820-3476 No PPBUS No PP3V42

[Bouba148]

Hi team,
here are the last news regarding that board:
I removed the SMC and I had a nice 3.42V

Reballed another smc, installed it and I have again the same issue
PP3V42G3H at 2.5V and slowly increasing , but if I reheat the smc area it goes quickly to 3.4V
the board is pulling around 270 mA and R7020 burning hot.

I'm suspecting 2 things:
bad capacitor around the smc (C5002/3/7/8/9) or bad via ( trace in the layers of the board )

Please advise

 

[Bouba148]

removed C5002/3/7/8/9 still the same issue

 

[Bouba148]

I've let it plugged something like 10 -15 min, and now pp3v42 is 3.33V ( it went slowly from 2.5v to 3.33v and ppbus went slowly to 2V then decreased to 0.7V)
But now if I unplug it and replug it it goes straight to 3.33v which is a good thing but ppbus stays at 0.7V.

3.33V is it too low? it's only 0.09V under what pp3V42 should be:
I'm asking that because I would like to know if I continue troubleshooting pp3v42 or try to fix ppbus

 

[Bouba148]

I think i know why :
I've read in a post that someone put a wronfg SMC and had very low ppbus just like me.
I my case i've a 820-3787 SMC because I didn't have a 820-3476, I know tat it has to be the exact same board but justed tried in case of.......
Nothing to do except waiting to find a 3476 board.......

 

[2informaticos]

You need SMC from donor board, same model.
Do NOT waste time trying other SMC...
However, you should get 8.2V at PPBUS_G3H without SMC even.

 

[Bouba148]

didn't payed attention for ppbus without SMC....I'll try
as usuall gracias 2informaticos