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

[kevinklinkmuller]

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
u7501

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

Thanks!

 

[JohnB8812]

If PP5v_S5 is pulsing, it could very well be from a poorly soldered or bad TPS51980.

 

[2informaticos]

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

 

[2informaticos]

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.

 

[kevinklinkmuller]

is SMC bypass where i have to run a wire to ground repeatedly? How do I do that? thanks!

 

[kevinklinkmuller]

ok, have tried smc bypass mode, doesn't work

 

[2informaticos]

Press power button, connect charger and maintain pressing 5-10s...

 

[kevinklinkmuller]

thank you,tried it on this one and nothing

 

[2informaticos]

"Check if SMC_RESET_L is stable."
???

Check for pulse at least on the coils...