820-3476 Board gets warm, no fan spinning, not booting up, Corrosion around U7501

[2informaticos]

So you have the sort to ground on L7520.
Only 2 ohms will allow you find the culprit injecting voltage there.
Be aware, do not overtake 5.5V and keep ampers below power lab supply limit.
Start with 2V, that should mean 2W dispation and increase until get a hot element.
4-5W should be easy detected with the finger...

Remember, do NOT power up the board before resolder U7501.

 

[SamMac]

should i remove L7520 before injecting the voltage or do it with the coil attached?

Many thanks for everything!

 

[2informaticos]

No matters L7520, just remove the burnt Q7520...

 

[2informaticos]

Did you put back U7501?

 

[SamMac]

Yeah I did I put a new U7501, Q7520, Q7630 and U7600.

Many thanks.

 

[2informaticos]

I hope you didn't power up the board without U7501 in any moment.
That is a good reason short U7560.

As you was able to eliminate the low values on 5V rail, you can do the same on 3.3V.
Be aware, this time PCH, or SMC could be burnt...