820-01949 stuck in recovery

[waterchill]

So I have this board here, no liquid damage, the macbook looks like new. I checked some voltages and found out that PP3v3_S5 is missing. There is no short on this line, resistance is 112kohm.

Some measurments:

PPBUS_G3H = 12,60V
PP3v3_G3H_RTC = 3,390V
PP3v3_G3H_PMU_VDDMAIN = 3,355V

PP3v3_S5 = 0V
PP3v3_S5 = 112kohm

PP2v5_NAND_SSD_0 = 2,52V
PP0v9_SSD_0 = 0,90V
PPVCCQ_ANI_SSD0 = 1,80V

I have managed to get in DFU mode, but same error message appears like in recovery mode:

The operation couldn’t be completed. (AMRestoreErrorDomain error 75 - Failed to handle message type StatusMsg (Missing data volume)) [AMRestoreErrorDomain – 0x4B (75)]

In my opinion the U7800 is faulty, because it is not producing the PP3v3_S5 line. Am I right?

What do you think guys?

 

[2informaticos]

"Missing data volume" sounds more like SSD problem.
Reflash SoC ROM and try again DFU.

Just in case, check diode mode to ground on all big coils; compare with good board.

 

[waterchill]

I have flashed a new Rom but result is same. only difference is now, that it starts directly in DFU mode not in recovery mode.

I checked following coils, unfortunately not have a good board, but for some coils the readings are in felxbv:

L8100 = 0,16V should be 0,072V
L3500_VWR = 0,18V should be 0,511V
L7660 = 0,47V is ok
L7030 = 0,51V is ok
L3500_VXT = 0,21V
L8410 = 0,9V

L7210 = 0,08V should be 0,331V
L7220 = 0,08V should be 0,330V
L7230 = 0,08V should be 0,330V
L7400 = 0,15V

 

[2informaticos]

CPU core coils have very low resistance to ground as normal; 0.08 should be good there.
You should compare the other coils with good board.

Also check all outputs on page 64.

 

[waterchill]

I don't know why, but today board stuck at 5V and will not switch to 20V. I swear yesterday it switched to 20V. I will take later some new measurments but for the first, it switches to 20v only if battery is connected. Without battery PPBUS_G3H is 12,61V -> too low

 

[waterchill]

PPBUS_G3H = 12,29V
PP3v3_G3H_RTC = 3,31V
PP3v3_G3H_PMU_VDDMAIN = 3,38V
PPDCIN_G3H = 5,06V

R7021 = 1ohm
R7022 = 1ohm
R7061 = 1ohm
R7062 = 1ohm

Looks like U7000 is faulty...

 

[2informaticos]

Why do you think U7000 is fault?
Did you check UPC_I2C_INT_L?

 

[waterchill]

UPC_I2C_INT_L = 0,0V / 2,4Mohm / 0,47V

Why do you think U7000 is fault? Because in the repair wiki manual, it says that is very likely that U7000 is faulty.

 

[2informaticos]

It can't generate PPBUS_G3H by itself.
It is controlled by SMC through SMBUS.
And SMC got an error from USB-C area; UPC_I2C_INT_L must be high.

 

[waterchill]

ok so any other ideas?

 

[2informaticos]

Can't complete DFU?

 

[waterchill]

It aborts always with same error

 

[waterchill]

I found something very weird. When I connect the charger on the same usb side as the thunderbolt cable to other macbook and the revive the macbook, after some seconds in step 4 of 4 (installing system) the voltage jumps to 20V. In this moment UPC_I2C_INT_L = 1,8V. But it aborts with same error. Now I'm totally confused. I tried this with naked board and also with all cables plugged but same result. PP3v3_S5 in this moment is still 0V

 

[2informaticos]

Battery also connected?

 

[waterchill]

The measurments were taken only board nothing connected. With battery connected the charger do instantly 20V. But error is same, doesn't matter if all components are plugged in or not. I found this topic here

A2251 not turning on. Probably corrupted T2

Hi, Got this machine, when plug chartger get all rails, it behaves like normal working machine but there is no signal on display. Tried to restore from DFU, got it in DFU mode and getting this error: AMRestoreERrorDomain 75: Failes to nadle message type StatusMSG (Missing data volumne)...

boards.rossmanngroup.com

Looks no solution for this.

 

[2informaticos]

Error 75 can be caused by faulty CPU.
"Missing data volume" sounds more like SSD problem.

Apple made all possible to confuse us.
There is no interest to repair its boards.

 

[waterchill]

I have some update on this board. I found a mess/short under the onboard display connector see pictures. Unsoldered the connector all pins are fine. Because I have not diode values of exact this board I took values from the A1989 board. Pin 1 and 3 are oL. These are connected directly to cpu. So faulty cpu? How can I found out if display is ok? Are there some values for displays?

 

[2informaticos]

If you've measured correctly (red probe on ground), the CPU's eDP output is damaged.

 

[waterchill]

Yes measurment was correct. What is eDP for? Is a cpu swap a solution for this?

 

[2informaticos]

eDP stands for embedded Display Port.
Is the actual video bus, used in almost all laptops.

As there is no series capacitor for any eDP line, you must change the CPU.