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820 3209 Macbook Air wont turn on

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SoroS

Member
Hi,
I have a 820 3209 that wont turn on, have green light for 3 sec and then orange without battery connected
PPBUS_G3H - 8.39V
PPDCIN_G3H - 19.88 but fluctuating to 19.99 v
PP3V42_G3H - 3.4V and rapidly changing to 3.6 or 3.9 when I removed R7252 PP3V42_G3H stayed on 3.9v

And also the fan it seems to want to take of for a half of second and stop and again tries to spin and stop

The board is liquid damaged but before it came to me someone cleaned it with alcohol.
Have no ideea where to start looking.
Thanks
 
Sykulski

Sykulski

Member
Start with an ultrasonic cleaning of the board. You cannot trust another guys cleaning with alcohol and toothbrush.
 
larossmann

larossmann

Administrator
Staff member
r7402 would cause it to turn on and stay on but with no vcore. what is the resistance over c7050, and also what does the rtc clock chip area look like? both of these are common "easy" causes of quarter fan spin
 
S

SoroS

Member
QUOTE=aprendiz;n3715]Probably bad R7402 or trace........[/QUOTE]
R7402 is 90.9K

Louis
C7050 is 3.3 ohms and the rtc clock area looks ok

Sorry for the delay of response.
 
S

SoroS

Member
So,
based on Louis ideea I've checked resistance over C7050 and everything was ok, then I've measured R7021 and got 175K so I replaced it then R7022 showed me 4.10Mohms, at this point I assumed the U7000 is broken so I replaced it an now I have a good 8.4 V on PPBUS_G3H, PP3V42_G3H is stable at 3.9v but is a little bit high (dont know the reason)and the quarter fan spin is gone.

Dont know where to go from here

Edit: quarter fan spin still here but only for 5 sec, missed him first time.
 
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S

SoroS

Member
Yep, is back on,
I've tried to see if I have something on the EN1 and EN2 pins of U7201
On EN1 0V
On EN2 3.9
If I remove R7251 I get
EN1 5V
EN2 4V

What am I missing?
 
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