820-3787: Not recognizing battery

[macRepairAmb]

I have this board that's not recognizing the battery but once i power on the computer with a magsafe, i can then run the system without the magsafe. On the display, it's not showing the battery.

I've replaced the SMC and U7100. I've also check check R7151/2, and R7121/2

 

[2informaticos]

Post voltage and diode mode to ground at SCL/SDA lines of battery bus.
Remove D7050, if present...

 

[piernov]

Check what it says about the battery under System Profiler.

 

[SMMRepair]

Try another battery first, of course.

 

[2informaticos]

Diode mode on these lines must be very similar, less than 1% difference.
Did you check that before changing SMC?

 

[macRepairAmb]

Unfortunately i didn't check the diode readings after i had got very low ohm resistance measurement on both lines. I proceeded to Pulled the smc to check for crap that may be underneath and then noticed resistance went up into the Kohms.

 

[2informaticos]

You should check these values without SMC, once out of board.

 

[macRepairAmb]

with SMC removed,

SMBUS_BATT_SCL - 0.65
SMBUS_BATT_SDA - 0.55

I checked resistors R5380 and 5381, both are good at 2K.

 

[2informaticos]

Too big difference; hope you checked both lines when board got cold.
Remove ISL6259 and check again.

 

[macRepairAmb]

You've saved the day again. So it appears the ISL6259 chip (which was a new chip and not from a donor board) that i had replaced earlier was also defective. Now both lines are reading 0.55 and the board now recognizes the battery.

Thanks again for the assist.