Help with A1990 / 820-01041

j07rdi

New member
Hello guys,

My MacBook Pro died after cycling the battery using Al dente. I been using aldente for years to keep my battery at 80% with great success but after upgrading to the PRO version, I decided to try the Cycling feature. It suppose to discharge the battery to 15%, charge it up to 100%, repeat, etc... Whoever it passed down the 15% mark, which I noticed around 3%, I tried to cancel it, so the charger will be enabled again and start charging but it didn't work. As expected the computer shut off, but because the battery is so dead (and old) and the SMC is commanded to disabled the charger to power it (and charge) it is stuck dead. I can't restart the SMC.. The computer was working 100% fine.

So I opened it up and I successfully recharge the battery externally, but when putting it back I accidently shorted batt+ with ground and I believe the bat management is dead (I know, it was stupid mistake, but I work with Lithium-ions so I know how to work with them as long as I don't short them). So I bought a new battery and I will try that as soon as it arrives, whoever, I just started to study the diagrams and schematics. There is a small possibility I might have damaged the board, but I don't think so, the short was from the battery + to the battery ground...

Repairing unknown electronics is whole different story, but it seems pretty straight forward. I need some help so I can restore the SMC and check if something else is not damaged. All I need to do is recover some files no matter what, even If I need to destroy it. If successful I'm willing to donate it for parts.

So far, the USB charger is stuck at 5V. I don't see I2C, which is bad. I believe the T2 is bricked. I been randomly checking voltages, but I didn't write them down, until the very end:

PPDCIN_G3H = 5.1V
PPBUS_G3H = 12.32V

More info: The motherboard looks very nice, no corrosion, no water spills, no water detectors triggered. Just a lot of dust. Not hot spots, the hottest part besides you guys is around the USB-C management chips at around 35C. The motherboard does nothing if I press the power button, button works I see is pulling the 3.3V line down. I'm waiting for the USB-C power meter to provide better details.

Questions:

1.- Seems like all the capacitors from the U7800 bucks are sorted, is that normal? It is a switched regulator, so it might be but is strange. PP3V3_G3H_SOCPMU has ~3.4V, so supply to the IC is good.
2.- It would be wise to follow this voltages in order? But is from a different laptop, so not all names match: Here
3.-What power rails and regs should be alive when the laptop is at S5?

I'm looking for suggestions to verify that the hardware is good, and try to force/restore the T2, maybe via the DFU, and recover the files or whatever suggestions you have. Thanks!

[You can skip this part]
I'm an engineer, I do complex PCB designs, RF, I rework BGAs, reball them, manually solder 01005 components, etc... Is part of my daily job. I work in company that designs and assembles electronics, whoever I don't have experience repairing laptops. I have access to all the tools, even x-ray.
 

2informaticos

Administrator
Staff member
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:
 

2informaticos

Administrator
Staff member
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

New member
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.
 
Last edited:

2informaticos

Administrator
Staff member
"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

New member
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

Administrator
Staff member
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

New member
Hello,

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

j07rdi

New member
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.
 

j07rdi

New member
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?
 
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