820--00840 CPU turns off after about a minute.

[bjf]

Liquid-Damaged board. Not terrible. I've only replaced some ugly or missing components but nothing changed before or after that. PPVCCCPU goes up to .95V and then dies after about 20 seconds. At that same time, PPVCCGT_S0G goes up to .69V. Not sure what's happening at that moment. This happens with nothing connected to the board. And ideas?

 

[bjf]

Measuring a good board, it switches down the voltage on the CPU to .69V right at about 20 seconds. The odd thing is that the bad board does the same thing but it's the PPVCCGT line that comes up to .69V, not the CPU.

 

[2informaticos]

Did you check USB activity?
All the CPU voltages go off?
Where was the spill?

 

[bjf]

No Title

PPVCCSA_S0G_R goes from 1V down to .85V. PPVCCPCH_S5G stays at 1V. PP1V_S5G_REG stays at around 1V.

I did check for activity and there's none.

The spill seems to have lightly hit a few places. The board was mostly cleaned before it got to me but I attached pictures of it before I cleaned it in the ultrasonic cleaner. There was a little corrosion above the CPU. Also below the backlight capacitors. And above U3100.

 

[2informaticos]

The new Apple board are very sensitive to liquid spill around LCD connector.
CPU video output dies many times, because of backlight overvoltage into video data lines.
In such case, usually board still works, having USB activity.
Your CPU could be damaged in other way, because of spill.

Use quality flux and reflow all BGA chips.
Heat them until 180 degrees, just to burn the crap.


"missing components"
Which ones?

 

[bjf]

C8503, and damaged C8504. And is that Celsius of Fahrenheit?

 

[2informaticos]

"C8503, and damaged C8504"
I bet backlight output damaged some data line.

"Celsius of Fahrenheit?"
Celsius, of course. I doubt you can burn something with 180 Fahrenheit degrees...

 

[bjf]

Any idea which data lines I should be looking at?

 

[2informaticos]

God knows which lines pass close to backlight line in a such high density board.
I wonder when Apple starts to solder chips one on top of other; Sandwich MacBook is what we miss now.
Liquid spill can affect including the internal copper layers...

 

[bjf]

I hear you, thanks, I'll start digging.