Macbook air 820-3437-b u3900 HoT

Hello all.
I have finally found what I believe to be the problem with this macbook.

this is not my first post regarding this repair.

The macbook does not boot.
main power rails are present.

u3900 gets hot fast after it has mag plugged in. But no boot and no power.

has anyone got any recommendation as to what I can do about this.
The board originally had water damage around r1661 the test point for r1661, r1663, r1669 were completely corroded.

R1663, r1662, r1664 have been removed.
but I dont see how they could cause u3900 to heat up so much.

any suggestions or advice is appreciated
thanks
 

2informaticos

Administrator
Staff member
"no boot and no power"
You mean the board doesn't even try to start?

"main power rails are present"
Which ones, if you told no power???

Camera (U3900) is only powered up in S0 state. via R5421.
Will stay U3900 cold if that resistor is removed?
It gets other voltages, but all in S0 state.
Please be clear in which sleep state stays your board.

However, U3900 is probably bad, it shouldn't go very hot nor even when is working.
You can rip it off and check if board starts.
 
Ok thanks.
the board shows no sign of life asides from having the power rails in state s5

I have put posts up about this board and gone through what rails are present.

I will remove that chip since it is not needed to run the machine. Thanks
 

2informaticos

Administrator
Staff member
U3900 is not needed to start the board.
But you need to replace it, once the board will start working properly; unless you don't need the camera...

BTW, we will not search other thread about the same board, to see which voltages are present, or not.
Keep one thread open only, so we have all the info "at hand"...
 
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