820-3476 green light, no boot. Weird 5V rail behaviour


New member
Have an 820-3476 with green light. I think it had liquid damage initially but someone else has already messed with the board so i can't really tell

It has green light. Have started going down the power rail list. everything looks normal and i've stopped at the 5v rails because they are acting strange. Evertime I measure it's a different number. Sometimes it's 0, sometimes it's 2.5 and sometimes it's 5. I don't see it change when i'm holding the probes on it but when i release the probes and put them back on it's a different number again.

The thing I see that has definitely been messed with is

Shall i keep going down the power rail list or am i on the right track?



Staff member
Post exact voltage for PPBUS_G3H.
Also post some voltages for U7501, pins 23, 13, 22, 29, 12, 21, 4.
Stable 3V42 power rail?


New member
PPbus is 12.58v

pin 23 is 12.58
pin 13 is pulsing between 0 and 2v
pin 22 is 3.3v
pin 29 is is sometimes 0, 2.5 and 5
pin 12 pulsing between 0 and 3.3
pin 21 pulsing between 0 and 3.4
pin 4 0v

3v42 is stable at 3.4v


Staff member
So SMC_PM_G2_EN is not stable; or SMC detects a problem and pull it down.
Try to start in SMC bypass mode first.
Check if SMC_RESET_L is stable.