820-00850 No USB Activity

No-Clean

Member
Board had some water damage near U7100, U8110, UB700
PPVCC_S0_CPU is 0V

U7100
PPVIN_S0_CPUVR_VIN 12.6V
PP5V_COREVR_VCC 5.1V
ALL_SYS_PWRGD_R 1.8V
 

No-Clean

Member
I could not think of a better name for the post, of course no CPU vcore voltage no USB activity.

L7702 0V
L8100 0.27V
L8102 0.63V
 

2informaticos

Administrator
Staff member
Do you really get ALL_SYS_PWRGD without correct voltage at L8100/02?
Please check on the output pin of the coils; where the filter cap is placed.
 

No-Clean

Member
Yes ALL_SYS_PWRGD present at 1.8V and both coils were measured at both ends, I just realized that PCH is heating up a little, mac sits at 20V 0.181A after a few seconds of connecting power.
 

No-Clean

Member
Are we talking about the same same board?
I do have ALL_SYS_PWRGD and L8100/02 voltages are too low, both those coils dont have caps at either end, both have a resitor R8118 and R8102 afther the coil, then after the resistor there are caps, I measured both ends a few times and get the same result.

Any other advice?
 

2informaticos

Administrator
Staff member
I didn't consider the Isense resistors, as they are 2-3 miliohm only.

Check U8100/10 power good signals; pins 20 & 9 respectivelly.
You should get 0V, as both coils are out of +/-20% of expected voltage.
 

2informaticos

Administrator
Staff member
Seems to have problems with U8100/10.
Post more voltages.
U8100, pins 12, 6, 15, 16, 17.
U8110, pins 13, 14, 3, 12.
 

No-Clean

Member
Upon further inspection I realized PP5V_G3S_CPU was only present in some part of the board, after making a jumper wire get connected to R8154 and now board boots up, your suggestions led me here, thanks a lot!
 
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