP it's running to determine issue.
great stuffs for fixing liquid spill and no video boards.. it works with all voltage below 16.5(a1278,all airs)...i just didn't realize for this model of air, even it's 14.8, it can't power on when power button pressed(although it can still power on when connected!that's the tricky thing). and it works perfect even with buttons for a1278 ..

anyway, problem solved, original issue was just no power, probably fixed it in 20 mins already at that time, i was just playing with this stupid charger thing for quite a long time man.

thanks a lot DUKE,real appreciation here.
 
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