820-00165-A,PPBUS_G3H sometimes 3v sometimes 8.53v,PP5V_S4 rail not present

[phist1987]

Merry Christmas to all

i have a unit of 820-00165-A,magsafe light is on,ppbus_g3h usually get 3.++v only,but sometimes after plug in the charger for long time or try to plug out and plug in charger for several times,can get 8.54v

here the measurement that i get when the PPBUS_G3H is 8.54v

PPBUS_G3H - 8.53v
PPBUS_S5_HS_COMPUTING_ISNS - 8.53v
PPBUS_S5_HS_OTHER_ISNS - 8.54v
PPDCIN_G3H_ISOL - 16.58V
PPDCIN_G3H - 16.06v
PP3V42_G3H - 3.43v
PPVRTC_G3H - 3.321v
PP5V_S5 - 5.00v
PP5V_S4RS3 - 0.00v
PP5V_S0 - 0.00v
PP3V3_S5 - 3.321v
PP3V3_S4 - 1.6mv
PP3V3_SUS - 3.321v
PP3V3_S3 - 58.6mv
PP3V3_S0 - 56.5mv
PP3V3_S4SW_SNS - 35.7mv
SMC_BC_ACOK - 3.4V

so far have done nothing to the board yet.board all clean,no corrosion at all.look new.

 

[aprendiz]

Resistance between pins 17-18 and 27-28 from U7100???

 

[phist1987]

hi aprendiz
pin 27-28 = 20.1ohm
pin 17-18 = 3.6ohm

 

[dukefawks]

That seems fine. Does it power on with a charged battery? Check all power rails for shorts to GND, starting with PPBUS of course.