(347) 552-2258 [email protected]

Macbook Pro 2019 820-01814 stuck at 5V USB-C

S

sekidata

Member
Board came with significant liquid damage around one USB-C connector and the NAND power circuitry around U9080. Found PPBUS_G3H shorted to ground, which I fixed by removing shorted C9073 (PPBUS_G3H_SSD0). Board then briefly produced 20V but is now stuck at 5V.

PPBUS_G3H: 0V diode mode 0.42V
PP3V3_G3H_T: 0V diode mode 0.43V
PP3V3_G3H_RTC_X: 0V diode mode 0.42V
PPDCIN_G3H_CHGR: 5.2V
CHGR_AUX_DET: 1.29V
CHGR_VDDA: 5.1V
CHGR_VDDP: 5.1V
The 3.3V and 1.8V LDOs are present on CD3215

On this board, PPBUS is generated before PP3V3, correct?
 
2informaticos

2informaticos

Administrator
Staff member
3V3_G3H_RTC comes from PPBUS_G3H as in any T2 board.
So you need to get PPBUS_G3H first.

I suspect more corrosion damage on USB-C area.
Do you get 1V1 LDO, when power corresponding port?

Be sure to use original 87/96W charger.
Check if board has activity with a good battery.
 
Last edited:
S

sekidata

Member
I do not get the 1V1 LDO on the plugged-in port. I only see 3V3 and 1V8 LDOs on each plugged-in port.

I checked the CC lines and there are no shorts to ground.

The battery is empty - waiting for a good original battery to arrive.
 
2informaticos

2informaticos

Administrator
Staff member
Check TBT ROMs and their traces.
You can try reflashing with known good dump.
Dont forget to make backup.
 
S

sekidata

Member
TBT ROMs U2890 and UB090 look fine. However, they are powered by two 3V3 LDO rails, which are not always present on this board. Shouldn't PP3V3_UPC_TA_LDO and PP3V3_UPC_XB_LDO be present no matter which USB-C port is plugged in? I only get 3V3 LDO on the one plugged-in port, not all four CD3215s.

Seems like the CD3215s are not talking to each other. What could that indicate?
 
S

sekidata

Member
Ok, so I need to figure out why U7000 is not producing PPBUS_G3H. What are the typical culprits on a T2 machine?
 
2informaticos

2informaticos

Administrator
Staff member
U7000 should generate (initial) PPBUS_G3H without T2 communication.
Once T2 starts, PPBUS_G3H is adjusted to final value.
Try changing U7000...
 
S

sekidata

Member
Apparently, it's not easy to find the ISL9240HI for this machine. Will need to order some reballed chips from donor boards...
 
S

sekidata

Member
You were dead right: replacing U7000 (ISL9240) restored PPBUS (12.6V), 3V3_G3H_RTC (3.4V), and 20V on the charger.

Now on to the rest of the board.
 
S

sekidata

Member
I'm just getting started with T2 boards and their architecture; can you point me to a post or page explaining basic troubleshooting? A bit confusing with the new SoC, PMU, and T2 chips...
 
2informaticos

2informaticos

Administrator
Staff member
Power on sequence available only for 01055 and 01598.
None of them help too much for T2 boards in general.

Check voltage on the big coils.
SSD and G3S voltages must come before S5 state.

Is the machine recognized in DFU mode?
 
S

sekidata

Member
Yes, board enters DFU mode.

I just found another corrosion-related short in U9080, one of the power supplies for the SSD. I removed U9080, waiting for replacement chip. So with the SSD nonfunctional it’s pointless to troubleshoot other power rails?
 
S

sekidata

Member
After U9080 replacement, all NAND power have been restored, although I'm worried about the low resistances on some of these lines. Can you confirm that these are right? I don't have another board to compare.

PP2V5_NAND_SSD0: 2.5V 240Ω
PP1V8_SSD0: 1.8V 5.2kΩ
PP0V9_SSD0: 0.9V 137Ω
 
2informaticos

2informaticos

Administrator
Staff member
Compare SSD0/1 values; should get very similar values.
I don't have comparison board here.
Also look at logi.wiki web page; they have diode mode readings for several boards.
 
You must log in or register to reply here.
Top