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820-00165 Battery Not recognized. Fully functional otherwise. PPBUS at 8.18V

bjf

bjf

Member
I've never had the low PPBUS voltage AND a functional SMC so I'm a little confused on this. Liquid spill. Pre-cleaning pics below. 3.4V on pin 2 of R5380 but 1.9V on pin 2 of R5381. Both pullup resistors are good though. Charging data lines tested for continuity. Known good test battery used. Any thoughts where to look on this?
 

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bjf

bjf

Member
So, heating the area of the pullup resistors below the SMC causes the voltage on R5381 to go back to 3.4V and PPBUS to go up to 8.6V. Once I plug a battery in, the voltage drops down to 1.9V again as the SMC begins to attempt to communicate with the battery. Not sure yet what that's telling me.
 
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bjf

bjf

Member
Ok, the back of the board (with the SMC) wasn't touched at all in the spill so I cleaned, and then just removed the battery connector. No change. Heat consistently gets the board to work though. What could I be heating that would change this? The SMC? A capacitor? Not sure how to track this down.
 
bjf

bjf

Member
Ok, I ran some flux under the SMC. I have consistent 8.6V and 3.4V on both data lines now. The board will now stay on with the battery plugged in but will always give a low battery warning. If I boot into the system it does not recognize the battery. I'm assuming this is still just an SMC issue but wanted to see if it might be something else. And if it is an SMC issue does the donor chip have to be from a 2016 version (with 8GB of RAM) or can I use an older 2015 version?
 
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A

aprendiz

Moderator
You should use an oscilloscope to check if there are pulses on both data lines, it is not enough just have 3.4V, if you replace SMC it should come from a 820-00165 board....
 
bjf

bjf

Member
Tried known good battery, and then 5 others because I felt like I was losing my mind. It says every battery is low though and will turn off after flashing the low battery symbol. They're all working in another Air. The voltage has been solid at 8.6V since I worked on the SMC. Both data lines are showing activity and are at 3.4V.
 
bjf

bjf

Member
No, not recognized. The only thing any battery will really do is run for about a minute or two after I unplug it. If I try to start it with just the battery it will give me the low battery symbol.
 
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