A2251 Apple MacBook Pro / water damage / 820-01949-A / 20.6v 0.05a

[zeydullak]

Hello,

We have a A2251 MacBook Pro that has water damage across the board, when connected to a port the board uses 5.09v and .28a and after a few seconds switches to 20.6v and 0.05a.

We have a measured some voltages on the board:

C6581/PPBUS_G3H -> 12.63v

C3504_VWR:1/PPBUS_G3H -> 12.32v

L6900/P3V3G3HRTC_PHASE1 -> 3.3v

R6900/PPVIN_G3H_P3V3G3HRTC_R -> 12.32v

C6908/PPVIN_G#H_P3V3G3HRTC_R -> 12.63v

F7000/PPBUS_G3H -> 12.63v

C3503_VXT/PPBUS_G3H -> 12.63v

Could you please advise us on what should be our next step and what the problem could be?

 

[2informaticos]

"C6581/PPBUS_G3H -> 12.63v
C3504_VWR:1/PPBUS_G3H -> 12.32v"
Different voltage on the same line???
You didn't mention any fluctuation on PPBUS_G3H...

Which areas have been affected by liquid?
Is the machine recognized in DFU mode?

 

[zeydullak]

Just double checked, C6581/PPBUS_G3H and C3504_VWR:1/PPBUS_G3H have the same voltages.

The machine is not recognized in DFU mode.

I have attached pictures for to see the damage, we washed with deionized water and it is now clean.

 

[2informaticos]

Check diode mode to ground on all big coils.
Don't forget L9080/580.

 

[zeydullak]

L3500_VWR -> 0v
L8100 -> 0v
L7400 -> 0v
L7230 -> 0v
L7220 -> 0v
L7210 -> 0v
L7660 -> 3.375v
L7600 -> 5.164v
L7030 -> 12.17v and then drops to 10.22
L8410 -> 0.013v
L3500_VXT -> 0v
L9080 -> 0.032v

 

[2informaticos]

"L9080 -> 0.032v"
Is this voltage reading?
I asked about diode mode...

 

[zeydullak]

sorry yes that was voltage reading, it say .4032 in diode mode and it beeps.

 

[zeydullak]

L3500_VWR ->.0230 with beep
L8100 -> .0494 with beep
L7400 ->.1118 with beep
L7230 -> .0216 with beep
L7220 -> .0216 with beep
L7210 -> .0216 with beep
L7660 -> .4365 with beep
L7600 -> .4257 with beep
L7030 ->.4951 with beep
L8410 -> .9504 with beep
L3500_VXT ->.1995 with beep

 

[2informaticos]

"L3500_VWR ->.0230"
Looks too low.
Should be similar with L3500_VXT.

 

[zeydullak]

What can be causing this issue and how can we fix it?

What should be our next step?

 

[2informaticos]

Remove U3500_VWR and check again in diode mode.
Do NOT apply power to the board without this chip!!!

 

[zeydullak]

L3500_VWR is .0236

 

[2informaticos]

So is not U3500_VWR the culprit.
Something else connected there pulls-down the reading.
Possibly one of U3100_R/W.
U5770 is also connected there, as few capacitors too.

 

[zeydullak]

Should we inject voltage to try detect the culprit?

 

[2informaticos]

You will probably don't heat anything; unless some chip enters in thermal avalanche.
However, a good thermal camera can help you to detect small differences.

 

[zeydullak]

So you mean we can inject it, but we need good thermal camera to detect slight temperature fluctuations?

 

[2informaticos]

Yeah...

 

[zeydullak]

I soldered a small wire to L3500_VWR and injected 1 volt but it did not use any amps.

 

[2informaticos]

1V is too low.
Even with 5V you may need to wait few minutes until detect something.
Do not go over 6V anyway...