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820-3435-B turns off without magsafe

A

arash

Member
The battery is working, tested on different laptops, the OSX shows battery charging and can read the cycle count and so on, however, as soon as magsafe is disconnected the laptop turns off.
Any idea? I have also tested it with different batteries, same result.

The board looks very good, has no burnt part, it went through a light water damage.

Thanks.
 

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A

aprendiz

Moderator
check battery sense resistors, measure resistance between pin 17 and 18 from U7100, should have about 3 ohm........ if no, check R7151 (2.2 ohm) and R7152 (0 ohm) and traces....
 
A

arash

Member
Voltages are all fine(or close to it, i get 2.4v instead of 3 between 17 and 18 and 2.4 on r7151). any other ideas?
 
A

arash

Member
Sorry i miss-typed ohm, time to go home and sleep!
The water damage was very light, it was around the LVDS and after a ultrasonic bath the board looked very clean. the laptop would even turn on before cleaning and had the same error.
 
A

arash

Member
Yes, you can read all the information related to the battery and it does charge and it's voltage does go up.
 
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A

arash

Member
An interesting development, Q7155 has 7,9v on 1,2,3 instead of 8,35v that it receives on 5 and it has 7v on pin 4(CHGR_BGATE) instead of 1v that i get on a working board.

I have replaced Q7155 and U7100 and get the same results.
 
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A

arash

Member
C7150 (17,18) 2,5ohm(on working and also on non-working boards) and C7120(27,28) is 19,9ohm on both working and non-working boards.
 
D

dukefawks

Administrator
I really have no idea then. There is no reason this shouldn't work. If you power on with AC+BATT and then remove AC it shuts down? The system should remain under power through the diode in Q7155 even if Q7155 is not switched on.
 
A

arash

Member
Yes it does turn off as soon as you unplug, Weirdly Q7155 has a lower voltage on the other side of diode than it receives, on the working board i have 8.35v on pin 5 and exact same 8.35 on pins 1, 2 and 3. on the broken board its 7.9v on 1,2,3, instead of 8.35.
also on pin 4 i get 1v on the working board and 7v on the broken one.
 
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