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[SOLVED]820-3476 PPBUS_G3H = 4v

rob777

rob777

Member
Board had liquid damaged exclusively around U7100, cannot find evidence elsewhere.

Board gets orange and green lights on charger but not power on. PPBUS_G3H measures a fluctuating 3.9 - 4.1v, removed F7140 and PPVBAT_G3H_CHRG_REG measures the same fluctuation.

Changed U7100 numerous times, Q7130 and a bunch of resistors and caps that looked bad/measured out of spec.

U7100 readings:
Pin 19 - 5.5v
Pin 20 - 5.5v schematics say 5.1v here for pin 19 and 20
Pin 2 - 16.45v CHRG_DCIN
Pin 12 - 3.4v
Pin 3 - 4v
Pin 1 - 0v CHRG_AGATE at R7186 pin 1 measures 6.78v

I'm stuck, is the 5.5v at Pin 19/20 something to be concerned about as schematics say 5.1v
Why is R7186 got 6.78v at one side and not the other? It's a resistor which has been changed and measures 326k instead of 332k
What typically causes a voltage to fluctuate like that?

Thanks for the help
 
rob777

rob777

Member
ok found sense resistors for charger, checked charger BMON current sense R5429 is 300k and R5439 AMON sense is 45.3k both read 0v
 
rob777

rob777

Member
Bloody hell, just found R7125 was missing, not even there. I can't believe I missed it.. Put one on and I have 12.57v at F7140 now. Put back and we have fan spin and a Apple logo
 
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