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A2159 (820-01598) liquid damage, PP5V_G3S power cycles to 5V

F

Fyo

New member
Hi guys,

A2159 with very minor liquid damage, most likely water. Cleaned in the ultrasonic twice.
No components are visually damaged, badly corroded or burnt. There were smoke traces of 20V short on the USB pcb connector.
Before cleaning there was no PD negotiation (5V, 0.4A). After cleaning, 20V is back.

Power on USB-C input is power cycling between 0.038 and 0.089A (20V).
Using original 90W charger, also tested 65W original.

PPBUS_G3H 12.36V (slight dip to 12.26V every 3s)
PPDCIN_G3H 20.30V
PP20V_USBC_XA_VBUS 20.30V (depending on which is connected)
PP20V_USBC_XB_VBUS 20.30V ^
PP3V3_G3H_RTC 3.3V
PP3V3_G3H 3.3V (slight dip to 2.26V every 3s)
PP5V_G3S 0.02V jumps to 5V every 3 seconds or so, 21kOhm to gnd
Confirmed with scope it is exactly 3.5s, attempt to power PP5V_G3S on.

U7650 looks fine, but:
R7672 measures 0.945k (datasheet says 4.4k)
R7673 measures 0.945k (datasheet says 1.2k)
P5VG3S_CSP1 (pin 7) pulsing 5V, pin 8 same.

I have looked around various rails for shorts, but have yet to find anything suspicious.
 
2informaticos

2informaticos

Administrator
Staff member
Onboard readings for resistors value are always lower than nominal value; in case of K/M range.

Do you get steady 3V3_G3S?
What about 1V8_G3S?
Also check all AWAKE and SLPS2R voltages, if stable.
 
F

Fyo

New member
3V3_G3S, 1V8_G3S both power cycling (can barely see blip with multimeter, would have to test with scope), both kOhms to gnd.
PP3V3_AWAKE 3.25V shows for about 1s, then 0 for 2s. PP1V8_AWAKE, PP1V8_SLPS2R same, 1.8V for 1s. All mOhm to gnd.
 
2informaticos

2informaticos

Administrator
Staff member
So all power rails are pulsing.
Check for short on all big coils (from secondary supplies).
 
Last edited:
F

Fyo

New member
The only coils near short are the CPU coils at around 3.4ohm, PVCCEDRAM around 30ohm, PVCCIO around 70ohm.
 
F

Fyo

New member
PP1V2_S3, PP1V8_S3 nothing
PP1V_S0SW nothing
PP3V3_TBT_X_S0, PP3V3_S0SW_LCD nothing

PP5V_S0_BKLT_A, PP5V_S0_BKLT_D:

20220311-0001.png
 
2informaticos

2informaticos

Administrator
Staff member
Remove audio board and check for liquid sign on both sides.
Also inspect audio flex and both connectors.
 
F

Fyo

New member
I'm doing all this with the logic board out of the case. Nothing connected except USB ports.
 
2informaticos

2informaticos

Administrator
Staff member
And is dificult to check what I've asked you???
We need to know if T2 data lines might be affected for liquid spill on audio board.
 
F

Fyo

New member
Yeah, looks like very slight corrosion. The liquid sensor is red. I don't see anything else that looks bad/corroded.
 
2informaticos

2informaticos

Administrator
Staff member
Wait, you have 01598 board, not 01958; mea culpa, sorry.
PPBUS_G3H doesn't go to J6600, but 16V for Touch ID.
If your picture is for Touch ID connector, from audio board, very likely that corrosion damaged T2.
Just in case, check diode mode to ground on T2 data lines, related with Touch ID; all of them have "MESA" in the name.
Compare with similar working board, if available.
 
F

Fyo

New member
All of the MESA lines are mOhm, a few kOhm, but nothing to compare to.
I tried connecting the board to another Mac and interestingly it takes 4.91V and stable 0.45A (about 2W).
The only areas that get warm are under the can (U3900, northbridge?) and L7030 (CHGR_LX1), but nothing around CHGR_LX1 is shorted.
 
2informaticos

2informaticos

Administrator
Staff member
U3900 is the f***g T2.

Do not use ohm scale when you check data lines to ground; diode mode is the way for comparison.

So no pulsing power on other shell?
Check all power rails above mentioned.
 
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