820-01041 - stuck at 5V

Atomrepair

Member
Customer says this machine stopped working from one day to the next. I went over the board and all connectors and found no signs of liquid or other damage.

All four ports sit at 5.18V with a 60mA current draw.
PP3V3_G3H_RTC_X is at 3.3V
PP20V not shorted to ground.

I understand what to do when PP3V3_G3H is missing (fix it), or if a single port is behaving different from the rest, but not sure what to do if they're all acting the same way.
 

Atomrepair

Member
U6940
1 PP3V3_G3H_RTC_X = 3.3V
3 PMU_ONOFF_L = 3.3V
4 PMU_RSLOC_RST_L = 3.3V
10 CHGR_RST_OM_R = 0V (no short to gnd)
 

Atomrepair

Member
PMU_ONOFF_L is 3.37V
PM_RSMRST_L and PM_PWRBTN_L are both 0V with a 100mV pulse (over 0.2 seconds) when connecting adapter.

U4760
PP3V3_S5 = 0V
PP1V8_SLP2SR = 1.8V
SMC_SYSRST_L = 0V
SMC_PCH_SYS_PWROK = 0V
SMC_PCH_PWROK = 0V
SMC_RSMRST_L = 0V
 

2informaticos

Administrator
Staff member
PMU_PVDDMAIN_EN comes from U7800; it is not realeased for some reason.
Start checking some voltages of U7800 (SYM 1 of 4) at page 76.
 

Atomrepair

Member
U7800 SYM 1 of 4:
PP3V3_G3H_SOCPMU = 3.37V
PP1V1_SLPS2R = 1.1V
PP3V3_G3H_RTC_X = 3.37V
PP0V8_SLPS2R = 0.8V
PP3V0_G3H_RTC = 3.0V
PP1V2_AWAKE = 1.2V
CPU_C10_GATE_L = 0V
PP1V05_S0SW = 0V
LDO_RTC = 1.5V
PP3V3_G3H_SOCPMU = 3.37V
PP3V3_AWAKE = 3.37V
PP3V3_S5 = 0V
 

baycomputers

New member
Wanted to chime into this to confirm I have a machine here with a seemingly identical problem, power rails measured same, all 4 CD3215s replaced (just in case), activity on i2c_pwr_scl/a lines.

My findings:

I think the 4.7k resistors (r5220/r5221) on SMC i2c G3H connections are wrong on schematic, or both on mine happened to fail down to exactly 2.1k at the exact same time. Seems odd to me.

Sometimes plugging in power repeatedly in and out triggers 20v but .5ma draw. This is DFU mode apparently. I confirmed with another type-c mac running mojave 10.14.6 and Apple Configurator 2, got a dfu icon when plugged into "front left" type-c. Did "restore" and got an error (AMRestoreErrorDomain error 10....) which is apparently just a generic error about the write process.

Bad mac apparently power cycled, and is now charging the battery (20v / 3A draw) and responds to click but still has black screen. I'll continue toying with DFU/bridge bios installing/wiping etc... but i've done this 3 times now and it's failed 3 times (different error message once, said it's booted to recovery mode instead of DFU)
 

2informaticos

Administrator
Staff member
Be sure to connect bad MacBook with its correct recovery USB-C port.

"I think the 4.7k resistors (r5220/r5221) on SMC i2c G3H connections are wrong on schematic, or both on mine happened to fail down to exactly 2.1k at the exact same time. Seems odd to me."
If you mean measured onboard, that could be OK.
Keep in mind, other components could interfer in the measuring process; because of parasitic loops created onboard.
 

baycomputers

New member
I had that thought also, they measured the same inline as when i removed them and measured to be sure. It's not entirely unknown for the schematics we use to have incorrect info on them (cd3215a) but they should still be able to make a data line at 4.7k, no?
 

Atomrepair

Member
Update on this one: the firmware update fixed the problem. Had to do it a couple of times and got an error about the thunderbolt cable, but it worked in the end. Laptop is booting and functioning fine now.
 

2informaticos

Administrator
Staff member
Thanks for feedback.
We now know that f***g T2 chip can generate a symptom which looks more like a power issue.
Just because of "reliable" Apple firmware...
 

BCN_Techs

Member
Update on this one: the firmware update fixed the problem. Had to do it a couple of times and got an error about the thunderbolt cable, but it worked in the end. Laptop is booting and functioning fine now.

did you put machine in dfu mode ? what king of cable you finally used? i am at same with 3 macbook air. 5V on port and 13V on logic board. All stopped working from one day to other.
 

Atomrepair

Member
did you put machine in dfu mode ? what king of cable you finally used? i am at same with 3 macbook air. 5V on port and 13V on logic board. All stopped working from one day to other.

Nope, didn't do anything special to the non functional or the connected macbook I used to update the firmware. I used a USB-C to USB-C cable that came with an (original) charger.
 
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