820-00840-A PP3V3_S5G missing

[p99p]

hi Guys
I'm new here and could use a little help.
I have an 820-00840-A board and pp3v3_s5g is not present.
USB-C AmpMeter says 20V and pulsing 6 and 60 mA
The board has no water damage and no corrosion. All components that have to do with pp3v3_s5g look good but I have 0.5 ohms to ground sounds like a short for me I think this board has dead CPU
maybe one of you can help me out with this or can anyone confirm my thoughts of a bad CPU

 

[2informaticos]

First of all, welcome to the forum!

PP3V3_S5G is dedicated power rail for PCH.
0.5 ohm resistance to ground is low enough to use voltage injection method.
Start with 1V and slowly go high (no more than 4V), if needed.
Set first amp limit to lab PSU at max.

Do you get correct PPBUS_G3H and 3V3_S5 (L7690)?

 

[p99p]

PPBUS_G3H: 13.02V
PP3V3_S5: Is pulsing between 0 and 3.3V (maybe I've overlooked this before but I remember 3v3_s5 at L7690 was stable last time I measured it)

i inject 3.3V into PP3V3_s5G but I don't notice a change nothing gets hot at this time

 

[2informaticos]

Remove CPU heatsink first...

 

[p99p]

was removed before

 

[2informaticos]

"Start with 1V and slowly go high (no more than 4V), if needed.
Set first amp limit to lab PSU at max."
Injecting 3.3V directly can block PSU and it will not inject anything instead.
0.5 ohm will sink more than 6A from 3.3V!!!

 

[p99p]

first of all, thank you for your help and your time
Today I tried again inject voltage into 3v3_s5g and cpu was getting clearly hot hat 2,2v and 3,5A
i think that confirms my thought of a dead cpu ?

 

[2informaticos]

Exactly, 7.7W is high enough to heat it...