820-00850 - No S5 voltages

overshoot

Member
Hi,

I got that board for data recovery.
Customer went to Apple after he cracked his screen.
MacBook was working prior to going to Apple as he said he could use it on an external screen + internal screen was lighting up.
Apple did diagnose that both screen and mainboard were dead.
Anyhow, Apple did not wanted to get his board replaced or fixed.

Customer needs data recovery now and hopefully would like to fix the laptop but he has crypto on it so data recovery is more important.

Inspection...
Board takes 20V and amperage will go to around 0.3A before going to 0 and does that over and over again.
There are no visual damage on the board, neither corrosion or knocked off parts.
With thermal cam I am only seeing the PMIC/T2 area getting warm.
I've tried a DFU revive with no luck on both Catalina/BigSur and I am always getting the same error message.

Measurements...
PPBUS_G3H jumps between 12.3V and 12.6V every 3-4 seconds

PPVDDCPU_AWAKE - 0.75V
PP1V2_AWAKE - 1.2V
PP1V8_AWAKE - 1.8V
PPVDDCPUSRAM_AWAKE - 0.8V
PP0V82_SLPDDR - 0.82V
PPVDDCPUSRAM - 1.06V
PP3V3_G3H_PMU_VDDMAIN - 3.34V
PP1V_PRIM - 0V
PPVPCORE_S5 - 0V
PP1V8_SLPS2R - 1.8V
PP0V9_SLPDDR - 0.9V
PP1V1_SLPS2R - 1.09V
PP0V8_SLPS2R - 0.8V
PP3V_G3H_RTC - 3V
PP1V8_S5 - 0V
PMU_ONOFF_L - 3.4V
PMU_RSLOC_RST_L - 3.4V
PM_SLP_S4_L - 0V
PM_SLP_SUS_L - 0V
 

overshoot

Member
While PPBUS_G3H is a 12.6V I am also getting the following SSD voltages:

- PP0V9_SSD0 - 0.9V
- PP1V8_SSD0 - 1.8V
- PP3V3_G3H_SSD0 3.3V
- PP2V7_NAND_SSD0 2.7V

EDIT: I have to mention that I can see the NANDs warming up as well as U9000 and U9080 under the thermal cam.
 
Last edited:

2informaticos

Administrator
Staff member
SSD voltages must be present all the time, as T2 requires access to its firmware partition.

Why the client accepted non-working machine back from Apple, if it was good with external screen?
Something happened in the Apple service; if they really disassemnled the machine.

Did you test the board alone on the desk?
 

overshoot

Member
Because here is Thailand and there are not much recourse...
Also they just mentioned that the board had an underlying problem that came after.

Anyhow, he needs data.

I did indeed test the board alone.
If those SSD voltages come up, stay for a few seconds and then drop (with PPBUS dropping to 12.2V), should I be concern about the PPBUS voltage or SSD voltages first?
 

2informaticos

Administrator
Staff member
PPBUS_G3H dropping denotes some problem with T2.
Somehow, it loses the communication with U7000.

PPBUS_G3H stays high for 3-4s and drops after, or viceversa?
Check diode mode to ground on all big coils and after Power FETs.
Also try starting in SMC bypass mode.
 

overshoot

Member
It stays high for 3-4s while amperage is climbing.
Once drop to 0, this is when PPBUS drops to 12.2V

So I have to suspect a short somewhere I guess.

Since I am not getting an S5 rail to pulse I was thinking it has to do first with the PMIC/T2 correct?
I am not getting the TRIM rails coming out of the PMIC. Is that a concern yet?
 

2informaticos

Administrator
Staff member
If PPBUS_G3H reaches 13V, T2 communicates with U7000 in this time.
Looks like something happens when the board tries to boot.
Do you get a pulse at least, on any S5 voltage?
 

overshoot

Member
PP5V_S5_LDO is the only S5 that has voltage.
Nothing, not even a pulse on the others.

Here are some measurements:

PP5V_S5_LDO 5V
PM_SLP_S5_L 0V (no short)
PP1V05_S5_PCH_VCCDSW 0V (no short)
PP1V24_S5_PCH_VCCDPH 0V (no short)
PP1V8_S5 0V (no short)
PP3V3_S5 0V (no short)
PPVPCORE_S5 0V (200ohms)

PP5V_G3S 5V
PP1V8_G3S 1.8V
PP3V3_G3S 3.3V
 

overshoot

Member
I understand that it could be all of these things.
Is there a chart of which signal in order we should be looking at to find out where it's hanging?

Like for instance, with no S5 rails coming up, what rails should I be checking before that. Any idea please?
 

2informaticos

Administrator
Staff member
If T2 stops to communicate with U7000, it will not continue power on sequence also.
Possibly detects a short in the sequence, if drops after 3-4s only.
Strange that no pulse at all on S5 voltages; check them for short.
 
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