820-00850 - No S5 voltages

[overshoot]

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.

 

[2informaticos]

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]

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]

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]

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]

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]

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

 

[2informaticos]

"Also try starting in SMC bypass mode."
?

 

[overshoot]

It did not make any difference from what I can tell

 

[2informaticos]

Could be broken trace, solders, knocked off components...

 

[overshoot]

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]

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.