A1466 , 820-3437-B , Green Light , No Fan Spin

[bftiedt]

I have an A1644 , 820-3437-B board I have been working on. I'll admit , I am not the best at reading schematics , but am trying to learn so please bear with me lol.

Visual inspection of the board showed corrosion on R7564 and C7564 . After looking futher both traces coming from U7501 to R7564 and C7564 were burnt in 2. Repaired both traces. I have short to ground on both 5v and 3.3v lines so I did remove U7501 to see if it may be the cause of the short but it's still present with it removed.
Below are my power rail measurements.

I'm not really sure where to go from here so hoping someone could point me in the right direction.

PPBUS_G3H 8.6v
PPBUS_S5_HS_COMPUTING_ISNS 8.6v
PPBUS_S5_HS_OTHER_ISNS 8.6v
PPDCIN_G3H_ISOL 16.7v
PPDCIN_G3H 16.7v
PP3V42_G3H 3.42v
PPVRTC_G3H 3.3v
PP5V_S5 cycles between 3.8-5v with u7501 attached / 1.2v with it removed - no short to ground
PP5V_S4RS3 0v - short to ground
PP5V_S0 0v - short to ground
PP3V3_S5 0v with u7501 attached / .6v with it removed -- short to grd

 

[2informaticos]

First of all, welcome to the forum!

Don't do again the same mistake.
NEVER ever apply power on the board without U7501 (or other similar chip) disconnected.
High-side MOSFETs remain with Gate floating (on air); a good reason to get burnt.

Bad connections on R/C7564 burnt Q7560.
Applying power without U7501 burnt Q7520 too.
Rebuild traces, and change the burnt components.

 

[bftiedt]

First of all, welcome to the forum!

Don't do again the same mistake.
NEVER ever apply power on the board without U7501 (or other similar chip) disconnected.
High-side MOSFETs remain with Gate floating (on air); a good reason to get burnt.

Bad connections on R/C7564 burnt Q7560.
Applying power without U7501 burnt Q7520 too.
Rebuild traces, and change the burnt components.

Thank you for the reply. Just so I make sure I'm hearing this right , replace both q7520and q7560? If so could you explain what led you to that? I'm trying to get a better understanding of how all this works together . Thanks

 

[2informaticos]

"could you explain what led you to that?
..........................
"Bad connections on R/C7564 burnt Q7560.
Applying power without U7501 burnt Q7520 too."

You may also need to replace U7501 (recommended).

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