Help with A1990 / 820-01041

[2informaticos]

First of all, welcome to the forum!

The first step with T2 machines, is trying DFU.
If machine is not recognized, then need to dig in hardware.
Follow the DFU tutorial linked in the forum:

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

 

[j07rdi]

Thanks a lot!

Can I do this without a battery connected?

 

[2informaticos]

No battery needed for DFU.
USB-C charger will stay in 5V all the process.

Write directly into reply box, instead of clicking Reply button.
Unless you have any reason to quote an entire text, visible few centimeters above.
Please, maintain forum aesthetic...

 

[j07rdi]

So I plugged a genuine USB-C Thunderbolt into the left/front USB and attached it to another MacBook pro with Apple Configurator 2. No luck.

 

[2informaticos]

"Write directly into reply box, instead of clicking Reply button."
This avoid the quote.

Check if all AWAKE and SLPS2R voltages are present; small coils surrounding U7800.

 

[j07rdi]

Hello, fixed the formatting of my comments. Here are the powers measured:

PP1V2_AWAKE = 0V
PP1V2_AWAKE_SOC_PCIEPLL_F = 0.03V Flickering
PP1V2_AWAKE_SOC_PCIEREFBUF_F = 0.04V Flickering
PP1V2_AWAKE_SOC_PLLCPU_F = 0.04V Flickers
PP1V2_AWAKE_SOC_PLLSOC_F = 0.04V Flickers

PP1V8_AWAKE = 0V
PP1V8_AWAKE_SOC_FMON_RC = 0V
PP1V8_AWAKE_SOC_TSADC_RC = 0V

PP3V3_AWAKE = 0V

PPVDDCPUSRAM_AWAKE = 0.2V Flickering
PPVDDCPU_AWAKE = 0V
PVDDCPUAWAKE_FB = 0V
PVDDCPUAWAKE_FB_R = 0V

PVDDCPUAWAKE_SW0 = 0V
PVDDCPUAWAKE_SW1 = 0V
PVDDCPUAWAKE_SW2 = 0V
PVDDCPUAWAKE_SW3 = 0V

PVDDCPUSRAMAWAKE_FB = 0V
PVDDCPUSRAMAWAKE_SW0 = 0V

SOC_BLUE_AWAKE = 0V (components around not populated).

PP1V8_SLPS2R = .2V Flickering

PP1V8_SLPS2R_PMUVDDGPIO = 0V
PP1V8_SLPS2RSW_DFR = 0V
PP1V8_SLPS2R_SOC_LPADC_RC = 0V
PP1V8_SLPS2R_SOC_LPOSC_RC = 0V

PP0V8_SLPS2R = 0V
PP1V1_SLPS2R = 0V
PP1V25_SLPS2R_SMC_AVREF = 0.2V Flickers

P1V1SLPS2R_FB = 0V
P1V1SLPS2R_SWO = 0V
P1V1SLPS2R_SW1 = 0V

 

[2informaticos]

No need to check all, if you find at least one missing.
Possibly bad U7800, if you get short to ground on several of its coils.

 

[j07rdi]

Got it. Do you have that part in stock?

 

[2informaticos]

Contact Rossmann store, if you are in US.
I'm in Spain and don't have it in stock.

 

[j07rdi]

Hello,

So I sourced it, and I was able to successfully rework the U7800, but it didn't work. Exactly the same behavior.

 

[2informaticos]

Do you still have short to ground on U7800 coils?
Did you check that when chip was removed?

 

[j07rdi]

Yes, I did. It is not exactly short, it is around 3-5 ohms. I did apply low voltage and the current was around 3-5A in some areas, and they are in agreement with the max amperage defined on the schematic.

 

[2informaticos]

Such low resistance on U7800 coils is not normal.
T2 must be fried...

 

[j07rdi]

So I'm fried then. Well, I have a motherboard with 1TB and 32Ram that could be used for parts. I also have an intact shell, LCD, and all the tiny pieces. Is anyone interested?