A2179 - 820-01958 - Heavy Coffee Damage - 20V 0.05A->0A->0.05A Fluctuating PP5V_G3S

[it-solve]

Merry Xmas, Healthy and Prosperous New Year.


PPBUS_G3H ok
PP5V_G3S - 5V -> 0V -> 5V

T2 heats up and down.

Heavy corrosion around the Tpad/KBD board
Corrosion around: U31/3200, U3060, C6406/6415, R5410 area, U9060, Q7660/80, Q7065, Q7401, R7430

There are no shorts anywhere. U7800 Diode mode seems to match a functioning board

 

[2informaticos]

Something else affected by corrosion.
Possibly accumulated crap underneath BGA chips.

 

[it-solve]

I have reflowed the BGAs CD32s/U6400/U6860 which had liquid around. Is there other way to localise why PP5V_g3S is fluctuating without a short?

Or do I need to keep pulling these BGAs out and resoldering them back?

 

[2informaticos]

Do you note the pulse on 1V8/3V3_G3S too?

Try to force the board in DFU.

 

[it-solve]

Tried DFU with no luck, both with a jumper on SOC_FORCE_DFU and a spare keyboard

1.8_G3S Pulsing
3.3_G3S not Pulsing

Resoldered most MOSFETs and ICs that had liquid around. Reflowed U28/2900 too
Reballed CD32's. They had quite a crap accumulated underneath.

The last reflow BGA left is T2 but didn't have much liquid around. Mainly between T2 and U9060

PPDCIN_G3S - 20V
PPBUS_G3H - 12.6-12.3V slightly pulsing

Seems all PMIC voltages are pulsing with the same beat as PP5V_G3S

 

[it-solve]

Any suggestions? This is a data recovery case, The Customer is desperate.

 

[2informaticos]

Compare diode mode readings on (many-many) points with good board, or reference table...

 

[it-solve]

Went through majority of the test points mostly match, some doesn't but i dont have them marked as test points on the board view so cant confirm what they are for.
Looking around these corroded ones in C6415,C6406 area.

I do not have any short to the PPBUS_G3H there and chip is not shorting. Only suspicious part seemed to be SPKRAMP_INT_L which still measures 0.46Vdc in diode mode at R6400 test point, which aligns with a functioning board board. However, this trace leads to T2 and I am wondering if trace leads from the test point instead from the R4600 to the T2.


Can you remind me what the _L was in the trace name? Would this line needs to be hold low for normal operation?

 

[2informaticos]

The "_L" refers to an active low signal.
An interruption sent from speaker amp to T2 may not be desired.
However, I recommend to compare the signals with good board.
I think we already got mismatch with speaker amp reset from Apple.

 

[it-solve]

Active low being low when it needs to communicate (being active) and should not stay low most of the time?

I get on both boards' same readings for these
SPKRAMP_INT_L - 0.46Vdc
SPKRAMP_RESET_L - 0.43Vdc

To compare the signals I will need a scope, I have a signal analyzer but I doubt it will be a fit.

 

[2informaticos]

These ared DC signals, no need to use o-scope.